Climate controlled, fabric destructive, reflux dolomitization and stabilization via marine- and synorogenic mixed fluids : an example from a large Mesozoic, calcite-sea platform, Croatia

The Jurassic-Cretaceous dolomites, Adriatic platform, Croatia resulted from climate-influenced post-depositional reflux dolomitization (as opposed to synsedimentary peritidal- and deeper burial dolomitization), and subsequent stabilization within a Mesozoic, “calcite sea” isolated platform. The dolomites are stratiform (10 to 200 m thick), fabric destructive (20 to over 500 μm crystals), nonluminescent, and zoned with respect to Ca. Bulk dolomites have low Mn (10 to 30 ppm), moderate Sr (60 to over 200 ppm), positive δ13C and δ18O values, only moderate ordering (0.25 to 0.6) and single-phase fluid inclusions (temperatures +3‰ VPDB and Sr>100 ppm) composes most Jurassic and 40% of Cretaceous dolomites, making up turbid dolomite cores and initial clear dolomite rims. A first generation of low-Ca dolomite (LCD-1 ; 50 to 53 mol% Ca ; δ18O +1 to >+3‰ VPDB ; 100-180 ppm Sr) forms cement and variably replaces (stabilizes) earlier HCD cores. HCD and LCD-1 formed in refluxing marine-dominated pore waters under semi-arid climate (55 mol%) phases. A second generation of much younger, low-Ca dolomite (LCD-2 ; fracture-associated, more negative δ18O from -1.4 to +1‰ VPDB, Sr