Abstract
Black and white dolomite crystals (mm to cm width) of different isotopic composition are associated with Triassic diapirism in central Tunisia, as well as with evaporite minerals and clays. The white dolomites occur mostly in the Jabal Hadifa diapir near the contact with Cretaceous limestones, whereas the smaller black dolomites occur in the Jabal Hamra diapir. The former dolomite has a narrow range of δ 18O and δ 13C values (− 3.83‰ to − 6.60‰ VPDB for δ 18O; − 2.11‰ to − 2.83‰ VPDB for δ 13C), whereas the latter dolomite has a wider range and more depleted values (− 4.92‰ to − 9.97‰ for δ 18O; − 0.55‰ to − 6.08‰ for δ 13C). However, the 87Sr / 86Sr ratios of most of the samples are near Triassic seawater values. Dolomite formation is due to at least two different fluids. The main fluid originated from deeper hydrothermal or basinal sources related to the Triassic saliferous rocks and ascended through faults during the diapiric intrusion. The second, less important fluid source is related to meteoric water originating from Cretaceous rocks.
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