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Geochemistry and source of solutes in ground water from the Marshall Sandstone regional aquifer, Michigan Basin

Conference · · Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5696168
; ;  [1]; ;  [2];  [3]
  1. Michigan State Univ., East Lansing, MI (United States) Geological Survey, Lansing, MI (United States)
  2. Geological Survey, Austin, TX (United States)
  3. Kent State Univ., OH (United States). Geology Dept.

Concentrations of dissolved solids in ground water near the limits of the subcrop of the Mississippian Marshall Sandstone are small and originate from meteoric-water/rock interactions. Concentrations of dissolved solids increase to that of brines toward the center of the basin: the dissolved solids are hypothesized to originate from evaporated seawater. This study examines the geochemistry of the solutes in this aquifer and compares these results to the geochemistry and source of solutes in Devonian formations that lie under this aquifer but that are separated from it by approximately 950--1,800 feet of shale. Analysis of geochemical data indicates that: (1) hydrochemical facies range from Ca-HCO[sub 3] in the subcrop area to Na-Cl and Ca-Cl in the basin center; (2) ion ternary diagrams and isotopic ratios indicate mixing of meteoric water with brine; (3) Cl:Br, Cl:Na, and Carpenter Function:Cl ratios suggest that the Marshall brine is similar to seawater evaporated beyond halite precipitation; (4) ion:Br ratios indicate that the Marshall brine is enriched in Ca and depleted in SO[sub 4], Mg, and K with respect to equivalently evaporated seawater; and (5) most of the brine samples are at or near equilibrium with respect to calcite, dolomite, and anhydrite, and the fresher meteoric water samples are near equilibrium with respect to calcite. Brine-freshwater mixes in the Marshall Sandstone are geochemically and isotopically similar to brines in the Devonian formations. Thus, the evolution of ground water in the Marshall Sandstone is hypothesized to be similar to that of the Devonian formations in which dilution of a marine brine by meteoric water is a dominant process and that other major geochemical processes, such as dolomitization, interaction with clays, and sulfate reduction occurred prior to dilution.

OSTI ID:
5696168
Report Number(s):
CONF-921058--
Journal Information:
Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
Country of Publication:
United States
Language:
English