Characterization of partial melting events in garnet-cordierite gneiss from the Kerala Khondalite Belt, India

Sorcar, Nilanjana; Joshi, Kumar Batuk; Oliveira, Elson P.; Tomson, J.K.; Nandakumar, V.

doi:10.1016/j.gsf.2019.05.013

Cited by 26 publications

(13 citation statements)

References 119 publications

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“…The reproducibility of the geochemical data was monitored using NOVA (Agnihotri, 2001;Amin et al, 1972) and MAG. The precision and accuracy for the major and trace elements through XRF and ICP-MS were better than 5% (Banerji et al, 2017(Banerji et al, , 2019Sorcar et al, 2020).…”

Section: Textural and Geochemical Analysismentioning

confidence: 93%

Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India

et al. 2021

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The climate variability over western India has been significantly influenced by the perturbations in the Indian summer monsoon (ISM) and thus, provides a crucial platform to investigate the paleomonsoon variations, weathering intensity, and sediment source. The mudflats of southern Saurashtra, western India are deprived of perennial rivers, but the region receives terrestrial contribution exclusively due to activation of seasonal rivers during the monsoon. In the present study, an attempt has been made to investigate the paleomonsoon and palaeoweathering using various geochemical proxies (detrital, productivity, redox, and weathering) on the mudflat sediment core of southern Saurashtra, western Gujarat. The core is chronologically constrained by 14 C, 210 Pb, and 137 Cs dating techniques. The study suggests ISM strengthening during 2000-1800 cal yr BP with intermittent marginal ISM weakening during 1950-1970 cal yr BP and 1930-1890 cal yr BP associated with the reduced solar irradiance. Further, ISM weakening has been invoked during Dark Age Cold period (1800-1300 cal yr BP) and Little Ice Age (800-200 cal yr BP) interrupted by a marginal ISM strengthening during Medieval Warm period and the last two centuries witness climate warming. Based on historical rainfall data and Al 2 O 3, an intermittent strengthening of ISM during 90-30 cal yr BP has been suggested while a gradual increase in the weathering intensity synchronous to the rise in sea surface temperature (SST) during the last 200 cal yr BP revealed the role of temperature on the intensity of chemical weathering in the study area. In spite of changes in the geochemical proxies as a function of ISM fluctuations, the palaeoweathering intensities has remained nearly consistent wherein the chemical weathering was less operative and accompanied by the deposition of texturally immature sediments. The sediments of Diu mudflat indicate mafic signatures thereby underscoring a major contribution of the Deccan basalts along with other variable sources.

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Section: Textural and Geochemical Analysismentioning

confidence: 93%

Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India

et al. 2021

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“…The SGT is a collage of several Precambrian high-grade crustal blocks with contrasting geological and geochronological signatures separated by brittle-ductile shear/suture zones [18][19][20][21][22][23][24]. The Salem Block, the Madurai Block, the Trivandrum Block, and the Nagercoil Block are the four distinct crustal domain in SGT which archive the multiple magmatic, metamorphic, and deformation history of the SGT [4,20,[25][26][27][28][29]. The Madurai Block in the north is separated from the Trivandrum Block by a 8-10 km wide NW-SE trending AKSZ [30,31].…”

Section: Geology Of the Study Areamentioning

confidence: 99%

“…In the past few decades, a number of studies have been carried out in AKSZ which interpreted it as a magnetic lineament [32,33], a dextral or Sinistral Shear Zone [31,34,35], a zone of coaxial deformation [36], subduction zone [28,37,38], a collisional suture [15], reworked margin of the Madurai Block [39], a sedimentary/ back-arc basin [40], and a single/two different shear zones [2,34,37,41]. The Achankovil Zone consists of a variety of magmatic and metamorphic lithologies including garnetbiotite gneiss, garnet-cordierite gneiss, khondalites, charnockite, two-pyroxene mafic granulite, calc-silicate, and quartzite [2,23,29,39]. The high-grade metamorphic rocks in AKSZ are intruded by felsic plutons, mafic dykes, and mafic to ultramafic bodies [42][43][44].…”

Section: Geology Of the Study Areamentioning

confidence: 99%

Crustal Density and Susceptibility Structure beneath Achankovil Shear Zone, India

Prasad¹,

Dubey

Joshi

et al. 2021

Lithosphere

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The Southern Granulite Terrain (SGT) is a large tract of exposed Archean continental crust, divided into the Madurai Block (MB), Trivandrum Block (TB), and Nagercoil Block (NB). These crustal domains are linked with the NW-SE trending Achankovil Shear Zone (AKSZ). We combine gravity and magnetic data with previously published ground observations and geochronological data to re-evaluate the crustal architecture, evolution of the AKSZ, and possible extension of AKSZ into Madagascar. Analyses indicate that the long wavelength trends of the magnetic anomalies originate at ~20 km depth of different SGT blocks. These observations are corroborated with the gravity as well as computed gravity gradient anomalies. The presence of khondalite outcrops in Trivandrum Block implies that high magnetization crust is the main source of positive magnetic anomalies. Such magnetic anomalies advocate that SGT preserves the remanent of Archean crustal blocks in South India, a part due to variation in thermal and geochemical processes. The AKSZ, TB, and MB exhibit contrasting magnetic crustal signatures. The joint modeling results reveal a three-layered crustal configuration with varying Moho ranging from 41 to 34 km in NE to SW, respectively. It is also noted that AKSZ is a narrow and deep structure near to the Western Ghats Escarpment while it is wide and shallow in the far-east, which implies that the evolution of the Western Ghats is a late geological event.

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“…Electron microprobe analyses (EPMA) on polished sections was carried out at the Indian Institute of Technology (IIT), Kharagpur using CAMECA SX-100. The operating conditions of the instrument were 15 kV accelerating voltage, 15 nA beam current, and 1-2 μm beam diameter (see Sorcar et al, 2020). Feldspar, biotite and amphibole analyses are obtained from all the granitoid (TTGs, high-K granitoids (hybrid granites)) types.…”

Section: Mineral Chemistrymentioning

confidence: 99%

Characterization of multiple episodes of melt generation from lower crust during Archaean using amphibole composition

et al. 2021

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Spatial association of tonalite trondhjemite granodiorites (TTGs) and high-K granitoids (anatectic and hybrid granites) from the Bundelkhand Craton (BC), Central India, is well known. Geochronological data indicates multiple episodes of formation of these high silica rocks showing a spread of ~1 Ga during Paleo to Neoarchaean. In the present study, we try to understand the evolution of TTGs and high-K granitoids (hybrid granites) from the BC using amphibole composition. The amphibole in both TTGs and high-K granitoids (hybrid granites) from the BC are characterised as magmatic, zoned, and calcic in nature. We find that the amphibole composition of the studied rocks is dominated by magnesiohornblende along with less common occurrence of tschermakite, magnesiohastingsite and edenite. Overall variation in amphibole compositions in terms of exchange vectors show a well defined linear trend (except for a late stage low-grade metamorphic readjustment), which suggests melt control over crystallization and evolution of amphibole chemistry. Moreover, the geothermobarometric analysis points towards higher pressure formation of TTGs in comparison to that of high-K granitoids (hybrid granites), with nearly the same temperature conditions in both the cases. Combining all our findings, we propose the evolution of the two considered rock types through lower crustal melting under varying P H2O conditions at different depths of emplacement.

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Characterization of partial melting events in garnet-cordierite gneiss from the Kerala Khondalite Belt, India

Cited by 26 publications

References 119 publications

Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India

Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India

Crustal Density and Susceptibility Structure beneath Achankovil Shear Zone, India

Characterization of multiple episodes of melt generation from lower crust during Archaean using amphibole composition

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