Recharged or modified-connate water in a carbonate bed within an evaporite aquitard, Texas panhandle
Hydraulic-head data and numerical modeling suggest that ground water in the Palo Duro Basin area of the Texas Panhandle has leaked downward through a Permian evaporite-carbonate-shale aquitard. Chemical composition of brine in a carbonate bed of the San Andres Formation within the aquitard gives ambiguous evidence of ground-water leakage. San Andres ground water varies chemically from potable Ca-HCO/sub 3/- and Ca-SO/sub 4/-type waters in the nonhalitic sections of the San Andres Formation below the Pecos Plains of eastern New Mexico to Na-Ca-Cl brine within the Palo Duro Basin. The composition of the 336 to 384 g/L brine can be explained by solution of dolomite, anhydrite, and halite, accompanied by exchange of some sodium for calcium. The brine is near oxygen isotopic equilibrium with San Andres dolomite. Problems with this recharged-water explanation are identification of the water-rock reaction that replaces dissolved sodium with calcium and the reaction that enriches deltaD of San Andres brine by 30 per thousand to 40 per thousand relative to modern regional meteoric water. Problems with explaining San Andres brine as modified-connate water are that hydraulic-head data and numerical modeling suggest leakage occurs and that ion ratios in brine differ from ion ratios in evaporatively concentrated, diagenetically modified seawater. However, because leakage rates are slow and variable, some modified-connate brine could be mixed with leaking recharged water, making interpretation difficult. Leakage rate and extent of flushing of old brine depend on whether flow is through fractures or through intergranular pore space in the evaporite aquitard.
- Research Organization:
- Univ. of Texas, Austin (USA)
- OSTI ID:
- 6649934
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580400* -- Geochemistry-- (-1989)
AQUICLUDES
BRINES
CARBONATE ROCKS
CHEMICAL COMPOSITION
CHEMISTRY
CONNATE WATER
DIAGENESIS
EQUILIBRIUM
EVAPORITES
FEDERAL REGION VI
GEOCHEMISTRY
GROUND WATER
HYDROGEN COMPOUNDS
HYDROLOGY
INTERSTITIAL WATER
ISOTOPE RATIO
NORTH AMERICA
OXYGEN COMPOUNDS
PALO DURO BASIN
PERMIAN BASIN
ROCKS
SEDIMENTARY ROCKS
TEXAS
USA
WATER