GEOCHEMISTRY OF PALEAO TO MESOPROTEROZOIC METASEDIMENATY UNITS, LAWA-MAYASERA AREA, CHANDIL FORMATION, EASTERN INDIAN CRATON: IMPLICATIONS FOR PROVENANCE AND SOURCE AREA WEATHERING

The Paleo to Meso Proterozoic meta-sedimentary units, comprising of mica schist, phyllite and quartzites from the Lawa –Mayasera area of Chandil Formation, were analyzed for major trace and REE to evaluate their provenance and source area weathering conditions. The pelitic rocks are characterized by moderate SiO₂ and Al₂O₃ contents and show consistent REE patterns with LREE enriched and HREE depleted patterns (LaN/YbN = 10.02–20.78). The total REE abundances of pelites are high (up to 201.212 ppm) with moderate negative Eu-anomalies (Eu/ Eu* = 0.54–0.75). Except high SiO₂ contents, the other major and trace element concentrations are significantly low in the associated quartzite. Although the quartzites contain low REE abundances (up to 24.46 ppm), their patterns characterized by negative Eu anomalies, are akin to pelites, suggesting that both the rock types may have been derived from similar source. The significant enrichment of LREEs, the distinctive negative Eu-anomalies and the flat HREE patterns of these Proterozoic pelites in the study area suggest derivation from an old upper continental crust composed chiefly of felsic components. The LREE-enriched and HREE depleted patterns with moderate negative Eu-anomalies of the quartzites strongly favors an evolved felsic source similar to that of pelites. The Chemical Index of Alteration and A–CN–K parameters indicate moderate chemical weathering in the source region of the meta-sedimentary rocks of Lawa– Mayasera area. The aim of this paper to characterize the geochemical composition of quartzite and phyllite rocks to deduce the provenance of the meta-sedimentary formation of the Lawa- Maysera area, to discuss source area weathering conditions and also to examine post-depositional and post-metamorphic changes using major, trace and rare-earth element geochemistry