Geochemical, Mineralogical and Petrological Characteristics of Lateritic Bauxite Deposits formed on Deccan Trap Basalt with Reference to High-level and Coastal (low level) Deposits of Maharashtra

Abstract

Lateritic bauxite are the products of intense subareal weathering of rocks. It is characterised by a particular enrichment of aluminium-hydroxide minerals such as gibbsite, boehmite and diaspore. Based on geological occurrences, bauxite is classified as lateritic, karstic, tikhvin type and about 86% deposits of the world are lateritic bauxite deposits. They typically are in stable areas of plateaux, where they had sufficient geological time to form and were protected from erosion. India is endowed about 3896 million tons of bauxite resources and Maharashtra state constitutes about 5 % of the total assets. The medium to high grade lateritic bauxite occurrences are located in western Maharashtra which spread up in two distinct belts, viz. high level and low-level coastal areas. The coastal bauxite deposits in Raigad, Ratnagiri and Sindhudurg districts are located at altitude varying between 50 to 350 m above mean sea level (msl), while high level bauxite deposits of Kolhapur, Satara and Sangli districts occur on the plateaus with an elevation 900 to 1300 m above msl. Most of the laterite of the western Maharashtra overlies the Deccan Trap basalt, except in some part of coastal areas, it either caps the Kaladgi sandstone or overlie the Dharwar pebble beds. The lateritic bauxite deposits of the western Maharashtra have been studied with reference to its geology, chemico-mineralogy and petrological characteristics. Field studies indicate the following successive stages developed during in-situ weathering: Deccan trap basalt (parent rock) → weathered basalt → saprolite/lithomargic clay → bauxite → duricrust (ferruginous, aluminous laterites). The geological, physical and chemico-mineralogical characteristics of the bauxite and laterite located in two belts is distinguished from one another. For the present study, two bauxite deposits namely Ringewadi and Velas located in Kolhapur (high-level) and Raigad (coastal) district of western Maharashtra respectively have been selected. The representative samples of bauxite, laterite, saprolite, parent rock have been collected. In present paper, comparative study has been done and the geological, geomorphological, geochemical, mineralogical, petrographic and physical characteristics of low level (coastal) and high-level lateritic bauxite deposits are highlighted.