Dolomitization of Precambrian limestone of Satari, North Goa

Abstract

The limestone comprises dominant dolomite and caitite followed by quartz, micas, chert and chalcedony. The CaO and MgO content varies from 29.88 to 42.68 percent and 2.69 to 16.04 percent, respectively. Insoluble residue varies from 1.03 to 12.70 percent. Based on mineralogy and chemical parameters the Satari limestone has been classified as (i) high magnesium to dolomitized and (ii) high calcium types. There is significant negative correlation between CaO-MgO and MgO-IR, but Fe-Mn and Fe/Mn-IR are positively correlated. Important diagenetic changes included recrystallization of calcite and replacement by dolomite, chert and chalcedony. The replacement origin of dolomite is clearly evidenced by various textural features such as xenotopic mosaic, continuity of cleavage planes from calcite to dolomite and relict features of calcite in dolomite grains. The possible source of Mg required for dolomitization can be ascribed in part to the Mg-rich brines probably result of igneous activity and partly during clay mineral transformations.