RELICTS OF SEDIMENTARY PRECURSORS IN ARCHEAN GNEISSES - MELUKOTE PARAGNEISS - AN EXAMPLE FROM DHARWAR CRATON, INDIA

Relicts of sedimentary precursors in the Peninsular Gneisses around Me lukote-Katteri area of Dharwar Craton are recognised on the basis of f ield, petrological and geochemical data. The Melukote gneiss has inter beds of carbonates, quartzites, iron-formations and para-amphibolites with a concordant planar fabric. These gneisses are devoid of mafic-ul tramafic xenoliths which are one of the essential characteristics of t he orthogneiss component of Peninsular Gneiss (PG). The Melukote parag neiss (MG) contains interstitial calcite, relict arkosic texture, subr ounded to round quartz, plagioclase and zircon. Two generations of qua rtz and plagioclase are conspicuous in the MG. The MG are high SiO2 an d low Al2O3, Cr and Ni are significantly enriched - up to 334 ppm and 73 ppm respectively. The Rb and Sr contents are lower than the typical tonalite-trondhjemite gneisses (TTG). The high HREE patterns of MG an d very low negative Eu anomalies are distinct from those of TTG in the surrounding areas. These data indicate that MG represent first cycle immature sediment derived from a heterogenous provenance.