The Aztlan Fault System: control on the emplacement of the Chichinautzin Range volcanism, southern Mexico Basin, Mexico. Seismic and gravity characterization
Por:
CamposEnriquez, JO, LermoSamaniego, JF, AntayhuaVera, YT, Chavacan, M, RamonMarquez, VM
Publicada:
1 ene 2015
Categoría:
Earth and Planetary Sciences (miscellaneous)
Resumen:
Gravity and seismic studies enabled us to establish the major features
of the shallow crustal structure beneath Chichinautzin Range.
Accordingly, the Chichinautzin Range evolved above Mesozoic calcareous
rocks lying on a metamorphic basement. To the north and south this
basement is downfaulted. Nevertheless the north dipping faults downward
displace the basement to larger depths (2 to 3 km) in the Mexico and
Toluca basins. In the Morelos Basin, the basin is shallower. As
block-faulting evolved, the basement edge migrated southwards, thus
widening an E-W oriented major depression south of the Mexico Basin. In
particular, gravity modeling enabled us to integrate the different
faults mapped up to today in and around the Chichinautzin Range into a
fault system that can be correlated from the Nevado de Toluca. This
system will be referred to collectively as the Aztlan Fault System.
The Xicomulco, Aztec (central and major fault) and La Pera faults are
featured by seismicity. Orientation and dips obtained from simple and
composite mechanisms indicate NW-SE to N-S extension with minor E-W
left-lateral movement. In particular, seismicity extends down to the
brittle-ductile transition crustal zone (maximum hypocentral depths of
about 15 km) but consequently the major faults, considering their
length, should reach lower crustal levels (approximately 40 km). This
system is a major active fault system of at least 100 km in length and
30 - 40 km in width, with a density of approximately 10 E-W faults in 30
km, and local extension of about 10 %.
In conjunction with pre-existing NW-SE and NE-SW faults, this E-W fault
system would have intensely fractured the crust beneath the Sierra de
Chichinautzin. This high degree of fracturing would have enabled the
relatively fast emplacement of large quantities of volcanic material to
give rise to the Chichinautzin Range, closing the Mexico Basin to the
south. The gravity model shows how the different styles of structures
north and south of the Chichinautzin Range (extensional and compressive)
accommodate themselves. In particular, faults of the Taxco-San Miguel de
Allende system affect the basement of the Morelos Basin well further
south.
Filiaciones:
CamposEnriquez, JO:
Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City 04510, DF, Mexico
LermoSamaniego, JF:
Univ Nacl Autonoma Mexico, Inst Ingn, Mexico City 04510, DF, Mexico
AntayhuaVera, YT:
Univ Nacl Autonoma Mexico, Programa Posgrad Ciencias Tierra, Mexico City 04510, DF, Mexico
Chavacan, M:
Univ Nacl Autonoma Mexico, Programa Posgrad Ciencias Tierra, Mexico City 04510, DF, Mexico
RamonMarquez, VM:
Univ Nacl Autonoma Mexico, Programa Posgrad Ciencias Tierra, Mexico City 04510, DF, Mexico
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