Dolomitisation of Micritic Limestones in Deeper Water Proterozoic Limestone-Shale Alternations, Larji Window, Lesser Himalayas, Northwest, India

The dun pink micritic limestone and purple shale alternations unit resemble the deeper Water carbonates. The dull pink micritic limestones of the unit give a weak 1:4 dilute acid reaction and negative test for Mann's stain solution for dolomite. Despite this, the samples showon XRD Charts, a prominent peak for ordered dolomite (104) 2.88 Å to the total exclusion of calcite. The important point of the present example is, despite complete dolornitisation, the resulting dolostone neither shows change in porosity nor in size and shape of the micritic particles. The kind and intensity of dolomitisation observed in the present example are difficult to explain in terms of the existing dolomitisation models for deeper water limestones.