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

Relicts of sedimentary precursors in the Peninsular Gneisses around Melukote-Katteri area of Dharwar Craton are recognised on the basis of field, petrological and geochemical data. The Melukote gneiss has interbeds of carbonates, quartzites, iron-formations and para-amphibolites with a concordant planar fabric. These gneisses are devoid of mafic-ultramafic xenoliths which are one of the essential characteristics of the orthogneiss component of Peninsular Gneiss (PG). The Melukote paragneiss (MG) contains interstitial calcite, relict arkosic texture, subrounded to round quartz, plagioclase and zircon. Two generations of quartz and plagioclase are conspicuous in the MG. The MG are high SiO2 and 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 and 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.