Abstract
Dolomitization and dedolomitization of the Middle Miocene carbonate sequence at Gabal EISafra resulted in the formation of fine-crystalline dolomite (type 1), coarse crystalline “sucrosic” dolomite (type 2) and dedolostone. The first type occurs as either scattered crystals or patches of hypidiotopic to idiotopic, nearly stoichiometric dolomite crystals ranging from 5–20 μm, whereas the second type occurs as xenotopic to idiotopic dolomite crystals ranging in size from 50 to 200 μm and composed of trace-element depleted, more stoichiometric, coarsely crystalline clear rims that enclose Ca- and trace element-enriched cloudy cores of the dolomite crystals. However, the dedolostone occurs as (1) polycrystalline rhombic pseudomorphs of calcite and gypsum after dolomite, (2) relicts of incompletely dissolved dolomite and dedolomite crystals, (3) hollow dolomite rhombs and rhombohedral pores due to dissolution of the cloudy cores or the whole dolomite rhombs, respectively and (4) filling of hollow dolomite rhombs by gypsum. Replacement and dissolution of dolomite crystals began from the cores and expanded outward.
Published Version
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