Geochemical Characteristics of Archean Clastic Metasediments of Gadag Gold Field, Southern India: Implications for Provenance and Tectonic Setting

Archean turbidite hosted orogenic gold mineralization in the Gadag greenstone belt, Western Dharwar Craton, Peninsular India

“…While a U-Pb SHRIMP zircon study of turbidite graywackes from the GGB constrains the maximum sedimentation age from the youngest detrital population as 2547 ± 5 Ma (Sarma et al, 2012). These volcano-sedimentary rocks had different tectonic settings of subduction complex and they occur juxtaposed, probably by accretion process during convergence of plate (Ugarkar et al, 2000;Ugarkar and Nyamati, 2002).…”

“…Mafic metavolcanics are low K, Fe-rich tholeiites derived by partial melting of the upper mantle source, while the intermediate and felsic metavolcanics were derived by re-melting of these tholeiites mainly in the crustal regimes (Ugarkar et al, 2000). Clastic metasediments had a sialic dominated mixed felsic and mafic source in the provenance (Ugarkar and Nyamati, 2002). The U-Pb zircon ages for felsic metavolcanics from the central part of the Gadag greenstone belt indicate volcanism at 2588 ± 10 Ma (Sarma et al, 2011).…”

“…The steep mylonitic zone, a major thrust-fault contact (Chitradurga Thrust Fault) along the eastern margin of the Chitradurga greenstone belt, extending over a length of 400 km from Gadag in the north to Mandya in the south is considered as the boundary between the two blocks (Kaila et al, 1979;Chadwick et al, 2000;Sengupta and Roy, 2012). The volcano-sedimentary association present in the greenstone terrains of the WDC and EDC displays distinct geodynamic settings, as deciphered by recent petrological and geochemical studies (Balakrishnan et al, 1999;Manikyamba et al, 2008Manikyamba et al, , 2014Manikyamba and Kerrich, 2011;Jayananda et al, 2013Jayananda et al, , 2014Ugarkar and Nyamati, 2002;Ugarkar et al, 2000Ugarkar et al, , 2013. Based on combined U-Pb zircon ages and Nd isotope data, the craton has been divided into three provinces western (3.4 to 3.2 Ga), eastern (3.4 to 3.2 Ga) and central with mixed old and younger crust (3.4 to 3.2 Ga and 2.56 to 2.52 Ga) and eastern with mainly younger (2.56 to 2.52 Ga) crust Jayananda et al, 2013).…”

Isotope (C and O) composition of auriferous quartz carbonate veins, central lode system, Gadag Gold Field, Dharwar Craton, India: Implications to source of ore fluids

“…For hydrothermal fluids, the temperature range was taken to be from 150°C to 350°C, based on temperature estimation from fluid inclusions of the present study and that of Ugarkar et al (2000). For metamorphic fluid, a temperature value of 350°C was considered based on the high temperature range of fluid inclusion data, and greenschist to lower amphibolite metamorphic assemblage reported by Ugarkar and Nyamati (2002) from Gadag area and Raase et al (1986) for the northern part of the Dharwar Craton. For magmatic fluids, as 2516 ± 10 Ma to 2512 ± 11 Ma granites are believed to have given rise to gold mineralisation (Ram Mohan et al, 2014;Sarma et al, 2011) a temperature range of 600°C-700°C has been considered.…”

“…Gadag schist belt has been reported to vary from greenschist to lower amphibolite facies (Ugarkar and Nyamati, 2002), implying a temperature range of 250°C to up to 500°C. In this temperature range, the average −0.75‰ δ 13 C of carbonate rock of Chitradurga schist belt during metamorphic devolatilisation would produce CO 2 having a δ 13 C CO 2 values in the range from 0.55‰ to 2.05‰.…”