Browsing by Author "Faulkner, D."
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- ItemDevelopment 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.
- ItemFrictional Melting in Hydrothermal Fluid-Rich Faults: Field and Experimental Evidence From the Bolfin Fault Zone (Chile)(2021) Gomila, R.; Fondriest, M.; Jensen, E.; Spagnuolo, E.; Masoch, S.; Mitchell, T. M.; Magnarini, G.; Bistacchi, A.; Mittempergher, S.; Faulkner, D.; Cembrano, J.; Di Toro, G.Tectonic pseudotachylytes are thought to be unique to certain water-deficient seismogenic environments and their presence is considered to be rare in the geological record. Here, we present field and experimental evidence that frictional melting can occur in hydrothermal fluid-rich faults hosted in the continental crust. Pseudotachylytes were found in the >40 km-long Bolfin Fault Zone of the Atacama Fault System, within two ca. 1 m-thick (ultra)cataclastic strands hosted in a damage-zone made of chlorite-epidote-rich hydrothermally altered tonalite. This alteration state indicates that hydrothermal fluids were active during the fault development. Pseudotachylytes, characterized by presenting amygdales, cut and are cut by chlorite-, epidote- and calcite-bearing veins. In turn, crosscutting relationship with the hydrothermal veins indicates pseudotachylytes were formed during this period of fluid activity. Rotary shear experiments conducted on bare surfaces of hydrothermally altered rocks at seismic slip velocities (3 m s(-1)) resulted in the production of vesiculated pseudotachylytes both at dry and water-pressurized conditions, with melt lubrication as the primary mechanism for fault dynamic weakening. The presented evidence challenges the common hypothesis that pseudotachylytes are limited to fluid-deficient environments, and gives insights into the ancient seismic activity of the system. Both field observations and experimental evidence, indicate that pseudotachylytes may easily be produced in hydrothermal environments, and could be a common co-seismic fault product. Consequently, melt lubrication could be considered one of the most efficient seismic dynamic weakening mechanisms in crystalline basement rocks of the continental crust.
- ItemHydrothermal alteration in an exhumed crustal fault zone : Testing geochemical mobility in the Caleta Coloso Fault, Atacama Fault System, Northern Chile(2014) Arancibia Hernández, Gloria Cecilia; Fujita, K.; Hoshino, K.; Mitchell, T.; Cembrano, José; Gomila, Rodrigo; Morata, D.; Faulkner, D.; Rempe, M.
- ItemPalaeopermeability structure within fault-damage zones : a snap-shot from microfracture analyses in a strike-slip system(2016) Gomila, Rodrigo; Arancibia Hernández, Gloria Cecilia; Mitchell, T.; Cembrano, José; Faulkner, D.