Madhavaram metavolcanic belt, Southern India: spatial continuity of Neoarchean Raichur–Gadwal schist belt, Eastern Dharwar Craton

Through detailed field and laboratory studies involving geological mapping, petrographic, geochemical and mineral chemistry studies, a metavolcanic belt comprising of basalt–basaltic andesite–andesite is reported from the Precambrian granitic terrain at Madhavaram area in southern India. The WNW-ESE trending Madhavaram metavolcanic belt is located along the southern extension of Raichur schist belt of Eastern Dharwar Craton. Field studies reveal that the major foliation recorded in the area is WNW-ESE to NW-SE trending with moderate to steep NE dips. Petrographically the andesite is essentially composed of hornblende, plagioclase, clinopyroxene and Fe Ti oxides, while the dacite is composed of plagioclase, amphibole, quartz and opaques. In the IUGS TAS diagram the studied rocks essentially fall in the field of basalt–basaltic andesite–andesite field. Major oxide analyses of the metavolcanic rocks indicate that the SiO2 ranges from to 49.68 wt.%, in basalt and 59.01 wt.% in andesite. The MgO ranges from 3.46 in andesite to 5.22 wt.% in basalt. Geochemically the basaltic rocks exhibit tholeiitic trend, while the andesitic rock exhibit calc-alkaline nature. Chondrite normalised REE plots reveal a general enrichment of LREE relative to HREE and a low magnitude Eu anomaly. In primitive mantle trace element spider diagram the metavolcanic rocks of Madhavaram area exhibit negative Nb and Ti anomaly indicating their eruption in subduction zone tectonic setting. The basalt–basaltic andesite–andesite metavolcanic rocks of Madhavaram area indicates the possible spatial continuity of the Neoarchean Raichur–Gadwalgreenstone belts in Southern India.