Browsing by Author "Arancibia, G."

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    Development of a self-similar strike-slip duplex system in the Atacama Fault system, Chile
    (PERGAMON-ELSEVIER SCIENCE LTD, 2011) Jensen, E.; Cembrano, J.; Faulkner, D.; Veloso, E.; Arancibia, G.
    Fault development models are crucial to predict geometry and distribution of fractures at all scales. We present here structures related to the development of the Bolfin Fault in the Atacama Fault System (AFS), covering a range of scales of 7 orders of magnitude. The AFS is a 1000 km-long trench-parallel fault system located in the Andean Forearc. The Boffin Fault is a first-order fault of the Caleta Coloso Duplex, has a trend similar to 170 degrees and length >45 km. It cuts mainly meta-diorites and exhibits a 100-200 m thick core of subvertical bands of altered fractured host rock and of foliated cataclasites. This foliation is made up of several trend-parallel cm-thick shear bands, composed of plagioclase fragments (>0.1 mm) surrounded by epidote.
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    Magnitude, timing, and rate of slip along the Atacama fault system, northern Chile: implications for Early Cretaceous slip partitioning and plate convergence
    (GEOLOGICAL SOC PUBL HOUSE, 2021) Seymour, N. M.; Singleton, J. S.; Gomila, R.; Mavor, S. P.; Heuser, G.; Arancibia, G.; Williams, S.; Stockli, D. F.
    Displacement estimates along the Atacama fault system (AFS), a crustal-scale sinistral structure that accommodated oblique convergence in the Mesozoic Coastal Cordillera arc, vary widely due to a lack of piercing points. We map the distribution of plutons and mylonitic deformation along the northern c. 70 km of the El Salado segment and use U-Pb geochronology to establish the slip history of the AFS. Along the eastern branch, mylonitic fabrics associated with the synkinematic c. 134-132 Ma Cerro del Pingo Complex are separated by 34-38 km, and mylonites associated with a synkinematic c. 120-119 Ma tonalite are separated by 20.5-26 km. We interpret leucocratic intrusions to be separated across the western branch by c. 16-20 km, giving a total slip magnitude of c. 54 +/- 6 km across the El Salado segment. Kinematic indicators consistently record sinistral shear, and zircon (U-Th)/He data suggest dip-slip motion was insignificant. Displacement occurred between c. 133-110 Ma at a slip rate of c. 2.1-2.6 km Myr(-1). This slip rate is low compared to modern intra-arc strike-slip faults, suggesting (1) the majority of lateral slip was accommodated along the slab interface or distributed through the forearc or (2) plate convergence rates/obliquity were significantly lower than previously modeled. Supplementary material: Full U-Pb, (U-Th)/He, petrographic, and structural data with locations is available at Thematic collection:This article is part of the Isotopic dating of deformation collection available at:
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    Nature and tectonic significance of co-seismic structures associated with the Mw 8.8 Maule earthquake, central-southern Chile forearc
    (PERGAMON-ELSEVIER SCIENCE LTD, 2011) Arriagada, C.; Arancibia, G.; Cembrano, J.; Martinez, F.; Carrizo, D.; Van Sint Jan, M.; Saez, E.; Gonzalez, G.; Rebolledo, S.; Sepulveda, S. A.; Contreras Reyes, E.; Jensen, E.; Yanez, G.
    The Mw 8.8 Maule earthquake on February 27, 2010 affected the central-southern Chilean forearc of the Central Andes. Here we show the results of field investigations of surface deformation associated with this major earthquake. Observations were carried out within three weeks after the seismic event, mostly in the central and northern part of the forearc overlying the rupture zone. We provide a detailed field record of co-seismic surface deformation and examine its implications on active Andean tectonics. Surface rupture consisted primarily of extensional cracks, push-up structures, fissures with minor lateral displacements and a few but impressive extensional geometries similar to those observed in analogical modeling of rift systems. A major group of NW-WNW striking fractures representing co-seismic extensional deformation is found at all localities. These appear to be spatially correlated to long-lived basement fault zones. The NW-striking normal focal mechanism of the Mw 6.9 aftershock occurred on March 11 demonstrates that the basement faults were reactivated by the Mw 8.8 Maule earthquake. The co-seismic surface ruptures show patterns of distributed deformation similar to those observed in mapped basement-involved structures. We propose that co-seismic reactivation of basement structures play a fundamental role in stress release in the upper plate during large subduction earthquakes. The fundamental mechanism that promotes stress relaxation is largely driven by elastic rebound of the upper plate located right above the main rupture zone. (C) 2011 Elsevier Ltd. All rights reserved.
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    Shallow anatomy of hydrothermal systems controlled by the Liquin?e-Ofqui Fault System and the Andean Transverse Faults: Geophysical imaging of fluid pathways and practical implications for geothermal exploration
    (PERGAMON-ELSEVIER SCIENCE LTD, 2022) Perez-Estay, N.; Molina-Piernas, E.; Roquer, T.; Aravena, D.; Vargas, J. Araya; Morata, D.; Arancibia, G.; Valdenegro, P.; Garcia, K.; Elizalde, D.
    We combined geoelectric and seismic ambient noise methods to image the shallow depth (<30 m) distribution of thermal waters in two fault-controlled hydrothermal systems located in southern Chile. The bedrock depth was constrained with seismics, while hotsprings and mapped faults were imaged by low-electrical-resistivity domains (<160 omega m) defined with electrical resistivity tomographies (ERT). The distribution and shape of low-resistivitydomains suggest that thermal fluids follow complex pathways, including deep vertical conduits hosted in fractured rock and shallow horizontal bodies hosted in sediments. These results indicate that the studied hydrothermal systems are at least twice longer within the sediments than the superficial area covered by hotsprings.