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The clay mineralogy and major and trace element geochemistry of the sediments deposited at the lower reaches of 90 medium and minor rivers from five states along the west coast of India indicate distinct clay mineral assemblages in the Archean–Proterozoic (A-P) terrain and Deccan Trap (DT) terrain. The sediments from A-P terrain are dominated by kaolinite, with minor illite and gibbsite and traces of goethite, and those from DT terrain are dominated by smectite with minor illite, kaolinite and chlorite. The sediments are depleted of Si, Ca, Mg, Na and K relative to those of Post-Archean average Australian Shale. The SiO2/Al2O3 ratio of the sediments suggests lateritic soils in the A-P terrain and non-lateritic, chemically weathered soils in the DT terrain. Weathering indices indicate strong weathering in the clay fractions of all sediments. The silt fractions of sediments from Goa, Maharashtra and Gujarat exhibit intermediate to weak weathering and influence by hydraulic sorting processes and source rock characteristics. The total trace element content (∑TE) was higher in the silt fractions than in clay fractions of all sediments, and peaks of high ∑TE occur in the silt fractions of Kerala and Maharashtra. The silt fractions exhibit relatively high Th, U, La, Zr and Hf from A-P terrain, and high Sc, Cr, Co, Ni, V and Ga from DT terrain. The Th/U and Rb/Sr ratios are controlled by the intensity of weathering and lithology of source rocks. The standard plots using trace elements reveal that the clay fractions of sediments are more mafic from both the terrains, while silt fractions exhibit intermediate provenance between felsic and mafic sources. Since mafic component-dominated clays are transported to the adjacent seas and oceans, it would be a challenge to identify the provenance of clays from granitic terrain in the oceans using trace element chemistry. [ABSTRACT FROM AUTHOR]

Landslides are global hazards and occur instantaneously with large destructions in terms of life and property. The present work is a case study of a large debris flow triggered by an intense rainfall event at Irshalwadi village on 19 July 2023 in Raigad district, Maharashtra, Western Ghats, India. The objective of this research is to study the large landslide using UAV data to get details information of the case of landslide trigger and geological information of Landslide. The rationale for this research is to enhance the understanding of landslide dynamics in basaltic terrain, which is essential for disaster preparedness and mitigation. UAV survey was performed using structure from motion (SFM) photogrammetry to generate high resolution orthomosaic images and digital elevation model (DEM) which were processed in a GIS environment. The methodology involved conducting a detailed geological study using high-resolution optical images (5 cm) from the UAV survey, along with field sampling and petrographic analysis of the sampled landslide material. The crown of the Irshalwadi landslide was situated in contact with the weathered basalt and compact basalt. Our observations revealed that the cracks in the compact basalt facilitated the transfer of rainwater to weathered basalt, promoting slope failure conditions. Validation using filed survey showed that the lithology and petrographic properties were crucial in landslide initiation. This study shows that UAV-based remote sensing in combination with petrographic analyses allows us to map and characterize the landslides with accurate dimensions, which is useful in analyzing the parameters that trigger landslides and this will help in the preparedness and mitigation of extensive landslide disasters globally in basaltic terrain. [ABSTRACT FROM AUTHOR]

High-velocity lower crust (HVLC) near the continent–ocean transition zone is significant for recording magmatic activity and early rifting history and is likely to be sourced from various types of magma supplies, including passive decompression melting, hot mantle plume, active small-scale mantle convection, and fertile source mantle. In the northern margin of the South China Sea (composed of the Dongsha Passive margin to the west and the SW Taiwan active margin to the east), a large amount of geophysical data, including refraction seismic data, enable us to prepare a map of the thickness distribution of the HVLC and estimate its volume. After revisiting published data, the volume of the HVLC in the northern margin of the South China Sea is found to be comparable but slightly less than that in continental large igneous provinces such as the Deccan Trap of west-central India or oceanic plateaus such as the Shatsky Rise in the northwest Pacific Ocean, probably indicating that they may have similar active source origins. Based on a more feature-based analysis (h–vp diagram; a scatter plot showing mean velocity of lower crust versus corresponding crustal thickness) to identify the source of the underplating material in a magma-involved margin, we tentatively suggest that the HVLC along the Dongsha passive margin showing no h–vp correlation is most likely dominated by small-scale mantle convection of the Peikang–Dongsha mantle convection cell, and the HVLC along the SW Taiwan active margin showing a negative h–vp correlation is more likely to be dominated by the pre-existing distal domain of the continental margin. We propose that rather than being dominated by a hot mantle plume, small-scale mantle convection may be more likely to be responsible for the opening of the South China Sea, and suggest that a more inclusive geodynamic model to reconcile geophysical and geochemical observations should be further investigated. [ABSTRACT FROM AUTHOR]

The Cretaceous–Paleogene (K‐Pg) boundary represents the extinction of ~70% of species, a prominent Chicxulub impact event and Deccan volcanism. This work reports the first attempt to extract the micrometeorites (MMs) from the Deccan intertrappean horizons. Eighty‐one spherical particles were studied for their morphological, textural, and chemical characteristics. Intact cosmic spherules with ferromagnesian silicates (6) and Fe‐Ni oxide (7) compositions correspond to MMs from the deep sea and Antarctica. Silicate and Fe‐Ni spherules in this study showcase remarkable preservation, a testament to the highly favorable conditions present. Fe spherules (38) with iron oxide compositions exhibit diagenetic alteration during preservation. Textural analysis of 30 Fe spherules reveals a dendritic, interlocking pattern and slightly elevated Mn content, suggesting these may be fossilized I‐type MMs. However, eight Fe spherules with blocky and cubical granular textures resemble oxidized pyrite spherules. Al‐Fe‐Si spherules (30) possess a significant enrichment of Al and Si within their Fe‐oxide‐dominated composition. Group‐I Al‐Fe‐Si spherules (15) display zoned Al‐Fe‐Si oxide composition, dendritic Mg‐Cr spinel grains, and aerodynamic features, all indicative of impact spherules. The finding of these impact spherules from sampled Deccan intertrappean layer raises the possibility that these paleosols were deposited during the Chicxulub impact event, the only identified impact event with global distribution during the Deccan volcanism time frame. This unique location provides an opportunity for the simultaneous collection of well‐preserved MMs, impact, and volcanic spherules. The exceptional preservation of the studied MMs is likely due to a combination of non‐marine environments, atypical climatic conditions, and rapid deposition. This study further investigates the potential role of cosmic dust flux in the K‐Pg extinction event. We propose that the enhanced cosmic dust flux, a likely scenario during the K‐Pg boundary period, synergistically mixing with impact dust in the upper atmosphere, may have intensified and extended the harsh climatic conditions at the K‐Pg boundary. Subsequently, the deposition of this dust, enriched in bioavailable iron, on Earth's surface might have contributed to the swift recovery of life and environmental conditions. [ABSTRACT FROM AUTHOR]

The heat transfer from the low latitudes to high latitudes is responsible for maintaining the earth's climate dynamics. Thus, deciphering the possible mechanism driving the variability of the Indian summer monsoon (ISM) during the Holocene Epoch has been critical to understand the hydroclimatic changes of the low latitudes. Despite several efforts, the teleconnection of ISM with the global climate dynamics remains under-represented and poorly understood. The present study aims to delineate the ISM variability and its possible forcing mechanism from western India (Gujarat). In this study, a sediment core (~65 cm long) was raised from the Jaffrabad mudflat (MIT) in western Gujarat. The sediment samples were subjected to geochemical analysis to investigate paleomonsoon, paleo-sediment source and paleoweathering changes. The results show that, with the addition of intermediate sources, the sediments were principally derived from the hinterland's Deccan basalts. Further, the study suggested a warm and wet climate due to strong ISM during 10,650−5500 cal yr BP associated with the solar as well as orbital forcings. The weak monsoon during 5500−2700 cal yr BP has been linked with southward migration of the Intertropical Convergence Zone (ITCZ) along with the increased El Niño-like conditions. Further, the wavelet analysis revealed that a combined influence of solar, orbital and North Atlantic forcings led to monsoon variability along western India, during the Holocene Epoch. By reconciling the geochemical proxies, the present study has implications in the reconstruction of paleomonsoon and establishing the possible teleconnection with the global climate system. [ABSTRACT FROM AUTHOR]

The present study records the earliest occurrence of a madtsoiid snake from the intertrappean sediments associated with the chronostratigraphically constrained lava piles of the oldest Deccan trap eruptions in India. The intertrappean sedimentary beds of the Malwa Group occur at multiple stratigraphic levels in the two lowermost formations between the lava flows that erupted during Maastrichtian C30n. The fossils described represent small-sized middle to posterior vertebrae assigned to Madtsoia. Preservation of these earliest late Cretaceous snakes in India has great significance due to their survival through the earliest Deccan volcanic eruptions. The overall faunal biodiversity of the Malwa Group is dominated by squamates and amphibians during the early stage of volcanism, indicating that volcanism has least affected the diversity of the snakes. [ABSTRACT FROM AUTHOR]

Indian fossil Squamata and Anura are known from the Upper Cretaceous-lower Paleocene Deccan Trap associated sediments for over last one century. However, current knowledge on their taxonomy and stratigraphic implications is poor for their scarce and fragmentary nature and lack of any stratigraphic constraints. We report newly found fossil Squamata and Anura from the new intertrappean locality Bharudpura in Malwa Plateau and describe (i) Scincomorpha (Scincoidea) lizards based on taxonomic study of dentary, maxilla and osteoderms, (ii) Anguimorpha (Anguidae) lizards based on osteoderms, (iii) Squamata indeterminate based on a vertebrae and (iv) Anura (Ranidae, Ranoidea and Anuran indeterminate) based on a ilium, a sacral vertebrae and single dentary. Currently, it is not possible to ascertain if the different fossil specimens belong to a single or more taxa. The lowermost lava pile of Mandleshwar and Kalisindh formations, associated with multiple intertrappean beds including the new Bharudpura fossil locality, have yielded40Ar/39Ar plateau ages from 66.834 Ma, the oldest Deccan Trap flow dated so far in India to 66.352 Ma. The present study records their earliest occurrence in India, from intertrappean associated with oldest Deccan Trap lava pile that erupted during magnetochron C30n of Maastrichtian in the Malwa Plateau. [ABSTRACT FROM AUTHOR]

The drainage basins of Peninsular India are characterized by silicate-dominated lithologies, and influenced by Indian Summer Monsoon (ISM) precipitation. The Godavari River Basin (GRB), the largest river basin in Peninsular India situated within the ISM region, represents an ideal case for assessing weathering and climate interaction at different timescales. In this contribution, major and trace elemental geochemistry of a radiocarbon-dated sediment core (CY; 54.2 m long) from the Godavari delta region was investigated to reconstruct erosional changes in the Godavari basin in response to ISM variations during the Late Holocene. Comparison of geochemical data for the CY sediments and their possible sources confirm dominant sediment supply from the Deccan basalts and Archean Gneisses to the site. A distinct increase in Ti/Al, Ca/Al, and Cr/Al, along with a decrease in CIA* and LREE/HREE at 3.2 ka BP, point to relative increase in sediment supply from the Deccan Traps. Inverse model calculations of Al-normalized ratios of selected elements (Ti, Fe, V, Cr, Cu, Co) estimate that the core site on average receives ∼41 % sediments from the Deccan regions, which increased by ∼20% since last 3.2 ka BP. This accelerated erosion is attributed to the coupled effect of aridity-induced Deccan upland erosion with a relative decrease from the Archean rock source. This period of accelerated erosion coincides with the abandonment of Chalcolithic settlements. [ABSTRACT FROM AUTHOR]

Tholeiitic basalts and picrites from the Deccan Traps were used to constrain the pressure and temperature conditions of mantle melting for their origin. Clinopyroxene thermobarometry indicates that all Deccan tholeiites crystallized at low pressures in the upper crust (< 6 kbar/1047–1221 °C). In comparison, the Deccan alkalic rocks crystallized at pressures up to ~ 12.7 kbar. Rare samples of the tholeiites plot on their low-pressure olivine-plagioclase-clinopyroxene (Ol-Pl-Cpx) cotectic boundaries or olivine control lines in phase diagrams. These samples represent unmodified magmatic liquids. Primary magmas of the basalts that plot on their cotectic boundaries were modeled through reverse fractionation by incrementally adding equilibrium Ol + Pl + Cpx, Ol + Pl and Ol ± spinel, until the liquid was multiply saturated with lherzolite at a high pressure. The high-Mg basalts are contaminated with continental crust. Hence, a crustal partial melt was simultaneously subtracted according to energy constraints at each reverse fractionation step for these samples. The results show that the high-Mg basalts are 41–53% fractionated and 1–6% contaminated, and the low-Mg basalts are 63–67% fractionated. Their primary magmas were last equilibrated with spinel lherzolite at 10–13 kbar/1289–1333 °C. A picrite and two very high-Mg basalts plot on their olivine control lines. So, their primary magmas were calculated by adding only equilibrium olivine. These samples are 9–25% fractionated, and their primary magmas were last equilibrated with garnet lherzolite at 25–36 kbar/1452–1531 °C. The estimated mantle potential temperatures are 1400–1500 °C for the Deccan tholeiites, consistent with their origin from a mantle plume. [ABSTRACT FROM AUTHOR]

The nature of the magma plumbing system of Large Igneous Provinces is still poorly understood. Among these exceptional magmatic events from Earth's past, the end-Triassic Central Atlantic Magmatic Province (CAMP) and the end-Cretaceous Deccan Traps (Deccan) coincided in time with two of the most catastrophic biotic crises during the Phanerozoic. In order to constrain the architecture of their magma plumbing system, glomerocrysts containing abundant bubble-bearing melt inclusions from basaltic lava flows of both CAMP and Deccan were investigated via in situ geochemical and microstructural analyses. The analysed glomerocrysts, dominated by augitic clinopyroxene crystals, represent fragments of a crystal mush entrained by basaltic magmas before eruption. The analysed melt inclusions, consisting of an intermediate to felsic composition glass and CO2-bearing bubbles, represent relics of interstitial melts and fluids within a porous crystal framework forming the crystal mush. The different volume proportions between bubbles and whole inclusions reveal that melt entrapment occurred after volatile exsolution. The minimum observed bubble/inclusion fraction indicates that the CO2 concentration in CAMP and Deccan melts was at least 0.3 wt.%, consistent with a maximum entrapment pressure of about 0.5 GPa at CO2–H2O fluid-saturated conditions. The MgO-rich composition of host clinopyroxene crystals and whole rocks is in contrast with the SiO2-rich composition of (trachy-) andesitic to rhyolitic glass of melt inclusions, pointing to disequilibrium conditions. Thermodynamic and geochemical modelling shows that fractional crystallization alone cannot explain the evolved composition of glass in melt inclusions starting from their whole rock composition. On one side, the oxygen isotope composition of clinopyroxene crystals in glomerocrysts ranges from +3.9 (± 0.3) to +5.8 (± 0.3) ‰ and their sample-averaged oxygen isotope composition spans from +4.4 (N = 10) to +5.6 (N = 10) ‰, implying that glomerocrysts crystallized from mafic melts with normal (i.e. mantle-like) to slightly low δ18O values. On the other side, the oxygen isotope composition of glass in melt inclusions ranges from +5.5 (± 0.4) to +22.1 (± 0.4) ‰, implying that melt inclusions entrapped intermediate to felsic melts with normal (i.e. mantle-like) to extremely high δ18O values, typical of (meta-) sedimentary rocks. Some melt inclusions are compatible with fractionation from the same mafic melts that crystallized their host mineral phase, but most melt inclusions are compatible with variable degrees of crustal assimilation and partial mixing, potentially followed by minor post-entrapment isotope re-equilibration. In the CAMP, where sedimentary basins are abundant, (meta-) pelites and occasionally granitoids were the most likely assimilants. On the contrary, in the Deccan, where sedimentary basins are rare, granitoids and metapelites were the most likely assimilants. Oxygen isotope compositions of glass in melt inclusions, spanning from mantle-like to crust-dominated signatures, suggest that the CO2 within their coexisting bubbles likely derived partly from the mantle and partly from assimilated crustal materials. The investigated glomerocrysts and their bubble-bearing melt inclusions are relics of a multiphase (i.e. solid + liquid + gas phases) crystal mush revealing a dynamic evolution for the magma plumbing system of both CAMP and Deccan, where crystals, silicate melts and exsolved fluids coexisted and interacted through most of the transcrustal section. [ABSTRACT FROM AUTHOR]

The sediments of 90 rivers from five states along the west coast of India were analysed for their chemistry. The major element ratios of sediments suggest lateritic soils in Kerala, lateritic soils admixed with particulates weathered from Fe–Mn ores in Karnataka and Goa and, non-lateritic, chemically weathered soils in Maharashtra and Gujarat. The sediments from the Archean-Proterozoic (A-P) terrain are strongly weathered, while those from Deccan Traps (DT) terrain are intermediate to strongly weathered. The mean total rare earth elements content (∑REE) of sediments from the rivers of Kerala is much higher than in other states. ∑REE shows strong positive correlation with oxides of Fe, Mn and P from A-P terrain and Al, Fe and Ti from DT terrain and, strong positive correlation with heavy metals (Zr, U, Hf and Th) from both terrains. The low Sm/Nd and Y/Ho ratios corresponding to high chemical index of alteration (CIA) and, high ratios corresponding to high and low CIA are typical. The Post-Archean average Australian shale (PAAS)-normalized REE shows LREE- and MREE-enriched patterns in the sediments of Kerala and MREE- and HREE-enriched patterns in other sediments. Distinct positive Ce anomaly occurs in the sediments of Karnataka, Goa and south Maharashtra and, weak positive to weak negative Ce anomaly in the sediments of other states. The Eu anomaly is negative in the silts of south Kerala and positive in all other sediments. The primary sources for REEs are adsorbed REEs onto secondary mineral phases and clay minerals and, heavy minerals. The change in REE patterns is primarily related to the source rock composition. Fractionation of REEs is related to the intensity of chemical weathering, supply of REE and transport processes. The average REE composition of river sediments from peninsular India is more mafic than in UCC and World Rivers Average Clay. [ABSTRACT FROM AUTHOR]

A comparative study of impact glasses from the Lonar crater, located on the Deccan basalt plateau, India, and impact glasses from lunar regolith delivered by the Soviet automatic stations (AS) Luna-16 and Luna-24 (Sea of Plenty and Sea of Crises) was carried out. Numerous natural alloys (Cu3Ni2, Ni2Cu and Ni3Cu) that were previously unknown in nature were discovered in the impactites of the Lonar crater and the regolith of the Moon. The discovery of such alloys expands the area of isomorphism in the Cu–Ni system. As a result of a comparison of impactites of the Earth and the Moon, similarities were discovered in the composition, size and morphology of particles of copper–nickel alloys, which may be an indicator of impact processes. One of the possible mechanisms for the formation of Ni–Cu particles was condensation from a gas–plasma cloud. A possible source of material for Cu–Ni alloys was both the impactor material and the target material. [ABSTRACT FROM AUTHOR]

Thermal Thellier type palaeointensity (PI) experiments are the most popular technique in determining strength of the past geomagnetic field (GMF). However, the method often encounters high failure rate. Mineral magnetic properties can provide useful information to enhance the success rate. We conducted the first ever detailed mineral magnetic and Thellier type PI experiments on lava flows within a 1250 m stratigraphic section of the largest end-Cretaceous (~ 65–66 Ma) Deccan flood basalt. The lava flows mostly contain pseudo single domain (PSD) titano-magnetite/magnetite with, low viscosity index (≤ 5), high/moderate Koenigsberger ratio (Qn > 10/ < 10), isothermal remanent magnetisation parameters typical of ferromagnetic minerals, saturation remanence magnetization to saturation magnetization ratio (Mrs/Ms: 0.05–0.31), coercivity of remanence to coercive force ratio (Hcr/Hc: 1.53–3.72) and a single magnetic component pointing to origin or a minor viscous component during alternating field (AF) demagnetizations,. Their thermomagnetic responses are broadly group into 3 categories. The type 1 displays near perfect reversible heating/cooling curves with high Curie temperatures of 570–600 °C; other two types have either widely separated (type2) or quite dissimilar (type 3) heating/cooling curves. 76 samples from 19 flows were subjected to ZI (Zero field-Infield) experiments with pTRM and pTRM tail checks. 24 samples from eight flows display reasonable NRM-TRM linearity and positive pTRM checks and satisfy strict reliability criteria. 42 samples from 11 flows do not satisfy the reliability criteria. Samples of reliable PI results are all characterized by reversible thermomagnetic behaviour with excellent stability during AF/thermal treatment. Samples that failed to meet reliability criteria possess irreversible/widely separated thermomagnetic heating/cooling curves or poor stability to AF/thermal treatment but not significantly different from the successful samples in other magnetic properties. Thus, thermomagnetic behaviour and stability to AF/thermal treatment appear to be the overweighing factors than other mineral magnetic characteristics that govern the success rate of thermal PI experiments. The PI values of upper normal (29N) flows are relatively higher than the lower reverse (29R) flows; this suggests minor time lag in cooling of successive flows. The time averaged PI estimate is an important end-Cretaceous contribution from the Indian subcontinent to the poorly represented database of southern hemisphere. [ABSTRACT FROM AUTHOR]

Meteoroid impacts produce different types of fractures and damage zones beneath impact craters. The 3D geometry of these features reflects the trajectory and energetics of an impact event. In this study, we mapped the impact damage zone beneath the 1.88‐km‐diameter Lonar crater, emplaced in Deccan basalts, using Ambient Noise Tomography (ANT). A network of 23 broadband seismic stations in and around the crater yielded a 1.2 km deep 3D shear wave velocity (VS) image covering ∼7 km by ∼5 km area. It revealed ∼500–900‐m‐thick heterogeneous target basalt flows, underlain by an undulating Archean granite‐gneiss basement. A substantial reduction in VS is observed beneath the crater. The original crater floor was found at a depth of 400 m below the crater rim, which is filled by impact breccia and lake sediments. Beneath the original floor, we found an oval‐shaped, asymmetric 200‐m‐thick lensoidal low‐velocity layer with a tongue‐like feature beneath the southwestern ejecta blanket. The damage zone is inferred to have formed as a result of oblique impact, in which the projectile arrived from northeast to southwest direction. The VS reduction in the low‐velocity layer was used to calculate the amount of impact damage in it. The oblique impact produced a more elevated southwestern crater rim. Impact‐related near‐surface fracture zones up to a radial distance of >1 km beneath the ejecta blanket were also found. We suggest that impact damage beneath impact craters on Earth and other planetary bodies may be imaged using ANT. Plain Language Summary: Impact craters are ubiquitous on planetary surfaces. The impact produces both surface and sub‐surface changes, including fracturing and damage beneath the crater floor. The 3D geometry of the damage zone depends on the impact angle and velocity. While vertical impacts generate symmetric damage zones beneath the craters, oblique impacts produce asymmetrical damage zones with greater damage in the downrange direction. Field geological mapping provides limited information about these features, while the Ambient Noise Tomography (ANT) brings out a complete shape and size of the damage zone in the sub‐surface. The shear wave velocity image also provides the characteristics of target rocks within and outside the impact crater. In this work, we carried out the ANT study of Lonar crater, emplaced in Deccan basalts in India, using a network of 23 broadband seismometers. This study revealed a ∼500–900‐m‐thick heterogeneous basaltic target underlain by an Archean granite‐gneiss basement, and an asymmetric damage zone beneath ∼400‐m‐deep original crater floor because of southwest directed oblique impact. We quantified the amount of impact damage beneath the original crater floor. The ANT can be used for imaging damage zones beneath impact craters on Earth and other solid planetary bodies, thus providing more insight into impactor trajectories. Key Points: Ambient noise tomography reveals a 500–900 m thick heterogeneous basaltic target underlain by Archean granite basement beneath Lonar craterAn asymmetric damage zone is found beneath the 400 m deep original crater floor filled by impact breccia and lake sedimentsAsymmetric topography and impact damage zone geometry are consistent with a southwest‐ward oblique impact trajectory [ABSTRACT FROM AUTHOR]

Major, trace, and rare earth element (REE) geochemistry of sediments from a tropical mountain river is investigated to understand the behavior of chemical elements during weathering and transportation in a Peninsular Gneissic terrain. The results from this study are compared with the Deccan Basalt‐derived River sediments and the eastern Arabian Sea sediments with an intent to highlight the challenges associated with the provenance determination of sediments along the continental margin of India. The geochemistry of suspended particulate matter (SPM) and mud sediments (<63 μm) of the Nethravati River indicate that sediments are derived from a relatively homogenous lithology, characterized by intermediate rocks of tonalitic (low‐Al TTGs) composition. The tectonic origin of the source rocks discriminated using sediment geochemistry suggests an ocean island arc origin. The sediments experience intense chemical weathering in the source region. The elemental composition and their inter‐element relationships suggest differential chemical weathering of mineral phases fractionate mafic components and their secondary mineral products in SPM, and mixed sources dominated by felsic components and their secondary mineral products in mud sediments. Intense chemical weathering induces significant geochemical splits among the suspended and mud sediments. The transport of mafic‐biased sediments from Peninsular India to Oceans, and the geochemical similarity with Deccan Basalt‐derived sediments makes it challenging to track the Peninsular Gneiss‐derived sediment provenance along the continental margin of India using conventional elemental geochemistry. The inferences from this study have important implications for determining the sediment provenance along the continental margin of India. Plain Language Summary: The focus of this study is to characterize the impacts of chemical weathering and hydrodynamic sorting on the chemical composition of river sediment along a river in Peninsular India. The Arabian Sea dominantly receives sediment from the Himalaya and Deccan Traps and thus other sources, like rivers draining Peninsular India, are overlooked as important sediment sources. However, the processes that govern river sediment chemistry in Peninsular India are not well characterized, which may lead to incorrect interpretations of sedimentary records in the Arabian Sea. To address this knowledge gap, the major and rare earth element (REE) compositions of river‐suspended sediment and mud sediments have been analyzed and compared with the sediment compositions of Deccan Basalt draining rivers and the sediments from the Indian Ocean. The composition of river‐suspended sediment differs from mud due to hydrodynamic sorting, where suspended sediment has a more mafic affinity and mud has a more felsic affinity. Moreover, the study shows that REE patterns in rivers with substantially different exposed bedrock types can be similar because of intense weathering, which complicates the interpretation of incompatible element patterns in geologic records. Key Points: Geochemical split among the granulometric grades of sediments observed in the Peninsular RiverFelsic‐biased coarser sediments and mafic‐biased finer sediments in the Peninsular Gneissic cratonic RiverGeochemical similarity among the Peninsular Gneiss derived finer sediments and Deccan Basalt‐derived sediments is observed [ABSTRACT FROM AUTHOR]

Extension tectonics responsible for intracratonic rift basin formation are often the consequences of active or passive tectonic regimes. The present work puts forth a plume-related rifting mechanism for the creation and evolution of two Proterozoic sedimentary basins outlining the Bundelkhand Craton, namely the Bijawar and Vindhyan basins. Using global gravity data, a regional-scale study is performed over the region encompassing the southern boundary of the Bundelkhand Craton consisting of the Bijawar Basin, Vindhyan Basin, and Deccan basalt outcrops. The gravity highs in the central part of the complete Bouguer anomaly and the upward-continued regional anomaly, derived from global gravity grid data, suggest that the Vindhyan sedimentary basin overlies a deeper high-density crustal source. The deepest interface as obtained from the radially averaged power spectrum analysis is observed to occur at a depth of ∼30.3 km, indicating that the sources responsible for the observed gravity signatures occur at larger depths. The 3D inversion of complete Bouguer anomaly data based on Parker–Oldenburg's algorithm revealed the Moho depth of ∼32 km below the Vindhyan Basin, i.e., south of the craton. The 2D crustal models along two selected profiles showcase a thick underplated layer with a maximum thickness of ∼12 km beneath the southern part of the Bundelkhand Craton. The inferred large E–W-trending underplating and deciphered shallower Moho beneath the regions south of the exposed Bundelkhand Craton point to crustal thinning compensated for magmatic emplacement due to a Paleoproterozoic plume activity below the craton margin. [ABSTRACT FROM AUTHOR]

The sedimentary sequence of the Ninama Basin is associated with the latest phase of the continental Deccan volcanism of the Indian peninsula. It occurs as inter-, intratrappeans with a 39-m thick sequence comprising Sukhbhadar Formation and Ninama Limestone. The investigation aims to reconstruct its depositional setting based on the lithofacies and inorganic geochemistry to understand the influence of paleosalinity, paleoredox, paleodepth, provenance and paleoclimate on the sedimentation pattern. It is characterized by clastic and chemically formed rocks, including shale, mudstone, siltstone, sandstone and limestone. Facies analysis has revealed seven lithofacies, amongst which four are clastic facies, shale (SH), calcareous shale (CSH), silty mudstone (SM) and lithic greywacke (LGW), and three are carbonate facies, namely, grey-black limestone (GBL), cherty limestone (CL) and marlite (ML). Using geochemical analysis of major oxides and trace elements, ratios of Ca/(Ca+Fe), Sr/Ba, V/(V+Ni), V/Cr, Fe/(Ca+Mg), Ti/Al, Na/K, K/(Fe+Mg), CIA-K and MAP were determined and used to interpret and note the changes in the depositional system. The combined results of the lithofacies and geochemistry indicate that the deposition occurred in three phases. Phase 1 is characterized by high energy conditions in the shallow to moderate depth brackish-saline lake with oxic to dysoxic conditions; Phase 2 is characterized by anoxic deep fresh to the brackish water basin; and Phase 3 is characterized by semiarid conditions, saline, anoxic waters, high evaporation leading to shallowing of the lake, and low to moderate terrestrial input. This lacustrine basin in the paleotopographic low of the Deccan Volcanic Province is characterized by distinct lithology governed by various depositional parameters. A composite depositional model is constructed for the Ninama Basin, reflecting three phases of evolution that are dominantly controlled by the paleoenvironment. Research highlights: The present study focuses on lithofacies and inorganic geochemical analysis of Ninama paleolake sediments, Saurashtra intertrappeans, to interpret their paleosalinity, paleoredox, water depth, provenance, detrital influx, and paleoclimate. Phase 1 deposition was initiated in paleotopographic low of Deccan Traps, in an oxic–dysoxic, high-energy turbulent brackish water environment, in humid conditions. Phase 2 characterizes fine-grained clastic facies deposited in anoxic, fresh-brackish, deep lake waters in humid conditions. Phase 3 marks the shallowing, evident by carbonate facies with low-moderate terrestrial input deposited in saline and anoxic paleolake in semiarid conditions with high evaporation and low-moderate precipitation. The Deccan Traps have influenced the paleolake intertrappean sequence. [ABSTRACT FROM AUTHOR]

In peninsular India, the Deccan Traps record massive, continental‐scale volcanism in a sequence of magmatic events that corresponds with the timing of mass extinction at the Cretaceous‐Paleogene boundary. Although the Deccan volcanism is linked with the Réunion hotspot, the origin of its periodic magmatic pulses is still debated. We developed a numerical model replicating the geodynamic scenario of the African superplume underneath a moving Indian plate to explore the mechanism of magmatic pulse generation during the Deccan volcanism. Our model results revealed a connection between the Réunion hotspot and the African large low shear‐wave velocity province (LLSVP), suggesting that the pulses were produced from a thermochemical plume originated in the lower mantle. The ascending plume had stagnation at 660 km due to phase changes in the transition zone, and its head eventually underwent detachment from the tail under the influence of Indian plate movement to produce sequentially four major pulses (periodicity: 5–8 Ma), each giving rise to multiple secondary magmatic pulses at a time interval of ∼0.15–0.4 Ma. This study sheds a new light on the mechanism of periodic hotspot activities from a global perspective. Plain Language Summary: Mantle plumes, originated in deep Earth's interior are thought to be a major source of enormous magma supply required for the formation of large igneous provinces (LIPs). This article focuses on the pulsating nature of Deccan volcanism in peninsular India, which is a remarkable LIP event at the end of the Cretaceous Period in the geological history. From thermo‐chemical model simulations, the present study establishes a link of this volcanic event with the Reunion hotspot, which originated from the African large low shear wave velocity province (LLSVP) at the core‐mantle boundary. The ascending Reunion plume eventually encountered the mid‐mantle transition zone and produced periodically a sequence of plume pulses. Each plume pulse then ascended to shallower depths and started to produce partial melts in developing secondary pulses. The model analysis suggests that the time‐periodicity of primary pulses depends mainly on the following physical factors: pile‐ambient mantle viscosity ratio, buoyancy number, and heat‐producing element concentration. Finally, the entire Deccan volcanic event is explained in terms of plume pulses with two distinct time periodicities: primary pulses with a periodicity of 5–8 Ma and secondary melt pulses with a periodicity of 0.15–0.4 Ma. Key Points: Pulsating Deccan volcanism originated from mantle plumes at the Eastern flank of African LLSVP, which is linked to the Réunion hotspotRéunion hotspot activity produced periodic plume pulses by perturbation at the mid‐mantle transition zone with a time periodicity of 5–8 MaThe primary plume head subsequently generated multiple melt pulses on a timescale of 0.15–0.4 Ma in the Deccan LIP formation [ABSTRACT FROM AUTHOR]

We perform Rayleigh‐wave group‐velocity dispersion measurements from 14,706 regional‐waveforms at periods of 10–120 s, followed by ray‐based tomography and inversion to obtain 3D‐Vs structure of the crust and upper mantle. The group‐velocity maps have 3–5° lateral resolution, and Vs models have ∼3%–7% average‐Vs uncertainty. The Moho depth is assigned to the bottom of the steepest‐gradient layer with Vs between 4.1 and 4.5 km s−1, and the sedimentary‐layers have Vs ≤ 2.9 km s−1. Indian cratons have high average‐crustal‐Vs of 3.6–3.9 km s−1 and thickness of 40–50 km. The intervening rift‐basins are filled with low‐Vs sedimentary‐rocks. The Himalayan Foreland Basin has along‐arc variation in sedimentary thickness with the thickest layer (8–10 km) beneath the Eastern Ganga Basin. The Indian lithospheric mantle has high‐Vs (>4.4 km s−1), and along with high‐Vs crust attest to a cold, rigid lithosphere. This lithosphere underthrust entire Western Tibet and up to the Qiangtang Terrane in Central‐Eastern Tibet. The top of the underthrusting Indian‐crust is marked by lower‐Vs and thrust‐fault earthquakes. The shallow crust beneath Tibet (0–10 km) has high‐Vs and is mechanically strong; whereas, the mid‐crust (20–40 km) has ∼5%–10% low‐Vs anomalies due to radiogenic/shear heating within the thickened crust. This layer is weak and decouples the deformation of the shallow and deep layers. Low‐Vs upper‐mantle with deeper high‐Vs layer is present beneath the Deccan and Raj‐Mahal Traps, suggesting plume‐volcanism related thermal anomaly and refertilization of the upper mantle. The intra‐cratonic basins with circular geometry, high‐Vs lithosphere and no basement earthquakes, possibly formed by thermal subsidence of isostatically‐balanced cratonic lithosphere. Plain Language Summary: We perform 1D‐path‐average surface‐wave dispersion measurements for 14,706 regional ray‐paths (10 and 120 s period), and combine these into 2D variation maps, followed by modeling to obtain 3D shear‐wave velocity structure beneath India, Himalaya and Tibet. The 2D maps have 3–5° lateral resolution and the 3D structure has 5%–7% average‐velocity uncertainty. The Indian Cratons have high average crustal‐velocity and crustal thickness of 40–50 km, and are underlain by high‐velocity upper mantle. The intervening rift‐basins are filled with lower‐velocity sedimentary‐rocks. The sedimentary layer thickness in the Himalayan Foreland Basin varies along‐arc and is thickest (8–10 km) beneath the Eastern Ganga Basin. The high‐velocity (cold, rigid) Indian plate underthrust entire Western Tibet and up to the Qiangtang Terrane in Central‐Eastern Tibet. A mid‐crustal low‐velocity‐layer is present beneath Tibet, which is weak and decouples the deformation of the shallow and deep layers. The upper‐mantle beneath Deccan and Raj‐Mahal Traps has low‐velocity overlying a high‐velocity layer suggesting plume‐volcanism related thermal anomaly. From the velocity‐structure and geometry we speculate about the origin of the intra‐cratonic Tarim and Eastern Tajik Basins. Key Points: Indian Cratonic lithosphere (ICL) has high average‐crustal Vs 3.6–3.9 km s−1, upper mantle Vs > 4.4 km s−1 and crustal thickness of 40–50 kmLow Vs upper‐mantle with a deeper high Vs layer beneath Deccan Traps suggest plume‐volcanism related thermal anomaly/refertilizationICL underthrusts entire W Tibet and up to the Qiangtang Terrane beneath Central‐E Tibet with a mid‐crustal low‐velocity anomaly of 5%–10% [ABSTRACT FROM AUTHOR]

This article explores the abundance and distribution of heulandite, a type of zeolite mineral, in various locations worldwide. It highlights the collections of heulandite specimens at the Geological Survey of New Jersey and the Smithsonian Institution. The article mentions specific localities where heulandite can be found, including New Jersey, Nova Scotia, Idaho, Connecticut, Oregon, Brazil, Iceland, Scotland, Germany, Italy, Madagascar, Japan, and India. It also notes the associated minerals found with heulandite in each locality. [Extracted from the article]

The H2 and CO2-utilizing chemolithoautotrophic microorganisms from the deep subsurface ecosystems have gained considerable importance for their significant role in biogeochemical cycling of carbon. In this study, ten basalt and granite rocks from the deep subsurface environment of the Deccan Traps, India, have been used to enrich chemolithotrophic microorganisms. Following incubation with H2 and CO2 for 90 days at 50˚C, the enrichments showed microbial growth as evident from protein (27–157 mg/L) and carbohydrate (0.1–2.9 mg/L) contents of the enrichment cultures along with a change in pH, dissolved oxygen, and oxidation-reduction potential values. 16 S rRNA gene amplicon sequencing of the metagenomes derived from the enrichment cultures showed selective enrichment of microbial communities compared to the native rock communities. The most abundant bacterial phyla within the native rock samples were Proteobacteria, Actinobacteria, and Firmicutes, whereas the enrichment cultures showed enrichment of Proteobacteria (members of Gamma-Alpha-subdivisions), Actinobacteria, Firmicutes, and others under the chemolithoautotrophic condition. Predictive metabolic profiling using PICRUSt of enriched communities revealed the presence of genes related to H2 oxidation (hyaCD) and CO2 fixation (PGK, ccl, fhs, accABC) as well as genes for value-added product formation (ACSS, LDH, adh, acmAB, adh1, adcBDH, phaC, phbCZB, etc.). A total of 14 bacteria were isolated and identified as Mesorhizobium sp., Ralstonia spp., Massilia spp., Acidovorax spp., and Sphingobium sp. Among the bacterial isolates, Ralstonia sp., and Massilia sp. obtained from basaltic rock showed higher CO2 (up to 8 mg/L) utilization ability, and most of them can produce acetate (up to 14 mg/L). PCR analysis of the functional gene (NiFe-hyd) revealed the presence of probable H2 oxidation pathway in the isolates for their energy metabolism. The study showed the potential of H2 and CO2 utilizing deep subsurface bacterial populations in CO2 capture and value-added product formation. [ABSTRACT FROM AUTHOR]

The present study encompasses petrographic variations in simple Deccan basaltic lava flows of the Rajura volcanics, central India. The Deccan basalt lava flows entirely covered the area and exposed in the form of moderate hillocks. During geological fieldwork, flows are identified and differentiated based on mineral content, relative grain size, presence of phenocrysts, and red bole horizons. Flow mapping reveals three basalt lava flows: mafic plagioclase microphyric basalt, phyric basalt, and plagioclase mafic microphyric basalt. The petrographic study of the lava flows was carried out to understand the mineralogy, textural patterns, crystallization, and genetic significance of the lava flows. The result indicates dominant plagioclase and clinopyroxene minerals with opaques exhibit porphyritic, glameroporphyritic, ophitic, and sub-ophitic textures. The petrographic variations are due to the combination of several factors like gravitational sinking of phenocryst, low viscosity, and slow rate of effusion of lava flows, as described by earlier workers. Plagioclase occurs as phenocrysts and in the groundmass phase, indicating early crystallization of phenocryst followed by crystallization of groundmass. The petrographic studies are further useful to correlate the lava flows exposed in different hillocks of the area. [ABSTRACT FROM AUTHOR]

The magma source for mafic dykes from South Rewa Basin (SRB) in central India is invariably linked to Rajmahal volcanism (117 Ma) for Damodar, Raniganj-Jharia, and Bengal basin (Permian - Quaternary) to the east, and Deccan volcanism (66 Ma) for Satpura Basin to the west of SRB. However, the magmatic events linked to the SRB are not explicit. To ascertain the dyke association with these volcanic events, we performed a comprehensive paleomagnetic study on the exposed dykes and basalts from Shahdol region in SRB. Rock magnetism indicate that magnetite or titano-magnetite is the main remanence carrier mineral in these dykes. The measured directions produce a mean declination (Dm) of 338° and mean inclination (Im) of - 35° (α95= 8.4°, k = 25.3, N = 13), is close to Deccan normal directions. The calculated Pole position (λp) is at 42.02°N, and (Lp) is at 289.33°E, suggesting that the studied dykes are emplaced simultaneously along with Deccan Traps (36.96°N/78.70°W) and not of Rajmahal Traps (11.37°N/297.58°E). These dykes can be the result of multiple Deccan magma intrusions along the Narmada-Tapti lineament and intra-basinal faults in the SRB of central India.

Delamination of the continental lithospheric mantle is well recorded beneath several continents. However, the fate of the removed continental lithosphere has been rarely noted, unlike subducted slabs reasonably well imaged in the upper and mid mantle. Beneath former Gondwana, recent seismic tomographic models indicate the presence of at least 5 horizontal fast-wavespeed anomalies at ~600 km depths that do not appear to be related to slab subduction, including fast structures in locations consistent with delamination associated with the Paraná Flood Basalt event at ~134 Ma and the Deccan Traps event at ~66 Ma. These fast-wavespeed anomalies often lie above broad slow seismic wavespeed trunks at 500 to 700 km depths beneath former Gondwana, with slow wavespeed anomalies branching around them. Numerical experiments indicate that delaminated lithosphere tends to stagnate in the transition zone and mid-mantle above a mantle plume where it shapes subsequent plume upwelling. For hot plumes, the melt volume generated during plume-influenced delamination can easily reach ~2 to 4 × 106 km³, consistent with the basalt eruption volume at the Deccan Traps. This seismic and numerical evidence suggests that observed high-wavespeed mid-mantle anomalies beneath the locations of former flood basalts are delaminated fragments of former continental lithosphere, and that lithospheric delamination events in the presence of subcontinental plumes induced several of the continental flood basalts associated with the multiple breakup stages of Gondwanaland. Continued upwelling in these plumes can also have entrained subcontinental lithosphere in the mid-mantle to bring its distinctive geochemical signal to the modern mid-ocean spreading centers that surround southern and western Africa. [ABSTRACT FROM AUTHOR]

High‐resolution Sr and Nd isotope compositions along with major and trace element abundances have been analyzed in silicate fraction of sediments core, SSD004‐GC03, from the Equatorial Indian Ocean (7.2°N and 77.9°E) at 1,540 m water depth with a depositional history of ∼38 ka to determine source variabilities and their controlling factors. 87Sr/86Sr (0.71978–0.72491), ƐNd (−14.8 to −21.9), and a couple of source diagnostic elements display profound variability over the depositional time scale and point toward major sediment contribution from the Peninsular Gneissic Complex (PGC) and the Deccan Basalts along with aeolian dust flux, their relative proportions being determined by climate variability. The cold/arid periods are characterized by an enhanced proportion of aeolian dust and the Deccan Basalts, whereas the sediment contribution from the PGC is augmented during the warm/humid periods. The sediment provenance variations at the Equatorial Indian Ocean coincide very well with known cold/arid (Heinrich Stadial events: HS 1–4, LGM, Younger Dryas, 8.2 ka, 5.2 ka, and 1.1 ka) and warm/humid (Early Deglacial, Holocene Intensified Monsoon) climatic events reported in the tropical region and sea‐level change which are strongly captured by the Sr‐Nd isotope and elemental composition of sediments. The present investigation underscores the significant role of climate, mainly the aridity, in modulating the dust fluxes and erosion intensity and the strong coupling between Indian monsoon and North Atlantic climatic oscillations and further demonstrates minimal time delay between the production and transport of sediment from source to sink. Key Points: High‐resolution 87Sr/86Sr, ƐNd and a few diagnostic elements track temporal variation of sediment sources in the Equatorial Indian OceanThe cold periods are characterized by enhanced proportions of aeolian dust and the Deccan Basalts, whereas the PGC dominates warm periodsNorth Atlantic climatic oscillations modulate Indian monsoon thereby controlling dust and erosional fluxes in the Equatorial Indian Ocean [ABSTRACT FROM AUTHOR]

The occurrence of landslides is not uncommon in the Western Ghats of Maharashtra, India. However, during the last week of July 2021, an unprecedented number of landslides due to heavy rainfall were reported in this region. To determine the cause of the large-scale landsliding, we mapped an event-based landslide inventory using high-resolution satellite imagery and identified 5012 landslides. We analysed rainfall data for the 2005–2021 period to identify the anomaly in rainfall quantity and its distribution which triggered such large number of landslides, particularly in 2021, even though heavy annual monsoonal rainfall is observed every year in this region. It is observed that the quantity of rainfall in 2021 is much lesser than that seen in most of the previous years. Analysis of antecedent rainfall for time-stamped landslides, such as Jui (2005), Malin (2014) and Taliye (2021), shows that two-day antecedent rainfall is the primary trigger of landslides in the region. An in-depth comparison of rainfall variability for all the years which recorded more rainfall than 2021 shows that the amount of two-day consecutive rainfall is significantly higher in 2021, although the cumulative seasonal rainfall is less than in preceding years. Further, this anomalously high rainfall was concentrated around the 600 m – 900 m elevation range. The probable consequence of such spatiotemporally localised heavy rainfall over higher elevations was rapid soil saturation triggering a large number of landslides in 2021. In times when the effect of climate change is visible in the form of weather extremes, the present study may aid in preparedness for response to such disasters. [ABSTRACT FROM AUTHOR]

An anomalous crust and lithospheric mantle in the Deccan Volcanic Province are imaged below a 160 km long W‐E profile through the joint inversion of receiver functions and surface wave dispersion. The upper crust has an unusually low S‐wave velocity (Vs ∼ 3.3–3.5 km/s) at 8–17 km depth, underlying a 4 km thick high‐velocity layer (Vs > 3.8 km/s). The low velocity possibly represents the frozen magma reservoir, the source for the magma eruption at ∼65 Ma due to the interaction of the Reunion plume with India. The shallow, high‐velocity layer could be basaltic mafic intrusions responsible for the production of massive CO2 degassing. The Moho deepens beneath the west coast to ∼45 km due to 10–15 km of magma underplating. The mantle plume scar is seen as thinned lithosphere (80–100 km), with the presence of long‐lived low‐velocity layers in the shallow mantle attributed to the presence of sulfide melts. Plain Language Summary: The Deccan volcanism occurred around 65 Ma ago when India and Seychelles, moving northward, interacted with the Reunion plume, leading to increased temperature and hence melting at the upper mantle. The buoyant magma moved upward and ponded toward the crust‐mantle boundary. When the overlying crust failed due to high overpressure and/or magma buoyancy, the magma ascended via dikes and assimilated into a shallow crust. The process is expected to produce significant crust and upper mantle modifications due to increased heat transfer and chemical transformation during magma ascent. Existing geophysical knowledge of the Deccan traps does not provide the signature of a magma ascent path and evidence for crustal transformations. Using data from a recent 160 km‐long broadband seismological experiment, we construct a detailed model of the crust and uppermost mantle, showing a complete magma plumbing system. The result shows evidence for lithospheric thinning and well‐preserved deformation in the shallow mantle in the form of sulfide melt, magma ponding at the crust‐mantle boundary beneath the coastal basin, an extensive low‐velocity layer in the upper/mid crust possibly representing the horizontally elongated frozen magma reservoir, and a densified high‐velocity layer in the shallow crust (4–8 km depth) representing basaltic mafic intrusions. Key Points: First seismic evidence of the magma plumbing system in the Deccan Volcanic Province, IndiaA thinned lithosphere with low‐velocity layers in the western segment adjoining the coastA low‐velocity layer at 8–17 km depth possibly represents a frozen magma chamber underlying a 4 km thick high‐velocity layer [ABSTRACT FROM AUTHOR]

The eruptive history of the Malwa Plateau Subprovince of the Deccan Traps is addressed by dating 21 lavas spanning the exposed stratigraphic extent, using the 40Ar/39Ar method applied to plagioclase separates. Major, minor, and trace element geochemistry was determined for each of the dated lavas and four additional ones. Dating results indicate that the eruptions began prior to 66.8 Ma, at least 400 ka before the oldest known lava in the more extensively studied Western Ghats, representative of the main Deccan province, to the south. Eruption rates peaked from 66.4 to 66.3 Ma and then diminished until 65.6 Ma. The peak in eruption rates coincides with the well‐documented Late Maastrichtian Warming event. Malwa lavas show some major and trace element affinities with geochemically defined lava flow formations of the Western Ghats, but are generally out of the stratigraphic sequence manifest in the Western Ghats. The distinct geochemical evolution of Malwa Plateau lavas compared with those of the Western Ghats is at least in part a consequence of differences in crustal composition between the two subprovinces. Modeling of REE concentration patterns of Malwa lavas suggests that they were derived by slightly lower degrees of partial melting, at lower mantle temperatures and depths, than those in the Western Ghats. The Malwa Plateau thus appears to record an earlier, cooler stage of the Deccan plume's evolution and continued to erupt through a large part of the lifetime of the main Deccan province. Key Points: New Ar‐Ar plagioclase dates and chemical data from the Malwa Plateau on the northern margin of the Deccan LIPData invalidate correlation to stratigraphy in the Western GhatsData support the presence of multiple eruptive centers for the Deccan LIP [ABSTRACT FROM AUTHOR]

A 2 to 4 °C warming episode, known as the Latest Maastrichtian warming event (LMWE), preceded the Cretaceous-Paleogene boundary (KPB) mass extinction at 66.05 ± 0.08 Ma and has been linked with the onset of voluminous Deccan Traps volcanism. Here, we use direct measurements of melt-inclusion CO2 concentrations and trace-element proxies for CO2 to test the hypothesis that early Deccan magmatism triggered this warming interval. We report CO2 concentrations from NanoSIMS and Raman spectroscopic analyses of melt-inclusion glass and vapor bubbles hosted in magnesian olivines from pre-KPB Deccan primitive basalts. Reconstructed melt-inclusion CO2 concentrations range up to 0.23 to 1.2 wt% CO2 for lavas from the Saurashtra Peninsula and the Thakurvadi Formation in the Western Ghats region. Trace-element proxies for CO2 concentration (Ba and Nb) yield estimates of initial melt concentrations of 0.4 to 1.3 wt% CO2 prior to degassing. Our data imply carbon saturation and degassing of Deccan magmas initiated at high pressures near the Moho or in the lower crust. Furthermore, we find that the earliest Deccan magmas were more CO2 rich, which we hypothesize facilitated more efficient flushing and outgassing from intrusive magmas. Based on carbon cycle modeling and estimates of preserved lava volumes for pre-KPB lavas, we find that volcanic CO2 outgassing alone remains insufficient to account for the magnitude of the observed latest Maastrichtian warming. However, accounting for intrusive outgassing can reconcile early carbon-rich Deccan Traps outgassing with observed changes in climate and atmospheric pCO2.

The article presents a study which suggested that volcanic sulfur degassing from such activity could have caused repeated short-lived global drops in temperature, stressing the ecosystems long before the bolide impact delivered its final blow at the end of the Cretaceous. Topics include Western Ghats volcanostratigraphy and sample set, in situ determination of sulfur and fluorine in clinopyroxene, and sulfur concentrations calculated for equilibrium melts.

The article discusses the discovery of India's first carbonatite at Amba Dongar, which had a significant impact on the field of petrology. The Amba Dongar carbonatite complex has been extensively studied for over 60 years and is considered one of the best-studied complexes in the world. It is known for its fluorite mineralization and the presence of rare earth elements, making India potentially rich in these resources. The document provides a list of references and publications related to the geology and mineral resources of the complex, including research papers and reports by renowned researchers in the field. [Extracted from the article]

Field studies around Pulivendla (14°33′36″N: 78°19′48″E) belonging to the Tadpatri Formation of Proterozoic Cuddapah Basin document three distinct lava flows (based on internal layering), associated sediments (shale and sandstone) and intrusive dyke-sill system. The presence of previously undocumented internal layering namely Lower Vesicular Zone (LVZ), Lower Colonnade Zone (LCZ), Entablature Zone (EZ), Upper Colonnade Zone (UCZ) and Upper Vesicular Zone (UVZ) helps to delineate three lava flows in the study area. The associated sedimentary beds either correspond to lava cessation-period or dynamic lava-sediment interaction due to lava-cascading. The present study in Tadpatri Formation reveals volcano-sedimentological features analogous to that of Deccan Traps. It is postulated that magmatism within Tadpatri Formation might have been largely controlled by Proterozoic syn-rift plume activity (needs further corroboration by high precision major/trace/isotopic analyses). [ABSTRACT FROM AUTHOR]

The end-Cretaceous mass extinction was marked by both the Chicxulub impact and the ongoing emplacement of the Deccan Traps flood basalt province. To understand the mechanism of extinction, we must disentangle the timing, duration, and intensity of volcanic and meteoritic environmental forcings. In this study, we used a parallel Markov chain Monte Carlo approach to invert for carbon dioxide (CO2) and sulfur dioxide (SO2) emissions, export productivity, and remineralization from 67 to 65 million years ago using the LOSCAR (Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir) model. Our results closely match observed and proxy data and suggest decoupled CO2 and SO2 emissions, a two-step decline in export productivity with a protracted recovery, and no clear volatile impulse at the boundary. More broadly, our methods provide a potential path forward for efficient parallel inversion of complex Earth system models. [ABSTRACT FROM AUTHOR]

Indian summer monsoon holds its core over Central Indian Region (CIR) through Bay of Bengal and Arabian Sea branches. The majority of CIR is occupied by the Godavari Drainage Basin (GDB) which generates a large and episodic flux of sediments in the Bay of Bengal indicating a major shift in the monsoonal pattern over CIR. The large part of Deccan basalt province of GDB is present in the semi-arid watershed governed by the precipitation mostly from Arabian sea branch. Whereas the cratonic province is present in a high monsoonal zone governed by the precipitation from Bay of Bengal branch. Both these zones also represent Cratonic (non-basaltic) versus Basaltic sources converging at the Pranhita/Godavari confluence before their mixing onwards into delta and finally in the Bengal fan. Based on the heavy mineral and low temperature magnetic mineral characteristics of bed loads from the Godavari River before, at and after the confluence we attempt to characterise these two sources as a function of shift in monsoonal pattern over central India. The quantitative heavy mineral studies show dominance of stable minerals derived from the non-basaltic sources with a downstream trend for stable heavy minerals in a long profile to indicate stronger cratonic sources. The surface textures of garnet, epidote and hornblende indicate rapid transport and low residence time for the sediments derived from Precambrian granites, Proterozoic and Gondwana sediments presently defining the Core Monsoon Zone. The opaque grains represented by discrete ilmenite, magnetite and magnetite inclusions in aggregated quartz characteristic of the Deccan basaltic source show decreasing order downstream. The low temperature magnetic susceptibility for heavy minerals indicate Multi Domain and Ti-rich magnetite from Deccan basalts and magnetic inclusion in siliciclastic grains derived mostly from local sources. More detailed heavy mineral and geochemical analysis of the core sediments would help in documenting the temporal shifts in monsoonal intensity and its core regime over the Indian continent. [ABSTRACT FROM AUTHOR]

The Lonar impact crater in the Deccan Volcanic Province of India is an excellent analogue for impact-induced structures on the Moon and other terrestrial planets. We present a detailed architecture of the crater using a high-resolution 3-D seismic velocity image to a depth of 1.5 km through the inversion of high-frequency ambient noise data recorded over 20 broad-band seismographs operating around the crater. The ambient noise waveform is dominated by cultural noise in the 1–10 Hz band. The shear wave velocity (Vs) model is created from Rayleigh wave group velocity data with a horizontal resolution of 0.5–1 km in the period range of 0.1–1.2 s. A key feature of the model is a velocity reduction of 10–15 per cent below the crater compared to outside the ejecta zone. The low-velocity zone below the crater is nearly circular and extends to a depth of ∼500 m. This estimated crater's depth is consistent with global depth–diameter scaling relations for simple craters. The basement, with a Vs of more than 2.5 km s−1, lies beneath the Deccan basalt, which has a Vs of ∼2.4 km s−1. These results are consistent with laboratory-measured data from the Lonar crater and borehole data in the western Deccan trap. This study opens a new window for exploring impact craters and sub-basalt structures using high-frequency ambient noise tomography. [ABSTRACT FROM AUTHOR]

Every geomorphic feature has its own distinct impact on the static groundwater level (SWL), seasonal water table fluctuation (WTF) and yield of the wells. The aim of this study was to analyze the role of geomorphic features over the groundwater regime and its possible implications on hydrogeological status within WRC-1 watershed. The watershed is covered by the Deccan basalt lavaflows and Quaternary alluvium. The geomorphic units of study area are HDP, MDP, residual hill, valley fills, scarp, pediment, pediplain, butte, alluvial plain and gullied land to identify the relationship between geomorphic units and corresponding hydrogeological status. The pre-monsoon SWL, WTF and yield of the open-dug wells are analyzed. The high groundwater level fluctuation is indicated by residual hill, plateau remnant, HDP, MDP, pediment as compared to pond, river, younger alluvial plain and pediplain. Pre-monsoon yield of dugwells in river older alluvium are comparatively high; butte, residual hill, pond, river, dam/reservoir and valley fill which are comparatively moderate to low. The overall findings indicate that seasonal WLF in the hard rock terrain(basalt) is high compared to soft rock formation(alluvium). The best suitable area identified is Pediplain which is categorized as very good groundwater prospectus zone with pre-monsoon SWL (5.8 mbgl), WTF (3.1 m) and yield of the well (108000 L/day) respectively. [ABSTRACT FROM AUTHOR]

Dike swarms are ubiquitous on terrestrial planets and represent the frozen remnants of magma transport networks. However, spatial complexity, protracted emplacement history, and uneven surface exposure typically make it difficult to quantify patterns in dike swarms on different scales. In this study, we address this challenge using the Hough transform (HT) to objectively link dissected dike segments and analyze multiscale spatial structure in dike swarms. We apply this method to swarms of three scales: the Spanish Peaks, USA; the Columbia River Flood Basalt Group (CRBG), USA; the Deccan Traps Flood Basalts, India. First, we cluster dike segments in HT space, recognizing prevalent linearly aligned structures that represent single dikes or dike packets, with lengths up to 10 − 30x the mapped mean segment length. Second, we identify colinear and radial dike segment mesoscale structures within each data set, using the HT to segment swarms into constituent spatial patterns. We show that for both the CRBG and Deccan Traps, a single radial or circumferential swarm does not well characterize the data. Instead, multiple and sometimes overlapping mesoscale linear and radial features are prevalent suggesting a complex history of crustal stresses. The HT can provide useful insights in a variety of geologic settings where many quasi‐linear features, at any scale, are superimposed spatially. Plain Language Summary: Dikes act as pipelines to transport magma from the deep Earth to the surface where it can erupt. Some of the largest concentrations of dikes on Earth occur in ancient continental flood basalts (CFBs), areas of massive volcanic output, but the spatial complexity and scale of these dike swarms has been a barrier to understanding the patterns within. We develop a new method to characterize distributions of linear features, such as dike swarms, inspired by tools and algorithms from image processing. We apply this tool to two CFBs, the Columbia River Flood Basalt Group, USA, and the Deccan Traps, India, as well as a smaller swarm in the Spanish Peaks, USA. We find numerous small packets of aligned segments and larger, radial, and linear patterns of dikes. Key Points: Superimposed spatial patterns in dike swarms are revealed by the Hough TransformDeccan Traps and Columbia River Flood Basalts exhibit multiscale overlapping dike swarm structuresLinear and radial mesoscale swarm structures are identifiable in Hough space [ABSTRACT FROM AUTHOR]

A new fossil occurrence of freshwater sponges (Porifera: Demospongiae) is reported from the Deccan volcanic associated Naskal intertrappean locality, deposited in an interval of

The present study emphasizes the seismic characteristics of earthquake swarm activity of the Palghar region that occurred in the hard strata of Deccan traps of the Indian peninsula. This activity is well monitored by National Centre for Seismology (NCS) from December 2018 to October 2020. The related data inferred that initially before the swarm activation there was a barricade to stop the entry of fluids into the permeable zone. Later the fluids are injected into the fault zone at a feasible place may be near the surface at the time of swarm initiation. Further the associated fluids percolated through several channels in many directions forming a multi-dimensional system of cracks and fissures at the level of swarm progression through two distinctive clusters during the time of present study along normal fault orientations. During this process, the heterogeneous material within the subsurface layers might have experienced a decrease in the effective stress due to the increase in the pore pressure which is the resultant of the percolation of fluids within the permeable zone. The outcome of the results shows a comparable strategic increase in the seismicity after the soil saturation during and after the rainfall in the affected zone. Also, the study of the seismicity accompanying fluid injections indicates that the fluid triggering seismicity is demonstrated by the increased slope of the magnitude frequency distribution in the form of spatial b-value which has been found reliable for a catalogue for Palghar swarm activity. The coulomb stress change is also examined to find out the consistency of stress patterns with the earthquake occurrences in the Palghar region which gives the characteristics of swarm sequence. The study emphasized the fundamental and geo-mechanical behavior of fluid migration through multi-directional cracks and fissures as the cause for the evolution and further growth of the Palghar swarm activity.

Extension tectonics responsible for intracratonic rift basin formation are often the consequences of active or passive tectonic regimes. The present work puts forth a plume-related rifting mechanism for the creation and evolution of two Proterozoic sedimentary basins outlining the Bundelkhand craton, namely the Bijawar and Vindhyan basins. Using global gravity data, a regional scale study is performed over the region encompassing the southern boundary of the Bundelkhand craton consisting of Bijawar basin, Vindhyan basin and Deccan basalt outcrops. The gravity highs in the central part of the observed Bouguer gravity anomaly as well as the upward continued regional anomaly, derived from global gravity grid data, suggests that the Vindhyan sedimentary basin overlies a deeper high-density crustal source. The deepest interface as obtained from the radially averaged power spectrum analysis is observed to occur at a depth of ~30.3 km, indicating that the sources responsible for the observed gravity signatures occur at larger depths. 3D inversion of Bouguer gravity anomaly data based on Parker-Oldenburg's algorithm revealed the Moho depth of ~32 km below the Vindhyan basin, i.e., south of the craton. 2D crustal models along two selected profiles showcase a thick underplated layer with maximum thickness of ~12 km beneath the southern part of the Bundelkhand craton. The inferred large E-W trending underplating and deciphered shallower Moho beneath the regions south of the exposed Bundelkhand craton points to crustal thinning compensated by magmatic emplacement due to a Paleoproterozoic plume activity below the craton margin. [ABSTRACT FROM AUTHOR]

Silicic magmatism, minor overall in the ∼65.5 Ma Deccan Traps continental flood basalt (CFB) province of India, was widespread in the Saurashtra region. We describe the physical volcanology of silicic volcanics and dykes exposed around Rajula–Savarkundla–Gariyadhar–Talaja towns in southeastern Saurashtra. The silicic volcanics conformably overlie basaltic lavas, suggesting rapid subaerial volcanism, and the sequence shows gentle tectonic dips (∼15°) towards the Arabian Sea. Rhyolites and dacites with preserved thicknesses of tens of metres show intense internal rheomorphic deformation, and a dacite shows a well-formed basal autobreccia. The rheomorphic rhyolites, and vitrophyres which often underlie them, lack vitroclasts (glass shards and pumice clasts). They have very similar mineral assemblages (quartz and alkali feldspar phenocrysts, and crystal cargoes dominated by calcic plagioclase and clinopyroxene or orthopyroxene, sometimes with olivine). The rheomorphic units are thus flood rhyolite and dacite lavas, apparently common in the northern-northwestern Deccan, and the vitrophyres their basal chilled parts. Tuffs (including crystal-vitric Plinian fallout ash) and eutaxitic ignimbrites formed from pyroclastic density currents; one tuff contains extraordinary numbers of lithophysae. Ridges of rhyolitic tuff breccias with pervasive secondary silicification and ferruginization represent pyroclastic eruptive fissures. The area thus records large-scale effusive and explosive silicic eruptions. Mafic and silicic dykes intrude the basaltic lavas and rarely the silicic volcanics. Mafic enclaves in several silicic dykes and some volcanics indicate magma mingling as a common phenomenon. The seaward-dipping volcanic units define a regional-scale flexure comparable to coastal flexures in CFB provinces worldwide, suggesting extensive block-faulting of this classical volcanic rifted margin. [ABSTRACT FROM AUTHOR]

A gravity survey was carried out to estimate the sedimentary thickness and to map upper crustal geometry over the northern part of the Cambay rift. Structural lineaments delineated using the total horizontal gradient of the Bouguer anomaly indicate a major lineament trend in the NW-SE direction. Results of the density modelling using residual Bouguer anomaly reveal the average thickness of the Quaternary and Tertiary sediments to be between 0.5 and 6 km, while the Deccan trap thickness varies between 0.5 and 3 km. It is seen that the Mesozoic sediment (maximum thickness ∼0.6 km) is sandwiched between the Deccan trap and granitic basement, which indicates the possible existence of a rift in the late Jurassic-early Cretaceous. Based on the residual Bouguer and density modelling results, the spatial locations of the NE-SW trending Unhawa ridge and the N-S trending Mehsana uplift are provided, which are believed to be the remnant rock of the Proterozoic age. A high-density body, interpreted as a magmatic underplating layer, is also found in the lower part of the middle crust along the central part of the rift, which continues in the lower crust. The magmatic underplating layer is formed during the Reunion hotspot and lithospheric interaction in the Cretaceous period. [ABSTRACT FROM AUTHOR]

Calc tufas are terrestrial, cold water precipitation deposits commonly formed in semi-arid to temperate climates from saturated waters due to carbon dioxide degassing, microbial processes or both. Several calc tufa sites occur along rapids and waterfalls in the upland plateau of the Deccan Traps in western India. Small deposits occur along the Harishchandragad ranges (Bhramanwada, Kotul), Kanhur plateau (Ane Ghat, Wadgaon Darya and Vambori) and the Sinhagad-Bhuleshwar Ranges (Katraj, Shindone, Ambale and Bhuleshwar) in the upland regions of western Deccan Traps. Calc tufa is porous and friable covered with dry organic debris, with encrusted stems, trunk and calcified roots representing phytoherm framestone facies. Well-developed clusters of stalactites are exposed on the roof of a cavern or along cascades. Mineralogically, the calc tufas are made of calcite and contain variable carbonate percentages (53 to 78%) with detrital basalt fragments, devitrified glass, plagioclase, quartz, agate, zeolites etc. The calc tufa from the study area shows δ18OV-SMOW values ranging from 25.3 to 28.9‰ and δ13CV-PDB values from − 3.6 to − 9.42‰ indicating significant regional variation in precipitation and source characteristics. The calc tufas were biological and physicochemically precipitated from waters at paleo temperatures of 16.3 to 27.1 °C (Kotul-Ane Ghat) and 29.5 to 34.6 °C (Bhuleshwar Ghat-Wadgaon Darya) in temperate to semi-arid climate. Despite their hydrogeological significance and importance as paleoclimatic indicators, the calc tufa occurrences from upland Deccan Traps have not received the attention they deserve. The calc tufa sites at Kotul, Wadgaon Darya and Vambori have very high (> 6.5) scientific values. The sites of Wadgaon Darya (6.75) and Vambori (8.8) have very high didactic value (VD) while most sites have high to very high touristic or recreational value (VT ~ 6 to 7.3). The high to very high assessment of the anthropogenic risk of degradation to some sites from this study calls for the preservation and conservation of these important geoheritage sites. [ABSTRACT FROM AUTHOR]

This study presents the probable environment from petrographical, mineralogical and geochemical analyses of representative samples from Bamhantara block, Kabirdham district, Chhattisgarh, India using EPMA and SEMEDS for petrological study, and XRF and ICP-MS for geochemical inference. Microscopic study revealed the dominance of boehmite minerals that specify the synenvironmental depositional condition, while circular/ well-rounded pisolitic texture indicated autochthonous deposits. The geochemical study determined the progressive changes in major, trace and REE concentrations from precursor rock to bauxite during weathering. Bamhantara bauxite has been formed under oxidizing (positive Ce anomalies; Ce/Ce*, 0.92–2.15) and near alkaline to alkaline ((La/Yb)N and La/Y ratio > 1) conditions. The analogous trend of REE for bauxite/laterite and precursor rock indicates that lateritic bauxite had an autochthonous origin and is a chemical disintegration product of Deccan Trap basalt under tropical to subtropical climates. The geochemical behaviour of REE revealed that bauxite/laterite was generated from type-2 basalt characterized by positive Ce, Eu and Dy anomaly. The low concentration of kaolinite indicates desilication under a hot tropical climate. [ABSTRACT FROM AUTHOR]

Palaeo-monsoon and palaeoclimate conditions over Southeast Asia are a matter of debate despite notable studies on the continental and oceanic sedimentary record. The present study investigates the environmental magnetic and geochemical records preserved in the deep marine sediments of the northeastern (NE) Arabian Sea to elucidate the erosion history of the western Himalayas and its link with the prevailing hydroclimatic conditions since the late Miocene. For this, the sediment core retrieved during International Ocean Discovery Program (IODP) Expedition 355 at Site U1457 in the NE Arabian Sea has been explored. The results reveal that the hydroclimatic conditions were predominantly arid during the late Miocene, except for humid intervals from 6.1 Ma to 5.6 Ma. Humid climate conditions in the Indus River Basin returned during the mid-Pliocene and continued to the Pleistocene with an intense chemical weathering regime from 1.9 Ma to 1.2 Ma. The dominant sediment source to the NE Arabian Sea at Site U1457 during the late Miocene and the Pliocene was the Indus River, while during the Pleistocene, mixed sediments brought by the Indus River and the Peninsular Indian rivers were observed. The sediment contribution from a chemically less altered mafic source (the Deccan basalts) increased between 1.2 Ma and 0.2 Ma, possibly linked to a weak Indian Summer Monsoon. The summer monsoon wind strength and associated shift in the Inter-Tropical Convergence Zone (ITCZ) influenced the dominant sediment provenance at Site U1457 of the Laxmi Basin. [ABSTRACT FROM AUTHOR]

Performance of TBM is significantly influenced by the ground conditions and machine variables. To achieve an optimum rate of penetration (ROP) during TBM excavation, it is important to assess the interaction between rock mass properties and machine operational/performance variables. This paper presents a systematic analysis of TBM performance based on the data collected from the MetroLine-3 UGC-01 project in Mumbai, India, and proposes a few performance prediction models for the Deccan Traps. The current work attempted to bring out the combined effect of RQD × Js as a single predictor variable while suggesting a reliable RSA modeling technique which considers the simultaneous interaction of variables. The database consisted of engineering-geological and machine variables; the selected variables were analyzed using artificial neural networks (ANN) for identifying the significant variables. Subsequently, multivariate regression (MVRA) and response surface analysis (RSA) were utilized to develop a model for predicting TBM ROP. The first model developed using MVRA as a function of rock mass variables yielded a coefficient of determination (R2) of 0.80, whereas the second composite model developed as a function of geological and machine variables yielded an R2 of 0.85. The third model was developed utilizing RSA which resulted in 2FI (two-factor interaction) model with improved R2 of 0.88. Further, the best-performing RSA model accuracy is compared with the existing models and subsequently validated using new datasets and yielded an R2 of 0.79. The developed model equation indicates that UCS, RQD × Js, and thrust variables show significant influence on the TBM ROP. [ABSTRACT FROM AUTHOR]

The Upper Cretaceous of central India is represented by a thin transgressive-regressive succession of tropical marine sediments deposited on a Precambrian basement and covered by massive Deccan Trap basalt flows. At the height of the transgression, a few meters thick succession of very thinly and rhythmically bedded, laterally continuous, muddy carbonates of the Turonian–Coniacian Bagh Group was deposited. The planar to wavy beds consist of nodular to massive limestones intercalating with marls. Eroded, bored, and encrusted hardgrounds occur at regular intervals in succession. Field appearance, results of thin-section petrography, and stable isotope signature of micro-sample carbonates suggest that the hardgrounds formed in a supra- to very shallow sub-tidal, restricted marine environment, which was characterised by repeated emergence and soil genesis. Knowing moments of zero-sea level in a regular rhythmically bedded succession with accurate chronostratigraphy allows for better reconstruction of Indian intracratonic basin dynamics during the Upper Cretaceous and its correlation to global events. [ABSTRACT FROM AUTHOR]

The c. 66 Ma Girnar Complex of the Deccan Traps consists of various mafic to silicic rocks and provides a unique setting for understanding the dynamics of magma chamber processes. The intrusive alkaline rocks in Girnar are diorites/monzodiorites and contain syenite/nepheline syenite veins. Several (alkaline) mafic dykes cut the alkaline rocks. These rocks are surrounded by intrusive tholeiitic gabbro and extrusive basaltic flows and a silicic (SiO2 > 65 wt%) ring dyke at the outer margin of the complex. The tholeiitic gabbro and basaltic lavas have relatively flat light rare earth element (REE) patterns (La/SmN ~ 0.8 to 1.8) with positive Eu anomalies of 1.1–1.3. The tholeiitic basalts formed by 3–5% partial melting of an incompatible element depleted mid-ocean ridge basalts (MORB)-like source. Accumulating c. 20–30% of (olivine, orthopyroxene, clinopyroxene, and plagioclase) crystals from the tholeiitic melt generated the tholeiitic gabbro. The alkaline rocks display enriched light REE patterns (La/SmN ~ 5.0 to 7.8) consistent with (~9%) partial melting of a spinel lherzolite source, different from the MORB-like source for tholeiitic rocks. The subsequent 58–72% fractional crystallization of olivine, clinopyroxene, plagioclase, orthoclase, spinel, and apatite mineral assemblage formed the alkaline rocks. Reverse and oscillatory zoning in plagioclase (An30 to An50) phenocrysts of the silicic rocks suggest that convective movement of crystals in a magma chamber led to initial crystallization of high-An plagioclase in the hotter zone of the magma chamber, followed by addition of low-An plagioclase in cooler regions of the magma chamber. Pressure estimates from shattered (xenocryst or antecryst) clinopyroxene crystals in silicic rocks give a minimum value of 450 MPa. Ti-in-quartz geothermometry gives a crystallization temperature between 690°C and 1080°C. The distinct isotopic composition of the silicic rocks (87Sr/86Sri = 0.7204–0.7275, εNd(i) = −6.8 to −7.3, 206Pb/204Pbi = 18.74–19.02, 207Pb/204Pbi = 15.76–15.79, 208Pb/204Pbi = 39.63–40.03, εHf(i) = −6.0 to −7.3) further indicates that the silicic rocks assimilated 7 to 9% granitic basement rocks. Overall, therefore, the Girnar Complex started to form with the emplacement of mafic rocks (both alkaline and tholeiitic) in the central part along a reactivated fault lineament and silicic rocks along the concentric marginal fault. Petrography, mineral chemistry, and whole-rock geochemical and Sr-Nd-Pb-Hf isotope ratios of the Girnar Complex rocks indicate that despite the close spatial association of tholeiitic gabbro and basalt, alkaline rocks, and silicic rocks, these rocks originated from multiple sources and evolved in a complex magma drainage and storage network in a continental setting of the Deccan Large Igneous Province (LIP). [ABSTRACT FROM AUTHOR]

The article profiles Shrikant Daji Limaye, a prominent Indian hydrogeologist known for his work in groundwater exploration and management, particularly in challenging basaltic terrains. Limaye has made significant contributions to the field over six decades, emphasizing the integration of scientific knowledge with community needs. He continues to inspire young hydrogeologists and is actively involved in philanthropic endeavors and environmental stewardship, promoting ethical groundwater management. His work has had a positive impact on groundwater resources and sustainable development, both in India and internationally. [Extracted from the article]