Mineralogical Studies of the Manganese Ores in Banswara Manganese Belt, Banswara District, Rajasthan

Abstract

A comprehensive study of the manganese ore deposits of Banswara manganese belt (23°10′-23°20′N to 74°15′-74°25′E) in the Banswara district, Rajasthan, has shown a characteristic assemblage of manganese ore minerals. The manganese ore deposits are associated with Aravali phyllite, schist, quartzite and limestone, etc., and occur within a narrow linear belt trending NW-SE. These meta-sediments hosted manganese ores that belong to the Aravalli Supergroup are of Paleo-Proterozoic age. The mineralogical investigation of a number of polished blocks showed the dominance of braunite accompanied by pyrolusite and cryptomelane. A number of mineral assemblages are recommended. The significant ore textures are, banding, replacement and colloform, while other textures identified are veined, granular, brecciated, relict, open space, and mutual boundary relationship. The micro-structural and textural relations are discussed and interpreted to disclose the paragenetic history of ore minerals crystallization, which are usually divided into primary (metamorphic) and secondary (supergene) ores. The aim of this study is to determine the presence of manganese oxides/silicates ore minerals, and to comprehend the sequence of their crystallization. This study is further correlated to a geochemical background of these Mn ores to depict the mode of their origin and depositional settings. The present study has come to the conclusion that the dominance of braunite, banded texture and conformable relations with the associated rocks, indicates the original deposition of syngenetic manganiferous pelitic-psammitic sediments, which, were regionally metamorphosed to form a low grade primary ore deposits but the dominance of pyrolusite, and cryptomelane, along with other secondary manganese ore minerals also pointed out a subsequent chemical weathering and leaching of these earlier formed primary ore, and silicate minerals, resulting in precipitation, and deposition of high grade secondary ore deposits of later origin.