Abstract—Gadag Schist Belt (GSB) is the northern continuity of Chitradurga Schist Belt (CSB) of Archean age (~ 2600 Ma). The GSB comprises of metavolcanics and metasediments and are surrounded by older TTG and younger granitoids. The gold mineralisation is confined to quartz veins hosted by metabasalt and metasedimentary and also associated with wall rock alteration (carbonitisation, chloritisation and seritisation). EPMA studies confirmed the gold association with pyrites. The analysis of the gold grain (3 to 6 micron) associated within the pyrite grain, the Au content varies from 84.64 to 82.64 wt. % and Ag content from 4.84 to 9.74 wt. % and other sulphides. The REE patterns shows enriched in LREE and depleted in HREE patterns, but with positive Eu anomaly indicates the hydrothermal fluids responsible for wall rock alterations and particularly LREE from host metabasalts or metasedimentory rocks. Fluid inclusion microthermometry in auriferous quartz veins reveal the existence of a metamorphogenic aqueous–gaseous (H2O–CO2–CH4+Salt) fluid that underwent phase separation and gave rise to gaseous (CO2–CH4), low saline (~5 wt.% NaCl equiv.) aqueous fluids. The estimated P–T range (240 to 360°C and 1.0 to 2.0 Kbar) compare well with the published P–T values of other orogenic gold deposits in general, considerable pressure fluctuation characterize gold mineralization at GSB. Ore fluids of the GSB with other gold deposits in the Dharwar Craton, confirms that fluids of low saline and aqueous–carbonic composition with metamorphic parentage played the dominant role in formation of Archean lode gold systems.

Index Terms—gadag, fluid inclusion, gold, dharwar craton.

Cite:Girish Kumar M, Korakoppa, M, M, Kalyana Krishna, Madhushree Mondal, and Ajit Singh, "Nature and Source of the Ore-forming Fluids Characterisation of Gadag Schist Belt, Dharwar Craton using Geochemistry and Fluid Inclusion Studies," International Journal of Geology and Earth Sciences, Vol. 8, No. 1, pp. 1-11, June 2022. doi: 10.18178/ijges.8.1.1-11

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