Compositions and Sources of Metasediments in the Upper Dharwar Supergroup, South India

Texturally mature, quartz-rich sandstones, texturally mature, mafic-rich sandstones, and texturally immature graywackes are abundant in the late Archean Chitradurga Group of the Dharwar craton in South India. When compared to graywackes of Paleozoic age from northeastern North America, the Chitradurga graywackes have slightly higher average concentrations of Na and ferromagnesian elements, indicating the existence of a more tonalitic and mafic-rich provenance during the late Archean in Karnataka. The regional tonalitic gneiss (Peninsular Gneiss) is the predominant source of these sediments, although mafic/ultramafic volcanic debris from unidentified sources is also important. Neither intermediate nor felsic volcanics nor an extensive metasedimentary terrane were prominent in the provenance. Although the composition of the craton was dominantly sialic, the presence of abundant ferromagnesian debris in some of the texturally mature sandstones that probably formed in shallow water, intracratonic, or platformal environments suggests that mafic rock was also situated on or near the craton during the late Archean.