Petrological and geochemical characteristics of Marunthurkota syenites from the Kerala khondalite belt, southern India

Sreejith, C.; Kumar, G. R. Ravindra

doi:10.1007/s12594-009-0018-8

Cited by 6 publications

(1 citation statement)

References 19 publications

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“…The major and trace element variations also show smooth patterns favoring differentiation from a common magma. However, the silica-oversaturated chemistry of Elagiri syenites is found to be gradational to A-type (granite) affinity and in this view, the Elagiri syenites are broadly correlatable with Marunthurkota syenites (Sreejith and Ravindra Kumar, 2009) and Kibaran rocks (Tack et al, 1994). The mechanism of differentiation for Elagiri was probably aided by liquid immiscibility.…”

Section: Role Of Liquid Immiscibility In Elagiri Plutonmentioning

confidence: 82%

Geochemistry and petrogenesis of syenites and associated rocks of the Elagiri complex, Southern Granulite Terrane, India

Mukhopadhyay

Ray

Balaram

et al. 2011

Journal of Asian Earth Sciences

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Section: Role Of Liquid Immiscibility In Elagiri Plutonmentioning

confidence: 82%

Geochemistry and petrogenesis of syenites and associated rocks of the Elagiri complex, Southern Granulite Terrane, India

Mukhopadhyay

Ray

Balaram

et al. 2011

Journal of Asian Earth Sciences

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MnNCKFMASH Phase Relations in Cordierite–Orthopyroxene Migmatitic Gneisses, Southern India: Implications for Low-pressure Crustal Melting under Granulite-facies

Sreejith

Kumar

2012

Journal of the Geological Society of India

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Cordierite-orthopyroxene migmatitic gneisses exposed in Achankovil unit of the Kerala Khondalite Belt, southern India show evidences of melting, melt extraction and in-situ crystallization of melt under granulite-facies conditions. The sequential mineral assemblages garnet + biotite + orthopyroxene + plagioclase + quartz (± melt) in the mesosomes and garnet + biotite + orthopyroxene + cordierite + plagioclase + K-feldspar + quartz + melt in the melanosomes makes the Achankovil cordierite-orthopyroxene migmatitic gneisses a good example of anatectic rocks, where substantial melt fractions remained in-situ during decompression and cooling. Therefore, the rocks provide an opportunity to investigate deep crustal processes and record of rheological (thermal and mechanical) reequilibration prevailed during the final stages of orogeny. The significance of cordierite formation and its possible relationship with melt formation are investigated applying theoretical calculations in the MnO–Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O (MnNCKFMASH) system. Results of numerical modelling of the mineral assemblages in pressure–temperature–composition (P–T–X) pseudosections using Perple_X infer that the sequence of reactions involving formation of cordierite-orthopyroxene-melt assemblage is consistent with an isothermal decompression (with a pressure drop of >1.5 kbars) at high temperatures (>800 °C), forming leucosomes. Biotite dehydration melting reactions, occurring above 4.5 kbars constrain prograde arm of the P–T trajectory and is interpreted as a product of crustal thickening, which was followed by rapid decompression. The final stage of exhumation is characterized by rehydration of cordierites in the melanosome by melt-solid interactions at exceptionally low-pressure (~3.2 kbars) conditions. The high-temperature isothermal decompression inferred from the mineral reactions and P–T–X pseudosections constitute a clockwise P–T path for the exhumation of the lower crust. This clockwise P–T path is consistent with the common tectonic model accepted for the genesis of granulite-facies migmatites during crustal thickening and later unroofing, accompanied with arc-continent collision. Our conclusions indicate low–P metamorphism and anatexis can be traced to convergent setting, where melt buoyancy considerably decreases density of the lithosphere and modifies rheology leading to rapid exhumation of the lower crust. Therefore, the crustal evolution in the Kerala Khondalite Belt is correlated with two stage processes: (i) thickening of the crust in relation to a continental-arc setting, followed by (ii) exhumation along a high-temperature stable geotherm with sufficient pressure release associated with syn- to post-convergence transpression and transtension.

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REE–HFSE–rich, Titanite-bearing Syenite - Pyroxenite Intrusive Suite from the Chilka Lake Domain of the Northeastern Eastern Ghats Belt

Bhattacharjee

Tripathy

Nanda

et al. 2022

Journal of the Geological Society of India

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A suite of REE - HFSE - rich syenite and associated clinopyroxenite hosted in charnockitic orthogneisses of the northeastern part of the Eastern Ghats province, south of the Mahanadi shear zone has been recorded for the first time. The mode of emplacement, petrography, mineralogy, chemistry and economic significance in terms of the REE and HFS elements of this magmatic suite of intrusive rocks are presented and discussed. The coarse grained syenite, composed mainly of Ba-bearing (with up to 8 wt% BaO) K-feldspar (hyalophane), and accessory greenish clinopyroxene is the main rock type of this magmatic unit. Associated segregations of clinopyroxene cumulates has formed a greenish grey coarse-grained pyroxenite. Sporadic concentration of sphene (titanite) in irregular patches in the syenite is also observed which displays high radioactivity. Sphene along with allanite, thorite, monazite and other REE bearing phases are characterized by high abundance of total-REE and HFSE. The syenite and pyroxenite do not exhibit features of discernible post-emplacement deformation and metamorphism and may represent a late-tectonic event of ferroan-felsic magmatism in the Chilka lake domain of the northeastern Eastern Ghats belt.

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Petrological and geochemical characteristics of Marunthurkota syenites from the Kerala khondalite belt, southern India

Cited by 6 publications

References 19 publications

Geochemistry and petrogenesis of syenites and associated rocks of the Elagiri complex, Southern Granulite Terrane, India

Geochemistry and petrogenesis of syenites and associated rocks of the Elagiri complex, Southern Granulite Terrane, India

MnNCKFMASH Phase Relations in Cordierite–Orthopyroxene Migmatitic Gneisses, Southern India: Implications for Low-pressure Crustal Melting under Granulite-facies

REE–HFSE–rich, Titanite-bearing Syenite - Pyroxenite Intrusive Suite from the Chilka Lake Domain of the Northeastern Eastern Ghats Belt

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