Riel N., Martelat J. E., Guillot S., Jaillard Etienne, Monie P., Yuquilema J., Duclaux G., Mercier J. (2014). Fore arc tectonothermal evolution of the El Oro metamorphic province (Ecuador) during the Mesozoic. Tectonics, 33 (10), p. 1989-2012. ISSN 0278-7407.
Titre du document
Fore arc tectonothermal evolution of the El Oro metamorphic province (Ecuador) during the Mesozoic
Riel N., Martelat J. E., Guillot S., Jaillard Etienne, Monie P., Yuquilema J., Duclaux G., Mercier J.
Source
Tectonics, 2014,
33 (10), p. 1989-2012 ISSN 0278-7407
The El Oro metamorphic province of SW Ecuador is a composite massif made of juxtaposed terranes of both continental and oceanic affinity that has been located in a fore-arc position since Late Paleozoic times. Various geochemical, geochronological, and metamorphic studies have been undertaken on the El Oro metamorphic province, providing an understanding of the origin and age of the distinct units. However, the internal structures and geodynamic evolution of this area remain poorly understood. Our structural analysis and thermal modeling in the El Oro metamorphic province show that this fore-arc zone underwent four main geological events. (1) During Triassic times (230-225Ma), the emplacement of the Piedras gabbroic unit at crustal-root level (similar to 9kbar) triggered partial melting of the metasedimentary sequence under an E-W extensional regime at pressure-temperature conditions ranging from 4.5 to 8.5kbar and from 650 to 900 degrees C for the migmatitic unit. (2) At 226Ma, the tectonic underplating of the Arenillas-Panupali oceanic unit (9kbar and 300 degrees C) thermally sealed the fore-arc region. (3) Around the Jurassic-Cretaceous boundary, the shift from trench-normal to trench-parallel subduction triggered the exhumation and underplating of the high-pressure, oceanic Raspas Ophiolitic Complex (18kbar and 600 degrees C) beneath the El Oro Group (130-120Ma). This was followed by the opening of a NE-SW pull-apart basin, which tilted the massif along an E-W subhorizontal axis (110Ma). (4) In Late Cretaceous times, an N-S compressional event generated heterogeneous deformation due to the presence of the Cretaceous Celica volcanic arc, which acted as a buttress and predominantly affected the central and eastern part of the massif.
