Sulphur Isotopic Composition of Ingaldhal Sulphides, Karnataka State, India

Abstract

Mineralisation at Ingaldhal, Kamataka State, comprises massive vein and disseminated sulphides within deformed Archaean metasedimentary rocks and metabasaltic rocks of tholeiitic affinity. Seven sulphur isotope ratio determinations on sulphide minerals separated from ore samples yield a narrow distribution of δ³⁴S values around the meteoritic mean (range -0.9 to +0.4 per mil; mean -0.2 per mil) values which arc similar to Archaean volcanogenic ores elsewhere.

The source of sulphur is considered to be magmatic, with possible contribution from Archaean seawater. The stockwork and massive nature of the Ingaldhal ores, their Cu-Fe content, poorly developed metal zoning and basic volcanic association in a submarine setting point strongly to subsurface and sea-floor sulphide accumulation from sulphur- and metal-bearing fluids of volcanic origin. The sulphur isotope data support this view.