Rocks of the Lesser Himalayan Sequence are important from a global tectonic perspective as they represent a crucial evolutionary chronicle of the Indian continent from the Paleoproterozoic to the Cenozoic Himalayan orogeny. Eroded remnants of tectonically transported crystalline thrust sheets overlying the Lesser Himalayan metasedimentary zone along the Main Central thrust are represented by the Almora, Baijnath, Askot, and Chiplakot klippen belts in the Kumaun Himalaya, India. In this work, we present the deformation history, geochemistry, and U-Pb zircon-apatite geochronology of the Baijnath klippe rocks and its footwall. Our age and tectonic setting results for the klippe rocks help to illustrate the continental accretion processes that prevailed during Paleoproterozoic-Neoproterozoic time along the northern Indian cratonic margin. Granitoids within the Baijnath klippen yield crystallization ages varying from ca. 1870 Ma to ca. 1850 Ma, while the supra- crustal sequence preserves a prominent age signature of ca. 1855 Ma. The metasediments of the Berinag Formation at the klippe foot- wall yield a detrital age of ca. 1810 Ma. Based on these results and the geochemistry, we infer that the Baijnath klippe rocks bear an affinity with the inner Lesser Himalayan Sequence, and the granitoid magmatism took place within a span of X 20 m.y. (1870-1850 Ma) in an arc setting linked to active subduction along the north Indian continental margin, possibly due to the formation of the Columbia supercontinent during the Paleoproterozoic. Textural and mineralogical data from the amphibolite-facies supracrustals of the Baijnath klippe suggest that the progressive metamorphism (M1) reached peak at X 580 degrees C and X 8.6 kbar followed by a decompression-dominated retrogression (M1R) down to X 450 degrees C and X 5.8 kbar, possibly through a clockwise pressure-temperature (P-T ) trajectory that was overprinted by the Cenozoic reworking (M2 metamorphism?) and deformation (D2) related to the Himalayan orogeny. Texturally constrained apatite grains from M1 metamorphic domains preserve traces of a Neoproterozoic-age tectonothermal imprint that affected the Lesser Himalayan Sequence rocks, possibly during the assembly of the Gondwana supercontinent.

Two contrasting Precambrian sources has been established for the Mesozoic sediments of the Dhrangdhara Group at the western margin of India based on the integration of petrography of sandstone, mineral chemistry of tourmaline and rutile, and U-Pb zircon and U-Th-total Pb monazite dating. The geochemical characteristics of rutile and tourmaline indicate sediment supply from metapelites, granites, pegmatite, quartz vein and tourmalinites. The potential source terrains for these stratigraphic zones are comprehended on the basis of the overlap of probability density of zircon and monazite ages. Zircon trace elements and REE concentrations suggest its derivation from granitoids. U-Pb zircon age data reveals four major populations at 3584-2502 Ma (Archean), 2499-1642 Ma (Paleoproterozoic), 1595-1010 Ma (Mesoproterozoic) and 993-539 Ma (Neoproterozoic). In contrast, U-Th-total Pb monazite age data show major age populations at 900-700 Ma and 500 Ma. The mineral chemistry signatures and zircon-monazite age data indicate predominant sediment derivation from metasedimentary rocks of the Aravalli and Delhi supergroup of rocks, with limited input from Archean gneissic (e.g., Mewar Gneisses and equivalents) and granitic (e.g., Berach Granite and equivalents) rocks. Besides, the predominance of zircon and tourmaline grains with high textural maturity supports significant input from sedimentary and metasedimentary rocks from the Aravalli Delhi Fold Belt (ADFB) and Marwar Supergroup. The detrital zircon and monazite age distributions are consistent with the major Precambrian supercontinent assemblies and corresponding orogenies. The Archean age (2.6-2.5 Ga) components correspond to the Bhilwara Orogeny of the ADFB, 1.8-1.7 Ga and 1.0-0.9 Ga correspond to the tectonothermal events associated with the assembly of Columbia and Rodinia supercontinents, respectively. The Neoproterozoic younger age -0.75 and -0.65-0.50 Ga corresponds to the breakup of the Rodinia supercontinent and the assembly of the Gondwana supercontinent, respectively. The mineral chemical and geochronological data track major global and local orogenies recorded within the ADFB. Therefore, the sedimentary succession of the Saurashtra Basin preserves the records of paleo-drainage pattern and paleogeography of the northwestern margin of eastern Gondwanaland, which is a repository of the sediments derived from the Aravalli-Delhi fold belt and Pan-African orogenies.

This study deals with petrology, textural, thermometry, and geochemical characterization of naturally magnetized Cr-V-Ti magnetite deposits within the layered mafic-ultramafic intrusions in Coorg massif of southern India using ore petrography and mineral/whole rock geochemistry. These deposits, also known as 'lodestones', occur as rhythmic layers within the lateritized host rock, with the underlying basement distinguished by the presence of charnockites and layered gabbro-anorthosites and pyroxenites, delineating a stratified intrusive setting. Lodestones exhibit complex mineral assemblage involving magnetite, ilmenite, ulv & ouml;spinel, spinel, corundum, hematite, goethite, pyrite, pyrrhotite, and amphiboles. The bulk rock chemistry of the lodestone is analogues to Fe-Ti magnetite iron ore deposits with elevated vanadium and chromium contents. Their resemblance to tholeiitic magma-type suggests their formation in a layered intrusive setting, evolved through multiple fractional crystallization under oxidizing conditions. Thermometric and fugacity calculations using different textural associations estimate the magmatic fractional crystallization stage at elevated temperatures (601-704 degrees C) and low fO(2) (-18.6 to -15.3), succeeded by the exsolution stage during subsolidus cooling at lower temperatures (379-540 degrees C) and high fO(2) (-38.2 to -22.1). The whole sequence of formation and evolution of lodestone encompasses primary magmatic crystallization, subsolidus re-equilibration, metamorphism, and secondary weathering. The study also suggests a genetic linkage of lodestone with the associated mafic-ultramafic units, depicting two possible magmatic processes either through slab melting and fractional crystallization associated with subduction or due to plume magmatism and associated rifting.

The Precambrian Southern Granulite terrane of south India has a crustal evolution history broadly bracketed between the late Archean and Cambrian with records of polyphase deformation, metamorphism, and magmatism. The Southern Granulite terrane comprises distinct crustal blocks bounded by shear/suture zones that have been variably correlated with supercontinent fragments including Madagascar, Sri Lanka, Africa, Eastern Ghats, and Antarctica. However, the timing and mechanism of assembly of different crustal blocks within the Southern Granulite terrane and its linkages with counterparts in East Gondwana are highly debated. This study aimed to unravel the complex crustal evolutionary pattern of the terrane by generating robust zircon U-Pb/Hf isotopic data from basement charnockites, gneisses, granitoids, and alkaline intrusive units from the central part of Southern Granulite terrane and comparing these results with similar data from different East Gondwanan terranes. The study identified four distinct crustal growth episodes in the Madurai block: (1) Neoarchean−early Paleoproterozoic, (2) Rhyacian−Orosirian, (3) late Tonian, and (4) Ediacaran−Cambrian. Analysis of zircon Hf isotope data revealed that the first two events are marked by juvenile magmatic signatures, whereas the latter two are distinctly associated with intense reworking and remelting of older crust with no significant juvenile input. Our new results combined with existing data from other Gondwanan terranes suggest a common Paleoproterozoic ancestry for the Southern Granulite terrane and its corresponding Gondwanan fragments, proposing a revision to the existing geodynamic models.

Accurate estimation of Moho topography plays a crucial role in understanding Earth’s structure, geodynamic processes, and resource exploration. This study presents a novel approach that utilizes conditional Generative Adversarial Networks (cGAN) to reveal Moho topography based on observed gravity anomalies. Synthetic training datasets of Moho topography were generated using the FFT filtering method due to the scarcity of true datasets. Spherical prism-based forward gravity modeling was employed to evaluate the resulting gravity anomalies. We compared the performance of our developed deep learning algorithm cGAN (conditional Generative Adversarial Networks) with a traditional inversion technique using various synthetic datasets, and a real case study in southern peninsular India, a geologically diverse region comprising ancient continental tectonic blocks. Bott’s inversion scheme was employed as a verification method for the Moho surface estimation using the presented deep learning model. Using spherical prism-based forward gravity modeling, observed gravity anomalies were corrected for multiple factors such as topography, bathymetry, sediments, crustal heterogeneities, and mantle heterogeneities. By removing these effects, we isolated the gravity contribution solely related to pure Moho undulation. The mean Moho depth and density contrast between the crust and mantle were derived from seismic constraints for improving estimation accuracy. The findings demonstrate the potential of the cGAN and spherical prism-based gravity modeling approach in accurately estimating the Moho topography, offering insights into Earth’s subsurface structures and enhancing our understanding of geodynamic processes and resource exploration efforts.

Tectonic evolution of Southern Granulite Terrane (SGT) of south India and its relationship with adjacent continental fragments in the context of supercontinent assembly/dispersal models has been a topic of debate. This is primarily due to the lack of robust zircon U-Pb and Hf isotopic data from different crustal blocks in SGT and its correlation with other terranes. The present study attempts to address this issue by generating new zircon U-Pb and Hf isotopic data of quartzites from a key segment in SGT and link them with similar results from adjacent continental fragments. Our new zircon U-Pb data reveal five distinct age peaks at -2500 Ma, -2000-1900 Ma, -1100-1000 Ma, -800-700 Ma and -550 Ma recorded in the samples. Hf isotopic composition of these zircons demonstrates distinct crustal growth and/or recycling episodes with juvenile magmatic addition restricted up to -1900 Ma, followed by large-scale crustal recycling episodes. The close resemblance of these detrital ages and their Hf isotopic signatures with adjacent terranes such as Madagascar, Sri Lanka, Africa, Eastern Ghats, and Antarctica point to a similar evolutionary history, suggesting a pre-Gondwanan ancestry for the assembly of these terranes.

Here, we report petrography, whole-rock geochemistry, and zircon U-Pb geochronology to understand the origin, source, geodynamic setting, and evolution of A-type granite and granite gneiss as well as establish their emplacement age from Mahakoshal Basin. Mineralogically, Sidhi granite gneiss and Madanmahal granite of the Mahakoshal Basin dominantly consist of quartz, K-feldspar, and plagioclase. Geochemically, Sidhi granite gneiss and Madanmahal granite are ferroan in nature. The studied rocks are akin to peraluminous A-type granites and have average zircon saturation temperatures of 955 degrees C and 977 degrees C, respectively. The studied rock types are derived from partial melting of pre-existing crust indicated by (Y/Nb)(N) >0.18, (Th/Nb)(N) >2, (Ce/Pb)(N) <1, and (La/Nb)(N) >2 accompanied by the Eu, Ba, Sr, Ti, and Nb negative anomalies. The zircon U-Pb geochronology yielded emplacement ages of 1723 +/- 16 Ma for the Sidhi granite gneiss and 1801 +/- 64 Ma for the Madanmahal granite. Based on similar geochemical characteristics such as rare earth element patterns, Eu anomalies, and Ce/Pb, La/Nb, and Th/Nb ratios, we propose that the Sidhi granite gneiss and Madanmahal granite are derived from the same source i.e. Bundelkhand gneisses and granites, and formed in a post-orogenic rift environment of the accretionary orogen setting.

The sedimentary rocks exposed in the peripheral foreland basin of a deforming orogen conserve the history of the geologic process, paleo-drainage and erosion. We present a new drainage scenario for the Late Miocene-Pliocene (Tipam Formation) and Pliocene-Pleistocene (Dupi Tila-Dihing Formation) fluvial deposits in the Assam-Arakan-Bengal Basin, based on 1869 detrital zircon U-Pb age distribution from Assam-Arakan Basin and published ages from Bengal Basin. This work provides constraints on the temporal and spatial changes in the provenance and paleo-drainage evolution of the Brahmaputra River. The detrital ages give signatures for both Himalayan and Trans-Himalayan sources. Early Paleozoic ages ca. 500 Ma population in the samples manifest Tethys Himalayan and Lhasa Terrane as the source. In comparison, U-Pb ages <300 Ma population convey source from Gangdese/Bomi-Chayu batholith and Lohit Plutonic Complex. Morphometric analysis of the source regions informs the existence of the YigongParlung-Lohit river system before the reversal of the Parlung flow direction. We suggest that during the Early Miocene, the Yigong-Parlung-Lohit and Yarlung-Siang rivers define the paleo-Brahmaputra River system rather than the lone Yarlung-Siang proposed by the earlier researchers. The YarlungSiang river joined the drainage of Yigong-Parlung-Lohit River system in the upper Assam plains. The fault-related surface uplift in the foreland zone of Indo-Burman Ranges (IBR) caused drainage disruption of Yarlung-Siang from the Yigong-Parlung-Lohit. The Parlung-Lohit disruption caused a reduction in the capacity of the eastern flowing drainage to sustain its original course. The upper Assam shelf uplift and IBR westward progression caused northward deflection of the drainage and meeting with the YarlungSiang-Brahmaputra drainage, flowing north of the Shillong Plateau. Based on our new Apatite Fission Track (AFT) and published ages, we argue that the Shillong Plateau uplift during the Middle to Late Miocene did not influence paleo-Brahmaputra diversion. (c) 2024 International Association for Gondwana Research. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The Precambrian Southern Granulite Terrane of south India figures prominently in the East African collisional orogen, linked to the assembly of the East Gondwana supercontinent along with Sri Lanka, Madagascar, Antarctica, and Africa. While the timing of this collision and associated magmatic-metamorphic processes are well constrained, the mechanisms governing the cooling and exhumation of these terranes remain uncertain. This study focuses on U-Pb rutile ages derived from granulites in the Southern Granulite Terrane and attempts to extract the cooling history of the terrane. Our new U-Pb rutile ages cluster between 422 to 458 Ma, postdating regional metamorphism and indicating an extended cooling period of similar to 35 Ma whereas trace element signatures suggest their formation during granulite facies metamorphism with temperatures reaching up to ultrahightemperature conditions. Calculated cooling rates using these rutile U-Pb ages range between 2-6 degrees C/Ma similar to the cooling rate of <= 7 degrees C/Ma from other East Gondwanan terranes. Based on these results it is proposed that the coeval exhumation of these terranes was assisted by surface erosion after the final assembly of the East Gondwana supercontinent.

Strongly peraluminous (SP) leucogranite typical of Himalayan-type collision orogen is reported from Kottayam, the western Madurai block, Southern Granulite Terrane (SGT). Low concentration of mafics (average ≈ 5

Supplemental File S1: Zircon U-Pb, trace-element, and Hf isotope data of samples and standards. Supplemental File S2: Data sources for Figure 8.

The Madurai block, the largest crustal block in the Precambrian Southern Granulite Terrane of south India, preserves rare assemblages of high- to ultrahigh-temperature metamorphic rocks. These rocks bear exclusive evidence for the high thermal regime prevalent during their formation and can be constrained from accessory phases such as zircon, monazite and garnet. Here, we present the P-T-t evolutionary history of garnet-cordierite-spinel granulites from different localities in the Madurai block. Combined petrography, mineral reaction, geothermobarometry and pseudosection modelling of the samples record HT to near-UHT metamorphic conditions with clockwise P-T trajectories. LA-(MC)-ICPMS U-Pb/Hf isotopic studies on zircons point to Paleoproterozoic high-grade metamorphism in the area with juvenile magmatic signatures. LA-ICPMS/EPMA monazite dating constrains the timing of HT to near-UHT metamorphism at ~580 and ~550 Ma. The heat source required for the Paleoproterozoic high-T event is correlated with the synchronous igneous emplacements reported in the region, whereas the heat source responsible for the Neoproterozoic HT to near-UHT event can be related to the processes associated with crustal thickening and synchronous mafic emplacement. The clockwise P-T trajectories of these granulites are interpreted as the signature of collisional orogeny prevalent in the region during the final stages of Gondwana assembly.

Massif type charnockite was emplaced in the lower crust of the Eastern Ghats Province and is now exposed over a large geographic area. The rock shows clear evidence of magmatic emplacement in lower crustal metasedi-mentary rocks, which occur as enclaves within the charnockite. Textural data suggest the magma underwent subsolidus cooling and subsequently metamorphosed to granulite facies (up to similar to 910 degrees C, 9 kbar). Geochemical data show that the charnockite magma had variable chemistry which was acquired by differentiation and possible crustal contamination. The rock shows both high-and low-SiO2 types, with weakly peraluminous to metaluminous characters. Trace and REE fractionation trends suggest the magma had calcic to calc-alkaline affinities and was emplaced in a continental arc type collisional setting. Theoretical modelling suggests that such a magma could be generated by melting of a hydrated basaltic slab under CO2-rich fluid. U-Pb analysis on oscillatory zoned zircon domains from eight samples yields crystallization ages for the magma. While the ma-jority of the samples show crystallization ages within ca. 980-940 Ma (978 +/- 16 Ma, 968 +/- 22 Ma, 951 +/- 9 Ma, 954 +/- 8 Ma, 951 +/- 13 Ma and 939 +/- 27 Ma), two samples yield crystallization ages of 1002 +/- 13 Ma and 1020 +/- 16 Ma. This implies two-phase emplacement of the charnockite magma which can be correlated with the tectonometamorphic evolution of the province. While the earlier pulse of charnockite magmatism is broadly synchronous with the first cycle (M1) of metamorphism, the later pulse followed when the lower crust was still hot. The two pulses of charnockite magmatism are broadly synchronous with those of the Mawson charnockite of the Rayner Province, East Antarctica. It is argued that the charnockite magmatism in the combined Rayner-Eastern Ghats Province was extensive and resulted from arc-continent accretion and collision between the India and East Antarctica during ca. 1030-900 Ma.

Petrology, geothermobarometry, and phase equilibrium modelling of garnetiferous felsic gneiss from Grovnes peninsula in the Larsemann Hills of Prydz Bay, East Antarctica provide pristine evidence for the preservation of high-grade metamorphic imprint in the area. The metamorphic evolution of the sample is demonstrated by the development of the assemblage Grt+Bt+Melt+Pl+Sill+Kfs+Qtz+Ilm at peak metamorphic conditions of-790 degrees C and-7.5 kbar, which subsequently underwent retrogression and cooling to lower P-T conditions along a clockwise path. Texturally constrained chemical dating of monazites constrain the timing of peak metamorphism and garnet formation at-575 Ma, whereas the apatite U-Pb ages constrain cooling ages at-518 Ma. The clockwise P-T-t trajectory of the studied samples, together with the Ediacaran-Cambrian metamorphic/cooling ages demonstrate the long-lived nature of metamorphism in Prydz Bay, which is ascribed to collisional tectonism prevalent during the final stages of the assembly of East Gondwana supercontinent. Similar results from adjacent continental fragments including Sri Lanka, Eastern Ghats Belt, Madagascar, and South India suggest their coeval metamorphic evolution during the East African orogeny.

The Nagercoil block, which is situated at the southernmost part of the Southern Granulite Terrane of south India, is dominantly comprised of garnet-bearing I-type massive charnockites. These charnockites preserve imprints of two major thermal events timed at Palaeoproterozoic (∼2.0–1.9 Ga) and Neoproterozoic (∼550 Ma). However, there is a lack of understanding on correlating the growth and stabilization of garnets within these charnockites, corresponding to these events. In the present study, rare earth element-based partition modeling between garnet and age-constrained accessory phases such as zircon and monazite is carried out to identify the exact timing of garnet formation in a representative sample from the area. U-Pb dating of zircon cores constrains the timing of protolith emplacement at ∼2.0 Ga and metamorphism at ∼550 Ma from zircon rims and monazites. REE modeling of zircon and monazite from these age domains suggests an equilibrium relation between the Neoproterozoic zircon rims and monazites, while the Palaeoproterozoic zircon cores are not in equilibrium with garnet. These results suggest that the formation of garnets in the Nagercoil charnockites is in response to the Neoproterozoic metamorphism recorded in the terrane associated with the final stage of the Gondwana supercontinent assembly.

The Mesoproterozoic Cuddapah Basin consists of four unconformity-bound sequences, i.e., Papaghni Group, Chitravati Group, Srisailam Formation and Kurnool Group. A fair amount of geochronological and geochemical data is available from the basal Papaghni Group and Chitravati Group as well as the overthrusted Nallamalai Group. Due to limited geochronological and geochemical constraints, the Srisailam Formation, however, remains a subject of speculation regarding the time of sediment deposition, sediment source locations, and tectonic setting. In this work, we present new geochronological and geochemical data (zircon U-Pb) from samples of the Srisailam Formation. The new data suggest that the Srisailam Formation correlates temporally with the basal Chitravati Group and is largely disparate from the allochthonous Nallamalai Group. The sediments of the Sri-sailam Formation contain a minor yet significant number of Palaeo-Mesoarchaean detrital zircon with traces of Haedean zircon. Based on our detrital zircon data, we argue that the sedimentation in the Srisailam sub-basin initiated after ca. 1840 Ma and continued till <= ca. 1770 Ma and the sediments were mainly sourced from Neoarchaean to Paleoproterozoic terrains including the Dharwar Craton, and sedimentation was initiated in a rift basin that subsequently evolved to a passive margin setting.

AbstractThe Precambrian Southern Granulite Terrane (SGT) of south India is well-known for the preservation of high- to ultrahigh-temperature (HT-UHT) granulites, prominently exposed in its central part forming a linear belt referred to as the Kambam UHT belt. This belt also hosts widespread occurrences of mafic granulites that are observed in close spatial association with the HT-UHT granulites. This study presents detailed petrology, geochemistry and geochronology of representative mafic granulites from the area to understand their petrogenesis and tectonic setting. The results demonstrate that mafic granulites are low- to medium-K tholeiites, with continental arc affinity, formed by the partial melting of a subduction-modified enriched mantle source. The composition of the parent mantle source is modelled with a spinel/garnet lherzolite contribution ratio between 100/0 and 70/30, suggesting the mixing of spinel and garnet bearing melts during asthenosphere upwelling. Zircon U–Pb geochronology of mafic granulites constrains their emplacement between 612 Ma and 625 Ma, that subsequently underwent metamorphism between 581 Ma and 531 Ma. This overlaps with the timing of HT-UHT metamorphism in the Kambam UHT belt bracketed between 593 and 532 Ma. Zircon Hf isotopic studies reveal parent magma generation from reworked melting sources involving Archean and Proterozoic components. These results propose an alternative heat source for the formation of HT-UHT granulites in the Kambam UHT belt which can be designated as a major terrane boundary within the SGT.

The Precambrian granulite terrane of south India is known for the preservation of regional-scale high to ultrahigh-temperature (HT-UHT) metamorphic rocks. In the Madurai block, the largest crustal block in the terrane, a significant proportion of these HT-UHT rocks occur along a narrow belt referred to as the Kambam ultrahigh-temperature belt. Understanding the P-T-t evolution of these HT-UHT granulites is vital in decoding the spatial and temporal evolution of the Madurai block in relation to other crustal blocks. Here we present the petrology, mineral chemistry, phase equilibrium modelling, and accessory mineral (zircon, monazite, rutile and apatite) geochronological and geochemical data for a hitherto unreported sapphirine granulite from the Kambam ultrahigh-temperature belt. Combined mineral reaction and phase equilibrium modelling indicate extreme P-T conditions up to 1130 degrees C at 11 kbar. The geometry of the P-T path is clockwise with initial isothermal decompression followed by near isobaric cooling. LA-ICPMS U-Pb geochronological studies on accessory phases report two distinct thermal events: (i) Paleoproterozoic high-T event and associated crustal anatexis at similar to 2.5 Ga from zircons and (ii) Neoproterozoic UHT event at similar to 550 Ma from monazites. The monazite ages suggest a 50-60 Ma prolonged thermal event, attributed to Ediacaran-Cambrian collisional orogenesis. Additional metamorphic pulses are also identified, demonstrating the polydeformed crustal evolution history of the terrane. U-Pb age dating of rutile and apatite in the sample provide ages of similar to 458 Ma and similar to 392 Ma and cooling rates of similar to 6 degrees C/Ma and similar to 0.3-2 degrees C/Ma respectively. This suggests a complex history of slow cooling followed by ultraslow cooling. The results bring forth the significance of the Kambam ultrahigh-temperature belt in understanding the tectonothermal evolution of Madurai block and provide additional evidence for long-lived Neoproterozoic UHT orogenesis in south India.