Fluid inclusion evidence for origin and diagenesis of sparry calcite cement in Capitan Limestone, McKittrick Canyon, Permian basin, west Texas

Conference · Thu May 01 04:00:00 EDT 1986 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:5268840

Crysdale, B L

Sparry calcite cement is responsible for major porosity loss in the reef and fore-reef facies of the Capitan Limestone, Permian basin. This cement occurs throughout the massive reef facies where it fills large vugs as much as 0.5 m in diameter, with individual crystals up to several centimeters in length. Sparry cement in the fore-reef facies is less extensive and fills smaller vugs than in the reef, although individual crystals can be as large. The cement is composed of coarse, equant, clear to milky calcite that is rich in fluid inclusions. Homogenization temperatures (T/sub h/) of primary fluid inclusions trapped during cementation record formation temperatures from 55/sup 0/ - 85/sup 0/C. A relatively low geothermal gradient of 2/sup 0/C/100 m suggests cementation occurred at moderate burial depths of 1-2 km. Precipitation of sparry cement in fractures and brecciated areas also indicates cementation postdates minor burial compaction. Freezing temperatures (T/sub f/) for primary fluid inclusions range from about -1/sup 0/ to 0/sup 0/C (1.7 wt. % NaCl equivalent or less), suggesting the cement was formed in fresh to brackish waters. This range of T/sub f/ data is consistent with cement formation in a relatively deep lens of meteoric to mixing-zone waters. Secondary fluid inclusions with T/sub f/ of about -12/sup 0/C (> 16 wt. % NaCl equivalent) indicate that highly saline brines may have migrated along secondary fractures in the cement during later deposition of evaporites in the adjacent Castile and Salado Formations.

• Research Organization: Geological Survey, Denver, CO
• OSTI ID: 5268840
• Report Number(s): CONF-860624-
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 70:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
DIAGENESIS
FEDERAL REGION VI
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOTHERMAL GRADIENTS
LIMESTONE
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PERMIAN BASIN
POROSITY
RESERVOIR ROCK
ROCKS
SEDIMENTARY ROCKS
TEMPERATURE GRADIENTS
TEXAS
USA