HR: 16:40h
AN: V24A-02    [Abstracts]
TI: Proto-Gulf volcanic sequences from Sierra Suvuk and Cerro Ladrilleros. El Pinacate Volcanic Field, NW Mexico.
AU: * Vargas Gutierrez, V R
EM: volcanovictor@hotmail.com
AF: UNAM-Centro de Geociencias, Carretera Queretaro-San Luis Potosí, km 15.5 , Queretaro, Qro 76230, Mexico
AU: Vidal Solano, J
EM: jrvidal@ciencias.uson.mx
AF: Universidad de Sonora, Blvd. Luis Encinas y Rosales S/N, Col. Centro, Hermosillo, Sonora, Son 83000, Mexico
AU: Paz Moreno, F
EM: paz@geologia.uson.mx
AF: Universidad de Sonora, Blvd. Luis Encinas y Rosales S/N, Col. Centro, Hermosillo, Sonora, Son 83000, Mexico
AB: The Pinacate Volcanic Field (PVF) lies at the northern end of the Gulf of California and is characterized by a complex tectonic history reflected in two main volcanic episodes: (1)alkaline Pinacate event; (2) Lower to Middle Miocene sequences that comprise mesa basalts with transitional alkali character, calc-alkaline andesites- dacites, and high silica rhyolites evolving toward peralkaline liquids, called pre-Pinacate. Our purpose here is to describe the stratigraphy and structural control of the pre-Pinacate Miocene volcanic sequences at Sierra Suvuk (SS) and Cerro Ladrilleros (CL). Different volcanic pulses with calc-alkaline affinities have been recognized within the SS and CL outcrops: [A] a dome-related Suvuk volcanism represented by complete lithofacies variations, from central-internal to external facies with associated pyroclastic flows. This dacitic dome is composed by a predominant mineralogy of Pl > Px >> Anf. [B] A dome-related Ladrilleros volcanism that differs from the Suvuk lavas by the fact that Anf >> Px and by its transition toward rhyodacitic compositions to the East. [C] A Fluidal Ladrilleros volcanism represented by lava flows with Pl + Anf as a characteristic mineralogy, representing the final phase of activity at Cerro Ladrilleros (ca 12Ma). [D] A Basic Suvuk volcanism represented by basaltic sub-horizontal lava flows cropping out at the summit of the SS. These lavas enclose Pl + Ol and have a thickness of about 50 m. Finally, [E] a Basic Suvuk valley volcanism represented by sub-horizontal basaltic lava flows and dikes located at the level of the actual valley, on the southeast flank of SS. The calc-alkaline affinity of the SS and CL lavas is not directly related to subduction. The occurrence of such a magmatism in an extensional tectonic setting could be explained by the persistency of a metasomatized mantle source, result of prolonged subduction processes since the early cretaceous. The behaviors of post-subduction volcanism in the Gulf of California area, and the peculiar petrology of Sierra Suvuk and Cerro Ladrilleros lavas, help us to constrain the tectonic evolution of the region since the Middle Miocene.
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly