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Geochemical evolution of groundwater in stratified‐drift and arkosic bedrock aquifers in north central Connecticut
Author(s) -
Rogers Robert J.
Publication year - 1987
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr023i008p01531
Subject(s) - aquifer , geology , bedrock , calcite , groundwater , feldspar , kaolinite , geochemistry , albite , dissolution , plagioclase , mineralogy , hydrology (agriculture) , geomorphology , quartz , chemistry , geotechnical engineering , paleontology
Groundwaters in both stratified‐drift and arkosic bedrock aquifers are dilute (dissolved solid concentration less than 300 mg/L), of similar chemical composition, and evolve along similar reaction paths. Calcite, potassium feldspar, sodic plagioclase, accessory silicates, and probably pyrite and barite are reactants in both aquifer types. Water in the stratified‐drift aquifers is in chemical equilibrium with kaolinite and generally has reached equilibrium with chalcedony, which controls H 2 SiO 4 concentrations. In the bedrock aquifers, kaolinite forms as a product in the less evolved water, and calcium‐montmorillonite and calcite form as products in the more highly evolved water. CO 2 is a major reactant in both types of aquifers, which are probably open with respect to CO 2 . The absolute dissolution rates of reactant minerals have a greater effect on groundwater chemistry than do their relative abundance. Calcite, a minor constituent, contributes to water chemistry significantly more than silicates in both types of aquifers. The greater degree of geochemical evolution of water in the bedrock aquifers compared to that of water in the stratified‐drift aquifers is attributed to its longer residence time in the bedrock.