Boletín de la Sociedad Geológica Mexicana Volumen 68, núm. 3, 2016, p. 395‒407 http://dx.doi.org/10.18268/BSGM2016v68n3a2

Caracterización geoquímica de las manifestaciones termales intermareales de Bahía Concepción en la Península de Baja California

María Luisa Leal-Acosta^1,*, Rosa María Prol-Ledesma²

¹ Instituto de Industrias, Universidad del Mar, Campus Puerto Ángel, Distrito de San Pedro Pochutla, Puerto Ángel, CP 70902, Oaxaca, México.
² Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, CP 04510, CDMX, México.

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Abstract

The presence of hydrothermal manifestations on the coast of Bahía Concepción is associated with an extensional tectonic regime related to the formation of the Gulf of California. In this work, the geochemical composition of the intertidal springs is analysed to characterize the geothermal reservoirs associated with different groups of superficial manifestations. The La Posada hot springs present the highest temperature of the intertidal springs in the study area (66 °C). The hot springs in Bahía Concepción correspond to the sodium-chloride type and its chemical and isotopic composition shows the incidence of mixing phenomena with seawater and probably with high salinity. Compared to seawater, the thermal water has lower concentrations of Na⁺, Cl^-, Mg²⁺, SO₄²⁺ and HCO₃^- ions, and higher concentrations of Si and cations such as Ca²⁺, Sr²⁺ and K⁺. The isotopic composition indicates that the thermal water from the intertidal manifestations in the northern part of the bay lies along a mixing line of sea water with groundwater with a shift towards oxygen enrichment due to water-rock interaction. Therefore, it is likely that one single reservoir feeds all sampled hot springs.

Keywords: geothermics, intertidal geothermal hot springs, geothermal reservoir, Mexico.