| Abstract |
Fault zones play an important role in the spatial distribution of the geothermal resources in crystalline rocks (non-porous media). They can control the location, emplacement and evolution of geothermal systems by acting as barriers and/or conduits to geothermal fluid circulation through the crust, generating a natural fractured system. So, it is critical to study the nature of the fault control permeability in low porous crystalline rocks at different scales because different processes associated to the failure of rocks promote a complex time-dependent and enhancing/reducing the fluid flow pathways and are occurring in all scales. Furthermore, the fracture are connected between them forming a network, and if it is well-connected the network would favor the fluid circulation through open fractures. We selected the Southern Volcanic Zone (Chile) as a case of study to evaluate the role of the structural permeability in low porous crystalline rocks corresponding to the North Patagonian Batholith. Previous studies propose a relatively well-constrained first-order role of two active fault systems in fluid flow at crustal scales: 1) the arc-parallel Liquiñe-Ofqui Fault System (LOFS) with a NS to NNE trending, and 2) the arc-oblique Andean Transverse Faults (ATF) with a NW trending. Now, we propose to examine the Liquiñe area (~39°S) as site of interaction between these active fault systems and the spatial localization of the several hot springs, in order to evaluate this natural fractured geothermal system. For that, in this study we focused in one representative outcrop of the ATF, analyzing the fracture features in thin sections and in the outcrop (millimetric to centimetric scale), and following the methodology proposed by Sanderson and Nixon (2015). The main results indicate that at centimeter scale the fractures are well connected with a connectivity per branch of 2.0 and Y-nodes is the main node type, meanwhile at millimeter scale the connectivity was 1.85, and the predominate node is also the Y-node. So, as much the pattern network and connectivity are similar at both scales, but the density and intensity of fractures are over estimate at smaller scales. Moreover, the fracture network in the selected outcrop is well-connected allowing the fluid circulation. Finally, for future works we will considerer more areas at different scales to analyze the connectivity. |