Orogenic fluids and the origin of a synfolding remagnetization, Belden FM. , NW Colorado

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5724592

Fruit, D; Elmore, R D ^[1]; Gao, G ^[2]

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1. Univ. of Oklahoma, Norman, OK (United States). School of Geology and Geophysics
2. Univ. of Texas, Austin, TX (United States). Dept. of Geosciences

The Pennsylvanian Belden Formation, consisting of shoaling upward carbonate cycles, was investigated on an asymmetric fold in MW Colorado to test for a connection between orogenic fluids and remagnetizations. The limestones have radiogenic Sr-87/Sr-86 ratios and are extensively mineralized by calcite along tectonic fractures. An apparent synfolding (Laramide) remagnetization varies in magnetic intensity and resides in magnetite that has replaced pyrite. This remagnetization superficially suggests a link with orogenic fluids which gained access to the rocks during deformation. There is no correlation, however, between intensity and proximity to the mineralized veins or to the degree of fracturing. There is a correlation between magnetic intensity and cyclical lithologic changes. In general, the intensity is highest in the coarser, grain-supported limestones in the upper part of the cycles. These results suggest a control by matrix permeability or chemical composition and not by fracture permeability. The remagnetization is interpreted to be chemical in origin, but is not related to the mineralizing syndeformational fluids. Two working hypotheses for the origin of the remagnetization are being tested: (1) a prefolding chemical mechanism, possibly fluid-related, and deflection of the magnetization into a synfolding configuration by strain or (2) a syndeformational chemical process such as diagenesis of organic matter that was mediated by low burial temperatures. Although the authors cannot as yet conclusively identify the chemical process responsible for the pyrite->magnetite reaction, the results raise doubts about a link between the Belden remagnetization and orogenic fluids.

• OSTI ID: 5724592
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CARBONATE ROCKS
CARBONIFEROUS PERIOD
CHEMISTRY
COLORADO
DEVELOPED COUNTRIES
DIAGENESIS
FLUIDS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC FORMATIONS
IRON ORES
LIMESTONE
MAGNETITE
MAGNETIZATION
MINERALS
NORTH AMERICA
ORES
OROGENESIS
OXIDE MINERALS
PALEOZOIC ERA
PYRITE
RESERVOIR FLUIDS
ROCKS
SEDIMENTARY ROCKS
SULFIDE MINERALS
USA