Petrochemical studies of metapelites of the area around Sonapahar, Meghalaya, India


Metapelites form a dominant component of the Precambrian basement complex in the Sonapahar area of Shillong Plateau, north-east India. In this paper, a new data on the major, minor and trace element compositions of these metapelites, an important member of the Precambrian basement rocks found in the Shillong plateau is reported. Petro-chemical data on these rocks were used to reproduce the nature and composition of their protolith. The mineral assemblages and petrographical observations indicated that metapelites of the study area were metamorphosed up to amphibolite to granulite facies metamorphism. Chemically, metapelites are characterized by relatively high Al2O3 (11.35-19.91 wt%), enrichments in MgO, FeO, MnO and TiO2; depletions in Na2O and especially CaO; low concentrations of Sc, Cr, Co, Ni, and Sr; high concentrations of Y, Nb, Zr, Hf, Ta, Th, U, and REE (rare earth elements) with prominent negative Eu-anomalies. Results indicated that these rocks were redeposited and metamorphosed products of Precambrian weathering crusts. The protolith of the metapelites was produced by erosion products of acid rocks, which were which are emplaced in volcanic arc environment.

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