HR: 11:35h
AN: T32A-06    [Abstracts]
TI: Structural variations within the Jalisco Block displayed by a magnetotelluric transect
AU: * Arzate, J A
EM: arzatej@geociencias.unam.mx
AF: Centro de Geociencias, Universidad Nacional Autónoma de México, Carretera QRO-SLP, km 15.5, Juriquilla, QRO 76230, Mexico
AU: Alvarez, R
EM: rab@leibniz.iimas.unam.mx
AF: Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Col. Copilco, México, D.F 04510, Mexico
AU: Corbo, F
EM: fcorbo@geociencias.unam.mx
AF: Centro de Geociencias, Universidad Nacional Autónoma de México, Carretera QRO-SLP, km 15.5, Juriquilla, QRO 76230, Mexico
AB: The Jalisco Block has been described as an uplifted domain by several authors; the term block has implicitly involved the whole structure. Alvarez et al. (2006) advanced the idea that the block is actually divided in two domains, which they called the uplifted and the static domains. The uplifted domain lays about 1000 m above the static domain; the latter occupies the coastal area. In addition to the topographic differences, the above authors pointed out at contrasting seismic, magmatic, and aeromagnetic responses between the two domains. In order to clarify the origin of such a difference a magnetotelluric survey was performed involving 13 stations, 10 of them constituting a transect of 200 km across the two domains, while the remaining 3 constituted probes in neighboring areas. The four stations across the coastal region suggest the presence of a dipping conductor, which might be associated with the down going slab of the oceanic plate. The following three stations of the transect show a high conductivity anomaly zone 30 km wide, starting at depths of 8-10 km, which coincides with a region of intense magmatism at the surface; these stations are located in the uplifted domain. Then, the last three stations along the transect reveal an abrupt transition in the subsurface from a conductive zone to a region of high resistivity. This division correlates spatially with the previous finding that the coastal region shows positive magnetic anomalies whereas the landwards portion of the Jalisco Block corresponds to a wide negative anomaly. These results support the idea of two tectonic domains within the Jalisco Block.
DE: 0905 Continental structures (8109, 8110)
DE: 0925 Magnetic and electrical methods (5109)
DE: 8104 Continental margins: convergent
SC: Tectonophysics [T]
MN: 2007 Joint Assembly