Reworked manganese ore bodies in Bonai-Keonjhar belt,Singhbhum Craton,India: Petrology and genetic study |
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| Institution: | 1. Department of Geology, Ravenshaw University, Cuttack, Odisha, India;2. Odisha Mining Corporation, Odisha, India;3. Utkal University, Bhubaneswar, Odisha, India;4. CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, Odisha, India 751013;1. Centre for Exploration Targeting and ARC Centre of Excellence for Core to Crust Fluid Systems, School of Earth and Environment, The University of Western Australia, Crawley, WA 6009, Australia;2. Géosciences Environnement Toulouse, CNRS, IRD, OMP, University of Toulouse, Toulouse, France;3. Avocet Mining PLC and Goldbelt Resources, Ouagadougou, Burkina Faso;4. GeoRessources, CNRS–CREGU, Université de Lorraine, France;1. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China;2. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | The genetic evolution of three types of reworked manganese ore bodies namely: Detrital, Concretionary (Mangcrete) and Wad in the Precambrian Iron Ore Group occurring in Bonai-Keonjahr belt, Singhbhum Craton, India are reported. All the reworked Mn-ore bodies are developed in a restricted area and have a limited resource. Mangcrete and wad are commonly exposed at the surface and extend to a maximum depth of 10 m while detrital ores are observed below 10–20 m from the surface.Detrital ore bodies occur as large boulders and are buried under a thick zone of laterite. Mangcrete is concretionary in nature; oolitic, spherulitic and nodular in shape. Broken fragmented of ooloids and pisoloids, often observed in mangcrete, are indications of reworking. Wad exposures are noticed above low to medium-grade bedded manganese ore bodies. Among three reworked ore types, the detrital is of low to medium-grade having Mn:Fe ratio > 5, while wad and mangcrete are of sub-grade (Mn:Fe ~ 1) and off-grade type (Mn:Fe < 1) respectively.Detrital ore bodies are of allochthonous nature and developed through several stages such as fragmentation of pre-existing ore, leaching and cementation followed by transportation and deep burial. Mangcrete represent chemogenic precipitates at several stages of contemporary Mn-Fe-Al rich fluid under supergene environment. Wad is of bio-chemogenic origin and developed in a swampy region under marine environment due to slow chemical precipitation of Mn-Fe enriched fluid, in several stages nucleating quartz/hematite/cryptomelane detritals. |
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