Laterites, bauxites and associated clays from western India

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Title: Laterites, bauxites and associated clays from western India
Author: Chitale, Dattatraya V
Abstract: Mode of occurrence , mineralogy and microtextures of laterites , bauxites and the associated clays from six bauxite deposits capping Deccan Trap basalts in western India were investigated . Light microscopy . X -ray diffraction and analytical electron microscopy were employed for the mineralogical and microtextural investigations . Deccan Trap basalts at Ratnagiri , Srivardhan , Panhala Fort and Nangrataswadi in western Maharashtra , and those at Matanumad , western Gujarath , India progressively weather in situ to laterites and bauxites via an intermediate stage of saprolitic clays . Laterites and bauxites at Naredi , western Gujarath , India , however , represent transported and redeposited sediments . The unweathered basalts are predominantly composed of a calcic plagioclase and a ferrous pyroxene , with minor proportions of magnetite , ilmenite , volcanic glass , iddingsite and palagonite . Dissolution etch pits form due to weathering on the surfaces of minerals in basalts . Weathered basalts are composed of various combinations of smectites , kaolinites , goethite , hematite and anatase . Kaolinite is the principal mineral in the saprolitic clays overlying the basalts in the residual bauxite deposits . It commonly forms a framework of submicron sized , irregular shaped platelets , and occasionally occurs as booklets of hexagonal platelets that rarely form spheroidal aggregates . Residual laterites overlying the saprolitic clays exhibit vesicular , spongy and pi soli tic macrotextures and are composed mainly of hematite and goethite with minor proportions of gibbsite , kaolinite and anatase . Bauxites , which occur as pockets and lenses within the laterites , display pisolitic , massive and nodular microtextures , and are predominantly composed of gibbsite with minor amounts of anatase , kaolinite , hematite and goethite . Laterites and bauxites are characterized by framework microtexture formed by three -dimensional packing of crystallites . Natroalunite , a sodium -aluminum -sulfate -hydrate is the predominant mineral in the saprolitic clays at Matanumad . Natroalunite occurs as a replacement product of kaolinite in these saprolitic clays . Natroalunite occurs in subordinate amounts in laterites where hematite and goethite are the predominant minerals . Natroalunite alters to kaolinite and oibbsite in the bauxites . Lateritic pebbly mudstone and bauxitic bouldery mudstone at Naredi represent debris flow deposits formed in two pulses . The residual laterites and bauxites capping the hills around Naredi were the sources rocks for these debris flow deposits .
URI: http : / /hdl .handle .net /2346 /18685
Date: 1986-06


Laterites, bauxites and associated clays from western India. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /18685 .

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