ORIGIN OF MULTIPHASE DOLOMITIZATION IN THE KINGRIALI FORMATION, NAMMAL GORGE SECTION SALT RANGE, PAKISTAN

Abstract

Kingriali Formation at Nammal Gorge Section in Salt Range, Mianwali is selected for research study. Research is based on geochemical analysis and petrographic analysis. Lithologically it consists of light grey to brownish thin to thickbedded, massive, fine to coarse-grained dolostone and dolomitic limestone with interbedded shale, marl, and dolomite. Petrographic observation revealed three types of dolomites which includes i) fine grained anhedral dolomite (D1) ii) medium grained subhedral to anhedral dolomite (D2) and coarse grained euhedral dolomite (D3) . Paragenetic sequence of Kingriali Formation revealed several other diagenetic events which are micritization, compaction, dissolution, calcitization and fracturing. Calcite veins, elephant skin weathering and brecciation was also observed in the studied formation. The stable oxygen isotopic signatures of D1 ranges from -2 to -2.8‰ VPDB and that of Carbon ranges from 0.8 to 1 ‰ VPDB, D2 oxygen isotopic signatures is -2.9 to -1.5‰ . VPDB, while its Carbon isotopic values ranges from 0.4 to 0.6 ‰. Dolomite D3 oxygen isotopic signatures ranges from -3.3 to -3.7‰ VPDB and its Carbon isotopic values ranges from 0.9 % to 1‰ VPDB this indicate Carbon and isotopic values lie within the late Triassic marine signatures. Elemental analysis of all 3 types of dolomite was carried out forManganese (Mn), Iron (Fe), Sodium (Na) and Stronium (Sr) in all the three types of dolomite that were identified during the petrographic study. Based on our field observation, petrographic analysis and geochemical analysis it is suggested that the dolomite is formed by evaporation and burial dolomitization.