Modeling alternative paths of chemical evolution of Na-HCO3-type groundwater near Oak Ridge, Tennessee, USA |
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Authors: | Laura E Toran James A Saunders |
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Institution: | (1) Temple University, Department of Geology, Philadelphia, PA 19122, USA Fax: +1-215-204-3496 e-mail: ltoran@nimbus.temple.edu, US;(2) Department of Geology, Auburn University, Auburn, AL 36849–5305,USA, US |
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Abstract: | This paper demonstrates that both cation exchange, a commonly invoked mechanism, and silicate hydrolysis, which is less commonly
considered, can produce Na-HCO3-type water in sedimentary rocks. Evolution of Na-HCO3 groundwater beneath the Oak Ridge Reservation, Tennessee, USA, was studied by comparing observed end-member groundwater composition
from multiport samplers to compositions generated by reaction-path geochemical models. Observed groundwater compositions could
be reproduced by either the silicate-hydrolysis model or the cation-exchange model. Secondary minerals precipitated in the
silicate-hydrolysis model are similar to those present along fractures in the shale and carbonate host rocks, and observed
molar Sr2+/Ca2+ ratios more closely resemble evolution from shale weathering. Both mechanisms should be considered to understand the evolution
of Na-HCO3 groundwater.
Received, April 1998 · Revised, January 1999 · Accepted, March 1999 |
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Keywords: | USA hydrochemical modeling sedimentary rocks groundwater quality |
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