Contact metamorphism of clay minerals in central Utah

Conference · Mon Mar 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5579425

Tannenbaum, T G ^[1]

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1. Alfred Univ., NY (United States). Geology Dept.

Smectite is the dominant alteration product identified in the contact aureole of a limey shale from the Carmel Formation. The Jurassic-aged shale from Emery County, Utah was intruded by Tertiary basaltic dikes and sills. Samples of the shale were taken in the contact zone and at increasing distances from the country rock-dike contact. Samples of the dike itself were taken from the chill margin, an intermediate zone, and from the center of the intrusion. The clay minerals in the country rock were studied using X-ray diffraction and whole rock analysis of the shale and dike rocks were done by X-ray fluorescence spectrometry. Discrete smectite and illite were identified in the shale at the country rock-dike contact. As the distance from the dike increases, the clay mineral assemblage changes to a mixture of illite and interstratified chlorite/smectite. The proportion of smectite in the clay mineral assemblage correlates with the distance from the dike contact. These data suggest that either a transformation of chlorite/smectite to discrete smectite occurred in proximity to the dike or that fluids associated with the dike promoted smectite formation. Chemical analyses of the whole rock samples reveal no change in bulk composition for the suite of country rock samples. Chemical analyses of the dike rocks, however reveal that calcium contents decrease toward the chill margin, indicating a chemical flux between the dike and surrounding country rocks. The transformation of chlorite/smectite to discrete smectite in the shale and the calcium decrease in the dike rock indicates that a geochemical relationship exists between the dike and country rock. The exact reaction path is not clear yet, but it is evident that intrusion of the small dikes in this area had a profound effect on the clay mineralogy of the surrounding country rocks.

• OSTI ID: 5579425
• Report Number(s): CONF-9303211--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:2
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CHEMICAL ANALYSIS
CHEMISTRY
CLAYS
COHERENT SCATTERING
DEVELOPED COUNTRIES
DIFFRACTION
DIKES
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
GEOLOGY
JURASSIC PERIOD
MESOZOIC ERA
METAMORPHISM
MINERALOGY
MINERALS
NONDESTRUCTIVE ANALYSIS
NORTH AMERICA
PETROGRAPHY
PETROLOGY
ROCKS
SCATTERING
SEDIMENTARY ROCKS
SHALES
SILICATE MINERALS
SMECTITE
USA
UTAH
X-RAY DIFFRACTION
X-RAY EMISSION ANALYSIS
X-RAY FLUORESCENCE ANALYSIS