Petrography and Geochemistry of Dolomites of Arlikatti Formation of Kaladgi Basin, Southern India: Depositional Conditions in a Proterozoic Intracratonic Basin Setup

ABSTRACT The dolomites of the Arlikatti Formation of Kaladgi Basin provide insights into understanding depositional conditions of carbonate sedimentation in an intracratonic Proterozoic basin. The dolomites were studied to their palaeo depositional conditions using petrography and whole rock geochemistry. Replacement of precursor calcite and quartz, ooids with primary concentric fabric of these dolomites suggests that they were formed by conversion of lime mud. Their high values of Fe (5460 ppm), Mn (164 ppm), Mn/Sr (6.96), U/Th (12.41) and low values of Sr (24.02 ppm), Y/Ho (37.50) and Er/Nd (0.12) compared to marine dolomites indicate that the dolomites of Kaladgi Basin were formed by subsurface anoxic or reducing dolomitizing fluids. The flat patterns of Post-Archean Australian Shale (PAAS) normalised Rare Earth Elements (REE) (La/YbSN = 0.86) along with moderate negative Ce anomaly (Ce/Ce* = 0.48) are also consistent with the non-marine anoxic dolomitizing fluids. An integrated field, petrographic and geochemical study indicates that the carbonate rocks of Arlikatti Formation were initially deposited as lime mud in the form of primary precipitates due to microbial activity and evaporation in a tidal flat shallow marine environment. The lime mud was converted into dolomite by subsurface reducing dolomitizing fluids during an episode of burial and diagenesis.