The Northern Boundary of the Michoacan Block: As Inferred From Aeromagnetic Data

Friday, 18 December 2015
Poster Hall (Moscone South)
Jose Rosas-Elguera1, Héctor Lopez Loera2, Emilia Fregoso3, Roberto Maciel4, Laura Peña4 and Miguel Angel Alatorre-Zamora5, (1)Universidad de Guadalajara, CUVALLES, Ameca, Mexico, (2)Instituto Potosino de Investigación Cientifica, Ciencias de la Tierra, San Luis Potosi, Mexico, (3)Universidad de Guadalajara, CUCEI, Guadalajara, Mexico, (4)Universidad de Guadalajara, CUCBA, Guadalajara, Mexico, (5)Universidad Nacional Autonoma de Mexico, Mexico City, Mexico
The western part of the Guerrero terrane is comprised of the Jalisco and Michoacan Blocks (Rosas-Elguera et al., 1996 and references therein), a fault-bounded crustal blocks at western of Mexico. The Michoacan block is bounded by the N-NE segment of the Rio Balsas in the east, and the Colima graben in the west, the Chapala-Oaxaca fault to the north, and the Middle America Trench to the south.

Northern boundary is formed with the Chapala-Oaxaca fault zone (Harrison y Johnson, 1985). The Cotija half-graben is the end-tip of this fault zone. A combined radiometric and paleomagnetic analyses in the Cotija half-graben were carried out (Rosas-Elguera, et al, 2003). Radiometric dates between 31.60 and 8.39 Ma confirm both the southern extension of the Sierra Madre Occidental and the early mafic Tans-Mexican Volcanic Belt succession at the northern part of the Michoacan block. Paleomagnetic data indicate a counterclockwise rotation of ~ 24° about a vertical axis for the Michoacan block.

The Michoacan-Guanajuato Volcanic Field forms an area of extensive monogenetic volcanism. This volcanic field contains more than 1000 eruptive centers distributed over an area of 40,000 Km2. The Chapala-Oaxaca fault zone separates the northern MGVF and the southern MGVF.

Hasenaka and Carmichael (1987) recognized three different petrologic associations in the MGVF: calc-alkaline rocks typical arc characteristic, K2O-rich alkaline rocks with relatively high MgO contents and TiO2-rich alkaline rocks with relatively low MgO contents.

We present the aeromagnetic results (after Consejo de Recursos Minerales, 1999) which suggest a clear relationship between the geologic features and the magnetic response.