Helium and carbon isotopes in thermal waters of the Jalisco block, Mexico
The Jalisco block is a geologically and tectonically complex part of western Mexico. It is considered a distinct crustal unitbounded toward the mainland by rifting and toward the Pacific ocean by the SW section of the Mid-America trench, a contactbetween the subducting Rivera plate and the continent...
| Autores: | , , , , |
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| Tipo de documento: | artigo |
| Estado: | Versão publicada |
| Data de publicação: | 2002 |
| País: | México |
| Recursos: | Universidad Nacional Autónoma de México |
| Repositório: | Redalyc-UNAM |
| OAI Identifier: | oai:redalyc.org:56841416 |
| Acesso em linha: | https://www.redalyc.org/articulo.oa?id=56841416 |
| Access Level: | Acceso aberto |
| Palavra-chave: | Ciencias de la Tierra tectonics Jalisco Block helium isotopes carbon isotopes water and gas geochemistry |
| Resumo: | The Jalisco block is a geologically and tectonically complex part of western Mexico. It is considered a distinct crustal unitbounded toward the mainland by rifting and toward the Pacific ocean by the SW section of the Mid-America trench, a contactbetween the subducting Rivera plate and the continent. On the basis of chemical, helium, and carbon isotopic analyses of 37groups of thermal springs widely distributed over the Jalisco block, several major tectonic environments can be distinguished. Thehighest R= 3He/4He ratios with R/Ra (Ra being the atmospheric 3He/4He ratio) approaching MORB values were observed along theTrans-Mexican Volcanic Belt (TMVB) and within the Colima volcanic complex. For springs in the inner part of the block andclose to the Pacific coast, including submarine springs at Punta de Mita, typical values were much lower, with R/Ra down to 0.4.A negative correlation between 3He/4He and δ13C of CO2 is suggested to be the result of coupling between radiogenic He and CO2formed by oxidation of organic-rich sediments. C/3He ratios vary from ~109 for TMVB, typical for volatiles released from themantle, to > 1011 thus suggesting a substantial addition of carbon from the crust. |
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