Sargur-Dharwar Relationship Around the Komatiite-Rich Jayachamarajapura Greenstone Belt in Karnataka

Abstract New geological and preliminary geochemical data presented here from J ayachamarajapura (JC Pura) reinforce the idea of orogenic separation of two sequences across a deformed angular un confonnity . The JC Pura belt forms a major structural dome linking a trail of enclaves to the north and south. Its main lithology is altered komatiites preserving excellent polyhedral joints, pillows, ocelli and spinifex texture. These peridotitic komatiites are closely associated with the basaltic komatiites now represented by dark shiny amphibolites.Cherty quartzites and BIF form minor units. This association is typical of the older greenstones (Sargur Group) of Kamataka. These lithologies are overlain unconformably by the basal quartz-pebble conglomerate and associated amygdular metabasalt - crossbedded quartz arenite alternations constituting the Bababudan Group in the Kibbanahalli arm of Chitradurga schist belt. Kibbanahalli volcanics are mainly tholeiites as distinct from the dominant komatiites of the JC Pura belt. Such chemical distinction, but of a different kind, is reported recently from the Kalasapura area of Bababudan belt. JC Pura area therefore offers yet another spectacle of Sargur-Dharwar orogenic discrimination in Kamataka.