E3S Web Conf.
Volume 98, 201916th International Symposium on Water-Rock Interaction (WRI-16) and 13th International Symposium on Applied Isotope Geochemistry (1st IAGC International Conference)
|Number of page(s)||7|
|Section||Applied Isotope Geochemistry|
|Published online||07 June 2019|
Origin of fluids in Las Tres Vírgenes Geothermal Field
GEOTOP-Research Centre on the dynamics of the Earth System, UQAM, Quebec, Canada
2 Facultad de Ingeniería Civil, UMSNH, Morelia, Mich., México
3 Dept. of Earth and Environmental Sciences, Univ. of Michigan, Ann Arbor, Michigan, USA
4 Isotope Traces Technologies Inc., Waterloo, ON, N2V 1Z5, Canada
5 Dept. of Earth and Environmental Science, Univ. of Waterloo, Waterloo, ON, N2L 3G1, Canada
6 School of Engineering, University of Guelph, Guelph, ON, N1G 2W2, Canada
7 Facultad en Ciencias de Ingeniería Química, UMSNH, Morelia, Mich., México
8 Comisión Federal de Electricidad, GPG, México
* Corresponding author: firstname.lastname@example.org
A geochemical survey of fluids in the Las Tres Vírgenes geothermal field (LTVGF) in Baja California Sur, Mexico, was carried out to describe their origins and evolution within the reservoir. Major and minor elements and noble gas isotopes (He, Ne, Ar, Kr, and Xe) were measured in fluids from three production wells, one injection well, and one fumarole (El Azufre). Stable isotopes of water (δD and δ18O) show mixing between Quaternary recharge, lighter than present-day rainfall, and a deep fluid of andesitic origin. The Na/Br and Cl/Br ratios indicate that deep brines from the LTVGF are seawater having leached evaporite deposits (i.e., halite). These deposits are presently absent in the area, but likely occurred during the Miocene, prior to the breakup of the Gulf of California, suggesting that the saline fluid end-member of the LTVGF is several million year old. Measured 3He/4He ratios of greater than 6.5 Ra (where Ra is the atmospheric ratio of 1.384 x10-6) show that LTVGF fluids are a mixture of meteoric waters and deep magmatic fluids, with the hotter and more pristine mantle fluids found in the southern part of the exploitation zone.
© The Authors, published by EDP Sciences, 2019
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