Geochemistry data of the nadergul granodiorite of the late archean hyderabad granite batholith part of eastern dharwar craton india; implications for composition of the lower continental crust

摘要

The Nadergul granodiorite (NG), is a part of Hyderabad Granite Batholith (HGB), exposed at ground level covering an area of 6 km2. Field observational data suggests that the NG is involved in the magma mixing mingling process. Petrographical data shows holocrystaline, phaneritic, coarse grained, inequigranular, mesocratic characteristics, essentially consists of quartz, orthoclase, plagioclase and microcline. The common accessory minerals are hornblende, biotite, clinopyroxene, zircon, fluorite, apatite and opaque. The myrmekitic texture is the most common intergrowth texture which seems to be magmatic origin. Geochemical data suggest that the NG is metaluminous and show calc-alkaline trend. It is charecterised by SiO2 content ranging from 63.55 % to 64.54%, moderate alkali content (Na2O + K2O = 5.6%), relatively high MgO content ranging from 2.8 % to 3.5 %. The total CaO-Na2O-K2O content ranges from 9.5 % to10.4 %. The normalised REE patterns show LREEs enrichment with slight negative europium anomaly. The High Field Strength Elements such as Zr (67.3 to 114.3 ppm), Y (21.1 to 30.1 ppm), Nb (6.3 to 8.5 ppm) and Th (8.4 to 13.8 ppm) are relatively enriched. The granodiorite is I type, falls in the Volcanic Arc Granitoid (VAG) field in tectonic discrimination diagram.