The Abanico extensional basin: Regional extension, chronology of tectonic inversion and relation to shallow seismic activity and Andean uplift

Improving seismotectonics and seismic hazard assessment along the San Ramón Fault at the eastern border of Santiago city, Chile

“…Furthermore, we find that the N-S band of seismicity near the Santiago basin, or type A, is well defined with a width \15 km along the E-W direction, focal depths around *10-15 km with little dispersion and epicenters having a distribution approximately parallel to the fault trace of the San Ramón Fault; the type B band, also of predominantly N-S direction and located within the Principal Cordillera, has a greater dispersion along the E-W direction and a range of variation of focal depths between 0 and 10 km, with a higher concentration of events in the southern end (34°S). This study confirms independently, conclusions pointed out by Barrientos et al (2004) and Charrier et al (2005), that most of the seismic activity is located near the Chile-Argentina boundary, which is aligned with the El Fierro Fault system. Between the type A and B strips (70.45°a nd 70.55°W), one can observe a sparse seismicity as shown in Fig.…”

“…The main Andes Cordillera in this region is mostly constituted by Mesozoic to Cenozoic volcanic and sedimentary rocks together with Cenozoic intrusives (Thiele 1980;Charrier et al 2002Charrier et al , 2005Farías et al 2010;Armijo et al 2010). The San Ramón Fault is an N-S fault system located at the eastern border of the city of Santiago at the foot of the mountain front associated with the continental-scale West Andean Thrust (Armijo et al 2010), where the San Ramón hill range reaches 3,249 m a.s.l.…”

Fission track thermochronology of Neogene plutons in the Principal Andean Cordillera of central Chile (33-35°S): Implications for tectonic evolution and porphyry Cu-Mo mineralization

“…Basin inversion and significant tectonic uplift of the Principal Andean Cordillera took place as a result of the Neogene compressive tectonism Sillitoe and Perelló (2005) with fold and thrust belt and synorogenic deposits from Ramos et al (1996) and faults in Chile from Farías et al (2008); the projection of the axis of the Juan Fernández Ridge after Gilbert et al (2006). (Godoy et al, 1999;Charrier et al, 2002Charrier et al, , 2005, but also the synchronous development of a foreland basin system farther east in Argentina (Giambiagi et al, 2001). A number of Miocene granodioritic to dioritic plutons are scattered throughout the Cordillera at these latitudes (e.g., Kurtz et al, 1997); some of them are composite intrusions and locally display sill geometry within the Oligocene-Miocene volcanic succession.…”

“…Traditionally the 1,300 to 1,900 m thick, folded lower section (Oligocene to early Miocene in age) has been mapped as the Abanico Formation or the equivalent Coya-Machalí Formation south of 34°S (Klohn, 1960;Aguirre, 1960;Thiele, 1980;Charrier et al, 2002Charrier et al, , 2005, whereas the upper unconformable subhorizontal volcanic rocks (1,300 to 3,000 m thick) are considered to be part of the Farellones Formation (Charrier et al, 2002). In fact, a progressive unconformity (time-transgressive) separates these units and the K-Ar ages of the two volcanic units overlap between 22 and 16 Ma (Nyström et al, 2003;Charrier et al, 2002Charrier et al, , 2005Charrier et al, , 2007. The volcanism of the Principal Andean Cordillera of central Chile appears to have initially developed during the Eocene-Oligocene under an extensional tectonic regime (Charrier et al, 2002).…”

El Cenozoico del alto rio Teno, Cordillera Principal, Chile Central: estratigrafia, plutonismo y su relacin con estructuras profundas

“…Numerosos estudios desarrollados en los Andes de Chile central (33-36°S), durante las últimas dos décadas, han revolucionado el conocimiento acerca de su evolución tectónica y paleogeográfica durante el Cenozoico, aportando evidencias para la comprensión de un episodio extensional con desarrollo de una extensa cuenca volcano-tectónica (Cuenca de Abanico, Charrier et al, 2002Charrier et al, , 2005Godoy y Lara, 1994;Godoy et al, 1999) en la vertiente occidental de la Cordillera Principal. Los procesos geológicos que habrían condicionado la evolución de esta cuenca de intraarco estarían asociados a un progresivo adelgazamiento de la corteza, sucedida por un episodio de contracción tectónica que se inicia en el Mioceno Temprano (Charrier et al, 2002, el cual habría causado la inversión de la cuenca, la deformación de sus depósitos y la reactivación de las fallas normales asociadas al episodio de extensión, algunas de las cuales controlaron el emplazamiento de cuerpos intrusivos sintectónicos (Godoy, 1998).…”