Boron, chloride, sulfate, δD, δ18O, and 3H concentrations in surface water and groundwater samples from the Sulphur Bank Mercury Mine (SBMM), California, USA were
used to examine geochemical processes and provide constraints on evaporation and groundwater flow. SBMM is an abandoned sulfur
and mercury mine with an underlying hydrothermal system, adjacent to Clear Lake, California. Results for non-3H tracers (i.e., boron, chloride, sulfate, δD, and δ18O) identify contributions from six water types at SBMM. Processes including evaporation, mixing, hydrothermal water input
and possible isotopic exchange with hydrothermal gases are also discerned. Tritium data indicate that hydrothermal waters
and other deep groundwaters are likely pre-bomb (before ~1952) in age while most other waters were recharged after ~1990.
A boron-based steady-state reservoir model of the Herman Impoundment pit lake indicates that 71–79% of its input is from meteoric
water with the remainder from hydrothermal contributions. Results for groundwater samples from six shallow wells over a 6–month
period for δD and δ18O suggests that water from Herman Impoundment is diluted another 3% to more than 40% by infiltrating meteoric water, as it
leaves the site. Results for this investigation show that environmental tracers are an effective tool to understand the SBMM
hydrogeologic regime.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Résumé Les concentrations en bore, chlorure, sulfate, δD, δ18O, et 3H d’échantillons d’eaux de surface et souterraine prélevés dans le banc de soufre de la mine de mercure (SBMM en anglais)
en Californie, USA, ont été utilisées pour étudier les processus géochimiques et pour fournir des contraintes à l’évaporation
et à l’écoulement des eaux souterraines. La SBMM est une mine de soufre et de mercure abandonnée, adjacente au lac Clear en
Californie et sous laquelle se trouve un système hydrothermal.Les résultats des traceurs autres que le tritium (bore, chlorure,
sulfate, δD, et δ18O) ont permis d’identifier des contributions de six types d’eaux à SBMM. Des processus tels que l’évaporation, le mélange,
l’entrée d’eau hydrothermale et de possibles échanges isotopiques avec des gaz hydrothermaux ont également été identifiés.
Les données de tritium montrent que les eaux hydrothermales et d’autres eaux profondes sont probablement d’age antérieure
à la bombe (avant ~1952), alors que la plupart des autres eaux sont issues de la recharge après ~1990. Un modèle de réservoir
représentant le lac situé dans la partie Herman Impoundment de l’ancienne mine, en régime permanent et basé sur le bore, montre
que 71–79% de l’eau provient des précipitations, le reste provenant de contributions hydrothermales. Les résultats de δD et
δ18O pour des échantillons d’eau souterraine de six puits peu profonds sur une période de 6 mois suggèrent que l’eau de Hermann
Impoundment est encore diluée entre 3% jusqu’à plus de 40% lorsqu’elle quitte le site du fait de l’infiltration d’eau météorique.
Les résultats de cette étude montrent que les traceurs environnementaux constituent un outil efficace pour comprendre le régime
hydrogéologique de la SBMM.
Resumen Se han utilizado datos de concentraciones de boro, cloruros, sulfatos, δD, δ18O, y 3H en muestras de aguas superficiales y subterráneas procedentes de la Mina de Mercurio Sulphur Bank (SBMM), California, USA,
para estudiar los procesos geoquímicos y caracterizar la evaporación y el flujo del agua subterránea. SBMM es una mina abandonada
de azufre y mercurio con un sistema hidrotermal subyacente, cercano al Lago Clear, California.Los resultados de los trazadores
que no son 3H (por ejemplo, boro, cloruros, sulfatos δD, y δ18O) identifican las contribuciones de seis tipos de agua en la SBMM. Se han identificado diversos procesos, como evaporación,
mezcla, entrada de agua hidrotermal y la posibilidad de intercambios isotópicos con gases hidrotermales. Los datos de tritio
indican que las aguas hidrotermales y otras aguas subterráneas profundas son probablemente pre-bombas (previas a ~1952) en
edad mientras que la mayoría de las otras aguas se han recargado después de ~1990. Un modelo estacionario basado en el boro
de la fosa del lago Herman Impoundment indica que el 71–79% de su entrada procede de agua meteórica con restos de contribución
hidrotermal. Los resultados para las muestras de aguas subterráneas procedentes de seis pozos superficiales en un periodo
de 6 meses para δD y δ18O sugieren que el agua procedente de Herman Impoundment se diluye en otro 3% hasta más del 40% debido a la infiltración de
agua meteórica., que sale del sitio. Los resultados de esta investigación muestran que los trazadores ambientales son una
herramienta efectiva para entender el régimen hidrogeológico de la SBMM.
Flow-through dissolution experiments were carried out on crushed granitoid rock (the Elat Granite) and three mineral separates (plagioclase, perthite, and biotite + chlorite) from this rock at pH 1 and 25°C. Major element concentrations were combined with Pb and Sr isotopic analyses of starting materials and output solutions and together enabled us to elucidate several important mechanisms related to granitoid rock weathering. We observed an initial stage of rock dissolution (<200 hours of reaction) that was characterized by elemental release from traces of calcite and/or apatite and to a lesser extent from the interlayer sites of biotite. Dissolution in the interval of 200 to 400 h was dominated by the release of elements from the interlayer sites of biotite, and at 400 to 1000 h of reaction the chemistry of output solutions was dominated by the release of elements from tetrahedral and octahedral sites of biotite as well as from plagioclase. After 1000 h, the dissolution of plagioclase, and to a lesser extent biotite, dominated the composition of elements released by the rock. We demonstrate that Pb and Sr isotope ratios in the output solutions can be used to identify each of these stages of dissolution. By comparing our experimental results on the release of Pb and Sr isotopes with field measurements of Pb and Sr isotopes in soil chronosequences from the Wind River and the Sierra Nevada Mountains (USA), we are able to show that similar isotopic patterns appear in both the pH 1 experiments and in soils formed under natural conditions at higher pH. By combining these experimental results with previous field studies, we are able to estimate the duration of most of these stages of granitoid weathering under natural conditions in temperate climates. In soils older than a few hundred years and younger than 10,000 yr the release of elements from interlayer sites of biotite controls the weathering flux. Soils between 10,000 and 100,000 yr old are dominated by biotite and plagioclase weathering, with biotite weathering controlling the first part of this period and plagioclase dominating the later part. After more than 100,000 yr, plagioclase, and to a lesser degree biotite, dominate the weathering flux within these granitoid soils. 相似文献
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