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

Abstract

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 petrographi-cal observations indicated that metapelites of the study area were metamorphosed up to amphibo-lite 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 proto-lith of the metapelites was produced by erosion products of acid rocks, which were which are em-placed in volcanic arc environment.