Geological setting, mineralogy, geochemistry and genesis of the Middle Archaean Kalyadi copper deposit, western Dharwar craton, southern India

摘要: The Kalyadi polymetallic copper deposit occurs within the Middle Archaean (≥3.0 Ga), medium-grade schist belt which consists predominantly of ultramafic-mafic schists interbedded with chemogenic chert, detrital high Al-Mg and siliceous schists. This sedimentary exhalative type (SEDEX type) ore-body is only hosted in cherts western Dharwar craton. supracrustal rocks are intruded by tonalite-trondhjemitic gneisses (ca. 3.0 Ga) granite 2.6 Ga). polygenetic nature. primary ores represented disseminations pyrite ± linneite chalcopyrite magnetite essentially along bedding lamination metachert referred to as metamorphosed chert-sulphide rhythmites a stratiform type. ore low-grade records imprints at least two events deformation. Pyrite characterised high-Co values (262–4524 ppm) high–Co/Ni ratios (3.0–19.7). Rare earth element patterns host metacherts identical, La enrichment, absence Eu anomalies flat depleted HREE δ34 S = −0.8‰. secondary (remobilised) structurally controlled occurring veins stringers discordant or schistosity. constituent chalcopyrite-pyrite-pyrrhotite minor pentlandite. These sulphides low-Co/Ni (0.87–1.80), have either strong positive negative anomaly show slight enrichment. value ranges from +2.64 −4.29‰. It interpreted that were derived volcanogenic hydrothermal fluids syngenetic/chemical deposits deep sea environment. epigenetic mineralisation related subsequent migmatisation, deformational granitic activity.