Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

M. N. Praveen ¹, Biswajit Ghosh ¹, H. S. Shrivastava ¹, M. L. Dora ², L. D. Gaikwad ¹

Affiliations
1 Geological Survey of India, E-5 Arera Colony, Bhopal - 462 016, IN
2 Geological Survey of India, Seminary Hills, Nagpur - 440 006, IN

Abstract

Sulphide mineralisation and syn-Volcanic hydrothermal alteration in the Betul Belt is associated with submarine bimodal volcanism. Felsic volcaniclastics form the favourable host rocks in most areas. Alteration zones have been metamorphosed to middle to upper-Amphibolite facies giving rise to various metamorphic mineral assemblages. Based on metal ratios, mineralisation can be classified into Zn-Cu and Zn-Pb-Cu types. The difference between the two types might be related to the composition of the footwall volcanics. Zn-Cu types are in close proximity to mafic volcanics towards their footwall side whereas, Zn-Pb-Cu types occur in areas dominated by felsic volcanics with little mafic volcanics towards the footwall. The sub-Parallel sheet like nature of the ore bodies and strata-Bound alteration might be related to the permeable nature of the host volcaniclastics.

Keywords

Sulphide Mineralisation, Classification, Hydrothermal Alteration, Subsea-Floor Replacement, Betul Belt, Central India.

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P. R. Golani ¹, M. L. Dora ¹, B. K. Bandyopadhyay ¹

Affiliations
1 Geological Survey of Indra, Project Thematic Mapping, Op Maharashtra, Seminary Hills, Nagpur - 440 006, IN

Abstract

The southeastern part of the Proterozoic Betul Belt exposes a Felsic-Dominated sequence around Bhuyari in the Kanhan river sector. The felsic volcanic rocks, identified as rhyolite occur in the form of two mappable bands in a milieu of biotite ± hornblende bearing Quartzo-Feldspathic rocks of subvolcanic affinity. A very well developed zone of hydrothermal alteration is recognized in rhyolite that occurs to the immediate south of Bhuyan village. The hydrothermal facies mapped in the alteration zone include sericite - muscovite-bearing rhyolite, phlogopite± spessartite biotite schist and trernolite (± actinolite) - rich rock with serpentine, talc, epidote and dolomitic carbonates. Discrete grains of fluorite and REE bearing flour carbonates form part of the hydrothermal mineral assemblage. Apart from the magnesian enrichment, the occurrence of spessartite garnet, epidote and sporadic development of staurolite indicate significant fluxes of manganese, calcium and alumina in the zone of hydrothermal alteration. The alteration is attendant with polymetallic base metal mieralisation which is invariably Zinc-Dominated. Bedrock samples and selected channel sampling indicate that the Tremolite-Rich facies is intensely mineralized, followed by phlogopite ± garnet biotite schist. Primary sulphides observed in a dug well section are pyrite, sphalerite galena and chalcopyrite which occur as disseminations and also as several millimeter thick semiconformable veins Rare quartz Phenocryst-Groundmass relationship in the mineralized host rock from the dug well provide incontrovertible evidence for the volcanic affinity of the base metal mineralisation.

Keywords

Base Metal Mineralisation, Hydrothermal Alteration, Volcanic Rocks, Chhrndwara District, Madhya Pradesh.

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