Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

V. K. Chittora ¹, Anil Maheshwari ², Massimo Coltorti ³

Affiliations
1 III/124 G.S.I. Colony, Malviya Nagar, Jaipur 302 017, IN
2 Department of Geology, University of Rajasthan, Jaipur 302004, IN
3 Istituto di Mineralogia, Universita di Ferrara, 44100, Ferrara, IT

Abstract

The Malani volcanics exposed in a curvilinear pattern around Bhadrajan are characterised by the presence of eight flows of rhyolitic to dacitic composition and have chemical characteristics similar to within plate, A-type granitic rocks. The pyroclastic unit present at the base of each flow marks the beginning of next pulse of discharge. The chemistry of Bhadrajan volcanics suggests two distinct rhyolite groups. Group "A" is characterised by high Ca, Al, Na₂O/K₂O and low Rb, Th, La, Ce and Rb/Sr as compared to group "B" rhyolites. The field and chemical data suggest a heterogeneous nature of protolith for Bhadrajan volcanics. The partial, melting of igneous and siliceous metapelitic protolith could result in "A" and "B" group of rhyolites respectively.

Keywords

Geochemistry, Malani Rhyolites, Flow Stratigraphy, Rajasthan.

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