| Abstract |
Shallow submarine hydrothermal activity has been observed in Western Mexico related to extensional tectonics faults. Hydrothermal vents occur at Punta Banda on the Pacific coast of Baja California, at Bahia Concepcion on the eastern coast of Baja California and in Punta Mita on the Pacific coast of central Mexico. Submarine discharge of geothermal fluids is located at depths that vary from 5 to 30m. Water and gas discharge at temperatures from 40 to more than 100? C. The composition of the thermal end-member can be calculated for Mg = 0 using the chemistry data of the water samples. A linear regression of the concentration values vs magnesium content is used to determine the concentration of the end-member thermal water. The chemical composition of the thermal end-member indicates that the water is more dilute than seawater and enriched in Ca, Mn, Ba, I, Cs, B, Li, Rb, Sr and Si. The results show that the water chemistry is similar in these coastal hydrothermal systems. The thermal water is probably of meteoric origin that penetrates through the extensional faults, and is heated by the high geothermal gradient. The components in the thermal water are contributed by the deep strata. |