Petrographic and isotopic examination of reef dolomite in the Permian reef complex, west Texas and New Mexico
Petrographically, three distinct types of dolomite are present in the Capitan reef facies of the Permian Reef Complex. Two are replacement phases, one characterized by 3-10..mu..m crystals that retain precursor fabrics, the other by 50-100..mu..m euhedral rhombs that are fabric destructive. The third type is a cement of 40-80..mu..m rhombs postdating marine cementation and predating calcite spar precipitation. Under cathodoluminescence, all dolomites are distinctly blotchy. Classically, three types of diagenetic fluids can cause dolomitization: hypersaline, schizohaline, and burial fluids. Analysis of marine and diagenetic calcite components has identified unique isotopic patterns for each fluid. Calcitized marine cements give a normal marine composition of -2.5 per thousand delta180 and +5.3 per thousand delta13C, and a hypersaline marine composition of 0.0 per thousand delta180 and 7.5 per thousand delta13C. After allowing for dolomite-calcite fractionation, the authors conclude that refluxing hypersaline brines were dominantly responsible for all types of dolomite in the reef facies. Some dolomites have isotopic values which diverge from the general dolomite pattern. These exhibit the greatest degree of luminescence heterogeneity and are believed to be hypersaline dolomites partially recrystallized in the presence of burial fluids. This implies that dolomite formed in near surface settings can be geochemically reset in much deeper burial environments.
- Research Organization:
- Univ. of Michigan, Ann Arbor (USA)
- OSTI ID:
- 6863867
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580100* -- Geology & Hydrology-- (-1989)
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
AGE ESTIMATION
ALKALINE EARTH METAL COMPOUNDS
BRINES
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHEMICAL COMPOSITION
CHEMISTRY
CRYSTALLOGRAPHY
DIAGENESIS
DOLOMITE
FEDERAL REGION VI
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC STRUCTURES
ISOTOPE DATING
ISOTOPE RATIO
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERALS
NEW MEXICO
NORTH AMERICA
OXYGEN COMPOUNDS
PALEOZOIC ERA
PERMIAN BASIN
PERMIAN PERIOD
PETROGRAPHY
REEFS
ROCK-FLUID INTERACTIONS
TEXAS
USA