Limpid dolomite in Permian San Andres halite rocks, Palo Duro Basin, Texas Panhandle; characteristics, possible origin, and implications for brine evolution

Abstract Minor quantities of diagenetic, ordered, and stoichiometric limpid dolomite (composition = Ca (sub 0.999) Mg (sub 0.982) Fe (sub 0.009) Mn (sub 0.010) [CO 3 ] 2 ) were found at the contacts between mudstone and halite and along the boundaries between halite crystals in San Andres halite rocks, Palo Duro Basin, Texas Panhandle. The dolomite is characterized by low Sr content (average 65 ppm), light delta 18 O values (average delta 18 O = -2.7 per thousand , PDB), light delta 13 C values (average delta 13 C = -3.0 per thousand , PDB), and radiogenic 87 Sr/ 86 Sr ratios (0.70723 to 0.70762) relative to bedded anhydrite (0.70714 to 0.70727). Our findings 1) document that the limpid dolomite was the latest diagenetic phase in the San Andres halite rocks; 2) confirm that meteoric water, preserved in mudstone interbeds within the halite rocks, was an important fluid source for the dolomite formation; and 3) suggest that the dolomite was precipitated, enhanced by sulfate-reduction process, during burial compaction of the mudstones from a halite-saturated brine which was derived from the mixing of mudstone-released water with evaporated brine from halite.