World Geothermal Congress 2020+1
March - October, 2021

Evidence of Dissolved Organic Compounds in a Mexican High-Temperature Geothermal Field

Juan Ignacio SÁNCHEZ-AVILA, Brenda GARCÍA-SÁNCHEZ, Gabriela VARA-CASTRO and Thomas KRETZSCHMAR

[Cicese, Mexico]

Dissolved organic compounds (DOC) of medium volatility in hydrothermal systems are attracting attention, due to the close relationship of the reactions involved in the formation of the compounds, with the origin of life on Earth. DOC have been recently reported by few authors as tools for comprehend the biogenic and abiogenic reactions within a continental hydrothermal system. In our case, we report herein for the first time, the presence and relative concentrations of (DOC) in samples from a high-temperature geothermal field in Mexico. The geothermal field of Los Humeros in Mexico is a super-hot steam-dominant geothermal system with temperatures superior than 300 °C. Within the Mexican-European collaboration Project Framework, called GEMex, were analyzed dissolved organic compounds from ten water/vapor condensate samples from active exploitation wells. Besides them, three samples from groundwater and three from cold springs were taken from the surrounding area. Sampling was performed on November-December 2018. For the characterization of the organic compounds, solid Phase Extraction (SPE) was used and analysis by Gas Chromatograph coupled to a Mass Spectrometry (GC-MS). In exploitation geothermal well condensates, a wide range of compounds (38) were identified, pertaining to eight homologue series (alkanes, alkenes, terpenes, aromatics, alcohols, aldehydes, ketones and Sulfur-containing hydrocarbons). In condensates, aromatics and sulfur-containing hydrocarbons were the predominant compounds. Differences in the composition of the DOC were noticed in the geothermal wells fluids with lower estimated temperature. The most typical compounds found in the six cold waters in appreciable concentrations were alkenes, followed by alkanes, alcohols and aromatic hydrocarbons. Monoaromatic hydrocarbons dominated the composition of aromatics in some wells and cold-springs. Our findings do not provide enough evidence to suggest circulation flow paths from the geothermal wells to cold-water sampling sites. Especially if the origin of monoaromatic hydrocarbons in cold springs and groundwater samples is unclear. However, is probable a hydrothermal influence of these compounds. The results of this study increase the scarce knowledge of dissolved organic fraction in hydrothermal systems. On the other hand, the information obtained herein will be useful to other similar studies dealing with the problem of the origin of primary forms of life under hydrothermal environments

        Topic: Geochemistry Paper Number: 14123

         Session 17D: Geochemistry 8 [Tuesday 11th May 2021, 02:00 pm] (UTC-8)
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