Mg Isotopes in Hydrothermal Saddle Dolomites; Current Data for Paleozoic Dolomites of Eastern Canada and Implications for Mg Source; #50350 (2010)

Hydrothermal dolomites are host to major hydrocarbon fields in North America. The process leading to the formation of these high temperature dolomites is controversial with end‐members of 1) early, tectonically controlled, high temperature fluid migration upward along faults and laterally in porous limestones and 2) late, burial‐dominated, regional migration of high temperature formation brines. In both cases, large amounts of magnesium are needed for the formation of the dolomite either as limestone replacement or void‐filling cement. We present magnesium stable isotope ratios in saddle dolomites as a potential tool for recognition of Mg source and hence new data that could be of use in the ongoing debate.