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Satellite bathymetry map of the western Indian Ocean basin. Approximate aerial extent of Deccan Traps lava flows are shown by the gray fields on the Indian subcontinent. Numbers in the shaded region correspond to sampling regions: 1-Kutch (samples 1-5), 2-Saurashtra (samples 6-46), 3-Pavagadh, Kalsubai, Amba Dongar and surrounds (samples 48-54, 63-78), 4-Dhule and surrounds (samples 55-62), 5-Mumbai, Western Ghats and coastal Maharashtra (samples 79-115, MMF7). Approximate trace of the Réunion hotspot is shown by the transparent black arrow, approximate plate motion vectors are shown by solid black arrows over land areas and are proportional to plate motions. Base map reproduced from the GEBCO world map 2014, www.gebco.net.

Satellite bathymetry map of the western Indian Ocean basin. Approximate aerial extent of Deccan Traps lava flows are shown by the gray fields on the Indian subcontinent. Numbers in the shaded region correspond to sampling regions: 1-Kutch (samples 1-5), 2-Saurashtra (samples 6-46), 3-Pavagadh, Kalsubai, Amba Dongar and surrounds (samples 48-54, 63-78), 4-Dhule and surrounds (samples 55-62), 5-Mumbai, Western Ghats and coastal Maharashtra (samples 79-115, MMF7). Approximate trace of the Réunion hotspot is shown by the transparent black arrow, approximate plate motion vectors are shown by solid black arrows over land areas and are proportional to plate motions. Base map reproduced from the GEBCO world map 2014, www.gebco.net.

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Article
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Geodynamical models of mantle plumes often invoke initial, high volume plume 'head' magmatism, followed by lower volume plume 'tails'. However, geochemical links between plume heads, represented by flood basalts such as the Deccan Traps, and plume tails, represented by ocean islands such as La Réunion, are ambiguous, challenging this classical view...

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Context 1
... best studied examples of plume head and tail relationships along a linear, age-progressive volcanic track is the Deccan-Réunion hotspot. There, a volumetrically massive continental flood basalt (CFB) province, the Deccan Traps, is linked by aseismic, submarine ridges to ocean island basalts (OIB) that actively erupt on the island of La Réunion (Fig. 1). A genetic link between Deccan CFB and Réunion OIB, and for other similar hotspot tracks, has often been implicitly assumed by mantle plume theory and is demanded by recent geody- namical models (Glišovi´cGlišovi´c and Forte, 2017). Such assumptions, however, are at odds with expected physical consequences of ancient mantle plumes; for ...
Context 2
... elemental and isotopic characteristics of Deccan Traps continental flood basalts (CFB) and determine their relationship to Réunion ocean island basalts (OIB). Sampling was performed throughout the western extent of the Deccan Traps, from northern expo- sures in the Kutch region of Gujarat, to southern exposures near Mahabaleshwar in Maharashtra ( Fig. S-1). These areas cover much of the chemostratigaphy of the Deccan Traps ( Fig. S-2), with the exception of the uppermost Desur and Panhala Formations, and possibly also the lowermost Jawhar Forma- tion. The availability of published maps identifying the surfi- cial extent of chemostratigraphic units, particularly far from the "main ...
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... Perspectives Letters Letter 2012; and likely results from sulphide satura- tion in evolved melts, causing rapid loss of IPGE to sulphide phases and preferential retention of PPGE in residual melts (Jamais et al., 2008). This process can be traced on a plot of PPGE versus Cu (Fig. S-10a), where PPGE contents below a certain level indicated by sulphur accumulation (traced by Cu) indicates previous extraction of sulphides. Many of our samples lie above the qualitative line separating S-saturated and S-undersaturated melts ( Keays andLightfoot, 2007, 2010), but still overlap with the field of S-saturated West Greenland ...
Context 4
... magma composition by regressing Ir versus MgO data for mineral separates and determining concentrations of the remaining HSE using the HSE/Ir ratios of the olivine separates. We can then quantify the effects of sulphide extraction using the partitioning data of Jamais et al. (2008) and empirically determined partition coef- ficients of Day (2013) (Fig. S-10b) and this assumed parental melt HSE concentration. With an assumed tholeiitic parental magma MgO composition of 16 wt. %, we model extraction of an olivine-clinopyroxene-orthopyroxene-plagioclase assem- blage and assimilation of upper continental crust (Peucker-Ehrenbrink and Jahn, 2001;Nishimura, 2012). Concentrations of MgO are ...

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Citations

... The concept of mantle plume was initially proposed by W. Jason Morgan in 1971 based on the observation of the Hawaii hot spots (Wilson, 1963) to explain the age-progressive chains of volcanic islands that stretch across the ocean basins (Morgan, 1971). A mantle plume is generally composed of a huge head and a narrow tail that is connected to the deep mantle (Campbell et al., 1989;Campbell & Griffiths, 1990, 1992Hill et al., 1992;Kent et al., 1996;Larson, 1991;Peters & Day, 2017). During the ascent of a mantle plume, the head would trap large amounts of mantle material to enlarge itself. ...
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... The concept of mantle plume was initially proposed by W. Jason Morgan in 1971 based on the observation of the Hawaii hot spots (Wilson, 1963) to explain the age-progressive chains of volcanic islands that stretch across the ocean basins (Morgan, 1971). A mantle plume is generally composed of a huge head and a narrow tail that is connected to the deep mantle (Campbell et al., 1989;Campbell & Griffiths, 1990, 1992Hill et al., 1992;Kent et al., 1996;Larson, 1991;Peters & Day, 2017). During the ascent of a mantle plume, the head would trap large amounts of mantle material to enlarge itself. ...
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The continental crust is unique to the Earth in the solar system, and controversies remain regarding its origin, accretion and reworking of continents. The plate tectonics theory has been significantly challenged in explaining the origin of Archean (especially pre-3.0 Ga) continents as they rarely preserve hallmarks of plate tectonics. In contrast, growing evidence emerges to support oceanic plateau models that better explain characteristics of Archean continents, including the bimodal volcanics and nearly coeval emplacement of tonalite-trondjhemite-granodiorite (TTG) rocks, presence of ∼1600°C komatiites and dominant dome structures, and lack of ultra-high-pressure rocks, paired metamorphic belts and ophiolites. On the other hand, the theory of plate tectonics has been successfully applied to interpret the accretion of continents along subduction zones since the late Archean (3.0–2.5 Ga). During subduction processes, the new mafic crust is generated at the base of continents through partial melting of mantle wedge with the addition of H2O-dominant fluids from subducted oceanic slabs and partial melting of the juvenile mafic crust results in the generation of new felsic crusts. This eventually leads to the outgrowth of continents. Subduction processes also cause softening, thinning, and recycling of continental lithosphere due to the vigorous infiltration of volatile-rich fluids and melts, especially along weak belts/layers, leading to widespread continental reworking and even craton destruction. Reworking of continents also occurs in continental interiors due to either plate boundary processes or plume-lithosphere interactions. The effects of plumes have proven to be less significant and cause lower degrees of lithospheric modification than subduction-induced craton destruction.
... It has been suggested, based on unradiogenic He and Ne, that the source of these samples is deep, undegassed mantle (Breddam et al., 2000;Moreira et al., 2001). The remaining samples come from several ocean island localities in the Pacific, Indian and Atlantic ocean basins and have been previously characterized for major-and trace-elements, radiogenic isotopes, and Si and Ga stable isotopic compositions (LeRoex, 1985;Albarède and Tamagnan, 1988;Breddam et al., 2000;Claude-Ivanaj et al., 2001;Breddam, 2002;Workman et al., 2004;Geist et al., 2006;Jackson et al., 2007aJackson et al., , 2007bMillet et al., 2008;Kurz et al., 2009;Day et al., 2010;Kawabata et al., 2011;Hart and Jackson, 2014;Garapić et al., 2015, Pringle et al., 2016, Peters & Day, 2017Kato et al., 2017). ...
... g Puchtel et al. (2013). h Peters and Day (2017). ...
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Article
The Kerguelen large igneous province (LIP) has been related to mantle plume activity since at least 120 Ma. There are some older (147–130 Ma) magmatic provinces on circum-eastern Gondwana, but the relationship between these provinces and the Kerguelen mantle plume remains controversial. Here we present petrological, geochronological, geochemical, and Sr–Nd–Hf–Pb–Os isotopic data for high-Ti mafic rocks from two localities (Cuona and Jiangzi) in the eastern Tethyan Himalaya igneous province (147–130 Ma). Zircon grains from these two localities yielded concordant weighted mean 206Pb/238U ages of 137.25 ± 0.98 and 131.28 ± 0.78 Ma (2σ), respectively. The analyzed mafic rocks are enriched in high field strength elements and have positive Nb–Ta anomalies relative to Th and La, which have ocean island basalt-like characteristics. The Cuona basalts were generated by low degrees of melting (3–5%) of garnet lherzolites (3–5 vol.% garnet), and elsewhere the Jiangzi diabases were formed by relatively lower degrees of melting (1–3%) of garnet lherzolite (1–5 vol.% garnet). The highly radiogenic Os and Pb isotopic compositions of the Jiangzi diabases were produced by crustal contamination, but the Cuona basalts experienced the least crustal contamination given their relatively low γOs(t), 206Pb/204Pbi, 207Pb/204Pbi, and 208Pb/204Pbi values. Major and trace element geochemical and Sr–Nd–Hf–Pb–Os isotope data for the Cuona basalts are similar to products of the Kerguelen mantle plume head. Together with high mantle potential temperatures (>1500°C), this suggests that the eastern Tethyan Himalaya igneous province (147–130 Ma) was an early magmatic product of the Kerguelen plume. A mantle plume initiation model can explain the temporal and spatial evolution of the Kerguelen LIP, and pre-continental break-up played a role in the breakup of eastern Gondwana, given the >10 Myr between initial mantle plume activity (147–130 Ma) and continental break-up (132–130 Ma). Like studies of Re-Os isotopes in other LIPs, the increasing amount of crustal assimilation with distance from the plume stem can explain the variations in radiogenic Os.
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The Steens Formation is one of the earliest and most primitive (>7 wt. MgO) eruptive products of the Columbia River Basalt Group (CRBG) and the CRBG-Yellowstone-Snake River large igneous province. New major-, trace-, and highly siderophile-element abundance and ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd and ¹⁸⁷Os/¹⁸⁸Os data are reported for the lower and upper Steens Formation to examine likely mantle sources and the nature of magmatic differentiation and crustal contamination acting on lavas. Examined Steens Formation basalts are relatively mafic (7–9 wt% MgO), incompatible trace element enriched, and have weaker Nb and Ta anomalies compared to other CRBG lavas. The most primitive basalts have isotopic compositions at the time of crystallization consistent with originating from a mantle source that was relatively depleted (⁸⁷Sr/⁸⁶Sr = ~0.7033; εNdi = ~ + 6.5; γOsi = ~ + 1). Primary magma compositions for the Steens Formation do not provide compelling evidence for a subducted slab component, instead suggesting derivation from primitive mantle sources more similar to those of other Mesozoic continental flood basalts (CFB; e.g., Deccan, North Atlantic Igneous Province). Onset of sulfide saturation in the CRBG occurs at lower MgO (<7 wt%) than in other CFB (~ 8 wt%) leading to the high Os contents in Steens Formation basalts. Collectively, the Steens Formation exhibits decreasing Os contents, εNdi values and increasing ¹⁸⁷Os/¹⁸⁸Os with decreasing MgO. These geochemical signatures are consistent with increasing crustal contamination to parent melts with time, a feature that is also shared for the CRBG as a whole. Calculations based on Os and Nd isotopes of likely mantle and crust components to different formations of the CRBG indicates a progressive increase in the quantities of crust from ~1 to 2% from Steens Formation magmatism to more than 6% during Grande Ronde and Wanapum eruptions. These results would indicate increasing crustal contamination and enhanced potential cryptic degassing of CO2 in the later, more voluminous stages of CRBG magmatism, after ~16.5 Ma. Unless mantle-derived melts can produce sufficient greenhouse gas emission, there is likely an offset between the inception of the mid-Miocene Climatic Optimum at 17 Ma and maximum CO2 release, indicating that CRBG eruption was a contributing factor to climate change at that time, but not the trigger for it.
Article
Geochemical data (major and minor oxides, trace elements including REE, and Sr, Nd, Pb, and O isotopes) have been obtained on a number of flow sequences and plutonic and volcanic complexes of the DVP by numerous groups since the early 1970’s. Evaluation of these data has led to the classification of the basalts and other rock types, inferences on their mantle sources, parental magmas and the numerous magmatic differentiation and crustal contamination processes that have caused the observed diversity. The DVP is predominantly composed of quartz- and hypersthenenormative tholeiitic basalts in the plateau regions (Western Ghats and adjoining central and eastern parts (Malwa and Mandla)). However, along the ENE-WSW-trending Narmada-Tapi rift zones, the N-S to NNW-SSE-trending Western coastal tract, the Cambay rift zone, and the Saurashtra peninsula and Kutch regions, the DVP shows considerable diversity in terms of structures, presence of dyke swarms and dyke clusters, and intrusive and extrusive centres with diverse rock types.Based on the geochemical and isotopic variations observed in the twelve different formations of basalts from the Western Ghats, it has been established that the least contaminated basalts among the Deccan Basalt Group lavas are represented by the Ambenali Formation of the Wai sub-group (c. 500 m thick), with εNd(t) = +8 to + 2, (87Sr/86Sr)t = 0.7040–0.7044 and (206Pb/204Pb)0 = 18.0 ± 0.5, average Ba/Zr = 0.3, and Zr/Nb = 14.4, indicating a depleted T-MORB-like mantle source. Slight enrichment in (87Sr/86Sr)t ratios (0.705), and εNd(t) = (+5 to −5) and depletion in (206Pb/204Pb)0 = 18.5–17.0 and δ18O = +6.2 to +8.3 ‰ as observed in the Mahabaleshwar Formation, that overlies the Ambenali Formation, indicate an enriched or metasomatised lithospheric mantle source. Such uncontaminated magmas appear to have been variably contaminated by a variety of crustal rocks (gneisses, shales, schists, amphibolites and granulites) as indicated in the εNd(t) vs. (87Sr/86Sr)t plots of all other eight formations that underlie these two formations. The flows of the Bushe Formation from the Western Ghats and one dyke from the Tapi rift zone represent the most crustally contaminated rock types with εNd(t) = −10 to −20.2 and (87Sr/86Sr)t = 0.713–0.72315 and very high (208Pb/204Pb)0 = 41.4, (207Pb/204Pb)0 = 16.03 and (206Pb/204Pb)0 = 20.93. Combined Sr-Nd-Pb, TiO2, MgO, Zr/Y and primitive mantle — normalised plots of basalts from flow sequences that are far away (c. 400–700 km) from the Western Ghats (e.g. Toranmal, Mhow, Chikaldara, Jabalpur and others) indicate their chemical similarity to those of the Western Ghats, especially Poladpur and Ambenali formations, except for some differences in the Pb-isotope ratios. Such features suggest either lithological continuity of flows over long distances from a single eruptive source or their coeval eruption from multiple sources providing basalts of analogous geochemistry. The DVP provides a plethora of crustal contamination processes such as assimilation and quasi- equilibrium crystallization (AEC) in the MgO-rich samples of the Western Ghats (e.g. Bushe) during emplacement or ascent, and assimilation- fractionation crystallisation (AFC-type) in intrusive and/or volcanic complexes (e.g., Phenai Mata, Pavagadh, Mumbai Island) in crustal magma chambers of the refilled, tapped and fractionated (RTF)- type. Operation of such RTF-magma chamber processes within the Mahabaleshwar sequence (c. 1200 m) indicates the complexities introduced in the magmatic process and hence in geochemical interpretations of such thick flow sequences.High- and low-pressure experimental petrological studies have led to petrogenetic models which indicate the production of primary melts of picritic compositions (c. 16% MgO), by 15–30% melting of an Fe-rich lherzolitic source at c. 2–3 GPa (c. 60–100 km depths). These melts evolved through olivine-fractionation near the Moho and then gabbroic fractionation within the shallow-intermediate crust (c. 6 km below the surface under c. 2 kb pressure) to produce the most dominant quartz- and hypersthene-normative tholeiitic basalts. In some rare cases (e.g., borehole sequence of Saurashtra, Pavagadh and others), the primary picritic liquids that formed at mantle depths, and the spinel-peridotie mantle-nodule- hosting melanephelinites from Kutch, have erupted without much modification. They occur spatially in close proximity to deep faults or rifts (e.g Narmada, Cambay, Kutch and others) which have apparently facilitated their rapid ascent and eruption without significant pause or modification during transport. εNd(t) vs. (87Sr/86Sr)t, chondrite- and primitive-mantle normalized variations in the picritic rocks and basalts of the DVP indicate several types of mantle sources such as transitional-midocean-ridge basalt (T-MORB), Ocean Island basalt (OIB)/Reunion- type of peridotitic compositions either metasomatised or normal.Geodynamic and plate-tectonic considerations during the emplacement of the DVP envisage both an asthenospheric- plume source (Reunion) and continental rift-related volcanism with eclogitic sources. The role of dual sources, capable of producing large volumes of basalts through near-total melting seem to provide the answer to DVP’s enigma of production of large volumes of lava in very short time as observed in the Western Ghats and the contiguous plateau, and also the extreme diversity in rock types found in the western parts from peridotitic-sources.Age data based on Ar-Ar, U-Pb, Re-Os isotopes, constrained by paleomagnetic data for the whole of DVP conforming to C30N-C29R-29N, indicate a protracted period of volcanism from 69.5 Ma (Upper Cretaceous) to 62 Ma (Palaeocene) including polychronous complexes (e.g. Mundwara, Sarnu-Dandali, Rajasthan). Based on precise U-Pb age data on zircons, it has been shown that the whole sequence of the Western Ghats with ten formations (c.1.8 km thick) erupted over a short period of time (< 1 Ma). The most dominant volcanic phase, however, represented by the Wai Subgroup, consisting of the Poladpur, Ambenali and Mahabaleshwar formations (c. 1.1 km thick) contain an estimated volume of c. 439,000 km3 of lavas that erupted over a short span of c. 700, 000 years. The precise timing of such large eruptions with reference to the Cretaceous-Palaeogene (K-Pg) boundary with or without links to the Chicxulub meteorite impact are being debated vigorously. In addition, the quantity of gases released (Cl, F, CO2, SO2 and others) during such large eruptions of the DVP and their influence on the mass extinctions of biota including the dinosaurs appear to be closely linked.Economic aspects of the DVP include deposits of hydrothermal fluorite and REE, Y, Nb, Ba and Sr mineralisatiom (e.g. Amba Dongar) and REE (e.g. Kamthai). Residual laterite and bauxite and fertile soils (e.g., Maharashtra, Madhya Pradesh and Gujarat) support the Al- industry and a robust agrarian sector. The DVP has also been a rich source for building materials. Indications for possible resources of native copper, PGE’s and micro-diamonds have also been indicated.
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There are disparate views about the origin of global rift- or plume-related carbonatites. The Amba Dongar carbonatite complex, Gujarat, India, which intruded into the basalts of the Deccan Large Igneous Province (LIP), is a typical example. On basis of new comprehensive major and trace element and Sr-Nd-Pb isotope data, we propose that low-degree primary carbonated melts from off-center of the Deccan−Réunion mantle plume migrate upwards and metasomatise part of the subcontinental lithospheric mantle (SCLM). Low-degree partial melting (∼2%) of this metasomatized SCLM source generates a parental carbonated silicate magma, which becomes contaminated with the local Archean basement during its ascent. Calcite globules in a nephelinite from Amba Dongar provide evidence that the carbonatites originated by liquid immiscibility from a parental carbonated silicate magma. Liquid immiscibility at crustal depths produces two chemically distinct, but isotopically similar magmas: the carbonatites (20% by volume) and nephelinites (80% by volume). Owing to their low heat capacity, the carbonatite melts solidified as thin carbonate veins at crustal depths. Secondary melting of these carbonate-rich veins during subsequent rifting generated the carbonatites and ferrocarbonatites now exposed at Amba Dongar. Carbonatites, if formed by liquid immiscibility from carbonated silicate magmas, can inherit a wide range of isotopic signatures that result from crustal contamination of their parental carbonated silicate magmas. In rift or plume-related settings, they can therefore display a much larger range of isotope signatures than their original asthenosphere or mantle plume source.