Article

Supercontinents in Earth History

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Abstract

Understanding the formation of cratons and orogenic belts is critical to the modelling of supercontinental assemblies. Continental cratons began to assemble by 3000 Ma or possibly earlier. The oldest assembly, Ur, was followed by Arctica at ∼2500 Ma and Atlantica at ∼2000 Ma. These three continental blocks apparently remained coherent until the breakup of Pangea. Nearly all of earth's continental blocks were assembled into one large landmass during at least three times in earth history. The oldest assembly comparable in size to Pangea was probably Columbia, which formed at ∼1800 Ma and began to rift at ∼1500 Ma. Columbia was followed by Rodinia, which lasted from ∼1100 Ma to 700 Ma. East and West Gondwana combined to form Gondwana at ∼500 Ma, and it joined with Laurasia to form Pangea at ∼250 Ma.

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... The major landmasses on Earth have assembled numerous times in the geological past, forming supercontinents (Rogers 1996;Rogers and Santosh 2003;Salminen et al. 2009;Bradley 2011). The supercontinent cycle describes the periodic assemblage and break-up of continental fragments (Nance et al., 1988;Rogers and Santosh 2004;Santosh et al. 2009;Touret et al. 2015). ...
... Ga), Rodinia (1.1 Ga), Gondwana (0.54 Ga), and Pangaea (0.3Ga) (Hoffman 1991;Rogers and Santosh 2004;Collins and Pisarevsky 2005;Meert and Lieberman 2008;Li et al. 2008;Eriksson et al. 2009). The reconstruction of older supercontinents is always a challenging task compared to the younger ones due to limited fossil record and scarcely preserved geological, paleomagnetic, and geochronological evidence (Halls 1982;Rogers and Santosh 2003;Pesonen et al. 2003;Bleeker and Ernst 2006;Salminen et al. 2009;Belica et al. 2014). ...
... These cratons were built by episodic juvenile magmatism, recycling pre-existing crustal materials, and accretion of blocks through multiple collisions (Manikyamba et al. 2017;Jayananda et al. 2018;Roberts and Santosh 2018;Santosh et al. 2020). The Ur supercontinent is believed to represent the oldest supercontinent that stabilized during the~3.0 to 2.5 Ga period (Rogers 1993;Rogers and Santosh 2003;Santosh et al. 2009). Though~3.0 ...
Article
Charnockites constitute an integral component of granulite belts exposed on the northern and southern flanks of the Godavari rift, which marks the contact between the Bastar and Eastern Dharwar cratons in peninsular India. In this study, we attempt to constrain the petrogenesis of granulites from Gondpipri, Bhopalpatnam on the northern flank and Karimnagar on the southern flank of the Pranhita-Godavari valley using petrography, mineral and whole-rock geochemistry, fluid inclusion studies, and UPb zircon geochronology. The presence of relict magmatic textures and orthopyroxene chemistry is suggestive of an igneous protolith while CO2-rich fluid inclusions in quartz correspond to subsequent granulite-facies overprint. Geochemically, charnockites from both granulite belts are metaluminous, magnesian, and calc-alkaline, having similar Sr and Y concentrations, Rb/Sr, Sr/Y, LaN/SmN, GdN/YbN, and Eu/Eu* ratios, and positive BaPb and negative Nb-Ta-Ti anomalies. Zircons in charnockites from both granulite belts furnish magmatic crystallization ages of ~2.5 Ga (UPb isotope) and also record a metamorphic overprint at ca. 2473 Ma. The similarity in protolith composition and UPb ages of zircons in charnockites on the northern and southern flanks of the Godavari rift suggest that they constitute a cogenetic and coeval suite emplaced at ~2.5 Ga in an undivided and continuous Palaeo-Mesoarchean landmass that included the Bastar and Eastern Dharwar cratons, possibly as a part of the Ur-supercontinent. This undivided landmass subsequently got split along the Pranhita-Godavari rift zone into the Bastar and Dharwar cratons. The rift valley eventually developed into a sedimentary basin hosting the Proterozoic and Gondwana Group of sediments sequentially, apparently separating the two cratons on the map.
... There is a consensus that subduction zone tectonics in the Earth was initiated during the Mesoarchean time [1,2]. Subsequently, the Neoarchean and the Paleoproterozoic periods experienced extensive subduction and rift-related magmatism leading to the cratonization of Archean blocks [3][4][5]. Jayananda et al. [4,6], Condie and O'Neil [7], Condie [8], Condie et al. [9] correlate the late Archean-Paleoproterozoic transition with the extraction of continental crust from the mantle, with a significant increase in large-ion lithophile and high-field strength elements and a decrease in Sr in the continental crust that reflect in the change in magma chemistry from tonalite-trondhjemite-granodiorite to calcalkaline-alkaline granite. ...
... Ur is the oldest known Archean supercontinent, which sta-bilized~3000 Ma by assembling the Dharwar and the Singbhum cratons of the Indian subcontinent, the Kaapvaal craton of South Africa and the Pilbara cratons of western Australia [3,126]. Saha et al. [26] report~3400-3500 Ma zircon from the Bundelkhand craton and correlate the same with crust formation events in the Dharwar and the Singbhum craton as a part of the original Ur supercontinent. ...
... Saha et al. [26] report~3400-3500 Ma zircon from the Bundelkhand craton and correlate the same with crust formation events in the Dharwar and the Singbhum craton as a part of the original Ur supercontinent. Rogers and Santosh [3] also, suggest that the Yilgarn craton and the Zimbabwe craton accreted with the original Ur 2500 Ma to form the extended Ur (Figure 11(a)). It is generally agreed that the configuration of crustal blocks in extended Ur exists till the stabilization of Mesozoic supercontinent Pangea. ...
... Thus, they share a number of magmatic events in addition to sharing similar Precambrian basement geology (e.g. Rogers and Santosh 2003;Naqvi 2005;Sharma 2009;Ramakrishnan and Vaidyanadhan 2010;Meert et al. 2010;Jain et al. 2020). In subsequent sections, we will provide detailed accounts of these shared magmatic units (see summary in Tables 1 and 2). ...
... 2.5 Ga) include Dharwar, Bastar and Singhbhum cratons of the Indian Shield (i.e. DHABASI), along with a number of other Archean cratons such as the Kalahari and Zimbabwe cratons of southern Africa, the Pilbara and Yilgarn cratons of western Australia, the Napier and Vestfold blocks of East Antarctica and Madagascar (see Fig. 9; Rogers 1986;Rogers and Santosh 2003;Srivastava 2008 Shankar et al. 2018) and the combined c. 1.9 Ga palaeopole for the Dharwar and Bastar cratons falls at 31°N, 330°E (cf. Meert et al. 2011;Pradhan et al. 2012). ...
... 3.1 Ga) and 'Expanded Ur' (c. 2.5 Ga) (modified afterRogers 1986;Rogers and Santosh 2003;Srivastava 2008). These supercontinents incorporate a number of Archean cratons, including the Kalahari (KC) and Zimbabwe (ZC) cratons of southern Africa, the Pilbara (PC) and Yilgarn (YC) cratons of western Australia, the Napier (NC) and Vestfold (VC) blocks of the East Antarctica, the Madagascar (MC), and the Dharwar, Bastar, and Singhbhum cratons of the Indian Shield (i.e. the herein proposed DHABASI megacraton). ...
Chapter
We propose a Precambrian megacraton (consisting of two or more ancient cratons), DHABASI in the Indian Shield, which includes the Dharwar, Bastar and Singhbhum cratons. This interpretation is mainly based on seven large igneous provinces (LIPs) that are identified in these three cratons over the age range of c. 3.35–1.77 Ga, a period of at least 1.6 Ga. In addition to their use in recognizing. We suggest that the megacraton DHABASI was an integral part of supercontinents/supercratons through Earth’s history, and that it should be utilized as a distinct building block for palaeocontinental reconstructions rather than using the individual Dharwar, Bastar and Singhbhum cratons.
... There is a consensus that subduction zone tectonics in the Earth was initiated during the Mesoarchean time [1,2]. Subsequently, the Neoarchean and the Paleoproterozoic periods experienced extensive subduction and rift-related magmatism leading to the cratonization of Archean blocks [3][4][5]. Jayananda et al. [4,6], Condie and O'Neil [7], Condie [8], Condie et al. [9] correlate the late Archean-Paleoproterozoic transition with the extraction of continental crust from the mantle, with a significant increase in large-ion lithophile and high-field strength elements and a decrease in Sr in the continental crust that reflect in the change in magma chemistry from tonalite-trondhjemite-granodiorite to calcalkaline-alkaline granite. ...
... Ur is the oldest known Archean supercontinent, which sta-bilized~3000 Ma by assembling the Dharwar and the Singbhum cratons of the Indian subcontinent, the Kaapvaal craton of South Africa and the Pilbara cratons of western Australia [3,126]. Saha et al. [26] report~3400-3500 Ma zircon from the Bundelkhand craton and correlate the same with crust formation events in the Dharwar and the Singbhum craton as a part of the original Ur supercontinent. ...
... Saha et al. [26] report~3400-3500 Ma zircon from the Bundelkhand craton and correlate the same with crust formation events in the Dharwar and the Singbhum craton as a part of the original Ur supercontinent. Rogers and Santosh [3] also, suggest that the Yilgarn craton and the Zimbabwe craton accreted with the original Ur 2500 Ma to form the extended Ur (Figure 11(a)). It is generally agreed that the configuration of crustal blocks in extended Ur exists till the stabilization of Mesozoic supercontinent Pangea. ...
Article
This communication reports novel geochemical and geochronological data of granite from the southeastern part of the Bastar Craton, Central India. The studied samples are leucocratic in appearance and composed of quartz, K-feldspar, plagioclase feldspar, and biotite in decreasing order of abundances. Apatite, sphene, and zircon occur as accessory minerals. The SiO2 and Al2O3 content of the studied sample varies between 61 and 69 wt.% and 13 and 15 wt.%, respectively. The alkali oxides, K2O, and Na2O content ranges between 3 and 6 wt.% and 2 and 3 wt. %, respectively. In the primitive mantle normalized spider diagram, the granites exhibit a negative Nb–Ti, Sr anomaly, and a positive Pb–Th anomaly. Similarly, in the REE normalized spider plot, the granites exhibit a strongly fractionated trend La/YbCN=10.90−28.4 with a negative Eu anomaly (0.42-0.70). The zircon saturation in silicate melt yields crystallization temperature (Tzr) ~650 to 800°C for the Eastern Bastar Craton rocks. The P-T pseudosection modeling implies EBC granites which are crystallized at 700-750°C, at 0.4 to 0.6 GPa. The SHRIMP U-Pb ages from magmatic zircon yield an upper intercept at ~2470 Ma and a lower intercept at ~2100 Ma. When combined with the results of P-T pseudosection modeling, the geochemical and geochronological data classifies the Eastern Bastar Craton rocks as A2 granites that were emplaced during the amalgamation of Archean blocks leading to extended Ur formation. The ~2100 Ma age is correlated with mafic dyke emplacement and the Bastar Craton–Yilgarn Craton block disintegration before Paleoproterozoic Columbia supercontinent assembly.
... La evolución geodinámica de la Amazonía Colombiana puede ser observada en términos de Supercontinentes (Rogers & Santosh, 2003) o Ciclos de Wilson (Wilson, 1966;Hartz & Torsvic, 2002;Stern, 2004). De forma simple, un Ciclo de Wilson comienza con la fragmentación de un continente (Figura 8) debido a la acción de un punto caliente (Fitcher & Poché, 1993;Condie, 1998;Courtillot et al., 1999;Condie, 2000;Dalziel et al., 2000;Condie, 2002;Eriksson et al., 2002). ...
... El océano tenderá a cerrarse a medida que la subducción de la corteza oceánica toma lugar, originando un cinturón montañoso colisional al plegar los sedimentos del borde continental y fracturar el borde del continente (Boutelier et al., 2003). A medida que este proceso sucede, se genera la acreción de arcos de islas, plateaus y masas continentales, formando un gran continente o supercontinente (Rast, 1997;Rogers & Santosh, 2003). Sobre este gran continente aparecerá de nuevo rift intracontinental debido a un punto caliente, dando origen al inicio de otro ciclo (Courtillot, et al., 1999;Courtillot et al., 2003). ...
... Las plumas del manto, desarrollándose a partir de una surgencia del manto (Courtillot et al., 1999;Golonka & Bocharova, 2000), en combinación con zonas debilitadas preexistentes de dimensión cortical o litosférica, definen los sitios actuales de fragmentación. De acuerdo con Rogers & Santosh (2003), (Pangea). El pico orogénico jóven de 100-50 M.a., según se expresó para los cinturones plegados Cordilleranos-Alpinos, puede ser considerado como el primer paso en la formación de un futuro Supercontinente. ...
... Meert, 2012;Torsvik & Voo, 2002;Wang et al., 2020). Further, Gondwana megacontinent consists of East Gondwana (Greater India, Antarctica, Australia, and Madagascar) and West Gondwana (South America and Africa; see Figure 1b; e.g., Bradley, 2011;Domeier et al., 2012;Li et al., 2008;Meert, 2012;Rogers & Santosh, 2003). Later, different blocks of East Gondwana were dispersed during the Early Cretaceous (e.g., Gibbons, Whittaker, & Muller, 2013). ...
... Later, different blocks of East Gondwana were dispersed during the Early Cretaceous (e.g., Gibbons, Whittaker, & Muller, 2013). Based on the available geological and geochronological data (e.g., Bradley, 2011;Ernst & Bleeker, 2010;Evans, 2013;Gibbons et al., 2013;Li et al., 2008;Meert, 2011Meert, , 2012Nance et al., 2014;Rogers & Santosh, 2003Stampfli, Hochard, Verard, Wilhem, & von Raumer, 2013;Wang et al., 2020;Worsley, Nance, & Moody, 1986 and references therein), evolution of the Pangaea supercontinent can be summarized as 1. The megacontinent Gondwana was amalgamated at ca. 540-530 Ma, which is also well supported by palaeomagnetic data (e.g., Collins & Pisarevsky, 2005;Li et al., 2008;Meert, 2003;Meert & Van der Voo, 1996). ...
... 3. At ca. 200 Ma, breakup of the supercontinent Pangaea began due to high-speed movement of the Indian subcontinent northwards. Yoshida and Hamano (2015) suggested that the primary driving force of continental dispersal was due to a combination of two F I G U R E 1 (a) Reconstruction of Pangea (modified from Meert, 2012;Torsvik & Voo, 2002;Wang et al., 2020); (b) Reconstruction of Gondwana (modified from Bradley, 2011;Domeier, Van der Voo, & Torsvik, 2012;Li et al., 2008;Meert, 2012;Rogers & Santosh, 2003); (c) Reconstruction of East Gondwana (modified after Schettino & Scotese, 2001;Singh, Chung, Bikramaditya, Lee, & Khogenkumar, 2020;Srivastava, 2020;Zhu et al., 2009) Olierook et al., 2016;Zhou et al., 2018;Zhu et al., 2009). ...
Article
A detailed contemplation is attempted to comprehend the likely connection of a large number of Early Cretaceous mafic, felsic, alkaline (kimberlite, lamproites, ultramafic lamprophyre, etc.), and carbonatite magmatic records of the eastern and north-eastern region of the Indian Shield and adjoining regions. All these Early Cretaceous magmatic records occupied a large area, covering adjoining regions of south-eastern Tibet, eastern and north-eastern India, western Australia, Eastern Indian Ocean, southern Kerguelen Plateau, and north-eastern Antarctica, are supposed to be part of the Greater Kerguelen Large Igneous Province (LIP) and likely to be related to the break-up of East Gondwana. Available age results, chiefly ranging from ca. 145 to 100 Ma, support a genetic connection with the Kerguelen mantle plume. However, there are other lines of evidences, particularly radiogenic isotope data that preclude direct involvement of any mantle plume component; likely to be derived from decompression melting related to passive rifting. Two major magmatic phases, ca. 145–130 Ma and ca. 124–100 Ma, have been distinctly identified, which could be related to distinct rifting events. Break-up of East Gondwana had happened at ca. 137 Ma with separation of Western Australia from Greater India. Later, ca. 124–122 Ma, separation of Antarctica from Eastern India occurred. The later magmatic phases (after ca. 120 Ma) are likely to have an indirect connection with the Greater Kerguelen LIP probably with the mantle plume providing extra heat for melting.
... However, due to billion years of denudation processes, the records of rifting or accretion and associated magmatism are often obliterated and become elusive. Therefore, combining the patchworks of partially destroyed information from cratons and/or orogens along with the delineation of ITSZs and its deformation history can establish suitable models for the amalgamation of continental blocks [12,13]. Global examples of ITSZs include Aggeneys terrane, Bushmanland, South Africa adjacent to Kaapvaal Craton [14], San Juan fault system at the Cascades Orogen, western USA [15], strike-slip shear zone in central Alaska [16], and Tabalah/Wadi Ta'al Tectonic Zone in the Asir Terrane of Arabian shield [17]. ...
... Assembly. It has been opined by several workers that the BC was a part of the Archean Bundelkhand-Aravalli nucleus of the Ur (~3.0 Ga) supercontinent along with Singhbhum, Dharwar, and Bastar [12,[125][126][127]. Earlier workers also suggested that till the Mesoarchean time, the Aravalli, Bastar, Bundelkhand, and Dharwar Cratons (Figure 1(a)) were fragments, rather than one united supercontinent [128]. ...
Article
Delineation and characterization of the intra-terrane shear zones (ITSZs) are very significant in establishing suitable models to understand the tectonic evolution of continental blocks, and often provide crucial information on supercontinent assembly. The granitoid rocks of the Bundelkhand Craton (BC) host mesoscale ductile shear zones of varying width and direction, and typically represent decoupling zones (high and low strain), characteristic of ITSZs. The detailed study on the structural anatomy and nucleation of the ductile shear zones in the BC suggests the presence of four distinct sets of ITSZs along ~N-S, ~NE-SW, ~NW-SE and ~E-W directions. The nucleation of the ITSZs in the granitoid rocks is possibly a result of reactivation of the precursor fractures due to the rheological transformation induced by the epidote-rich fluid, which percolated through the fractures. Also, the thickness of the ultramylonite zone in the ITSZs is attributed to the width and style of the brittle fracturing. Here, we also construe a relative chronology of the development of fabric elements related to the ITSZs in BC with the help of cross cutting relationships as observed in the field and further corroborated it to the available chronological data. This suggests, ~E-W trending ITSZs along the Bundelkhand tectonic zone (BTZ) and Raska shear zone (RSZ) as the oldest followed by the evolution of ~N-S, ~NE-SW, and ~NW-SE trending ITSZs. The kinematic analysis of these ITSZs, with the help of angular relationship between the measured mylonitic foliation and determined magnetic foliation data (by AMS analysis) suggests that, fabric development in the ITSZs is dominantly governed by general shear except the oldest ~E-W trending ITSZs, which shows pure shear dominated progressive deformation. Also, with the help of field evidences and magnetic fabric analysis we conclude that transpression was involved over a protracted period for the evolution of the ITSZs in the BC. Finally, we argue that the BTZ served as the site for the localization of the ~E-W trending ITSZs and represent the zone of amalgamation between North BC and South BC during the formation of Kenorland at ~2.5 Ga.
... Arcs are the fundamental building blocks of continents, with arc-arc parallel collision generating composite arcs that amalgamate to form primitive continents, and these, in turn, grow through vertical and lateral accretion (Santosh, 2013 and references therein). The stabilization of continental blocks involves various processes like juvenile crustal growth, deposition of supracrustal rocks, and orogenic processes, together with anorogenic plutonism and deposition of platform sediments (Rogers and Santosh, 2003;Santosh et al., 2009;Nance et al., 2014;Santosh et al., 2014Santosh et al., , 2016. ...
... Peninsular India is one of the key regions of the world to investigate Precambrian crustal evolution, and is composed of a collage of cratonic nuclei and continental blocks that were part of various supercontinents in the Earth history starting from Ur at 3.0 Ga through Columbia at 1.9 Ga, Rodinia at 1.0 Ga and Gondwana at 0.54 Ga (Rogers and Santosh, 2003;Meert et al., 2010;Nance et al., 2014;Santosh, 2020). The southern part of Peninsular India is composed of the Archean Dharwar craton with granitegreenstone belts in the north, and the granulite-facies rocks of the Southern Granulite Terrain to the south (Harris et al., 1994;Chetty, 1996;Peucat et al., 1993;Nutman et al., 1996;Chadwick et al., 2000;Ghosh et al., 2004;Santosh et al., 2015Santosh et al., , 2016Santosh, 2020;Jayananda et al., 2008Jayananda et al., , 2013Jayananda et al., , 2015Jayananda et al., , 2020. ...
Article
As one of the oldest crustal blocks in Southern Peninsular India, the Coorg Block has been the focus of investigations related to crustal evolution in the early history of the Earth with implications on Mesoarchean plate tectonic processes. The Coorg Block is dominantly composed of arc magmatic rocks and bordered on the north by the Mercara Suture Zone, a Mesoproterozoic subduction-collision zone hosting extruded high-pressure and ultra-high temperature metapelitic and meta-mafic rocks. Here, we report the occurrence of a dismembered gabbro-anorthosite complex corresponding to a layered intrusion from the northern margin of the Coorg Block. We present results from an integrated study on the petrology, mineral chemistry, P-T phase equilibria, whole-rock geochemistry, and zircon and monazite U–Pb geochronology to understand the magmatic and metamorphic evolution of the layered intrusion and associated rocks. The geochemical data suggest that the parental magma was generated within a suprasubduction zone setting. Phase equilibrium modelling of garnet-bearing metagabbro from the Coorg Block suggests metamorphic P–T range of 10.5-11 kbar at 1000-1100°C corresponding to ultra-high temperature conditions. The zircon U-Pb data from the various rock types of the mafic-ultramafic suite yield weighted mean ages at 3176 Ma, 3174 Ma, 3143 Ma, and 3124 Ma whereas the associated charnockite shows a slightly older age of 3319±12 Ma. Metamorphic zircon from charnockite yield an age of 3101 Ma, close to the monazite age of 3110±24 Ma from the same rock, constraining the timing of metamorphism as Mesoarchean, and marking the collisional event between the Coorg Block and the Dharwar Craton along the Mercara Suture Zone. We propose a tectonic model involving southward subduction of the Western Dharwar Block beneath the northern margin of the Coorg Block that can explain the extensive arc magmatism and suprasubduction zone rock suites, followed by ocean closure and collision along the Mercara Suture Zone, accompanied by high P-T metamorphism.
... It is pertinent here to mention that the first supercontinent Ur [112,113] formed at about ca. 3.1-3.0 ...
... Thus, presence of the transpressional belt, as documented in the current contribution, within SIOG (Figures 2(b), 17, and 18(e)) resulting from oblique convergence along the Sukinda thrust points to existence of dynamics of mobile plates akin to Phanerozoic realm in the Neoarchean along SC margin. The Ur after its congregation at ca. 3.0 Ga evolved into an "Expanded Ur" [113] through repeated accretion till ca. ...
Article
A number of crustal-scale shear zones have developed along the southern margin of the Singhbhum Craton, in the boundary with the Neoarchean Rengali Province and the Meso-Neoproterozoic Eastern Ghats Belt. The cratonic part, evolved in a suprasubduction zone setting, bears imprints of late Mesoarchean orogenic episode (D1C) at ca. 3.1 Ga with folding and thrust imbrication of the cratonic rocks. The succeeding orogenic imprint is etched in the Neoarchean (~2.8 Ga) with development of the Sukinda thrust along the craton margin and thrust-related deformation of the rocks of the Rengali Province (D2C-D1R). The latter event remobilized cratonic fringe with development of a spectacular E-W trending transpressional belt in the Southern Iron Ore Group rocks cored by the Sukinda ultramafics. In the Eastern Ghats Belt, the major ultrahigh-temperature orogeny took place during the Grenvillian-age (~1.0-0.9 Ga) assembly of the supercontinent Rodinia. This belt eventually got juxtaposed against the expanded Singhbhum Craton in the end-Neoproterozoic time (~0.5 Ga) along the Kerajang Fault Zone. This latter event remobilized a large part of the Rengali Province (D2R) with development of an intraterrane transpressional belt bounded by the Barkot Shear Zone in the north. The northern fringe of the intruding Eastern Ghats Belt developed a complex network of strike-slip fault system under this impact, probably an outcome of tectonic activity along the Kuunga suture, which signifies the joining of greater India with East Antarctica. The present synthesis visualizes early development in the craton through formation of a typical orogenic sequence, imbricated in thrust piles, resulting from a ca. 3.1 Ga orogeny. Further cratonic expansion was achieved via repetitive accretion and remobilization, development of crustal-scale faults and transpressional belts at ca. 2.8 Ga and ca. 0.5 Ga, much in a similar fashion as documented along oblique convergent margins of all ages.
... Interactions between Laurentia and Amazonia generated collisional orogens called Grenville in Canada and the USA and Sunsás in Brazil and Bolivia. Those who have proposed Mesoproterozoic paleogeographic reconstructions of these ancient cratons include Casquet et al. (2006), Cawood and Pisarevsky (2017), Chew et al. (2011), Dalziel (1991), Elming et al. (2009), Evans (2009, 2013, Hoffman (1991), Keppie and Ortega-Gutierrez (1999), Li et al. (2008), Loewy et al. (2003Loewy et al. ( , 2004, Rogers and Santosh (2003), Santos et al. (2008), and Tohver et al. (2004). Further revisions considering specifically the Andean Mesoproterozoic basement and the western part of the Amazonian Craton in Brazil and Bolivia are synthesized by Cardona et al. (2010), Cawood and Pisarevsky (2017), Cordani et al. (2009Cordani et al. ( , 2010, Cordani and Teixeira (2007), Fuck et al. (2008), Johansson (2009Johansson ( , 2014, Li et al. (2008), Miskovic et al. (2009), and Ramos (2008Ramos ( , 2010. ...
Article
New geological and LA-ICP-MS U–Pb geochronological data, combined with literature data, are used to characterize more precisely the timing of tectonic events in the Nova Brasilândia belt in the southwestern Amazonian Craton, Rondônia, Brazil. The U–Pb ages of zircon crystals were obtained in the rocks of the Rio Branco domain in the southern part of the belt. They reveal a period of sedimentation between 1241 ± 7.5 and 1137 ± 9 Ma and high-grade metamorphism between 1137 ± 9 and 1127.6 ± 2.3 Ma. Mafic-felsic magmatism of the Rio Branco Suite was dated between 1119.7 ± 2.7 and 1106.2 ± 2.8 Ma. U–Pb ages from specific groups of recrystallized zircon (cores and rims) extracted from high-grade calc-silicate gneiss (1019 ± 15 Ma), metagabbro (1016.7 ± 3.9 Ma), and anatectic granite (1011.3 ± 9.6 Ma) may represent episodes of metamorphic recrystallization and the youngest migmatization. The LA-ICP-MS U–Pb zircon ages establish the timing of two orogenic phases: an accretionary phase between approximately 1137 and 1106 Ma and overprinted metamorphism during the final collisional phase between approximately 1096 and 1011 Ma. The Nova Brasilândia orogeny recorded on the southwest margin of the Amazonian Craton can be described as an accretionary-collisional type that developed between approximately 1137 and 1010 Ma.
... At least seven micro-blocks including Jiaoliao, Qianhuai, Ordos, Jining, Xuchang, Xuhuai and Alashan blocks in the NCC (Fig. 14) which were formed through the oldest crustal accretion at ca. 2.70 Ga were welded along Neoarchean greenstone belts and incorporated within a supercraton at the end of late Neoarchean (Zhai and Santosh, 2011). The Neoarchean greenstone belts are interpreted to represent arc-continent collision, resulting in the amalgamation of various microblocks and the formation of the NCC at ca. 2.50 Ga (Rogers and Santosh, 2003;Zhai and Santosh, 2011) and coincides with the ca. 2.50 Ga supercraton event on the globe (Condie et al., 2001;Condie, 2004). ...
Article
The transition in tectonic regime of our planet during the late Archean with the initiation broadly modern style subduction system is one of the major topics of interest in earth science. The North China Craton (NCC), one of the oldest cratonic nuclei in the world, preserves important records of Archean and Paleoproterozoic crustal evolution, cratonization and related geodynamic history that are important in understanding the continental growth of the early Earth. Here we investigate a suite of Archean to Paleoproterozoic rocks including hornblendite, amphibolite, gabbro, diorite, basalt, plagiogranite, granite porphyry and greenschist from Shandong Peninsula within the southwestern Jiaoliao block of the eastern NCC using zircon U-Pb geochronology, Lu-Hf isotopes, and whole-rock geochemistry. We aim to understand the timing and petrogenesis of the rock suite and its implications on the geodynamic history of the NCC. Zircon U-Pb data show ²⁰⁷Pb/²⁰⁶Pb ages in the range of 2.68–1.83 Ga, and is divided into three groups of 2.68–2.43, 2.38–1.96 and 1.95–1.83 Ga. Among these, the 2.68–2.43 Ga group confirms with the major magmatic phase during Neoarchean-Paleoproterozoic transition in the eastern NCC, whilst the other groups of 2.38–1.96 and 1.95–1.83 Ga ages might represent the Paleoproterozoic orogenic events in the NCC. Zircon Lu-Hf isotopic data display εHf(t) values ranging from −0.4 to 10.0 and TDMC of 3074–2080 Ma, which are subdivided into one group with U-Pb ages of 2672–2445 Ma characterized by εHf(t) values from −0.4 to 7.0 and TDMC of 3074–2588 Ma and another group (2134–2009 Ma) with εHf(t) values in the range of 2.8–10.0 and TDMC ranging from 2458 to 2080 Ma. These results indicate that the magmas (2672–2445 Ma group) were sourced mainly from Late Mesoarchean to Neoarchean juvenile components with minor input of reworked Mesoarchean crustal components, whereas the 2134–2009 Ma group was derived from Paleoproterozoic juvenile components. Whole-rock geochemical data of the granite porphyry and plagiogranites show typical subduction-related arc signature with the enrichment of LREEs and LILEs and depletion of HREEs and HFSEs (e.g. Nb, Ta, Ti), and mainly belong to I-type granites generated at arc-related setting. The ultramafic–mafic magmatic suite corresponds with tholeiitic to calc-alkaline series which were formed by partial melting of enriched mantle within an island arc setting in an active continental margin. In conjunction with the results from previous studies in the NCC, we correlate the 2.68–2.43 Ga ages with Late Neoarchean amalgamation of microblocks and cratonization of the NCC driven by late Neoarchean oceanic plate subduction, and the 2.38–1.83 Ga ages represent Paleoproterozoic orogenic events including the assembly of major crustal blocks in the NCC within the Paleoproterozoic supercontinent Columbia, and the final collision of these crustal blocks and cratonization.
... Our 18S rDNA phylogenetic analyses consistently placed the udonellids in the present study into four lineages (Fig. 3 the early divergent species. Such results show that chondrichthyans must have served as hosts for the initial lineages of the udonellids, and additionally suggest a scenario of initial irradiation for udonellids, referring to the Pangea supercontinent ~250 MY ago sensu Rogers and Santosh [39]. Similarly, Boeger et al. [17] suggested, based on ultrametric analyses (using the 18S rDNA fragment) that the initial divergence of the Gyrodactylidae + Oogyrodactylidae clade with Udonellidae occurred about ~468-216 MY ago, largely coinciding with the timing of a scenario of initial irradiation of udonellids in the Pangea supercontinent. ...
Article
The present study describes Udonella brasiliensis n. sp., an epibiont found on Caligus sp., a parasite the ariids Genidens barbus (Lacepède) and Aspistor luniscutis (Valenciennes), caught on the coast of the state of São Paulo, Brazil. Morphological and molecular analyses (partial 18S rDNA) were carried out. The morphological data showed that U. brasiliensis n. sp. can be distinguished from current valid species by its morphometric attributes (e.g., body, pharynx, ovary and testis), while the molecular information supports the proposal of a new species. The 18S rDNA phylogenetic analysis shows a close relationship between the new species and Udonella australis Carvajal & Sepulveda, in a subclade formed of species that parasitize South American fish. Finally, this study also discusses a scenario of initial irradiation for udonellids.
... Carboniferous through Cretaceous sandstones in the Zongba terrane show a large cluster from 920 to 1200 Ma with prominent peaks centered in 989-999 Ma and three subordinate peaks at 571-595, 1750-1850, and 2457-2600 Ma, with a small cluster around ∼3128 Ma (Xie et al. 2017). The period of 3000-2500 Ma is related to the oldest supercontinental assembly, named as Ur, which mainly consists of Western Dharwar and Singhbhum cratons of India, the Kaapvaal craton of southern Africa, and the Pilbara craton of western Australia (Rogers and Santosh 2003). ...
Article
Full-text available
Ophiolites in the southern belt (SB) occur as much larger peridotite massifs compared with those of the northern belt (NB), sporadically overlain by a thin layer of isotropic gabbro in the western part of Yarlung Zangbo suture zone (YZSZ) in Tibet, which in turn is tectonically thrusted over a volcanic-sedimentary sequence. Geochemical data and radiolarian fauna of cherts, detrital zircon ages of litho-quartz sandstones in the sequence provide robust constraints to elucidate the stratigraphic and paleo-depositional environments in which these rocks formed. Eight cherts from Purang, Dongbo, Daba Qu, East Daba and Labuzha massifs in the SB reveal Late Jurassic – Early Cretaceous radiolarians, they are coeval with minimum detrital zircon U-Pb ages of 132 Ma and 149Ma, respectively, from two litho-quartz sandstones in the northwestern part of Purang massif. Thirty chert samples from five massifs geochemically show that they have high SiO2 contents of 86.51–95.93 wt%, and high mean ratios of Al/(Al+Fe+Mn) ranging from 0.59 to 0.78, indicating a non-hydrothermal, biogenic and terrigenous origin. Ce/Ce* ratios of cherts ranging from 0.93 to 1.52, combined with claystone interlayered with radiolarian chert sporadically overlying litho-quartz sandstone and quartzose sandstone, suggesting a continental slope setting. Structural and stratigraphical evidences of ophiolites associated with sedimentary strata and no arc-related magmatism in the SB, we propose that SB ophiolites and ophiolitic mélanges represent southward thrusted nappes from the NB.
... It has been suggested that the Ur supercontinent (Rogers, 1996;Rogers and Santosh, 2003) comprising several cratonic nuclei such as the Kaapvaal, Dharwar, Singhbhum and Pilbara, and with possible involvement of other Archean continental fragments like Aravalli, Bundelkhand, Madagascar, Napier, Grunehogna, Vestfold, Gawler and Fig. 13. Tectonic setting discrimination diagrams based on major and trace elements concentration in shales/slates/phyllites: (a) discrimination function diagram for high-silica [(SiO 2 ) adj = > 63%-≤ 95%] (after, Verma and Armstrong-Altrinb, 2013). ...
Article
The Simlipal Complex is a circular/elliptical structure at the eastern margin of the Singhbhum Craton in eastern India. The complex comprises metavolcanic and metasedimentary rocks and may represent the remnant of an Archean impact structure. Major and trace element abundances and zircon U–Pb ages from the metasedimentary rocks of the complex, which possibly constituted the target rocks of the impact, are used to constrain the provenance of the sediments and the tectonic environment of their deposition. The metasedimentary rocks include sandstones/quartzites and shales/slates/phyllites. CIA index and the A-CN-K discrimination diagram suggests moderate to extensive weathering of the source areas. The shales/slates/phyllites plot along the weathering trend of granite-granodiorite-tonalite, implying an average granodioritic source. The rare earth element (REE) patterns of shales/slates/phyllites are fractionated (LaN/YbN = 2.86–13.5) with nearly flat heavy-REE (GdN/YbN = 0.92–1.84) similar to Post Archean Australian shale. The Zr/Sc and Th/Sc ratios indicate zircon addition to sandstones/quartzites and mixing of mafic and felsic igneous rocks to shales/slates/phyllites. The shales/slates/phyllites are enriched in Sc, Cr, Ni, Y, Zr, Hf, Th, and U compared to Archean Upper Crust and have positive Cr and Ni anomalies suggesting contribution from mafic/ultramafic source. The major age peaks retrieved from detrital zircons in the metasediments are at 3.63 Ga, 3.46–3.26, 3.17–2.95, 2.87–2.75 Ga, and 2.54 Ga which correlate with ages reported for granitoid suites from different lithodemic units of the Singhbhum Craton. The sediments from the central and NW regions of the complex are dominated by zircons with an age of 3028 ± 15 Ma, while those from the NE regions and areas outside of it (e.g., the Kuliana region) have a preponderance of older zircon ages (ca. 3.25–3.38 Ga). The ages of the oldest metamorphic and the youngest detrital zircon population are suggestive of deposition of the sediments between ca. 2.8 Ga and 2.5 Ga. Crystallization ages and the shape of zircon crystals along with the geochemical signature of the sediments suggest that they were derived locally from the Singhbhum Craton and its surroundings.
... The age population of 2502-2697 Ma in the present study can be compared with the supercontinent Kenorland (or Superia and Sclavia; Bleeker, 2003) that formed at ca. 2700 Ma and broke up after 2500 Ma (Nance et al., 2014 and references therein). The ages range from 1999 to1637 Ma (with a prominent mode at 1800 Ma) corresponds with the global events associated with the Paleo-Mesoproterozoic supercontinent Columbia (Rogers and Santosh, 2002;Rogers and Santosh, 2003;Rogers and Santosh, 2009). Also, the 1800 Ma mode broadly corresponds with collisional events that led to the assembly of Columbia (Zhao et al., 2004;Rogers and Santosh, 2002;Rogers and Santosh, 2009). ...
Article
The southwestern coast of India is known for its rich beach placer deposits. So far, there have been no substantial attempts to determine the provenance of these deposits on a regional scale. Here we present for the first time geochronology, trace element chemistry and Hf isotope systematics of zircon and monazite from representative beach placer deposits along the southwestern coast of India to constrain provenance. Detrital zircon grains display a wide variety of ages, with modes in the ranges of 650–450 Ma, 1100–650 Ma, 2300–1600 Ma, 2800–2300 Ma and 3500–2800 Ma. A high proportion of ages fall within the Neoproterozoic–Late Cambrian range (1066–490 Ma). Growth zoning in zircon grains shows magmatic growth of many generations with ages affected by Neoproterozoic Pb loss, along with overgrowths typical of those formed during high-T metamorphism. Grains of metamorphic zircon, along with grains of monazite from the same samples of sediment, have strong modes between 570 and 470 Ma, indicating derivation from sources in the Southern Granulite Terrane affected by a major Late Neoproterozoic to Cambrian tectonothermal event. Mineral geochemistry of zircon grains indicates continental derivation, especially with older zircon from TTG-type sources. The geochemistry of late Neoproterozoic–Cambrian zircon and monazite are consistent with derivation from amphibolite to granulite-facies source rocks. Zircon ages and Hf isotope systematics can be ascribed to provenance from various source terranes exposed along the Western Ghats. This young rift-flank escarpment formed along the coast at a high angle to the distribution of different Precambrian terranes in the Indian Peninsula. Erosion promoted by a tropical climate and a steep coastal geomorphology, in combination with strong southward along-shore ocean currents, led to the concentration and distribution of heavy minerals from multiple sources along southwestern coast of India. The relative intensity of age modes in detrital zircon differs between localities, demonstrating differing inputs from proximal sources (from rivers dissecting steep terrain) versus distal sources from more northerly cratons and terranes brought to deposition sites by along-shore drift.
... The numerous comparable petrographic, geochemical, isotopic and geochronological features are cogent evidence for a close relationship between the granulite terranes of the Madras Block (SGT, South India), Yishui Terrane (Shandong Peninsula, E-NCC) and Daeijak Island (NW-GM, Korean Peninsula) in the Neoarchaean, a relationship best explained by their contiguity in a single landmass at that time (Fig. 14). Rogers and Santosh (2003) considered that the Dharwar Craton (Ratheesh- Kumar et al., 2020) in India was part of the oldest supercontinent -Ur, that formed at ca. 3.0 Ga. The eastern Dharwar and the northern blocks of the SGT are younger -Neoarchaean (Jayananda et al., 2020;Li et al., 2018;Peucat et al., 2013;Samuel et al., 2014). ...
Article
The composition and configuration of possible Archaean supercontinents remain unresolved. Kenorland, a Neoarchaean supercontinent containing the Southern Granulite Terrane (SGT) in South India, the eastern block of the North China Craton (E-NCC), and the north-central Korean Peninsula, was probably assembled at ca. 2.5 Ga. A detailed comparison of meta-granitoid samples from the Madras Block (SGT), the Yishui Terrane (Shandong Peninsula, E-NCC), and Daeijak Island (NW-Gyeonggi Massif, Korean Peninsula) demonstrates their close similarities in geological setting, age, petrochemistry, isotopic composition and metamorphic history. They were all formed at 2.6–2.5 Ga and metamorphosed at a high grade soon after ca. 2.5 Ga. All are LREE-enriched and HREE-depleted, have low ⁸⁷Sr/⁸⁶Sri (0.70201–0.70375) and similar near-chondritic ƐNd(T) (+1.2 to −1.9). These factors, and their close match of geological features, suggest that the three terranes were once contiguous as part of a Neoarchaean supercontinent.
... Pangea is the most recent supercontinent. It formed on Earth at the end of Paleozoic time (e.g., Rogers and Santosh, 2003), and it is probably the best case of study to understand the tectonic processes that produced the breakup and separation of supercontinental masses. However, the kinematics and dynamics of Pangea breakup are still not completely understood in some places, such as continental Mexico. ...
Article
Full-text available
During Pangea breakup, several Jurassic extensional to transtensional basins were developed all around the world. The boundaries of these basins are major structures that accommodated continental extension during Jurassic time. Therefore, reconstructing the geometry of Jurassic basins is a key factor in identifying the major faults that produced continental attenuation during Pangea breakup. We reconstruct the tectono-sedimentary evolution of the Jurassic Tlaxiaco Basin in southern Mexico using sedimentologic, petrographic, and U-Pb geochronologic data. We show that the northern boundary of the Tlaxiaco Basin was an area of high relief composed of the Paleozoic Acatlán Complex, which was drained to the south by a set of alluvial fans. The WNW-trending Salado River–Axutla fault is exposed directly to the north of the northernmost fan exposures, and it is interpreted as the Jurassic structure that controlled the tectono-sedimentary evolution of the Tlaxiaco Basin at its northern boundary. The eastern boundary is represented by a topographic high composed of the Proterozoic Oaxacan Complex, which was exhumed along the NNW-trending Caltepec fault and was drained to the west by a major meandering river called the Tlaxiaco River. Data presented in this work suggest that continental extension during Pangea breakup was accommodated in Mexico not only by NNW-trending faults associated with the development of the Tamaulipas–Chiapas transform and the opening of the Gulf of Mexico, but also by WNW-trending structures. Our work offers a new perspective for future studies that aim to reconstruct the breakup evolution of western equatorial Pangea.
... Periodic amalgamation and dispersal of supercontinents since the late Archean, which profoundly influenced the lithosphere, atmosphere, hydrosphere, and biosphere, have been one of the hot topics in solid earth sciences for the past decades Young, 2013;Nance et al., 2014). Although the Pangea supercontinent has been widely accepted (e.g., Zhao et al., 2018aZhao et al., , 2018b, the constituents and configurations of the Nuna (i.e., Columbia) and Rodinia supercontinents are still highly debated (e.g., Zhao et al., 2002Zhao et al., , 2018aZhao et al., , 2018bRogers and Santosh, 2003;Li et al., 2008;Merdith et al., 2017;Cawood et al., 2018Cawood et al., , 2020. One of the most controversial issues is the role and position of the South China Block (SCB) in these two supercontinents (e.g., Cawood et al., 2018Cawood et al., , 2020Liu et al., 2020;and references therein). ...
Article
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The Huili Group, one of the most representative late Mesoproterozoic strata in the Yangtze Block, bears key information for the tectonic history of the South China Block in the context of the supercontinent cycle. We present an integrated dataset involving field observation, petrology, detrital zircon U-Pb dating, and Hf isotope analyses for the Huili Group. Our new detrital zircon U-Pb ages, in combination with available magmatic age data, confirm that the Huili Group was mainly deposited at ca. 1.1-1.0 Ga. The lower Huili Group is characterized by subrounded to rounded detrital zircon grains with age intervals of 2.80-2.40 Ga (~21%), 2.34-1.72 Ga (~64%), and 1.68-1.19 Ga (~14%). In contrast, zircon grains from the upper Huili Group have variable morphologies and yield two pronounced age populations of 2.00-1.25 Ga (~50%; subrounded to rounded grains) and 1.2-1.0 Ga (~46%; euhedral to subhedral grains). The majority of zircon grains have εHf(t) values and depleted mantle two-stage (TDM2) model ages comparable to those of magmatic rocks or older sediments in the Yangtze Block. Multiple sources are suggested to have contributed older detrital zircon grains to the lower Huili Group, whereas the upper part received greater proportions of zircon grains with ages close to or equal to the depositional age from proximal magmatic sources. This observation indicates a drastic provenance shift most likely occurred within the Huili Group at ~1.04 Ga. Through reappraising our detrital zircon results and available geological datasets, we suggest that the terrigenous clastic and carbonate rocks of the lower-middle Huili Group were deposited on a passive continental margin, but the upper volcano-sedimentary sequences were formed in a back-arc extensional setting. We further propose that the Yangtze Block was spatially separated from (i.e., not yet part of) the Rodinia supercontinent during the sedimentation of the Huili Group, supporting that a global supercontinent did not exist yet in the late Mesoproterozoic.
... and Rogers and Santosh (2003) defined it as "an assembly of all or nearly all the Earth's continental blocks". The Neoproterozoic era of the Earth history is thought to be punctuated by the amalgamation and breakdown of the two most discussed supercontinents: Rodinia and Gondwana ( Fig. 1.1 a) (e.g. ...
Thesis
Remnants of ancient orogenic events provide a synoptic view on the Supercontinent amalgamation and breakup and hence enhance our understanding related to continental evolution. The Neoproterozoic Era is known to have registered rapid continental-scale movements and archived at least two major grouping of formerly dispersed continents known as Rodinia and Gondwana. The assembly of Rodinia and Gondwana is marked by the Grenvillian (~1000 Ma) and the Pan-African (500 Ma) events, respectively, which are well-recorded across continents. Present work attempts to characterize the time frame separating the two orogenic events by investigating the two widely spaced domains of India and Antarctica to understand the continental reconstructions of the Neoproterozoic era. Both these domains have reported Grenvillian orogenic event, however, the time span from Rodinia to Gondwana amalgamation remains enigmatic. Domain 1 is part of the north-western Indian shield. Towards the southern end of the Grenvillian aged Delhi Fold Belt, a NW-SE trending magnetic anomaly, at high angle to the NNE-SSW ‘Delhi trend’, is recorded by a recent geophysical survey. Various granitic outcrops belonging to the Erinpura granite suite and an argillaceous-calcareous metamorphosed sequence of the Sirohi group, present near the Revdar town are examined. The petrographic and geochemical characteristics of the Erinpura granites have also been studied in context of the focus of the present work. Presence of amphibole bearing granite, besides other types, confirms the intermixed I-type characteristics. Orogenic characteristics of Erinpura granites is ascertained by strontium-neodymium isotopic analyses (87Sr/86Sr and 143Nd/144Nd). Mixing of three contrasting crustal components successfully explains the isotopic compositions of the granites and throws light on the continental orogenic magmatism which followed the Delhi orogeny. The Revdar metasedimentary sequence is deposited over the post-Delhi granitic basement. Investigation of the Revdar metapelite indicates presence of an upper-amphibolite grade metamorphic assemblage developed at 831±13 Ma which was partially reset at 718±34 Ma as estimated from chemical geochronology of texturally constrained monazite. The granites are dated to be 892±10 Ma and this age was partially reset at 815±43 Ma i.e. around the time of the younger Sirohi orogeny. The partial resetting of the Revdar metapelite can be ascribed to the extensive anorogenic Malani eruption that manifests the Rodinia breakup. An attempt is also made to decipher relationship of Erinpura granite emplacement to the older Delhi orogeny as well as the younger Sirohi orogeny. It is contended that the Rodinia break-up marked by MIS was preceded by an orogenic event which is reported during this work for the first time. Domain 2 is Princess Elizabeth Land (PEL) of East Antarctica. It is one of the least explored inland sectors of East Antarctic shield, specifically in terms of sub-ice geology. Svenner Islands-Brattstrand Bluffs-Larsemann Hills constitutes ~70 km long coastal outcrops of PEL comprising complexly deformed and interlayered metapelites and orthogneisses. Investigations of pelitic granulites from these outcrops indicate high to ultra-high temperature (800-950°C) at low to medium pressure (2-5 kbar; exceptionally 10 kbar) conditions of metamorphism. A high pressure (~10 kbar) relict metamorphic event is inferred by using cordierite poor assemblage as a barometer, which is validated by the presence of rutile (present as inclusion in ilmenite) bearing field at high pressure in Effective Bulk Constrained (EBC) pseudosection modelling. Extensive development of cordierite coronas around restite phases and pseudosection analyses suggests a strong component of decompression of ~5kbar. Two set of ages are estimated (~700-800 Ma and ~500 Ma) by using chemical geochronology of texturally constrained monazites, corresponding to Tonian and Pan-African metamorphic events, respectively. Field data, petrographic studies and ages estimated from orthogneiss samples from the Brattstrand Bluffs and Grovnes Peninsula suggest that the orthogneiss unit is a product of in-situ melting of the pelitic granulites. It is proposed that the PEL and the Eastern Ghats Mobile Belt represent a contiguous terrane with two major orogenic imprints, reflecting Rodinia and Gondwana amalgamations. An attempt is made to mark out paleo-orogenic belt axes supported by both field as well as recent aero-magnetic signatures in interior PEL. Presence of a thinned lithosphere along the system of subglacial lakes-canyons confirmed by ICECAP/PEL consortium, in sub-ice PEL is interpreted. Analog modelling is used to demonstrate influence of pervasive mechanical anisotropy of the basement in defining orientation of this rift system and its connection to the Lambert Graben. This work substantiates evidence of swift configurational changes from Rodinia assembly to Gondwana amalgamation in Indo-Arabian as well as Indo-Antarctic terrains. It specifically highlights the geodynamic importance of a hitherto poorly recognized ~800 Ma orogeny in both the domains.
... The Precambrian supercontinent cycles of Nuna (a.k.a. Columbia) and Rodinia have been hot topics in solid earth science for past years (e.g., Zhao et al., 2002;Rogers and Santosh, 2003;Li et al., 2008;Bradley, 2011;Evans, 2013;Young, 2013;Nance et al., 2014;Cawood et al., 2018;Cawood et al., 2020). The late Mesoproterozoic to early Neoproterozoic era (1.3-0.9 ...
Article
The late Mesoproterozoic tectonic history of the Yangtze Block, South China in the context of the supercontinent cycles remains poorly understood due to the scarce preservation of geological records of this age. In this study, we report petrology, whole-rock geochemistry, zircon U-Pb ages and Hf-Nd isotopes for newly identified late Mesoproterozoic monzogranites from the southwestern Yangtze Block. SHRIMP and LA-ICP-MS zircon U-Pb dating results reveal that these monzogranites crystallized at ca. 1.18-1.14 Ga. All the studied samples possess typical geochemical signatures of A1-type granite, such as relatively high SiO2 (73.31-77.50 wt.%), Na2O + K2O (7.14-8.09 wt.%) and Zr + Nb + Ce + Y (362-445 ppm) contents, zircon saturation temperatures (825-851 ºC), and low Y/Nb ratios (0.78-1.04). They have negative whole-rock εNd(t) values from -6.9 to -5.7 and zircon εHf(t) values from -7.4 to -2.5, with consistent Nd and Hf model ages of 2.4-2.1 Ga. The parental magmas for these monzogranites were generated by partial melting of the early Paleoproterozoic crustal materials at low pressure and high temperature. Taking into account of the coeval within-plate mafic magmatism in the southwestern Yangtze Block, these ca. 1.18-1.14 Ga A1-type monzogranites were most likely emplaced in a continental rift setting. Available data indicate continental rifting may have occurred extensively in the Yangtze Block at 1.2-1.1 Ga, followed by oceanic plate subduction starting at 1.1 Ga. We propose the Yangtze Block was an isolated plate during 1.2-1.1 Ga and started to drift toward the Rodinia supercontinent at ca. 1.1 Ga, favoring the proposal that a coherent supercontinent did not yet exist in the late Mesoproterozoic.
... A craton is commonly the rigid ancient nucleus of a particular continent and is composed of old, strong, thick, and stable remnants of ancient crystalline basement that survived from long-term amalgamation and breakup of (super)continents (Jordan, 1975;Pollack, 1986;Hirth et al., 2000;James and Fouch, 2002;Kamber and Tomlinson, 2019). Cratons stabilized mainly in late Archean (Rogers and Santosh, 2003;Zhai, 2011;Pehrsson et al., 2015) and are generally subjected to little deformation, overlain by sediments, and surrounded by accreted terranes and orogenic belts (Griffin et al., 2003;Lee et al., 2011;Zhai, 2011). After the craton stabilization, the growth and reshaping of continents continuously operated throughout the Earth's history, with the former process being determined by the balance between mantle input and recycling of crust into the mantle, while the latter defined by continental rifting and accretionary orogenesis. ...
Article
The Yangtze Block exemplifies the gradual formation of cratons since the Archean, and its pre-Neoproterozoic basement constitution needs to be clarified by a study of the combination of spatiotemporal relationship, geochemistry, and radiogenic isotopes of pre-Neoproterozoic rocks within and around the continent. It is suggested that the Yangtze Block could be divided into the north (NYB) and south (SYB) parts before the Neoproterozoic due to distinct rock configuration and tectonic evolution. The NYB consists of extensive Archean lithosphere and witnessed nascent stage (~2.0 Ga) of Columbia (Nuna)-assembly tectonics and was less involved in subsequent supercontinent breakup. It was then surrounded by a series of early Neoproterozoic (1.0–0.93 Ga) intra-oceanic accretionary system, which facilitated the tectonic emplacement of ~1.1–0.95 Ga ophiolite suites and the accretion of allochthonous terranes. The SYB, as well as the south Qinling Orogenic Belt and western Cathaysia Block, in part or in whole, may serve as one of the accretionary terranes around the NYB. These accreted terranes were generally involved in the extensional tectonics in response to the breakup of Columbia supercontinent, with the post-1.5 Ga rift locally evolved to seafloor spreading as evidenced by the occurrences of relic oceanic lithosphere in some areas. We highlight the progressive continental growth from a large-scale, long-term continental rifting during Columbia breakup to subsequent Rodinia-assembly-related tectonics around the NYB. The former stage is characterized by the consuming of ancient continental lithosphere and creation of thick, juvenile volcanic-sedimentary rocks within continents (failed rift) or along passive margins (successful rift). In contrast, the latter stage may have driven the subduction–accretion of allochthonous rift terranes around the NYB and promoted the emplacement of circum-NYB 1.1–0.9 Ga ophiolite suites and island-arc units. We suggest that the significant mantle input in both extension and convergence stages and the successive lateral accretion of terranes may have contributed to the continental growth and reshaping of the Yangtze Block.
... Kaapvaal, Pilbara, Dharwar, and Singhbhum (Rogers, 1996;Rogers & Santosh, 2003). It is assumed that the Archaean Dharwar and Sarmatia cratons were located next to each other, suggesting that they formed part of a single protocraton (Pisarevsky et al., 2013). ...
... The crustal density inversion is considered as one of the dominant processes that caused the formation of granite-greenstone terranes (Nebel et al., 2018). The marginal zones of such terranes are characterized by Precambrian orogenic belts, along which Archean cratons, having distinct geological histories, were amalgamated (Rogers and Santosh, 2003). These orogenic belts are the product of tectonic events that occurred during two distinct stagesaccretionary and collisional orogensand mark the onset of plate tectonics ( Fig. 1; Cawood et al., 2009;Grenholm et al., 2019). ...
Article
The Aravalli Craton, representing the Precambrian nucleus of northwestern India, consists of the Archean Banded Gneissic Complex (BGC; 3.3–2.5 Ga) overlain by Paleoproterozoic (~2.2–1.7 Ga) and Paleo- to Neoproterozoic (~1.7–0.7 Ga) metasedimentary sequences of the Aravalli and Delhi supergroups, respectively. The extensively reworked Late Paleoproterozoic terrane located between the Aravalli and Delhi supracrustal sequences is known as the Sandmata Complex. The BGC, Sandmata Complex and supracrustal sequences, collectively known as Aravalli Craton, were developed by multiple accretionary-collisional processes from ~3.3 to 0.7 Ga and are regarded as classical terranes for understanding Precambrian crustal evolution. The previous multidisciplinary studies have invariably described the litho-tectonic relationships of the Aravalli Craton. Considering the voluminous literature and arguable interpretations, we present a holistic review addressing the Mesoarchean to Neoproterozoic tectonic evolution of the basement and the polydeformed supracrustal sequences of Aravalli and Delhi supergroups. We suggest that the Aravalli Craton evolved by the accretionary-collisional interactions between three major crustal domains, viz., the Mewar gneissic terrane and intrusive granitoids (~3.3–2.5 Ga), the Aravalli fold belt (~2.2–1.7 Ga) and the Delhi fold belt (~1.7–0.7 Ga). The Mewar gneissic terrane formed between 3.3 Ga and 2.7 Ga by partial melting of hydrated mafic crust, where the terrane evolved continuously and finally stabilized due to the collision between the Bundelkhand and Aravalli cratons, resulting in the emplacement of several granitoids between 2.6 and 2.4 Ga. The subsequent development of the Aravalli fold belt (~2.2–1.7 Ga) to the west of Mewar gneissic terrane was characterized by the ~2.2–2.1 Ga mafic-ultramafic volcanism and ~1.8–1.7 Ga felsic magmatism, marking the opening and closing of the Aravalli Basin, respectively. The final closure of this basin was contemporaneous with the exhumation of the Sandmata granulite terrane along the western margin of Aravalli fold belt. Although the Sandmata Complex was previously interpreted as a reworked equivalent of the basement gneisses, based on contrasting lithology, deformation styles and metamorphic grade, we infer that the Sandmata Complex possibly represents an independent terrane with a distinct tectonothermal history. The tectonic evolution of the Delhi Basin most likely took place in two stages from ~1.7 to 0.7 Ga. The initial stage (~1.7–1.4 Ga) led to the development of the north Delhi fold belt and emplacement of A-type granitoids (~1.5–1.4 Ga), whereas the high-grade metamorphism and I- and S-type granite magmatism in the southern part characterize the later stage (~1.3–0.7 Ga) of the Delhi Basin. Following the Delhi Basin closure, the areas to the west of the Aravalli Craton witnessed the emplacement of the Malani Igneous Suite and the development of the Sirohi and Marwar basins. Altogether, the available key information on structural patterns, magmatic-metamorphic histories and geochronology allows more detailed correlations with possible contiguous orogens of the Great Indian Proterozoic Fold Belt. Our synthesis and tectonic interpretations help us discuss and provide alternate explanations for some of the controversial issues from existing tectonic models. Further, we summarize important unresolved issues, which require special attention to improve our knowledge of the Archean to Proterozoic crustal evolution in northwestern India.
... There are several attempts made by many researchers to reconstruct continents, large continental masses, and cratons, to provide a primary information for understanding what has been happened in the past during the Earth's history. This information includes ancient paleogeography, paleoclimatology, paleobiology, earth tectonics, mantle dynamics, and important knowledge on the origin of regional metallogenesis (e.g., Bleeker 2003;Rogers and Santosh 2003;Evans and Pisarevsky 2009;Vérard 2019a, b;Vérard 2021). According to the "continental drift" theory of Wegener (1912), the current continents resulted from breakup, fragmentation, and drifting of what so-called as "Pangaea" supercontinent, some 200 Ma ago. ...
Chapter
The “Supercontinents” constitute the majority of the ancient Earth’s surface and play an important role in Earth’s history.
... Since the Archean, there have been a number of supercontinent amalgamations and dispersal cycles (Murphy & Nance, 2008;Rogers & Santosh, 2003), among which Pangea was the last one. As per the current understanding based on geochemical studies, the amalgamation and formation of the Pangea supercontinent took place from 350 to 170 Ma (Cawood, Pisarevsky, & Leitch, 2011). ...
Article
The paradigm of plate tectonics has aided in the identification of the journey of continents on the globe, their assembly into supercontinents, disruption, and re‐assembly. Here, we use meteorite impact craters as proxies for tracking the voyage of lithospheric plates. Employing the provisions in GPlates, an interactive geographic information system‐based plate tectonic reconstruction model, we were able to identify the palaeo‐position, and velocity of the 174 terrestrial impact craters, formed after 1,100 Ma, across the globe. These parameters of craters were evaluated for independent tectonic plates and were correlated with global tectonic events. For example, the similarity in the velocity of Beaverhead (900 Ma) and Holleford (550 Ma) craters since 550 Ma is traced to the connection between the Eastern Basin and North America Craton commencing 1,100 Ma, and through the South Basin and Range. Likewise, the drastic reduction in the velocity of Spider Crater (700 Ma) in Australia after 600 Ma can be attributed to the subduction between east and west Gondwana. The accelerated motion of the Indian Plate at 63 Ma, when the lithosphere was hovering over the Réunion hotspot, is also explained. With the advent of more improved plate tectonic models and the discovery of more impact craters, improvised interpretations will be possible. Voyage of Ramgarh Crater.
... This led to long periods of relative stability for previously formed deposits that were only rarely disturbed by distant tectonic events, which caused basin fluid flow and reestablished geochemical equilibria. The long interval between the breakup of the supercontinent Columbia (Nuna) and the assembly of Rodinia saw the formation of many marine basins; it was, however, a time of fewer large continental sedimentary basins (Rogers & Santosh 2003, Cawood & Korsch 2008, Cawood & Hawkesworth 2013. What is not clear is why the post-Rodinia breakup, at least until the appearance of land plants at ca. 420 Ma, is not marked by unconformity-related uranium deposits. ...
Article
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Proterozoic continental sedimentary basins contain a unique record of the evolving Earth in their sedimentology and stratigraphy and in the large-scale, redox-sensitive mineral deposits they host. The Paleoproterozoic (Stratherian) Kombolgie Basin, located on the Arnhem Land Plateau, Northern Territory, is an exceptionally well preserved, early part of the larger McArthur Basin in northern Australia. This intracratonic basin is filled with 1 to 2 km-thick, relatively undeformed, nearly flat-lying, siliciclastic rocks of the Kombolgie Subgroup. Numerous drill cores and outcrop exposures from across the basin allow sedimentary fabrics, structures, and stratigraphic relationships to be studied in great detail, providing an extensive stratigraphic framework and record of basin development and evolution. Tectonic events controlled the internal stratigraphic architecture of the basin and led to the formation of three unconformity-bounded sequences that are punctuated by volcanic events. The first sequence records the onset of basin formation and is comprised of coarse-grained sandstone and polymict lithic conglomerate deposited in proximal braided rivers that transported sediment away from basin margins and intra-basin paleohighs associated with major uranium mineralization. Paleo-currents in the upper half of this lower sequence, as well as those of overlying sequences, are directed southward and indicate that the major intra-basin topographic highs no longer existed. The middle sequence has a similar pattern of coarse-grained fluvial facies, followed by distal fluvial facies, and finally interbedded marine and eolian facies. An interval marked by mud-rich, fine-grained sandstones and mud-cracked siltstones representing tidal deposition tops this sequence. The uppermost sequence is dominated by distal fluvial and marine facies that contain halite casts, gypsum nodules, stromatolites, phosphate, and “glauconite” (a blue-green mica group mineral), indicating a marine transgression. The repeating pattern of stratigraphic sequences initiated by regional tectonic events produced well-defined coarse-grained diagenetic aquifers capped by intensely cemented distal fluvial, shoreface, eolian, and even volcanic units, and led to a well-defined heterogenous hydrostratigraphy. Basinal brines migrated within this hydrostratigraphy and, combined with paleotopography, dolerite intrusion, faulting, and intense burial diagenesis, led to the economically important uranium deposits the Kombolgie Basin hosts. Proterozoic sedimentary basins host many of Earth's largest high-grade iron and uranium deposits that formed in response to the initial oxygenation of the hydrosphere and atmosphere following the Great Oxygenation Event. Unconformity-related uranium mineralization like that found in the Kombolgie Basin highlights the interconnected role that oxygenation of the Earth, sedimentology, stratigraphy, and diagenesis played in creating these deposits.
... They assumed that the NCC would have accomplished its first episode of cratonization by 2.5 Ga, and experienced a rift-related extension in the early Paleoproterozoic. This extensional tectonism is viewed as part of the global rift events due to breakup of an inferred late Archean supercontinent "Kenorland" or "Superior" (e.g., Aspler and Chiarenzelli, 1998;Bekker and Eriksson, 2003;Bleeker, 2003;Strand and Köykkä, 2012;Rogers and Santosh, 2013;Gumsley et al., 2017). ...
Article
Tectonic switch from rift zones to subduction zones is common along convergent plate boundaries. While this process is susceptible to retrieving from Phanerozoic rock records, the difficulty has been encountered for Precambrian rock records because of the relative lack of characteristic geological signatures. Nevertheless, such a difficulty can be overcome by finding of specific geochemical signatures in ancient rock records. This paper reports our finding of low δ¹⁸O zircons from the Trans-North China Orogen (TNCO) in the North China Craton (NCC), where the tectonic switch would occur during the early to middle Paleoproterozoic in association with the amalgamation of supercontinent Columbia. A combined study of zircon U-Pb ages and Hf-O isotopes as well as whole-rock major-trace elements and Nd isotopes were carried out for magmatic rocks from the Taiyue complex in the southern part of the TNCO. Zircon U-Pb dating yields two episodes of magmatism at ca. 2.34–2.31 Ga and ca. 2.2–2.1 Ga. These magmatic rocks are dominated by the ca. 2.18–2.16 Ga granites, 2.18–2.17 Ga diorites and 2.17–2.11 Ga mafic–ultramafic cumulates that intruded the 2.34–2.30 Ga granites and diorites. The 2.2–2.1 Ga diorites, mafic-ultramafic cumulates, and the regional mafic dykes/intrusions exhibit continuously varying major element compositions, arc-like trace element patterns, and consistent zircon Hf and whole-rock Nd isotope compositions, indicating their derivation from the same suite of continental arc magmas. Such primitive arc magmas would evolve through fractionation and accumulation of pyroxenes and plagioclase into dioritic magmas. The two episodes of granites are similar in major and trace element compositions, generally belonging to alkali-calcic or calc-alkalic A-type granitoids. Although both groups show a small difference in their zircon Hf isotope compositions, they exhibit a big difference in their zircon O isotope compositions. The 2.31 Ga granites show variably low zircon δ¹⁸O values of 3.4–5.5‰, mostly lower than normal mantle zircon values. The 2.18 Ga granites also exhibit variable zircon δ¹⁸O values from 3.6 to 6.0‰, but mostly mantle-like values. It is inferred that the 2.31 Ga granites would acquire their low δ¹⁸O signatures from partial melting of the high-T seawater-hydrothermally altered Archean crust in an early Paleoproterozoic continental rift. This rift would extend for at least 300 km along the TNCO. The 2.18 Ga granites are closely associated with the 2.2–2.1 Ga diorites and mafic–ultramafic cumulates. They would be most likely to form through differentiation of the 2.2–2.1 Ga continental arc magma, with their low ¹⁸O signatures being contaminated by the low δ¹⁸O 2.3 Ga granites. The low ¹⁸O signatures in the 2.3 Ga and 2.18 Ga granites indicate that the southern part of the TNCO would have probably evolved from a lithospheric rift to an active continental margin during ca. 2.3–2.1 Ga.
... Fundamental geodynamic regimes of crustal-mantle interactions in early Earth changed from pre-plate tectonic featuring mainly vertical processes to lateral plate tectonic as the mantle began to cool and lithospheric rigidity increased during the late Archean (Chowdhury et al., 2020;Debaille et al., 2013;Dhuime et al., 2015;Gerya, 2014;Griffin et al., 2014;Laurent et al., 2014;Palin et al., 2020;Smithies et al., 2007). This transition to plate tectonic made a dramatic change in crustal-mantle interaction processes, which led to gradual maturation of the crust (Dhuime et al., 2012(Dhuime et al., , 2015Laurent et al., 2014;Moyen and Laurent, 2018;Tang et al., 2016;Wan et al., 2014;Wang et al., 2017), assembly of cratonic fragments (Reid et al., 2014;Zhai and Santosh, 2011), stabilization of lithosphere Wang et al., 2017;Yu et al., 2021;Zhai, 2014;Zhao et al., 2012), and formation of a global supercontinent (Pehrsson et al., 2013;Rogers and Santosh, 2003). However, detailed processes of pre-plate tectonic crustal-mantle interactions directly emphasizing the interactions between felsic continental nucleus and plume and their tectonic influence are still unclear due to the extremely limited geological records (Korenaga, 2018(Korenaga, , 2021Liu et al., 2021;Palin et al., 2020). ...
Article
Plate tectonics play an important role in crustal-mantle interactions since late Archean, yet detailed processes of pre-plate tectonic crustal-mantle interactions remain enigmatic. In the Western Shandong Complex of the North China Craton, magmatic rocks recorded successive tectonic transition processes from vertical (plume) to lateral (subduction) during the early Neoarchean. These magmatic records, together with our newly discovered a pre-Neoarchean continental nucleus in the Western Shandong Complex, documented key information on pre-plate tectonic crustal-mantle interactions. In this study, petrology, whole-rock geochemical and Sm–Nd isotopic data, and zircon U–Pb and Lu–Hf isotopes are reported for Neoarchean supracrustal and intrusive rocks for the Western Shandong Complex. Early Neoarchean komatiitic basalts and ultramafic rocks (~2.77 Ga) were plumerelated and generated by crustal contamination of fractional crystallized komatiitic magma. A series of Mesoarchean (~3.0–2.8 Ga) xenocrystic zircon grains were discovered in the Late Neoarchean charnockites (~2.56–2.52 Ga), indicating contributions of continental crustal material earlier than regional oldest magmatic records. Based on our new geochronological and geochemical data, a trondhjemitic Mesoarchean (~3.1–2.8 Ga) continental nucleus was identified and reported for the first time in the Western Shandong Complex. During the early stage of the early Neoarchean, this continental nucleus dismembered during the bottom-up plume processes and the correlated plume-continental nucleus interactions occurred and ubiquitously documented in regional Neoarchean magmatic rocks with different degrees. The plume-continental nucleus interactions consequently resulted in the opening of an oceanic basin and different continental evolutionary processes during the subsequent lateral subduction in the early Neoarchean. The buoyant oceanic plateau was possibly dragged to the trench and blocked subsequent subduction and led to a ~40 Myr magmatic hiatus between 2.60 Ga and 2.56 Ga.
... Subsequent slab break-off and mantle upwelling resulted in the post-collisional thermal event. The metamorphism of mafic granulites marks the assembly of the Coorg Block with the Dharwar craton, possibly coinciding with the construction of the putative earliest supercontinent Ur (Rogers and Santosh, 2003). ...
Article
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Lower crust mafic granulites are key components in understanding the formation and growth of the continental crust. Here we investigate the mafic granulites and associated rocks from the Paleo-Mesoarchean Coorg Block in southern India with a view to gain insights into the crust-mantle dynamics and the subduction–accretion‐collision history. We present petrology, mineral chemistry, conventional thermobarometry and computed pseudosections, whole‐rock geochemistry including major, trace element, and rare earth element (REE), and zircon U–Pb and Lu-Hf isotopes to trace the magmatic evolution and metamorphism of these rocks. The petrological features, mineral chemistry data and phase equilibria modelling suggest that the rocks underwent HP metamorphism at peak temperatures up to 900 °C and pressures up to 9.5–10 kbar along a clockwise P–T path followed by near isobaric cooling. Zircon U–Pb data from the mafic granulites place the peak emplacement time of the protolith at 3.1 Ga with a minor group of younger zircons indicating a post-collision thermal event at 2.7 Ga. Zircon REE patterns suggest the involvement of continental crust components in the magma source. Zircon Lu-Hf analysis yield positive εHf(t) values from 0.5 to 4.1 with model ages (TDM) of 3.3 Ga for rocks from the northern margin of the block and the bordering Mercara suture zone while samples from the southern margin display slightly older (3.4 Ga) ages. Our data indicate that the parent magmas were derived from both juvenile and reworked Paleoarchean sources. The mafic granulites record Mesoarchean subduction-related magmatism and crust building in the Coorg block. Our study contributes to the understanding of geodynamic processes and continent formation in the Early Earth.
... 2010 Another abiotic factor comes from pure geological events, and, contrary to the previous one, may be damaging but also fruitful. As tectonic plates move, interact with earth's mantle and rub with one another (Wegener, 1912;Hess, 1954;Heezen et al., 1965;White et al., 1970), new territories, be they land, sea or lake, emerged or merged (Heezen et al., 1965;Rogers et al., 2003), mingling biology with geology into biogeography (Wallace, 2011(Wallace, -(1876 McIntyre et al., 2017). When continents merge, a burst of extinction may occur as organisms formerly isolated suddenly engage in a new competition. ...
Thesis
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Since Life was born, its tireless evolution has created an exceptional diversity of entities spanning an extravagant range of sizes, from the microscopic molecules underlying heritability and the expression of phenotypes to multicellular organisms and their societies. This great variety of the living world, present both between classes of biological entities and within these classes (e.g. proteins), has often been explained theoretically by assuming the existence of trade-offs – impossibility to optimize multiple traits at once – and / or specific niches as produced by the co-occurrence of multiple nutrients. However, the way in which these internal compromises emerge at the cellular level has remained in general elusive, especially since models of evolution most often overlook the mechanistic foundations and the very functioning of cells. Across this thesis, I try to build mechanistic evolutionary models by studying one of the most fundamental property of living things: how to produce energy, and grow, faster than others? This property is based at the cellular level on the structure and expression of enzymes. Rather than the extreme optimization this role suggests, enzymes have extremely diverse characteristics – some are close to achievable physical limits while others are very far from them – that should be explained. Through a modeling approach of the kinetic processes involved, I have shown that these differences can be explained by different selective contexts, characterizing in particular the reactions in which these enzymes are involved. Furthermore, the expression of an enzyme is the result of a complex selective process involving the obvious interest of catalyzing a given reaction but also overall costs for the cell, both in terms of production of the enzyme and of crowding within the cytoplasm. These constraints can promote the evolution of a selective (partial) expression of a metabolic pathway, leading to the release into the medium of metabolites, which can be used as an energetic source. In turn,this can give rise to the evolution of organisms specialised at these metabolites through a process called cross-feeding. Taking into account these processes in an adaptive dynamic model while also integrating an ecological dimension allowed me to establish the restricted conditions in which the cross-feeding may evolve, shedding light on the preponderant implication of certain metabolites (acetate, glycerol). In a last part, outside the strictly mechanistic framework of the thesis, I develop a model of population genetics intended to clarify the mainsprings of metabolic (weakest link) epistasis and its deleterious consequences on fitness at the mutation-selection-drift equilibrium. Finally, I discuss the perspectives opened up by this whole work, the vocation of which would be to contribute to the development of more realistic genotype- phenotype-fitness maps and to document their quantitative influence on evolution, through the combination of population genetics and systems biology.
... The Indian Shield is made of two crustal blocks, viz., the southern Indian block and the northern Indian block, which are sutured along the CITZ. The Dharwar, Bastar, and Singhbhum Cratons amalgamated by mid-Archean to form the southern block (e.g., Rogers and Santosh, 2003;Srivastava et al., 2022). This means that all the investigated dyke swarms of the three cratons were emplaced after their amalgamation. ...
Article
The Indian Shield is comprising of the Dharwar, Bastar, Singhbhum, Bundelkhand, and Aravalli Cratons, intruded by distinct mafic dyke swarms of different generations (ca. 2.8–0.8 Ga). Most of these dykes are tholeiitic basalt to basaltic-andesite, including boninite. Some other subordinate dyke rocks are of komatiitic, picritic, and andesitic compositions. The vast areal extent of these dykes indicates that they are remnants of Precambrian Large Igneous Provinces (LIPs). The present study reviews the existing geochronological and geochemical data of various Precambrian mafic dyke swarms intruding in all Indian cratons, to track temporal changes in composition of the underlying subcontinental lithospheric mantle (SCLM). Most of these dykes have crust-like abundances of incompatible trace-element. Even the primitive dykes (Mg# = 82–64) exhibit crust-like incompatible element patterns. However, some also have depleted mantle-like abundances of incompatible elements. Most of the dykes also have high concentrations of compatible trace elements (e.g., Cr and Ni). The age-corrected radiogenic Nd isotope compositions (ɛNd(i)) of these dykes vary between the upper continental crust and depleted mantle ɛNd growth arrays. The elemental composition and ɛNd(i) of these dykes suggest their derivation from a heterogeneous SCLM comprising enriched (metasomatized) and depleted mantle components. The negative as well as positive ɛNd(i) values exhibited by the ca. 2.8 Ga (oldest) dykes suggest the presence of enriched mantle materials distributed within a depleted-SCLM already by ca. 2.8 Ga. The enrichment must have occurred before ca. 2.8 Ga due to subduction-released fluids. Later, the SCLM beneath Indian cratons evolved with a composition consisting of an enriched/metasomatized mantle component and a depleted mantle component.
Article
The poorly documented Daduhe gold belt on the western margin of the Yangtze Craton, an important metallogenic belt in southwest China, is characterized by typical orogenic gold systems against a highly anomalous geodynamic setting. A synthesis of regional and deposit geology, mineralization ages, and S-O isotopic compositions of 33 gold deposits from the Danba-Kangding-Shimian-Mianning area of the belt reveals regional metallogenic patterns, establishes a consistent genetic model, and demonstrates a source equivalent to other diverse mineral systems on the western margin of the Yangtze Craton. The Daduhe orogenic gold deposits are controlled by the lithosphere-scale Xianshuihe and Anninghe strike-slip faults in the northern and southern segments of the belt, respectively. The alteration and ore mineral assemblages of the Daduhe orogenic gold deposits define a wide range of hypozonal, mesozonal, and epizonal sub-types. They formed during two episodes: 1) Early Jurassic gold mineralization related to closure of the Paleo-Tethys Ocean, with a large hypozonal gold deposit on the margin of the Danba dome in the northern segment; 2) Cenozoic gold mineralization associated with continental collision on the Tibetan Plateau, with small mesozonal and epizonal gold deposits in shear zones in migmatite basement and at contacts with cover sequences in both northern and southern segments. At the belt and deposit scales, the ore-controlling structures for both mineralization episodes are NNE-trending second-order extensional faults or their intersections with the dominant NW-trending compressional faults. The three deposit sub-types have overlapping δ³⁴S of 0∼10‰, δ¹⁸Ofluid of 6∼11‰, and low He-Ar isotope ratios, all consistent with derivation of ore fluids from metasomatized mantle lithosphere. Importantly, the Daduhe orogenic gold deposits have similar S-O-He-Ar isotope compositions to the giant IOCG, Cu-Ni-PGE, Fe-V-Ti, anomalous porphyry Cu-Mo-Au, and carbonatite-related REE deposits in the Panxi region on the shared margin of the western Yangtze Craton. This suggests that these diverse mineral systems have a common source of ore fluids and metals derived from fertile mantle lithosphere during different geodynamic and metallogenic events. Such a widespread hydrous metal-rich deep source with lithosphere-scale faults as ore fluid pathways, and a depth continuum of orogenic gold deposits in the Daduhe belt suggest a high prospectivity and a higher future gold endowment for the belt. This study adds to an increasing awareness of the diversity of mineral systems on specific craton margins globally.
Article
Molar-tooth structures (MTS) are enigmatic, micro-crystalline calcite filled fissures, confined in Proterozoic carbonates. Here we present petrography, carbon isotope, total organic carbon (TOC) and morphological attributes in context of interpreted palaeoenvironment to understand its development in the Mesoproterozoic carbonates of Lesser Himalaya. Lack of any detrital infill, uniform crystal size and gradational contact with host limestone indicate rapid calcite precipitation in fluid filled cracks. Reworking of MT as intraclast, folding and offset of MT ribbons supports for early formation before significant lithification. Moderate TOC (0.1 to 0.9) is possibly due to organic matter preservation under sub-oxic to slightly anoxic/ dysoxic condition. Storm generated bed forms indicates deposition in between fair weather- and storm wave base. Average 1.4‰ depletion of δ13C in MT relative to host limestone, presence of relict microbial laminae along the margin of the MT cracks and storm generated bed forms at outcrop scale indicates that the cracks might have formed by the combined effect of degassing of CO2 generated during the microbial oxidation of organic matter and wave loading by storm. Precipitation of microcrystalline calcite within the cracks may have been triggered by alkalinity generated by the mixing of the outflowing CO2 with sea water.
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In the Mesoproterozoic, there was an epic transition on Earth, the final breakup of the Columbia supercontinent. Understanding the dynamic mechanism responsible for the final breakup of Columbia supercontinent is crucial for establishing Earth’s evolution that includes geology, environment and life. However, there is little research on what drove the breakup of the Columbia supercontinent. Here we focus on this issue by integrating new zircon U-Pb ages, Lu-Hf isotopes, and whole-rock geochemical data for metamafic rocks from the Oulongbuluke Block in the southeast of Tarim Craton. These data show that the protoliths of these metamafic rocks were emplaced at ca. 1.37–1.35 Ga and were divided into high-Fe and low-Fe groups. The high-Fe and low-Fe groups show geochemical character similar to normal mid-ocean ridge basalt (N-MORB) and enriched mid-ocean ridge basalt (E-MORB), respectively. The high-Fe group was formed by high degree (7%-9%) partial melting of spinel-phase lherzolite mantle source, whereas the low-Fe group was derived from low degree (5%-6%) partial melting of spinel-phase lherzolite mantle source. We propose that the high-Fe and low-Fe groups may have been derived from magmas from different parts of a mantle plume. The formation of the 1.37–1.35 Ga metamafic rocks in the Oulongbuluke Block may be related to the separation of the Tarim Craton into North and South Tarim cratons, which resulted in the opening of the initial Middle Tarim Ocean Basin. By comparison with the plume-induced Yanliao Rift of North China Craton and McArthur Basin of North Australia Craton, we present that these three cratons may potentially dominated by a superplume, forming circular rift zone and radiating dykes. This superplume triggered the continuous extension to most parts of Columbia and led to the final breakup of the Columbia supercontinent.
Article
The global ‘type area’ charnockites and those in the surrounding localities within Madras block of the Southern Granulite Terrane in India dominantly comprise felsic to intermediate, coarse to medium grained, orthopyroxene-bearing anhydrous granulite facies rocks with sporadic garnet. In several localities, the charnockitic suite contains mafic magmatic enclaves of gabbroic to dioritic composition showing calcic and peraluminous composition. The charnockite suite shows compositional range from monzonite through granodiorite to granite, and are calcic and calc-alkalic, peraluminous, including both magnesian and ferroan types. Their major and trace element variations are consistent with progressive magmatic differentiation. The charnockites show high BaSr content with a trend from normal arc-related rocks to adakites. The geochemical features of the charnockites and mafic enclaves are consistent with subduction-related arc setting, with slab-derived magmas interacting with mantle wedge peridotite. The P-T conditions as estimated through mineral phase equilibria modelling and pseudosection computations of representative charnockite and mafic enclave samples show a range of ca. 7 to 9 kbar and 870 to 960 °C, suggesting high- to ultra-high temperature granulite facies conditions during the peak metamorphism. The zircon grains from the charnockites show magmatic features with oscillatory or banded zoning, and in many cases display core-rim structure indicating dissolution and metamorphic overgrowth. The magmatic grains/domains show typical steep LREE to HREE pattern, whereas the metamorphic domains show relatively flat HREE. Magmatic zircon UPb data indicate crystallization ages of ca. 2.53 Ga to 2.57 Ga. The identical age from magmatic zircon grains in the mafic enclaves suggests bimodal magmatism with underplated mafic magmas intruding into the felsic magma chamber. The UPb data from metamorphic zircon and monazite indicate that all the rocks were metamorphosed coevally at ca. 2.47 Ga to 2.49 Ga, soon after their emplacement. The close timing between magmatism and metamorphism of ca. 40 Myr also suggests the formation of the magmatic suite along an active convergent margin, followed by collisional metamorphism during the termination of subduction and ocean closure. The LuHf analyses of magmatic domains in zircon show mostly positive ɛHf(t) values up to +8.7, with only a few spots showing slightly negative values up to −0.8. Zircon grains in the mafic enclaves also show mostly positive ɛHf(t) values up to +4.3. The U-Pb-Hf data are consistent with juvenile arc building during late Neoarchean, with no significant older components. Together with the Hf model ages, the data indicate that the magmas were derived from depleted mantle components of Meso- to Neoarchean age, which would suggest an active subduction regime that continued until the ocean closure during end Neoarchean-earliest Paleoproterozoic. The granulite blocks surrounding the southern margin of the Dharwar craton including the Madras block are interpreted as multiple arcs that coalesced and accreted onto the craton during the Neoarchean-Paleoproterozoic transition. These blocks, which are dominated by charnockites and ranging in age from Mesoarchean to late Neoarchean, and their equivalents in other cratonic fragments over the globe, can be correlated to the ‘expanded Ur’, in building the oldest supercontinent on Earth.
Article
Mineral systems with their core of ore deposits require a rare conjunction of geodynamic settings, crustal or lithospheric fertility, crustal architecture and suitable host rocks, and presentation potential. They are thus an integral component of Earth’s thermal and tectonic evolution which also control the supercontinent cycles with progressive assembly and breakup such as those of Ur, Kenorland, Columbia, Rodinia, Gondwana, and Pangea. Despite the ongoing debate, some form of plate tectonics has operated on Earth since the Eoarchean. However, the hotter Archean mantle generated a long-term double-layered convection system which was disrupted by episodic mantle overturns, with the largest in the early Neoarchean potentially enriching the mantle in metals that form the Earth’s core. Cratons with thick subcontinental mantle lithosphere (SCLM) or tectosphere keels commenced to form in the Mesoarchean as small continents amalgamated. The conjunction of pre-4.0Ga crust, giant Ti, Cr, Fe, Ni and PGE-enriched layered mafic intrusions and major diamond fields provide strong evidence that the Kaapvaal and Zimbabwe Cratons and Wyoming Craton formed part of Ur with its early potentially core-metal-fertilized SCLM. Orogenic gold deposits and VMS Cu-Zn-Pb deposits with their high preservation potential were deposited in subduction-related convergent margins that activated the assembly of all supercontinents with giant provinces related to assembly of Kenorland, Columbia and Gondwana-Pangea. Erosion-susceptible porphyry Cu-Au and epithermal Au-Ag deposits were most abundant at the time of Gondwana and Pangea and in Cenozoic convergent margins and collisional orogens, although there are rare examples associated with assembly of all supercontinents. Magmatic intrusion-related Ni-Cu-PGE, and magmatic-hydrothermal IOCG Cu-Au and Kiruna-type Fe-P deposits formed near craton margins. However, although giant Ni-Cu-PGE deposits formed during the breakup of all supercontinents, giant IOCG deposits were largely restricted to extensional episodes related to Kenorland and Columbia and Kiruna-type deposits to those involved in Columbia. The evolution of the Earth’s atmosphere-hydrosphere-biosphere was an additional influence on that of the supercontinent cycle in terms of the evolution of metallogenic provinces. The Great Oxidation Event (GOE) at ca. 2.4-2.0 Ga witnessed the end of the great era of deposition of BIFs that became the hosts to high-grade Fe and Mn deposits which formed under more oxidizing conditions, with Oligocene sediment-hosted Mn deposits and late-Cenozoic Mn nodules becoming the dominant Mn resources and potential resource, respectively. The GOE was also responsible for the evolution of U deposits from the Mesoarchean paleoplacer uraninite deposits of the Witwatersrand, through Mesoproterozoic unconformity-related deposits to Phanerozoic sandstone roll deposits. The Cambrian ‘explosion of life’, following a second GOE event, magnified the importance of organisms, particularly those secreting Ca and Mg, carbonate in the formation or ore deposits in sedimentary basins. Late Paleoproterozoic-Mesoproterozoic shale-hosted SEDEX Zn-Pb-Cu deposits were progressively replaced by Phanerozoic carbonate-hosted MVT Pb-Zn deposits and Neoproterozoic-Cambrian Zambian-type Cu-Co deposits hosted in calcareous sedimentary sequences. Carlin-type Au-Ag deposits hosted by calcareous and carbonaceous sequences appeared in the Cretaceous to Paleogene epochs to rival the more ubiquitous orogenic gold deposits in terms of global importance. It is evident that the evolution of the great metallogenic belts of the Earth was intrinsically linked to the thermal and tectonic evolution of the Earth and particularly to plate tectonics and the supercontinent cycles. The nature of contained mineral deposits of elements with multiple valency states and those requiring particularly reactive host rocks was strongly influenced by the evolution of the atmosphere-hydrosphere-biosphere system.
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This Special Publication combines results obtained by interdisciplinary groups from numerous academic institutions working on Paleoproterozoic formations to decipher the origins of the main mineralization resources in the West African Craton (WAC) and their impacts on African economic development. Structural, geophysical, sedimentological, stratigraphical, geochemical, petrophysical and mineralogical analyses have been used to highlight the complexities involved in mineralization emplacement and its origin and evolution within the WAC. Fourteen articles, mainly of basic research carried out in the WAC and surrounding areas, contribute to new knowledge in mineral research with updated references. They show that the geodynamic evolution of the WAC is complex from one area to another: it involves subduction, collision and obduction during several deformation phases ranging from Birimian (2.3-2.0 Ga) to Pan-African (650-450 Ma) events. Mineralization is mainly controlled by tectonics within shear zones, orogenic belts, basins and faulting systems occurring in the various corridors. Mineralized fluid circulation is stressed and injected into appropriate formations and precipitate several types of well-documented ore deposits: porphyry, metal-bearing, volcanogenic massive sulfide, sedimentary exhalative and lateritic. Various modelling techniques, when integrated help to understand the mechanisms of mineralization emplacement, some of which are still a matter of debate. Traditional and industrial exploitation of ore deposits, mainly gold, may inadvertently cause pollution to water tables and rivers, thus affecting the environment including watersheds. The challenge for further studies is mitigation for sustainable development that can be appropriately used to minimize such damage. The aim of this volume is thus to bring new insights to research activities on ore deposits within the WAC.
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Huanggang Dabieshan Global Geopark (DBGG), which is situated in central China, is notable for watershed of geology, climate, geomorphology, hydrology, and species between North China and South China. Scientific value of orogenic belt landscapes in the Dabieshan territory was globally recognized when the Dabieshan geopark gradually promoted under effective management framework of Dabieshan National Geopark was approved by UNESCO Global Geopark Network in 2018. DBGG has abundant geodiversity, showcasing a high representativeness and rarity of the orogenic belt landscapes, in matter of ultrahigh metamorphism, magmatism, bioecology, and culture. In order to assess and evaluate the potential of geoheritages, a detailed field investigation and description has been carried out in several localities of orogenic belt landforms within the DBGG, including Neoarchean gneiss, primitive epeirogenic granites, grotesquely shaped rocks, sedimentary rocks, gorge and floral landforms. And then both qualitative and quantitative approaches are launched to elaborate the values (scientific, educational, aesthetic, recreational, cultural, etc.), levels of significance, as well as their strengths, weaknesses, opportunities, and threats (SWOT analysis). The outcomes show that orogenic belt landforms obtain high assessment values, especially in Tiantangzhai, Bodaofeng, Guifengshan, and Longtan gorge localities. The educational utility (Ved, Vsa) and convenience and attraction for geotourism (Vtr, Vti) achieve high evaluation ratings. The distinct standings of geosites owe to easy accessibility and positive promotion by the community. Finally, valuable experiences have been summarized on the promotion of sustainable local economic development. This useful information could be given to global geoparks which are in its initial stage of development, in terms of preserving geoheritage, developing geotourism, and rural tourism.
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El Obeid area consists of a suite of ~1.0 Ga amphibolites that are associated with the gneisses and migmatites. Petrographic and geochemical analyses of these amphibolites indicated that they correspond to basalts that derive from sub-alkaline magmas and classified into two groups. Group A which is cropped out in J. El Eiza’a suffered from weakly anatexis of the first metamorphic event and characterized by low Nb contents (0.44–0.96 ppm), and REE and multi-elemental patterns similar to N-MORB. Group B amphibolites within the gneisses and migmatites in J. Kordofan, only undergone the second metamorphic processes and has high Nb contents ranging from 2.00 to 18.7 ppm, displaying an E-MORB and Pickle Nb-enriched basalt geochemical signature. The low silica and MgO concentrations for the two groups respectively (SiO2= 47.8–49.3 and 46.7–50.7 wt %) and (4.40–6.44 and 5.69–7.91%), suggested a mantle source for both groups. Their variable values of La/Ta (15.6–20.3 and 9.20–22.8), La/Nb (1.19–1.96 and 0.91–2.59) and Ba/Nb ratios (13.9–51.9 and 0.70–5.02), respectively, suggesting that they were likely derived from an average melt modified sub-continental lithospheric mantle, also their completely different REE profiles indicated authenticated their heterogeneous mantle source. Both groups have an arc-like and back-arc settings and show inputs of newly subduction-derived melt in the wedge source. Regional relationships indicated that the formation of these rocks resulted from the episodic amalgamation event during that time, an exterior accretion orogeny along the margin of Rodinia during ~1.0 Ga.
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The East European Craton is a collage of Early Precambrian crustal fragments including Fennoscandia, Sarmatia, and Volga-Uralia, which are welded by Palaeoproterozoic collisional orogens. Here, we present a detailed overview of the sedimentary basins in Sarmatia that incorporate giant belts of banded iron formations (BIFs) and are therefore important in understanding the geological history and global correlations during the Archean-Proterozoic transition. Among the two sedimentary basins in Sarmatia (Mikhailovsky and Tim-Kryvyi Rih), the Mikhailovsky Basin is characterized by the presence of a carbonate platform underlying BIFs. The BIFs are locally overlain by thin clastic deposits. Thick-bedded dolomites occur with BIF in the Tim Kryvyi Rih Basin. In the Mikhailovsky Basin, after their deposition there was a long-lasting hiatus. In the Mikhailovsky Basin, there are no sedimentary rocks after the regional hiatus except for glacial deposits. Sedimentation resumed with the development of continental rift-related structures, where the accumulation of terrigenous sediments was accompanied by, and culminated with, outflows of basalts at 2.1 Ga. A detailed evaluation of the history of sedimentary basins in Sarmatia record transgression (~2.6–2.4 Ga) with the accumulation of giant BIFs (~2.50–2.45 Ga), regression (~2.4–2.2 Ga), hiatus and glaciations (~2.4–2.2 Ga), and rift-related volcanism (~2.2–2.1 Ga). We attempt a correlation of the sedimentary sequences in Sarmatia with those of Pilbara, Kaapvaal, and São Francisco cratons which show that the geological events on all these cratons were similar during 2.6–2.4 Ga. We thus propose that the Sarmatia Craton may serve as a link in the palaeocontinental correlations of the Vaalbara Supercraton and the São Francisco Craton, based on the striking similarity in the Neoarchean-Early Palaeoproterozoic sedimentary basins.
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Using data from 186 stations belonging to the USArray Transportable Array, a three‐dimensional shear wave velocity model for the southeastern United States is constructed for the top 180 km by a joint inversion of receiver functions and Rayleigh wave phase velocity dispersion computed from ambient noise and teleseismic earthquake data. The resulting shear wave velocity model and the crustal thickness and Vp/Vs (κ) measurements show a clear spatial correspondence with major surficial geological features. The distinct low velocities observed in the depth range of 0–25 km beneath the eastern Gulf Coastal Plain reflect the thick layer of unconsolidated or poorly consolidated sediments atop the crystalline crust. The low κ (1.70–1.74) and slow lowermost crustal velocities observed beneath the eastern Southern Appalachian Mountains (including the Carolina Terrane and Inner Piedmont) relative to the adjacent Blue Ridge Mountains and Valley and Ridge can be interpreted by lower crustal delamination followed by relamination. The Osceola intrusive complex in the central Suwannee Terrane has similar crustal characteristics as the eastern Southern Appalachian Mountains and thus can similarly be attributed to crustal delamination/relamination processes. The Grenville Province and adjacent areas possess relatively high κ values which can be attributed to mafic intrusion associated with crustal extension in a recently recognized segments of the eastern arm of the Proterozoic Midcontinent Rift.
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The Morro do Onça suite is a package of ultramafic rocks in the southern São Francisco Craton, Brazil. Owing to the complete alteration of primary silicate minerals, the Morro do Onça suite has been the subject of diverging interpretations, including: part of a retrogressed eclogite-facies Paleoproterozoic ophiolite/accretionary wedge or an Archean komatiite flow(s). In this paper, we utilize spinel-group mineral chemistry—alongside field mapping, petrography, silicate mineral chemistry and bulkrock geochemistry—to decipher the magmatic and metamorphic evolution of the Morro do Onça suite. A komatiite origin is supported by the identification of spinifex-textured layers, as well as primary spinel-group mineral compositions (mean Cr-number = 79; mean TiO2 = 0.3 wt%) and chondrite-normalized bulk-rock rare-earth element values ([Sm–Lu]N = 1.2–5.1). Metamorphism reached mid/upper amphibolite-facies and was likely responsible for Al mobility on mineral and bulk-rock scales, demonstrating that the bulk-rock Al/Ti proxy commonly used to classify komatiites is susceptible to alteration. Thus, the Morro do Onça komatiites record variable bulk-rock Al/Ti values (17–47) that overlap with both Munro- (Al/Ti = 22) and Weltevreden-type (Al/Ti = 30) komatiites. Based on immobile trace-element ratios ([Gd/Lu]N = 0.6–2.0) and primary spinel-group mineral compositions, we classify the Morro do Onça komatiites as Weltevreden-type. Mesoarchean komatiites related to mantle plume-magmatism are now recognized throughout the southern São Francisco Craton, potentially suggesting that its precursor lithosphere was continuous during this Era.
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The Bastar Craton is one of the oldest cratonic nuclei of the Indian shield, comprising Paleoarchean to Mesoproterozoic crust that preserves the record of protracted crustal evolution and metallogeny. This study describes whole-rock geochemistry, U-Th-Pb ages of zircon and monazite from Neoarchean TTGs/sanukitoids, and Paleo- to Mesoproterozoic granites, and Sm-Nd isotope data from mafic enclave within TTGs of the Western Bastar Craton (WBC). The TTGs-sanukitoids represent Neoarchean crust formed by collision-accretion processes. The TTGs are of two types: low-HREE and high-HREE with both groups derived from low-K mafic sources. The sanukitoids have moderate SiO2 (55.1-65.1 wt. %, average=61.7 wt. %), Mg# (20-36, average=24.7), Ni (10-40ppm; average=14 ppm), Sr (339-528; average=418 ppm) and moderate to high concentrations of incompatible elements like Rb (26-112 ppm, average=48), Ba (482-2300 ppm, average=1542), Zr (69-593 ppm, average=334 ppm), Nb (3.8-14.8 ppm, average=8.7 ppm), Y (13.2-24.5 ppm, average=19.5 ppm), and REE (91-301 ppm, average=212)]. They post-date TTG emplacement and formed by mixing between metabasalt-derived and mantle wedge-derived melts in an arc environment. The Mul granite represents a younger Paleo- to Mesoproterozoic suite of granites that was derived by reworking of pre-existing crust. U–Pb ages of zircon constraints the TTG magmatism to 2544–2496 Ma, while Nd-model ages (3259-3142 Ma) of mafic enclaves within the TTG suggest the presence of Paleoarchean crust in the WBC. Zircon and monazite ages indicate that the emplacement of the Mul granite was synchronous with 1666-1547 Ma regional tectonothermal event. These granites were produced by reworking of older granitoid crust. The Neoarchean TTGs/sanukitoids were affected by 1666-1547 Ma tectonothermal event which constitutes a widely documented Paleo- to Mesoproterozoic orogeny in the Central Indian Tectonic Zone and Bhopalpatnam granulite belt to the south of the WBC. Copper and gold mineralization in the Thanewasna belt along the craton's western margin is linked to this tectono-magmatic event. In the global supercontinent outlook, the WBC preserves the imprints of Neoarchean events related to the Ur supercontinent as well as Paleo-Mesoproterozoic and Neoproterozoic (Grenville-age) events associated with the Columbia and Rodinia supercontinent. Keywords: Tonalite–trondhjemite–granodiorite, Geochemistry, LA-ICPMS zircon age, EMP monazite age, Western Bastar Craton
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The breakup of Pangea fundamentally shaped modern continents and controlled the climatic distribution and biodiversity on Earth. Although our knowledge on the processes that control the assembly and breakup of supercontinents has significantly improved, the timing of supercontinent assembly and breakup initiation remains in some cases controversial. According to the available data, the assembly of Pangea was completed in middle Permian time, resulting in the formation of major orogenic belts and transform faults like the N–S-trending, dextral, Caltepec fault in Mexico. Pangea breakup initiation is bracketed to early Middle Triassic time. In this work, we present new sedimentological, structural, and U-Pb geochronological data from a fluvial unit, the Matzitzi Formation of southern Mexico, the age and tectonic setting of which have remained an enigma for the past century. Our data document that the Matzitzi Formation is the stratigraphic record of a late Permian, anastomosing fluvial system that flowed in a ~ NNE-trending extensional trough developed on top of the Caltepense belt, a transpressive belt formed along the Caltepec fault. We propose and discuss three possible scenarios for the tectonic setting of the Matzitzi Formation. In the first scenario, the unit is the stratigraphic record of the Caltepec fault late activity, which caused local NW–SE extension along the western margin of Pangea during its final assembly. In the second scenario, the Matzitzi Formation was deposited in an extensional basin formed by slab rollback along the western equatorial Pangea margin. In the third scenario, the extensional basin of the Matzitzi Formation was formed in the framework of Pangea breakup. In this case, our data would suggest that Pangea breakup initiation must be dated back to late Permian time, which is ~ 15 m.y. older than the Middle Triassic age documented by previous work. Considering that evidence of Permian extension has also been reported along the Appalachian belt, we suggest that the Matzitzi Formation was deposited during regional-scale extension of western equatorial Pangea; therefore, we preliminarily support the third scenario. The distribution of Permian extension along suture belts developed during Pangea assembly highlights the fundamental role played by pre-existent zones of weakness in the breakup of a supercontinent.
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The Tarim Craton located in the northwest of China, where the Paleo-Mesoproterozoic extensional magmatism related to the Columbia supercontinent is widely developed. However, the process and time of the extension and initial breakup of the Tarim Craton are still controversial during Paleo-Mesoproterozoic era. In this contribution, we present a systematic petrographic, geochemical, and zircon U-Pb-Hf investigation on Aketashitage granite dykes, Wulan granitic gneisses and Astingbulake metadiabases from the Tarim Craton. Results from our study indicate that the ca. 1.88–1.86 Ga Aketashitage granite dykes belong to I-type granites, which were probably derived from low degree partial melting of thickened Archean crust during early post-collisional setting. The ca. 1.55 Ga Wulan granitic gneisses also show the characteristics of I-type granites, which mainly came from partial melting of mafic lower crust with minor mantle-derived magma input during the rift setting. The ca. 1.55 Ga protoliths of Astingbulake metadiabases show affinity to ocean island basalts and/or continental flood basalts and were produced by partial melting of enriched continental lithospheric mantle under continental rifting setting. In conjunction with previous studies, it can be concluded that the Tarim Craton experienced episodic extension to initial breakup: the South Orogen underwent early post-collisional extension during ca. 1.90–1.85 Ga, followed by late post-collisional extension during ca. 1.80–1.73 Ga; the North Orogen experienced early post-collisional extension at ca. 1.80–1.73 Ga and then entered the late post-collisional extension at ca. 1.67–1.60 Ga; finally, the South Orogen and North Orogen simultaneously entered the initial breakup stage during ca. 1.55–1.47 Ga. Based on a comparison of the global Mesoproterozoic (ca. 1.58–1.45 Ga) magmatic activities as a response to the initial break up of the Columbia supercontinent, we suggest that the Tarim Craton (including the Oulongbuluke Block) and North China Craton were close to India, Australia, Yangtze, Siberia, Congo, São Francisco and West African.
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The tectonic and magmatic processes contributing to the heterogeneous nature of the upper mantle posit important constraints on the composition and differentiation of the Earth at various scales. Mid-oceanic ridges of intermediate, slow and very-slow spreading rates across the world's oceans are characterized by different crustal configurations portraying the compositional diversity of the upper mantle. The two viable processes that are attributed to chemical and isotopic heterogeneity of the mantle are: (i) multiple episodes of melt replenishment and melt-rock interaction in open magma systems; and (ii) recycling of oceanic and continental crustal materials and components of sub-continental lithospheric mantle. Here we present petrological, geochemical and zircon UPb geochronology data from the lower crustal oceanic gabbros from the Central Indian Ridge (CIR) of the Indian Ocean. This study presents continental (2525 Ma–173 Ma) zircons from the lower oceanic crust gabbros of the Central Indian Ridge and invokes Indian Ocean MOR mantle heterogeneity through episodic entrainment of ancient continental lithosphere of Madagascan and Gondwana origin prior to Indian Ocean opening. The geochemical features show a marked deviation from typical depleted N-MORB compositions and conform to an E-MORB affinity, which might suggest enriched lithospheric input into the depleted asthenospheric mantle. The transitional depleted to enriched mantle signature substantiates the role of lithosphere-asthenosphere interaction contributing towards accretion of lower oceanic crust gabbros beneath the CIR. The HFSE and REE compositions can be translated in terms of melt extraction by shallow level melting of a chemically heterogeneous upper mantle carrying depleted asthenospheric and recycled lithospheric components. Zircon UPb geochronology reveals a wide spectrum of ages ranging from 2525 Ma to 173 Ma suggesting multiple episodes of recycling of older crust into asthenospheric mantle. The continental inheritance of the dated zircon grains can be interpreted to represent trapped relics of older continental lithosphere into the Indian Ocean MOR mantle. Our results envisage delamination and recycling of older continental lithosphere into mantle asthenosphere during (i) the Mozambique ocean closure and Gondwana amalgamation at around 750 Ma, and (ii) in response to the dispersal of Gondwanaland at ~167 Ma ensued by opening of the Indian Ocean.
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The Dabieshan area in China is rich in geodiversity, in terms of representative and comprehensive system of granite landscapes, with huge scientific value for studying the Phanerozoic orogenic belt magmatism, as well as aesthetic, recreational and cultural values for tourism. The importance of granite landscapes in Dabieshan was globally recognised when the Huanggang Dabieshan UNESCO Global Geopark (DBGG) was accepted in the Global Geoparks Network in 2018. With over 10 years of experience and a concerted effort to develop geotourism and alleviate poverty, the DBGG has followed a mature system of development, providing a well-developed example of successful geotourism and poverty alleviation in China. This study explores the current geotourism and geopark activities in relation to sustainable rural development and poverty alleviation in the DBGG and proposes expanding the geotourism industry, emphasising the cultivation of agricultural pillar industries and supporting policies and projects as an effective measure to alleviate poverty in the geopark area. Geodiversity, geotourism and geoparks exhibit essential credentials for poverty alleviation and sustainable rural development in the Dabieshan area. Through these effective measures and unremitting efforts, the DBGG has become a major tourist destination that can be used as a model for the development of geotourism and poverty alleviation. • KEY POINTS • Huanggang Dabieshan UNESCO Global Geopark is rich in geodiversity that has huge scientific value for studying the orogenic belt magmatism. • Measures have been undertaken to alleviate poverty in the Huanggang Dabieshan UNESCO Global Geopark area. • Huanggang Dabieshan UNESCO Global Geopark provides a model for the development of geotourism and poverty alleviation in China.
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Incorporates the majority of the papers presented at a symposium on the Middle Proterozoic evolution of the North American and Baltic Shields, held in St. Johns, Newfoundland, May 1988. Following an introductory chapter the 31 papers are divided into eight sections: isotopes and crustal evolution; geochronology; regional case histories; structural studies; anorthositic magmatism; anorogenic felsic magmatism; mafic magmatism; and sedimentary depocentres. A subject index concludes the volume. -S.J.Stone
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Prior to the Grenvillian continentcontinent collision at about 1.0 Ga, the southern margin of Laurentia was a long-lived convergent margin that extended from Greenland to southern California. The truncation of these 1.8-1.0 Ga orogenic belts in southwestern and northeastern Laurentia suggests that they once extended farther. We propose that Australia contains the continuation of these belts to the southwest and that Baltica was the continuation to the northeast. The combined orogenic system was comparable in length to the modern American Cordilleran or Alpine-Himalayan systems. This plate reconstruction of the Proterozoic supercontinent Rodinia called AUSWUS (Australia-Southwest U.S.) differs from the well-known SWEAT (Southwest U.S.-East Antarctic) reconstruction in that Australia, rather than northern Canada, is adjacent to the southwestern United States. The AUSWUS reconstruction is supported by a distinctive "fingerprint" of geologic similarities and tectonic histories between Australia and the southwestern United States from 1.8 to 0.8 Ga, and by a better agreement between 1.45 and 1.0 Ga paleomagnetic poles for Australia and Laurentia.
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The early geological development of the Pilbara and Kaapvaal cratons has many features in common. Attempts have been made to correlate geologically similar features of the two cratons, and it has been postulated that they originated as contiguous components of a single continent, ‘Vaalbara’, during this time. The early geological histories of the Pilbara and Kaapvaal cratons are here compared in detail and the evidence that they were initially contiguous is assessed. These comparisons indicate significant differences in the chronologies of magmatic events within the granite–greenstone crusts of the Pilbara and Kaapvaal cratons. In addition, igneous correlatives emplaced during ca 2985 and 2782 Ma magmatic events on the Kaapvaal Craton have not been identified on the Pilbara Craton, and a well-defined 2760 Ma magmatic event, manifest as widespread emplacement of granitic rocks into the Pilbara granite–greenstone basement and eruption of flood basalts of the lower part of the Fortescue Group, is absent from the Kaapvaal Craton. Furthermore, similarities in first- and second-order transgression–regression cycles within the sedimentary supracrustal sequences may be attributable to global sea-level fluctuations, and thus may be irrevelant to the question of former contiguity. However, similarities in some aspects of the geological development of the Pilbara and Kaapvaal cratons imply that there were periods, extending for between 60 and 200 Ma, of the Archaean era during which the style of crust formation, intensity of volcanism and subaerial erosion, and magnitude of sea-level fluctuations may have varied on a global scale. Such similarities include the overall duration of formation of the granite–greenstone crusts from ca 3650 to 3100 Ma, the onset of craton-wide erosion in the interval ca 3125 to 3000 Ma, the major episodes of flood basaltic volcanism between 2760 and 2680 Ma, the predominance of chemical (carbonate and banded iron-formation) sedimentation between ca 2630 and 2440 Ma and the transition to widespread clastic sedimentation within the interval 2440 to 2200 Ma.
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Mantle Plumes and Their Record in Earth History provides a timely and comprehensive review of the origin and history of mantle plumes throughout geologic time. The book describes the new and exciting results of the last few years, and integrates an immense amount of material from the fields of geology, geophysics, and geochemistry that bear on mantle plumes. Included are chapters on hotspots and mantle upwelling, large igneous provinces (including examples from Mars and Venus), mantle plume generation and melting in plumes, plumes as tracers of mantle processes, plumes and continental growth, Archean mantle plumes, superplumes, mantle plume events in Earth history, and their effect on the atmosphere, oceans, and life.
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A new fit for Siberia and Laurentia in the Late Proterozoic places Siberia north of the Franklin orogenic front in the Canadian Arctic such that the Akitkan fold belt in Siberia aligns with the Thelon magmatic zone in Canada. Zircon ages from both belts range from 2.0 to 1.9 Ga and appear to record additions of juvenile crust. The match between the Archean Slave province in Canada and the Aldan province in Siberia also supports this fit. Common plutonic zircon ages in both provinces are >3.5 to 3.2 Ga, 3.1-2.9 Ga, and 2.8-2.6 Ga. The ˜1 Ga Grenville orogen may have extended northward between southern Greenland and Scandinavia, passing through east-central Greenland and adjacent Barentsia, and possibly into the Angara fold belt in Siberia. It is possible that three Early Proterozoic fold belts associated with the Aldan province are extensions of the Coronation Supergroup, an Early Proterozoic rift- to passive-margin succession deposited on the western margin of the Slave province.
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The supracrustal rocks of the Older Metamorphic Group (OMG), consisting of metasediments and ortho-amphibolite, constitute the oldest unit in the Archaean nucleus of Singhbhum. However, there are indications that still older (3.4–3.8 Ga) crust of both sialic and mafic composition existed in this region. The OMG ortho-amphibolites were formed by partial melting of mantle with near chondritic composition ca. 3.3 Ga ago, probably as a result of plume activity. Shortly afterwards, partial melting of the underplated mafic material produced a tonalitic melt (Older Metamorphic Tonalitic Gneiss — OMTG), which intruded the OMG supracrustals and the entire suite was deformed and metamorphosed to upper amphibolite facies. Subsequent to this, melting of the OMG ortho-amphibolites and the lower crustal material of probable andesitic composition produced melts varying in composition from tonalite to granite and these intruded in different phases to produce plutons of Singhbhum Granite, Bonai Granite and Kaptipada Granite, which together form volumetrically the major part of the Archaean nucleus. The older OMG and OMTG occur as enclaves within these younger granitoids. The time difference between the emplacements of the OMTG and the early phases of younger granitic intrusion was of the order of 100–200 Ma. Thus, serial additions of juvenile material led to the formation of a stable microcontinent by 3.2 Ga. Thermally triggered stretching in this microcontinent produced basins peripheral to the present day Singhbhum Granite pluton, and in these basins the younger supracrustal rocks of the Iron Ore Group (IOG), consisting of BIF, associated argillaceous and subordinate arenaceous rocks, and mafic lavas were laid down. There is inadequate field or geochronological evidence to resolve the issue of whether the different iron ore basins were coeval or not. Meagre geochronological data suggest that some of the BIFs are older than ca. 3.1 Ga. Post-IOG activity is confined to the intrusion of mafic dyke swarms and formation of intracratonic basins, the ages of both being uncertain.
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The results of field, geochronologic, geochemical and isotopic studies are presented for the granitoids that occur east of the Closepet batholith up to the Kolar schist belt (KSB). Field data, such as common foliation, strong shear deformation occasionally leading to mylonitization, together with petrographic data, including reduction in grain size with corroded borders, show characteristics of the syn-kinematic emplacement of the granitoids. Single zircon evaporation ages define a minimum age of 3127 Ma for the tonalitic–trondhjemitic–granodioritic (TTG) basement and 2552–2534 Ma plateau ages for the emplacement of the granitoids, which slightly predate (20–30 Ma) the emplacement of the 2518 Ma Closepet batholith.Major and trace element data, together with isotopic data, suggest at least four magmatic suites from Closepet batholith to the east, which have independent magmatic evolution histories. The observed data are compatible with magma mixing for the Closepet batholith, melting of TTG and assimilation–fractional crystallization processes for Bangalore granites, either melting of heterogeneous source or different degree of melting of the same source for the granitoids of Hoskote–Kolar and fractional crystallization for the western margin of the KSB. Isotopic (Nd–Sr) and geochemical data (LREE and LIL elements) suggest highly enriched mantle and ancient TTG crust for the Closepet batholith, enriched mantle and TTG crust for the Bangalore granites, c.a. chondritic mantle source for the granitoids of Hoskote–Kolar and the quartz monzonites of the western margin of the KSB and slightly depleted mantle for granodiorites of the eastern margin of the KSB.We interpret all these geochronologic, geochemical and isotopic characteristics of granitoids from the Closepet batholith to the east up to the KSB in terms of a plume model. The centre of the plume would be an enriched ‘hot spot’ in the mantle that lies below the present exposure level of the Closepet batholith. Melting of such an enriched mantle hot spot produces high temperature magmas (Closepet) that penetrate overlying ancient crust, where they strongly interact and induce partial melting of the surrounding crust. These magmas cool very slowly, as the hot spot maintains high temperatures for a long time; thus they appear younger (2518 Ma). On the contrary, to the east the plume induces melting of c.a. chondritic or slightly depleted mantle that produces relatively colder and less enriched magmas, which show less or no interactions with the surrounding crust and cool rapidly and appear slightly older (2552–2534 Ma). This plume model can also account for late Archaean geodynamic evolution, including juvenile magmatism, heat source for reworking, inverse diapirism and granulite metamorphism in the Dharwar craton.
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The Rodinia hypothesis for the Neoproterozoic Supercontinent reconstruction is associated with five major problems: (i) The palaeomagnetic test requires continental break-up hundreds of millions of years before the geological evidence for this event is recognised near the dawn of the Cambrian. (ii) The reconstruction separates cratons with strong Late Archaean–Early Proterozoic affinities by large distances and then recombines them into Gondwana by early Phanerozoic times. (iii) The stratigraphic correlation, upon which it was originally based, incorporates successions dated ∼ 850–550 Ma during which interval palaeomagnetic data fail to predict continuity between Western North America, Australia and South China. (iv) The protracted history of break-up from 800–550 Ma is in conflict with the global subsidence record of passive margins defining initial continental break-up at ∼ 600 Ma and diverse isotopic/environmental signatures concentrated between 600–500 Ma. (v) It predicts no intrinsic link (such as a peripheral subduction zone) to large-scale mantle constraining forces.
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A new statistical method is proposed to compare crustal terranes and to cluster terranes into crustal provlnces, regions and realms. Geochronological data on mafic igneous rocks, felsic igneous rocks, deformation history and Nd model age were collected from the recent literature for over 100 terranes. The 54 selected Laurentian terranes cluster into 9 provinces including a previously well recognized very distinctive SW USA province, region and realm. The 38 selected Australian terranes cluster into six provinces including a distinctive Gawler Province. A combined dendrogram of the 100 terranes from Laurentia, Australia and Antarctica results in 8 superprovinces and 11 provinces. Five of the superprovinces contain both Laurentian and Australian terranes. The inclusion of the Nevada-Califomian Mojave and the San Gabriel terranes in an otherwise Australian superprovince that includes Broken Hill and Mt Isa terranes, strongly supports the AUSWUS Laurentia-Australia reconstruction rather than the SWEAT reconstruction. Low statistical similarities between western Laurentia and eastern Antarctica fail to support the SWEAT hypothesis whilst high similarities between Canadian and north Australian terranes provides weak support for AUSWUS.
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Recent geological information allows us to constrain a re-assembly of Mesoproterozoic East Gondwanaland. Juxtapositions of South Africa-Antarctica, India-Sri Lanka-Antarctica, and Australia-Antarctica do not conflict each other, supporting the reliability of the proposed re-assembly. A Mesoproterozoic Circum-East Antarctic Mobile Belt (CEAMB) is identified in the re-assembled East Gondwana. Lithologic characteristics indicating continental margin and shallow marine sedimentary conditions, and the association of extensive acid to intermediate magmatic rocks are common to many areas of CEAMB. Possible dismembered ophiolitic rocks are also known sporadically. These structural and lithologic characteristics point to a convergent tectonic setting. The Pan-African tectonothermal events are principally intracratonic, developed in most areas of the CEAMB and its surroundings, and are less intense eastwards. -from Author
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Estimates of stabilization ages of the world's Precambrian cratons reveal a pattern in which all blocks stabilized at ages ≥3.0 Ga occur in one area of the end-Paleozoic supercontinent Pangea. These blocks center around India, where at least two cratons (Western Dharwar and Singhbhum) show evidence of crustal growth terminating at or before ~3.0 Ga. This concentration of ≥3.0-Ga blocks is regarded as an Archean supercontinent referred to as "Ur'. -Author
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Evidence supports the hypothesis that the Laurentian and East Antarctic-Australian cratons were continuous in the late Precambrian and that their Pacific margins formed as a conjugate rift pair. A geometrically acceptable computer-generated reconstruction for the latest Precambrian juxtaposes and aligns the Grenville front that is truncated at the Pacific margin of Laurentia and a closely comparable tectonic boundary in East Antarctica that is truncated along the Weddell Sea margin. Geologic and paleomagnetic evidence also suggests that the Atlantic margin of Laurentia rifted from the proto-Andean margin of South America in earliest Cambrian time. -from Author
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Central Indian Tectonic Zone (CITZ), which divides the Indian subcontinent into Bundelkhand Block in the north and the Deccan Block in the south, is represented by a collage of different lithotectonic terranes ranging in age from Archaean to Recent. It comprises two parallel structural domains, namely the Son-Narmada (SONA) subzone in the north and the Sausar mobile belt (SMB) in the south. The ancestry of the SONA subzone is indicated by the Neoarchaean - Palaeoproterozoic ages yielded by the rocks of Mahakoshal fold belt; the Sausar belt, on the other hand, has yielded Meso- to Neoproterozoic ages. The present response of CITZ to accumulation of stress and attendant seismicity is governed by the structures generated due to early tectonic history of rocks within it, particularly the development of number of E-W to ENE-WSW striking, brittle and ductile shear zones. While the Sausar belt has remained more or less stable since the late Precambrian, the SONA and Tapti lineament zones have been reactivated several times. Two prominent ENE-WSW trending deep faults, termed the Son-Narmada North Fault (SNNF) and Son-Narmada South Fault (SNSF) have been episodically active from Neoarchaean onwards. The SNSF in particular has witnessed protracted reactivation well into the Phanerozoic. Intraplate seismicity in continents is commonly concentrated along ancient fault zones. Reactivation of faults or shear zones is favoured over new fault generation, since the SNSF is in a high shear stress orientation. Although the Sausar mobile belt is marked by a number of E-W trending parallel ductile shears, mass transfer processes such as silicification, recrystallization and grain growth during Precambrian appear to have healed them.
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Peninsular India can be separated into 5 discrete crustal areas: the Bhandara, Singhbhum, and Aravalli (Bundelkhand) cratons; the Eastern Ghats; and a block in S India containing the Dharwar craton and adjoining Granulite terrain. These areas are separated by 4 major joins: Eastern Ghats front, Godavari rift, Mahanadi rift/Sukinda thrust, and Narmada-Son lineament and associated thrusts. All joins except the Godavari rift are former orogenic belts, where thrusts juxtapose rocks of different metamorphic grade. These thrusts, and the absence of clear correlation of suites among different cratons, suggest that the Indian shield formed by accretion of separate continental fragments. Epicontinental Late Archean/Early Proterozoic sediments throughout India, however, may indicate that the joins are intracontinental, formed within a coherent block. -from Author
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The Rodinia reconstruction of the Neoproterozoic Supercontinent has dominated discussion of the late Precambrian Earth for the past decade and originated from correlation of sedimentary successions between western North America and eastern Australia. Subsequent developments have sited other blocks according to a distribution of ~1100 Ma orogenic belts with break-up involving a putative breakout of Laurentia and rapid reassembly of continent crust to produce Gondwana by early Phanerozoic times. The Rodinia reconstruction poses several serious difficulties, including: (a) absence of palaeomagnetic correlation after ~730 Ma which requires early fragmentation of continental crust although geological evidence for this event is concentrated more than 150 Ma later near the Cambrian boundary, and (b) the familiar reconstruction of Gondwana is only achieved by exceptional continental motions largely unsupported by evidence for ocean consumption. Since the geological evidence used to derive Rodinia is non-unique, palaeomagnetic data must be used to evaluate its geometrical predictions. Data for the interval ~1150-500 Ma are used here to test the Rodinia model and compare it with an alternative model yielding a symmetrical crescent-shaped analogue of Pangaea (Palaeopangaea). Rodinia critically fails the test by requiring Antarctica to occupy the location of a quasi-integral Africa, whilst Australia and South America were much closer to their Gondwana configurations around Africa than implied by Rodinia. Palaeopangaea appears to satisfy palaeomagnetic constraints whilst surmounting geological difficulties posed by Rodinia. The relative motions needed to produce Gondwana are then relatively small, achieved largely by sinistral transpression, and consistent with features of Pan-African orogenesis; continental dispersal did not occur until the Neoproterozoic-Cambrian boundary. Analogies between Palaeopangaea and (Neo)pangaea imply that supercontinents are not chaotic agglomerations of continental crust but form by episodic coupling of upper and lower mantle convection leading to conformity with the geoid.
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Stratigraphic correlations and tectonic analysis suggest that the Yangtze block of South China could have been a continental fragment caught between the Australian craton and Laurentia during the late mesoproterozoic assembly of the supercontinent Rodinia. The Cathaysia block of southeast China may have been part of a 1.9 1.4 Ga continental strip adjoining western Laurentia before it became attached to the Yangtze block around 1 Ga. This configuration provides a western source region for the clastic wedges in the Belt Supergroup of western North America which contain detrital grains of 1.8 1.6 Ga and 1.22 1.07 Ga. The breakup of Rodinia around 0.7 Ga separated South China (Yangtze plus Cathaysia blocks) from the other continents.
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The recognition of Precambrian ophiolite suites and their dismembered remnants in association with intraoceanic island-arc volcanic and plutonic terrains across much of the Arabian-Nubian Shield of E Egypt, Sudan, Ethiopia, Yemen, W Saudi Arabia, and Sinai has been used by many authors to support the hypothesis of crustal accretion during late Proterozoic time (approx 950-550 Ma). Reassembly of the various fragments provides a mosaic of Proterozoic microplates in a regular pattern in which at least 5 oceanic terrains, bounded by the remains of ophiolite belts, lie between remobilized continental plates to E and W.-Author