HR: 11:05h
AN: T42A-02    [Abstracts]
TI: Pre-Cenozoic History of the Jalisco Block (Guerrero Terrane of West-Central Mexico) From U- Pb Geochronology
AU: * Valencia, V A
EM: victorv@email.arizona.edu
AF: Department of Geosciences, University Of Arizona, Tucson, AZ 85721, United States
AU: Righter, K O
EM: kevin.righter-1@nasa.gov
AF: NASA, Johnson Space Center, Houston, TX 77058, United States
AU: Gehrels, G
EM: ggehrels@email.arizona.edu
AF: Department of Geosciences, University Of Arizona, Tucson, AZ 85721, United States
AU: Ruiz, J
EM: jruiz@geo.arizona.edu
AF: Department of Geosciences, University Of Arizona, Tucson, AZ 85721, United States
AU: Ducea, M
EM: ducea@email.arizona.edu
AF: Department of Geosciences, University Of Arizona, Tucson, AZ 85721, United States
AU: Rosas-Helguera, J
EM: jrosas@ccip.udg.mx
AF: Ciencias de La Tierra, Universidad de Guadalajara, Guadalajara, Jal 44100, Mexico
AB: The Jalisco Block is a fault-bounded crustal fragment, located along the western edge of the Trans-Mexican Volcanic Belt of west-central Mexico, and it forms part of the Triassic-Jurassic Guerrero terrane. Because of its extensive Miocene-Quaternary volcanic cover and Early Cretaceous-Tertiary intrusions, little is known about its Pre-Tertiary history. U-Pb (LA-MC-ICPMS) zircon geochronology of metasedimentary (Quartz Feldespathic Schist), marine sedimentary and plutonic rocks from several localities of the Jalisco Block (southern Mexico) were determined to constrain the geological evolution of this region. Results for the metasedimentary rocks, which are present as roof pendants, indicate a depositional age between the Late Triassic and Middle Jurassic. The older depositional sequence (Late Triassic) shows an important continental influence with subordinate clusters from the Carboniferous (297 Ma), Ordovician (446 Ma), Late and Middle Proterozoic (760, 1041, 1200, 1500 Ma) and Archean (~~2700 Ma), whereas the youngest depositional sequence (Middle Jurassic) have mainly Jurassic zircons, indicating sedimentation in a restricted basin. Ages of turbiditic marine sediments reveal a maximum depositional age of ~~130 Ma (Early Cretaceous), comparable to zircon populations from other areas of the Guerrero Terrane, and with minor age peaks at 320, 480-560, 743, 997-1260, and ~~2750 Ma. Magmatic granitic rocks from Atenguillo, Puerto Vallarta, Mascota and Tomatlan have ages of ~~60 Ma, ~~74 Ma and 80-90 Ma. These ages overlap with previously determined ages of granites and rhyolitic ash flow tuffs from the Jalisco Block, Baja California, Sonora and Sinaloa states. On the other hand, a granitic sample of Cuale region yielded a middle Jurassic age. Metasedimentary and sedimentary rocks of the Jalisco Block have a depositional evolution similar to coeval formations in the Guerrero and Alisitos terranes. We conclude that this region has been under a modest to large- scale arc plutonism from the Middle Jurassic to the Tertiary.
DE: 1115 Radioisotope geochronology
DE: 8104 Continental margins: convergent
SC: Tectonophysics [T]
MN: 2007 Joint Assembly