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Geochemistry and U–Pb Geochronology of the Neoproterozoic-Cambrian Koettlitz Glacier Alkaline Province, Royal Society Range, Transantarctic Mountains, Antarctica
... In situ igneous and metamorphic 40 Ar/ 39 Ar cooling ages are compiled from data presented in this paper, as well as [37,45,46,48,51,52,54,[79][80][81][82][83]. U-Pb crystallization ages from [33][34][35][36][37][38][44][45][46][47][48]82,[84][85][86][87][88][89][90][91][92][93][94][95][96][97][98][99]. 40 Ar/ 39 Ar cooling ages for detrital muscovite from the Starshot Formation along Ramsey Glacier are from [54] and those within the central Transantarctic Mountains (CTAM) are from [37]. ...
... Detrital zircon Yb/Gd data include all zircons regardless of concordance with Th/U > 0.1 (~igneous proxy) and Th, U, Y, Yb, and Gd values > 0. Interpreted zircon ages are 206 Pb/ 238 U ages for grains with 206 Pb/ 207 Pb ages < 1500 Ma. 40 Ar/ 39 Ar cooling ages are compiled from data presented in this paper, as well as [37,45,46,48,51,52,54,[79][80][81][82][83]. U-Pb igneous crystallization ages are presented in [33][34][35][36][37][38][44][45][46][47][48]82,[84][85][86][87][88][89][90][91][92][93][94][95][96][97][98][99]. ...
... Detrital zircon Yb/Gd data include all zircons regardless of concordance with Th/U > 0.1 (~igneous proxy) and Th, U, Y, Yb, and Gd values > 0. Interpreted zircon ages are 206 Pb/ 238 U ages for grains with 206 Pb/ 207 Pb ages < 1500 Ma.40 Ar/ 39 Ar cooling ages are compiled from data presented in this paper, as well as[37,45,46,48,51,52,54,[79][80][81][82][83]. U-Pb igneous crystallization ages are presented in[33][34][35][36][37][38][44][45][46][47][48]82,[84][85][86][87][88][89][90][91][92][93][94][95][96][97][98][99]. ...
Changes in magmatism and sedimentation along the late Neoproterozoic-early Paleozoic Ross orogenic belt in Antarctica have been linked to the cessation of convergence along the Mozambique belt during the assembly of East-West Gondwana. However, these interpretations are non-unique and are based, in part, on limited thermochronological data sets spread out along large sectors of the East Antarctic margin. We report new 40Ar/39Ar hornblende, muscovite, and biotite age data for plutonic (n = 13) and metasedimentary (n = 3) samples from the Shackleton–Liv Glacier sector of the Queen Maud Mountains in Antarctica. Cumulative 40Ar/39Ar age data show polymodal age peaks (510 Ma, 491 Ma, 475 Ma) that lag peaks in U-Pb igneous crystallization ages, suggesting igneous and metamorphic cooling following magmatism within the region. The 40Ar/39Ar ages are similar to ages in other sectors of the Ross orogen, but younger than detrital mineral 40Ar/39Ar cooling ages indicative of older magmatism and cooling of unexposed inboard areas along the margin. Detrital zircon trace element abundances suggest that the widespread onset of magmatism in outboard localities of the orogen correlates with a ~560–530 Ma decrease in crustal thickness. The timing of crustal thinning recorded by zircon in magmas overlaps with other evidence for the timing of crustal extension, suggesting that the regional onset of magmatism with subsequent igneous and metamorphic cooling probably reflects slab rollback that coincided with possible global plate motion changes induced during the final assembly of Gondwana.
... In the Dry Valleys, owing to detailed mapping, the Granite Harbour Intrusive Complex was subdivided into several petrological suites (Smillie, 1992;Allibone et al., 1993a, b;Allibone and Wysoczanski, 2002;Read et al., 2002). Though such subdivision is not reported in the map, Cox et al. (2012) recognised that in the Benson and Mackay glaciers area the magmatic rocks mainly belong to the DV1a (hornblende-biotite granitoids) and DV2 (alkali-calcic monzonite, quartz monzonite and granitic plutons) suites, whereas in the northern part of the map the Granite Harbour rocks are mainly undifferentiated. ...
... To improve our understanding of the tectonic evolution of the Ross-Delamerian orogen, we compiled and synthesized as much U-Pb geochronological data as available from the literature [9,11,13,16,[18][19][20]22,27,28,32,41,[52][53][54]60,76,79,[88][89][90][91][92][93][94][95][96][97][98] (Table S2), which are graphically shown in Figure 7. The geochronological data for the pre-to syn-tectonic calc-alkaline granitoids are systemically younger northward from~590-520 Ma in the Central Transantarctic Mountains, through~565-505 Ma in the Southern Victoria Land, and~535-500 Ma in the Northern Victoria Land to~520-490 Ma in the Southeast Australia (Figure 7). ...
It has been accepted that granitoids of the Irizar unit in the Central Victoria Land (Antarctica), as an important part of the Granite Harbour Intrusives, were formed in a post-collisional setting during the Ross orogeny along the margin of east Gondwana. However, the emplacement ages of the Irizar unit remain poorly constrained, making it difficult to form a more complete picture of the geodynamic evolution of the Ross orogen and its counterpart (Delamerian orogen) in southeast Australia. In this work, four syenogranite samples from the Irizar unit were chosen for SHRIMP zircon U-Pb dating, which yielded ages of 507.8–489.7 Ma. The new geochronological data indicate that the post-collisional extension in the Central Victoria Land had begun by ~508 Ma, much earlier than previously thought (i.e., 490–480 Ma). Integrated with U-Pb ages for Early Paleozoic granitoids from the literature, the Ross–Delamerian orogen shows that the post-collisional granitic magmatism initiated at ~515 Ma in the Central Transantarctic Mountains and northward systematically decreased to ~508 Ma in the Victoria Land, and then to ~487 Ma in southeast Australia. This can be explained well by the propagating northward transition from pre- and syn-collisional compression to post-collisional extension.
... Despite the dominant~1.1 Ga detrital zircons seen in these metasediments (Wysoczanski and Allibone, 2004;Cooper et al., 2011), the only known Rodinian-aged crust in Southern Victoria Land is a single ~940 Ma metamorphosed sandstone (Wysoczanski and Allibone, 2004). From the Neoproterozoic to Ordovician, the Skelton Group was extensively intruded by the Ross Orogen Granite Harbour Intrusive suite (e.g., Grindley and Warren, 1964;Cox et al., 2000;Allibone and Wysoczanski, 2002;Read et al., 2002;Read, 2010;Cox et al., 2012;Hagen-Peter et al., 2015;Cottle, 2016, 2018). ...
Osmium isotopes, whole rock and mineral geochemical data from peridotite xenoliths from two Miocene McMurdo Volcanic Group cinder cones in the Transantarctic Mountains (TAM) in Southern Victoria Land, Antarctica, reveal that the underlying mantle preserves evidence for major mid-Proterozoic lithosphere formation despite the crust being dominated by late Neoproterozoic-Ordovician (∼0.65-0.47 Ga) rocks. The Hooper Crags xenolith suite is dominated by harzburgites with highly refractory olivine Mg# (up to 92.3) and depleted bulk rock major and platinum group element + Re abundances, with ¹⁸⁷Os/¹⁸⁸Os ratios indicating depletion in the mid-Proterozoic. Pipecleaner Glacier xenoliths, 18 km distant, are lherzolites with olivine Mg# (< 91) and fertile major and platinum group element abundances, with Os isotope abundances defining an aluminochron that also indicates mid-Proterozoic depletion. Although exposed crust along this portion of Antarctica reveals only minor evidence for Proterozoic magmatism, the major episode of lithosphere formation indicated by the Os isotope data is supported by published bulk rock Sm-Nd isotope and zircon εHf mantle model ages of Neoproterozoic to Ordovician plutonic rocks. The heterogeneous circum-cratonic mid-Proterozoic mantle under Southern Victoria Land has therefore persisted on a Ga timescale, including through the formation and destruction of Rodinia and Gondwana supercontinents as well as extensive crustal melting and emplacement of the Ferrar large igneous province. This longevity may be due to the thick (>250 km) East Antarctic Craton lithosphere shielding the immediately adjacent circum-cratonic mantle from being affected by convective asthenosphere-driven erosion. This contrasts with mantle lithosphere accreted distally to the East Antarctic Craton (represented by the now-detached Zealandia continent), which did not attain extreme thickness and has therefore been more susceptible to tectonic reworking and lateral translation.
... In southern Victoria Land, granitoids of the Koettlitz Glacier Alkaline Province were emplaced mainly between 557 and 542 Ma, with reset ages of 538-534 Ma (Read et al., 2002;Read, 2010). In the Byrd Glacier (BG) area most granites crystallized at 550-539 Ma, then 537, 532-530 Ma with age gaps to 525, 510 and 503 Ma. ...
New insights into the Late Precambrian-latest Devonian evolution of the Pacific margin of Gondwana are obtained by treating the margin in terms of three key tectonic elements: i) the in situ part of the Ross Orogen of Eastern Antarctica (Wilson Terrane) built on, and fringing, older crust; ii) the largely in situ southern Tasmanides of eastern Australia; and iii) offshore basement and island arc terranes now accreted either to the Ross Orogen, the Tuhua Orogen of southwestern New Zealand or, in one case, to the Australian Tasmanides. Detailed correlations between these elements suggest that the onset of convergence was essentially simultaneous along the margin over an original distance of ~1000 km. The first appearance of subduction-related igneous rocks occurred at ~540–530 Ma in the Tasmanides; ~535–530 Ma in the Tiger Arc of northern Victoria Land; and 550 Ma in southern Victoria Land of the Ross Orogen.
New correlations of this paper suggest possible but unconstrained trajectories of offshore terranes. The Bowers Terrane was accreted to the East Gondwana margin at ~491 Ma, producing the main Ross Orogeny. The adjoining Takaka Terrane had docked briefly with that margin at ~497–494 Ma (Haupiri Disturbance in New Zealand) before crustal extension rifted it oceanward to drift away in the latest Cambrian to become subsequently amalgamated with the sedimentary Buller Terrane at ~390 Ma. The West Tasmania Terrane was accreted to the East Gondwana margin beginning at~500–499 Ma (generating phase 3 of the Tyennan Orogeny) and the connected Selwyn Block to the Tasmanides at ~500 Ma (main Delamerian Orogeny).
Our new interpretations suggest that previous lithological correlations of subduction-related volcanics between the Ross Orogen and southern Tasmanides did not take into account major rollback in the Tasmanides from ~514 to ~503 Ma. Similarly, they suggest that the ~550–480 Ma Granite Harbour Intrusive roots of the continental margin Ross Arc are not correlatives of 514, 505 and ~ 495–470 Ma granites intruding the Kanmantoo Group in the Delamerian Orogen of South Australia, either in time or in tectonic setting. We also recognize an early (~520–516 Ma) boninitic infant arc event in the outboard West Tasmania, Bowers, and Takaka terranes that predated ~500 Ma more mature arcs in the last two. Arc-related magmatism in the Ross Orogen reflects the interplay between two main subduction systems — that which generated the Ross Arc and an outboard one that generated intraoceanic arcs.
Three major turbidite fan systems developed along the East Gondwana margin as responses to major deformations. Early Cambrian fan system 1 postdates the Beardmore Orogeny and includes the Kanmantoo Group in the Delamerian Orogen and the Berg and upper Priestley formations in the Wilson Terrane. Cambrian-Ordovician fan system 2 (the Robertson Bay Group, the Swanson Group in Marie Byrd Land, the Greenland Group in the Buller Terrane and the St Arnaud Group in the Delamerian Orogen) and Lower-Middle Ordovician fan system 3 (turbidites of the Eastern Lachlan Orogen, the Buller Terrane (New Zealand) and East Tasmania Terrane) both postdate different parts of the Ross Orogeny. Cessation of fan system at ~458 Ma correlates with ‘accretion’ of the Robertson Bay Terrane in northern Victoria Land.
The Ross Embayment is a key region to study the dynamics of the ice sheets during colder andwarmer than present climatic conditions, because both the East and West Antarctic Ice sheets shed into the Ross Sea. Numerical modeling and reconstructions of the paleo ice flows during the Last Glacial Maximum show variable contribution of East and West Antarctic Ice sheets based on a variety of proxies. In this study, we present the first petrographic and minero-chemical investigation of the gravel-sized fraction of Last Glacial Maximum subglacial-glacimarine
sediments collected with piston cores in a W–E transect across the Ross Sea. The clast petrographic features are compared with outcropping geology to individuate the sediment source regions. The gravel content of the glacigenic diamictite was classified on the basis of petrographic and minero-chemical features, and three main petrofacies were identified. They reflect changes in the basement geology of the source regions, allowing the reconstruction of the paleo ice flowpattern and their comparison with scenarios built upwith other datasets.Moreover, the comparison with the Oligocene to Pleistocene glacigenic sediments provided information about the changes of the gravel signature across the Ross Sea and the erosion history of the source regions during Cenozoic
The Lower Permian tillites of the Beacon Supergroup, cropping out in Victoria Land (Antarctica), record climatic history during one of the Earth’s coldest periods: the Late Paleozoic Ice Age. Reconstruction of iceextent and paleo-flow directions, as well as
geochronological and petrographic data, are poorly constrained in this sector of Gondwana. Here, we provide the first detrital zircon U-Pb age analyses of both the Metschel Tillite in southern Victoria Land and some tillites correlatable with the Lanterman Formation in northern Victoria Land to identify the source regions of these glaciogenic deposits. Six-hundred detrital zircon grains from four diamictite samples were analyzed using laser ablation–inductively coupled plasma–mass spectrometry. geochronological and petrographic compositional data of the Metschel Tillite indicate a widespread reworking of older Devonian Beacon Supergroup sedimentary strata, with minor contribution from Cambro-Ordovician granitoids and meta-sedimentary units as well as Neoproterozoic metamorphic rocks. Euhedral to subhedral Carboniferous–Devonian zircon grains match coeval magmatic units of northern Victoria Land and Marie Byrd Land. This implies, in accordance with published paleo-ice directions, a provenance from the east-southeast sectors. In contrast, the two samples from northern Victoria Land tillite reflect the local basement provenance; their geochronological age and petrographic composition indicates a restricted catchment area with multiple ice centers. This shows that numerous ice centers were present in southern Gondwana during the Late Paleozoic Ice Age. While northern Victoria Land hosted discrete glaciers closely linked with the
northern Victoria Land-Tasmania ice cap, the west-northwestward flowing southern Victoria Land ice cap contributed most of the sediments comprising the Metschel Tillite.
The Transantarctic Mountains (TAM) are one of Earth's great mountain belts and are a fundamental physiographic feature of Antarctica. They are continental-scale, traverse a wide range of latitudes, have high relief, contain a significant proportion of exposed rock on the continent, and represent a major arc of environmental and geological transition. Although the modern physiography is largely of Cenozoic origin, this major feature has persisted for hundreds of millions of years since the Neoproterozoic to the modern. Its mere existence as the planet's longest intraplate mountain belt at the transition between a thick stable craton in East Antarctica and a large extensional province in West Antarctica is a continuing enigma. The early and more cryptic tectonic evolution of the TAM includes Mesoarchean and Paleoproterozoic crust formation as part of the Columbia supercontinent, followed by Neoproterozoic rift separation from Laurentia during breakup of Rodinia. Development of an Andean-style Gondwana convergent margin resulted in a long-lived Ross orogenic cycle from the late Neoproterozoic to the early Paleozoic, succeeded by crustal stabilization and widespread denudation during early Gondwana time, and intra-cratonic and foreland-basin sedimentation during late Paleozoic and early Mesozoic development of Pangea. Voluminous mafic volcanism, sill emplacement, and layered igneous intrusion are a primary signature of hotspot-influenced Jurassic extension during Gondwana breakup. The most recent phase of TAM evolution involved tectonic uplift and exhumation related to Cenozoic extension at the inboard edge of the West Antarctic Rift System, accompanied by Neogene to modern glaciation and volcanism related to the McMurdo alkaline volcanic province. Despite the remote location and relative inaccessibility of the TAM, its underlying varied and diachronous geology provides important clues for reconstructing past supercontinents and influences the modern flow patterns of both ice and atmospheric circulation, signifying that the TAM have both continental and global importance through time.
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