--> ABSTRACT: Epigenetic and Deep-Burial Dolomitization of Middle Ordovician Antelope Valley Limestone (Pogonip Group), Central Nevada, by Ali Kaya and Gerald M. Friedman; #91030 (2010)

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Epigenetic and Deep-Burial Dolomitization of Middle Ordovician Antelope Valley Limestone (Pogonip Group), Central Nevada

Ali Kaya, Gerald M. Friedman

Pervasive dolomitization of strata in the Antelope Valley Limestone (AVL) is chiefly related to faulting and burial depth. At Clear Creek Canyon and Keystone Canyon, north-south and northeast-southwest-trending parallel extensional faults juxtapose entirely dolomitized sections of the AVL and shaly units of Cambrian, Ordovician and Silurian age. Magmatic intrusives and related quartz veins that cut this formation are post-dolomitic and not responsible for dolomitization. At Martin Ridge, dolomitization gradually decreases with increasing distance from the fault zones. At Lone Mountain, dolomitized strata are conformable with non-dolomitic units and their associations with faulting have not been observed.

Petrographic study indicates that xenotopic mosaics of dolomite crystals with curved and penetrative boundaries and undulose extinction are the dominant kinds of crystals in pervasively dolomitized strata. These mosaics postdate styloties, and replaced calcite-filled veins as well as idiotopic dolomite crystals in selectively dolomitized particles. These mosaics are postdated by saddle dolomite, and by quartz and calcite veins of probably hydrothermal origin. Most of the dolomites are uniformly dull or nonluminescent, indicating a possible high iron content typical of burial dolomite. Homogenization temperatures (Th) of two-phase fluid inclusions range from 105° to 285°C. Thermal alteration indices (2.7-3.1) and vitrinite reflectance data (R = 0.93-1.13) are consi tent with high Th.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.