Structural controls on fluid migration: an example from the Absaroka sheet, Idaho-Wyoming thrust belt

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:5944811

Wiltschko, D V; Budai, J M

Combined structural and stable isotopic analysis of vein and slip surface mineralization have temporally constrained the three major stages of deformation in the Madison Group (Miss) within the Absaroka thrust sheet near Afton, Wyoming. Calcite- and rarely dolomite-filled vines are oriented normal to bedding parallel to tectonic transport (I). These veins are the earliest evidence of fluid migration as they are cut by all later deformation fabrics. Stage I veins commonly have C-O isotopic compositions nearly identical to surrounding host limestone suggesting low water/rock volume ratios or complete equilibration with the host carbonate. In contrast to earlier veins, mineralization of slip surfaces reflect high water/rock ratios based on their strongly depleted oxygen compositions. Carbon ratios of calcite fibers reflect partial equilibration with the host rock. Secondary calcite filling in stage I veins have an isotopic composition similar to stage II fiber calcite. The final phase of deformation produced low-angle, unmineralized faults which parallel the strike of stage I veins and have offset all earlier structures. This history of fluid/rock interactions during deformation is complicated by a wide range of oxygen compositions within both stage I and II calcites indicating episodic fluid migration and reactivation of earlier veins during later events. The authors interpret stage I veins as having formed before and during motion on the Absaroka thrust, perhaps originating as hydrofractures due to the emplacement of the overlying Meade-Crawford thrust system.

• Research Organization: Texas A and M Univ., College Station (USA)
• OSTI ID: 5944811
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152003* -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBON ISOTOPES
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
DEFORMATION
DOLOMITE
EQUILIBRIUM
FEDERAL REGION VIII
FEDERAL REGION X
FLUIDS
GEOCHEMISTRY
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOTHERMAL FLUIDS
IDAHO
ISOTOPE RATIO
ISOTOPES
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MIGRATION
MINERALIZATION
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
QUANTITATIVE CHEMICAL ANALYSIS
ROCK-FLUID INTERACTIONS
ROCKS
SEDIMENTARY ROCKS
USA
WESTERN US OVERTHRUST BELT
WYOMING