Mineralogy, origin and diagenesis of golden oolitic limestones of Jhurio Formation (Middle Jurassic) Kachchh mainland, Gujarat, western India

Abstract

CAFET-INNOVA TECHNICAL SOCIETY

The Jhurio Formation, is a carbonate-siliciclastic succession deposited during Bathonian in Kachchh sedimentary basin. The petrographic analysis indicate presence of three types of ooids, tangential, radial and micritic with subordinate superficial and composite ooids. The diagenetic cements include isopachous fringe cement, equant calcite cement, mosaic sparry calcite cement and syntaxial rim cement. XRD-analysis of ooids, mud intraclasts and groundmass of oolitic limestones indicate that the low magnesian calcite and goethite are the predominant minerals. Both pettrographic studies and XRD-analysis indicate that the original mineralogy was dominated by aragonite and the golden coloured coating over the ooids is goethite. Based on different cement textures, four diagenetic environments could be identified, marine phreatic, meteoric phreatic, meteroic vadose and burial diagenetic and a plausible depositional and diagenetic model is proposed.