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Titolo:
REGIONAL CONTROLS ON THE GEOCHEMICAL EVOLUTION OF SALINE GROUNDWATERSIN THE EDWARDS AQUIFER, CENTRAL TEXAS
Autore:
OETTING GC; BANNER JL; SHARP JM;
Indirizzi:
UNIV TEXAS,DEPT GEOL SCI AUSTIN TX 78712 UNIV TEXAS,DEPT GEOL SCI AUSTIN TX 78712
Titolo Testata:
Journal of hydrology
fascicolo: 1-4, volume: 181, anno: 1996,
pagine: 251 - 283
SICI:
0022-1694(1996)181:1-4<251:RCOTGE>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOUTH-CENTRAL TEXAS; TRACE-ELEMENT; ORIGIN; WATER; ROCKS; USA; SODIUM; BRINES; FLUIDS; BASIN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
62
Recensione:
Indirizzi per estratti:
Citazione:
G.C. Oetting et al., "REGIONAL CONTROLS ON THE GEOCHEMICAL EVOLUTION OF SALINE GROUNDWATERSIN THE EDWARDS AQUIFER, CENTRAL TEXAS", Journal of hydrology, 181(1-4), 1996, pp. 251-283

Abstract

Geochemical and isotopic parameters are used to evaluate models for the evolution of saline groundwaters in the Edwards aquifer, which lieson the northwestern margin of the Gulf of Mexico sedimentary basin. Saline groundwaters, termed 'badwaters', rang in salinity from 1000 to 12 500 mg l(-1) total dissolved solids. Models for badwater evolution must account for complexities owing to: (1) the range in compositions of saline basinal fluids that may migrate into the Edwards aquifer from its down-dip section and from underlying hydrostratigraphic units; (2) the range of depositional, diagenetic, and mineralogic variations in the host aquifer rocks; (3) volcanic and intrusive igneous rocks that locally crosscut the aquifer; (4) extensive faulting, which in places juxtaposes Edwards aquifer units with adjacent hydrostratigraphic units. Calcium, Mg, Na, SO4, Cl, and HCO3 variations define six badwaterhydrochemical facies. Strontium isotope values of freshwaters (Sr-87/Sr-86 = 0.7077-0.7086), badwaters (0.7076-0.7094), and brines from aquifer rocks down-dip (0.7078-0.7097) are nearly all higher than the range of most Edwards aquifer rocks (0.7074-0.7077) and volcanic and intrusive igneous rocks that crosscut the aquifer (0.7032-0.7055). Argillaceous carbonate rocks that underlie the Edwards aquifer are likely sources of Sr with high Sr-87/Sr-86 values. Transitions between the hydrochemical facies in some locations correspond to changes in depositional environments in aquifer rocks and to changes in the intensity of faulting through the aquifer. Major element, mineral saturation state, and Sr/Ca-Sr-87/Sr-86 variations in badwaters of the westernmost aquiferregion indicate that incongruent dissolution of gypsum and recrystallization of calcite control the geochemical evolution of these badwaters. Sr/Ca-Na-Cl-Sr-87/Sr-86 variations in badwaters of extensively faulted areas to the east of the westernmost aquifer region are consistentwith fluid mixing processes involving at least five endmember fluids,including (1) saline groundwaters from two underlying hydrostratigraphic units, (2) two endmember brines from down-dip Edwards aquifer equivalent units, and (3) freshwaters that have interacted extensively with aquifer rocks. The compositions of badwaters from the north-easternmost region reflect fluid mixing between freshwaters and saline groundwaters from underlying hydrostratigraphic units.

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Documento generato il 05/12/20 alle ore 20:17:06