Petrology, geochemistry, and fluid/rock interactions in Cambro-Ordovician carbonates from the Reelfoot rift
- Univ. of Missouri, Rolla, MO (United States). Dept. of Geology and Geophysics
- Univ. of Missouri, Columbia, MO (United States). Dept. of Geological Sciences
- Div. of Geology and Land Survey, Rolla, MO (United States)
Replacement dolomite and associated dolomite and calcite cements in cores and cuttings from four test wells penetrating the Reelfoot rift were studied. These Cambro-Ordovician rocks were deposited in a shallow platform setting on rapidly subsiding fault blocks in southeast Missouri. Replacement dolomite textures include fine crystalline (0.05--0.1 mm), non-ferroan, planar dolomite that is interpreted to be early diagenetic. Coarse to very coarse crystalline (0.5--5 mm), ferroan, nonplanar dolomite formed either as a recrystallization product of the preexisting planar dolomite or as a replacement of previously undolomitized limestone after deep burial. Rift-related open space filling dolomite cements display: (1) an inner ferroan, non-cathodoluminescent (CL) zone which has further internal Fe zonation, and (2) an outer non-ferroan CL zone. Uncorrected fluid inclusion homogenization temperatures show an increasing trend from < 90 C to > 250 with paragenetic time. These temperatures indicate a diagenetic environment up to 100 C hotter than has been suggested for shallower MVT related carbonates. Stable carbon and oxygen isotope values become progressively more negative with paragenetic time, becoming distinctly more negative than for dolomites in nearby MVT deposits. Average values of [sup 87]Sr/[sup 86]Sr for dolomites become increasingly radiogenic with paragenetic time. The paragenetic trends observed in the isotope data suggest progressively increasing fluid/rock ratios in a system dominated by a primitive basinal fluid. This contrasts with shallower MVT associated dolomites where isotope data suggest buffering of fluids in a rock dominated system.
- OSTI ID:
- 5011952
- Report Number(s):
- CONF-9303210--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:3; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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