Provenance, Paleoweathering and Paleotectonics of Cobalt Bearing Metasedimentary Rocks of the Delhi Supergroup, North Delhi Fold Belt, NW India

Cobalt bearing metasedimentary rocks from the Nasibpur and surrounding areas of North Delhi Fold Belt, NW India has been studied to elucidate their provenance, palaeoweathering, palaeoclimatological conditions and depositional environment. The investigated area is characterized by metasedimentary formations such as quartzites, mica schists, garnet mica schist, phyllites, gneiss, amphibolites and magmatic phases like granites and pegmatites. Petrographic analysis affirmed that quartzites are mineralogical mature, fine to medium grained. On the basis of modal compositions these quartzites range from Fe-sand and quartz arenite in composition. The calculated chemical index of alteration (CIA) values (31.98 to 75.87 with an average of 48.60 indicates low to moderate weathering under semiarid to humid climatic conditions. Most of the quartzites samples have SiO₂/Al₂O₃ (>10, avg. 43) which indicates high maturity. Cobalt concentration in these quartzites, mica schist, pegmatites range from 166 to 3657, 62–166, and 167–519 ppm respectively. Quartz dilution during hydraulic sorting has led to low concentrations of rare earth elements in the quartzites. The rocks exhibit enrichment in LREE with (La/Sm)_n (1.2–7.41 avg. 4.56) with noticeable negative Eu anomalies (Eu/Eu* = 0.34–0.74). Evaluation of mineral and whole rock geochemistry collectively indicate their predominant derivation from a felsic source and deposition in an active to passive continental setting.