Geology of the boundary between the Sierra Madre Occidental and the Trans-Mexican Volcanic Belt in the Guadalajara region, western Mexico
To investigate the time-space relationship between the Sierra Madre Occidental (SMO) andthe Trans-Mexican Volcanic Belt (TMVB), as well as the early volcanic activity of the TMVB, a fieldstudy was carried out in the region north of Guadalajara City, along the boundary between the twovolcanic provinc...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2002 |
| País: | México |
| Institución: | Centro de Investigación Científica y de Educación Superior de Ensenada |
| Repositorio: | Redalyc-CICESE |
| OAI Identifier: | oai:redalyc.org:57219101 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=57219101 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias de la Tierra Trans Mexico Geology Guadalajara Mexican Volcanic Belt |
| Sumario: | To investigate the time-space relationship between the Sierra Madre Occidental (SMO) andthe Trans-Mexican Volcanic Belt (TMVB), as well as the early volcanic activity of the TMVB, a fieldstudy was carried out in the region north of Guadalajara City, along the boundary between the twovolcanic provinces. Detailed field mapping at 1:50,000 scale, supported by published and new isotopicages allow to propose a new stratigraphy (30 lithostratigraphic units) and to clarify the volcanicevolution of the region. The SMO succession is made of about 400 m of regional ash flows tuffsof early Miocene age, capped to the south by a basaltic sequence for which we obtained an 40Ar/39Arage of 21.8 ± 0.3 Ma. The SMO units are sub-horizontal north of García de la Cadena but dip up to25° to the south of this town, where they are covered in unconformity by the TMVB volcanism.A gap of about 10 Ma in the volcanism is observed between the two volcanic provinces. Volcanismpertaining to the TMVB is largely bimodal and can be divided into four stages: 1) a late Miocenemafic episode; it produced the Río Santiago group that consists of a >800 m thick basaltic successionextending toward the east into the Los Altos de Jalisco; 2) a latest Miocene (7-5 Ma) silicicepisode with the emplacement of domes and flows that form the Guadalajara group; 3) an earlyPliocene (4.7-3.7 Ma) episode characterized by the emplacement of ignimbrites that show evidenceof mingling between a mafic and a silicic magma (San Gaspar and Guadalajara ignimbrites) andalkali-basalts with an intra-plate affinity (Mirador de Ixcatán basalts); 4) a late Pliocene to Pleistoceneepisode with the eruption of rhyolitic domes and flows (Cerro Chicharrón group) and alkalibasalts,also showing an intra-plate affinity (Santa Rosa basalts).New K/Ar ages of 10.2 ±0.4 and 7.5 ± 0.8 Ma, together with previous dates, confirm that mostof the Río Santiago Group was emplaced between 11 and ~8 Ma. Its aggregate volume in the Guadalajararegion is about 1,800 km3. The silicic volcanism covers more than 1,000 km2 and has an aggregateestimated volume of 300 km3, which is about nine times the volume of magma extruded bythe late Pleistocene La Primavera caldera. The vents of the silicic domes belonging to the Guadalajaragroup and Cerro Chicharrón group follow an average N-S trend, and represent the surficial expressionof a long-lived silicic upper crustal chamber with the La Primavera caldera at its southernend. By contrast, the Mirador de Ixcatán and Santa Rosa alkali-basalts are associated with the Plio-Pleistocene WNW-ESE trending faults of the Plan de Barrancas-Santa Rosa graben and their eruptioncoincide with the beginning of two extensional pulses along these faults. This agrees with modelssuggesting that mafic volcanism preferentially erupt along arc-parallel, high strain rate faults,whereas arc-normal, low strain rate faults control the location of more differentiated la |
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