Strontium and sulphur isotopic constraints on the formation of the Mangampeta barite deposit, Cuddapah basin

Strontium (Sr) isotope analyses of barite and associated pyrite-bearing carbonaceous tuff are carried out to understand the nature of mineralizing fluids for Mangampeta barite deposit, which is one of the largest barite deposits in the world. 87Sr/86Sr ratios of barite and pyrite-bearing carbonaceou...

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Bibliographic Details
Published in:Current science (Bangalore) 2013-08, Vol.105 (4), p.499-504
Main Authors: George, Bivin Geo, Shalini, N., Pandian, M. S., Rai, Vinai K., Bhutani, Rajneesh, Balakrishnan, S.
Format: Article
Language:English
Subjects:
Barite
Fluid dynamics
Fluid flow
Fluids
Homogenizing
Isotope ratios
Isotopes
Lapilli
Pyrites
RESEARCH COMMUNICATIONS
Sea water
Sediments
Shales
Strontium
Sulfur
Tuff
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Summary:Strontium (Sr) isotope analyses of barite and associated pyrite-bearing carbonaceous tuff are carried out to understand the nature of mineralizing fluids for Mangampeta barite deposit, which is one of the largest barite deposits in the world. 87Sr/86Sr ratios of barite and pyrite-bearing carbonaceous tuff range from 0.70754 to 0.728951 and 0.72969 to 0.819633 respectively. These ratios, high compared to the Proterozoic sea water, preclude the well-mixed sea water or mantle to be the immediate source of Sr, and by association of barium (Ba). We infer that Sr and Ba were derived from the Cuddapah sediments by a sedimentary exhalative process. This is further substantiated by the fluid inclusions in the barites which yield a limited range of salinity, but a wide range of homogenization temperatures (from 300°C to 120°C), indicating that ore deposition took place due to cooling of hydrothermal fluid with limited mixing of ambient sea water, thereby preserving the salinity as well as Sr isotope ratios of the ore fluid. The relative sulphur isotope ratios (δ34S) reported from the barites of Mangampeta fall in a narrow range 41.3–45.5‰, whereas the δ34S of pyrites falls in two distinct categories. Pyrites with δ34S close to 0‰ are interpreted to have formed by magmatic S acquired by the hydrothermal fluid, whereas pyrites with δ34S values ranging from 8.1‰ to 38.8‰ are the result of biogenic reduction of sea-water sulphate.
ISSN:0011-3891