Thermal characterization of lacustrine dolomite from the Sambhar Lake playa, Thar desert, India

Abstract

The Sambhar Lake playa sediments in Thar desert, western India, host a variety of evaporite minerals.Carbonates form a major proportion of the evaporites in a 23 m deep core and several dolomite-rich ho-rizons are recorded. Our XRD and DTA based investigations show that these dolomites arenon-stoichiometric and disordered (proto-dolomites) except at one level (4.08 m) from where awell-ordered dolomite is reported. We also record frequent variation in the characteristics of dolomiteswith depth in terms of structural ordering, Ca/Mg ratio and Fe content. Dolomites reported form theSambhar Lake playa are interpreted to be authigenic due to the absence of any carbonate rock in thecatchment and seem to be derived from a precursor calcite under (sub-) evaporitic conditions.