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| Format: | Artículo científico |
| Language: | en |
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Universidad Nacional Autónoma de México
2004
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| Online Access: | https://www.redalyc.org/articulo.oa?id=56843307 |
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Table of Contents:
- Geochemistry and origin of high-pH thermal springs in the Pacific coast of Guerrero, Mexico Alejandro Ramírez Guzmán María Aurora Armienta Yuri Taran Ciencias de la Tierra High water rock interaction pH thermal waters computer simulation Thermal waters (40-43°C) discharging from crystalline rocks of the Xolapa complex, near Acapulco, Mexico, within anarea of approximately 100 km x 50 km are characterized by a low salinity (TDS<0.5 g/kg) and very high pH (9.5-10). Theyrepresent a regional aquifer or a group of aquifers with similar conditions of water circulation and water-rock interaction. Springgases are nitrogen- and He-rich, with a high proportion of radiogenic He (R/Ra=0.12 to 0.3). Methane from a spring with a highconcentration of CH4 (10-12%) is relatively enriched in 13C (δ13C=-26, PDB). All gases are very low in CO2 (<0.5%) andrelatively low in Rn (8 to 25 Bq/l). Numerical simulation of water-rock interaction in a multistep flow-through reactor, using a 1stwave approximation, suggests that this type of high-pH diluted water can be produced by step-by-step dissolution of granite andredeposition of secondary equilibrium minerals along a flow-path. This models the infiltrating meteoric water to the depth of100°C and its ascending to the surface with conductive cooling to 40°C. Closed system conditions in respect to CO2 and a lowconcentration of the carbonate carbon in the aquifer rock are needed to attain the high pH in thermal water from initially neutral orslightly acidic rain water. The presence of the carbonaceous material in the aquifer rocks can explain the observed concentrationsof methane in the CH4-rich spring, as well as its carbon isotopic composition. 2004 artículo científico 0016-7169 https://www.redalyc.org/articulo.oa?id=56843307 en http://www.redalyc.org/revista.oa?id=568 Geofísica Internacional application/pdf Universidad Nacional Autónoma de México Geofísica Internacional (México) Num.3 Vol.43