Bimodal magmatism in the Eastern Dharwar Craton, southern India: Implications for Neoarchean crustal evolution

Wang, Jingyi; Santosh, M.; Jayananda, M.; Aadhiseshan, K.R.

doi:10.1016/j.lithos.2019.105336

Cited by 11 publications

(4 citation statements)

References 62 publications

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“…Southern part of the Peninsular India is composed of the Paleo-to Neoarchean Dharwar Craton in the north and the mosaic of Archean-Proterozoic lower crustal blocks accreted to it towards the south (Figure 1; Radhakrishna, 1989;Chadwick et al, 2000;Jayananda et al, 2018;Wang et al, 2020; Wang and Santosh, 2019;Mathew et al, 2022). These lower crustal blocks include the Mesoarchean Coorg Block, and the Neoarchean Nilgiri (NIL)-Biligirirangan (BR)-Shevaroy (SH)-Namakkal (NM)-Madras (MD) Blocks (Peucat et al, 2013;Santosh et al, 2013;Samuel et al, 2014;Santosh et al, 2015;George et al, 2019;Ratheesh-Kumar et al, 2020;Santosh, 2020;Yang et al, 2021;Anoop et al, 2022) adjacent to the Dharwar Craton.…”

Section: Geological Setting Dharwar Craton and Lower Crustal Blocksmentioning

confidence: 99%

Role of acidic fluids in Earth’s deep lithosphere: Insights from the Neoarchean magmatic roots of the Nilgiri Block, southern India

Samuel

Santosh²,

Jang³

et al. 2022

Front. Earth Sci.

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Fluids play a major role in facilitating igneous/metamorphic processes in the Earth’s crust and mantle. In this study, we investigate the nature and composition of fluids in Earth’s interior by studying the lower crustal rocks. We compare accessory minerals (e.g., apatite, monazite, allanite, and titanite), their texture, mineral reactions and composition among regionally distributed metamorphosed mafic and felsic rocks representing the roots of Neoarchean arc magmatism from the Nilgiri Block of the Southern Granulite Terrane in India. Regional trends in accessory minerals show the formation of monazite, allanite, and titanite in the felsic rocks. Apatite is depleted in REEs in all the rock types, irrespective of the difference in their whole-rock chemistry. Textural features and mineral reactions show that these accessory minerals were affected by fluids present in the lower crustal conditions. By comparing our results with those from previous experimental results, we further show that acidic CO2-H2O-HCl-HF fluids stable in lower crustal conditions could have resulted in these chemical and textural features. Dielectric constant of water is high (10–35 compared to lower crustal conditions) in high-pressure and low-temperature conditions of subduction zones and the upper mantle. Such conditions would enhance dissociation of HCl (compared to lower crust) and result in acidic fluids during dehydration reactions in subduction zones and in the upper mantle. Our results have important implications in understanding the nature and composition of fluids in Earth’s interior and would be helpful to model the tectonic and deep geochemical processes in both early and modern conditions in planetary interiors.

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Section: Geological Setting Dharwar Craton and Lower Crustal Blocksmentioning

confidence: 99%

Role of acidic fluids in Earth’s deep lithosphere: Insights from the Neoarchean magmatic roots of the Nilgiri Block, southern India

Samuel

Santosh²,

Jang³

et al. 2022

Front. Earth Sci.

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“…As an important magmatic process in plutonic systems, magma mixing sometimes plays a vital role in the formation of granitoids in various tectonic settings and is the main mechanism leading to the diversity of igneous rocks (Laurent et al, 2017). Evidence for magma mixing not only provides petrogenetic information related to crust-mantle interaction, but can also to some extent constrain the tectonic setting (Bonin, 2004;Dong et al, 2006;Wang, Santosh, Jayananda, & Aadhiseshan, 2020).…”

Section: Introductionmentioning

confidence: 99%

Evidence for magma mixing during Triassic magmatism in West Qinling, China: Constraints from petrology, geochemistry, U–Pb zircon geochronology, and Sr–Nd–Hf isotopic of the Baguashan pluton

Dong

et al. 2021

Geological Journal

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The West Qinling Orogen, which forms the western part of the Qinling Orogenic Belt, is characterized by the voluminous distribution of Triassic granitoids. Here, we investigate the Baguashan monzogranite which hosts numerous mafic microgranular enclaves (MMEs). We present zircon U–Pb–Hf and whole‐rock geochemical as well as Sr–Nd isotopic data of the monzogranites and MMEs with a view to gain insights on the petrogenesis and geodynamic setting. Zircon LA‐ICP‐MS U–Pb dating yields ages of 219.0 ± 1.7 Ma and 219.5 ± 1.6 Ma for the MMEs, and 214.2 ± 1.3 Ma for the host monzogranite, suggesting formation from coeval magmas. The host monzogranites show high SiO2, Rb, Ba, and Th contents, but low TiO2, MgO, P2O5 values, with A/CNK of <1.1. Zircon grains from monzogranites show εHf(t) values in the range of −6.3 to +3.2 with corresponding two‐stage Hf model ages (TDM2) of 1.39–2.25 Ga. The MMEs are mostly elliptical or spherical in shape and have lower SiO2 and Th contents, but higher MgO, TiO2, and CaO, and εHf(t) values ranging from −6.1 to +5.7 with TDM2 of 1.17–2.23 Ga. The Sr–Nd isotopic data for MMEs and monzogranites show (87Sr/86Sr)i ratios ranging from 0.7059 to 0.7069 and low εNd(t) values ranging from −6.07 to −4.18, suggesting a crustal origin. Based on the relatively homogeneous Sr–Nd–Hf isotopic compositions, we suggest that the MMEs represent magma mixing, and the mafic magma injected into the felsic magma chamber was probably derived by the reworking of mafic lower crust with a contribution of juvenile materials. We propose a model involving delamination of thickened lower crust below the West Qinling Orogen after the collision between the North China Block and the South China Block in the Late Triassic. Subsequently, the lower crust was partially melted by the heat input from the upwelling asthenosphere and produced the mafic magma. Partial melting of the ancient metamorphic rocks generated the granitic magma. The interaction of mafic and felsic magmas occurred within a post‐collisional tectonic setting in the Late Triassic.

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“…The MMEs hosted by the granitoids in these regions represent either xenoliths captured from country rocks (Maas, Nicholls, & Legg, ), residual material that unmixed from the host melt (Chappell, White, & Wyborn, ), early formed crystals from the parental magma or cognate fragments of cumulate minerals (i.e., cumulates) (Donaire, Pascual, Pin, & Duthou, ), or products of mixing of magmas derived from different sources (Baxter & Feely, ; Q. Chen et al, ; Ma et al, ; Zhou et al, ). Understanding the nature and origin of the granitoids and their MMEs is important in constraining the source and tectonic evolution of magmatism (Wang, Santosh, Jayananda, & Aadhiseshan, ).…”

Section: Introductionmentioning

confidence: 99%

Anisian granodiorites and mafic microgranular enclaves in the eastern Kunlun Orogen, NW China: Insights into closure of the eastern Paleo–Tethys

Wei

Santosh

et al. 2020

Geological Journal

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Granitoids and their mafic microgranular enclaves (MMEs) provide important insights into magmatic activity and tectonic evolution associated with accretionary orogens. Here we investigate the origin of Middle Triassic granodiorites and MMEs in the central segment of the eastern Kunlun Orogen (EKLO) in NW China, which is an important region to evaluate the history of closure of the Paleo–Tethys, through zircon U–Pb geochronology, major and trace element geochemistry, and Sr–Nd–Hf isotopes. Zircon U–Pb ages indicate the coeval formation of granodiorites and their MMEs during the Anisian (ca. 245 Ma). The granodiorites are calc‐alkaline and metaluminous with high SiO2 contents and Mg# values. They are characterized by enrichment of LREEs and LILEs, and depletion of Nb, Ta, and Ti. Their Sr–Nd –Hf isotopic compositions indicate that the magmas were derived from enriched mantle and Paleoproterozoic basement. The monzodioritic‐dioritic MMEs exhibit low SiO2 contents and high Al2O3 and MgO with high Mg# values, enrichment in LREEs and LILEs, and depletion in HFSEs with negative Nb, Ta, Ti, and P. In contrast, the gabbroic MMEs show higher Mg# values and Cr contents. Both types of MMEs have Sr–Nd–Hf isotopic compositions similar to the host granodiorites, and originated from mixing of lower crust‐ and enriched mantle‐derived magmas. The mantle‐derived sources were metasomatized by slab‐derived melts. The Middle Permian to Middle Triassic magmatism, metamorphism, sedimentation, and tectonics in the EKLO suggest northward subduction of the Paleo–Tethys Ocean as represented by the A'nyemaqen Ocean. The magma mixing that generated the Anisian granodiorites and MMEs was likely associated with slab break‐off of the Paleo–Tethys Ocean. The formation of the Anisian magmatic rocks in the EKLO suggest that the cessation of subduction of the Paleo–Tethys Ocean and onset of collision took place during the late stage of Middle Triassic.

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Bimodal magmatism in the Eastern Dharwar Craton, southern India: Implications for Neoarchean crustal evolution

Cited by 11 publications

References 62 publications

Role of acidic fluids in Earth’s deep lithosphere: Insights from the Neoarchean magmatic roots of the Nilgiri Block, southern India

Role of acidic fluids in Earth’s deep lithosphere: Insights from the Neoarchean magmatic roots of the Nilgiri Block, southern India

Evidence for magma mixing during Triassic magmatism in West Qinling, China: Constraints from petrology, geochemistry, U–Pb zircon geochronology, and Sr–Nd–Hf isotopic of the Baguashan pluton

Anisian granodiorites and mafic microgranular enclaves in the eastern Kunlun Orogen, NW China: Insights into closure of the eastern Paleo–Tethys

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