Occurrence of wellcrystallized nontronite in the

Authors: P K Sarkar D V Upasani A C Soman

Publish Date: 2013/10/13

Volume: 82, Issue: 4, Pages: 363-367

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Abstract

Occurrence of well crystallized nontronite in a megaporphyritic basalt flow from Nighoj area Maharashtra India is reported Thin section studies of the vesicles from periphery to the centre reveal the presence of greenish palagonite probably indicating the stages of devitrification of glass and the weathering of palagonite to the formation of nontronite The centre of the vesicles is marked by the presence of dark greenishbrown radiating and fibrous sheets of nontronite Xray diffraction XRD analysis reveals the dominant presence of smectite nontronite as the major phase with traces of pyroxene Scanning Electron Microscopy SEM shows well developed sheets of nontronite within the gas vesicles of the megaporphyritic basalt flows In the present investigation the nontronite within the gas vesicles of the megaporphyritic basalts at Nighoj was formed insitu due to the devitrification of glass containing palagonite Palagonite is an intermediate step in the alteration that may be accomplished by the steam generated in quenching of the lava Weathering of palagonite under conditions of poor drainage is essential to the genesis of nontronite as has been suggested by Victor and Vernon 1946

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