Changes in the fluid regime during successive reactivations of a Pyrenean thrust fault
| Autor: | Muñoz-López, D., Alías, G., Cruset, David, Cantarero, I., John, C. M., Martín-Martín, J. D., Travé, Anna |
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| Rok vydání: | 2020 |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname Digital.CSIC: Repositorio Institucional del CSIC Consejo Superior de Investigaciones Científicas (CSIC) |
| Popis: | 3rd Conference of the Arabian Journal of Geosciences (CAJG), Sousse, Tunisia, November 2-5 2020. The Estamariu thrust, in the Pyrenean Axial Zone, resulted from a long-lived Variscan to Neogene tectonic history. Structural data together with petrological and geochemical analyses of synkinematic calcite veins and host rocks, constrain the fault-fluid system evolution during two successive tectonic events. Despite the Estamariu thrust is known to be Variscan in origin, in the study area, it places a Devonian pr-eVariscan unit on top of a Stephano-Permian late- to post-Variscan sequence, indicating that the structures present within this fault zone have to be post-Variscan. Analytical data suggests that during the Alpine compression, the thrust was reactivated allowing the transposition of the Variscan regional foliation (Sr) within the main thrust zone and generating a subsidiary thrust zone in the footwall of the main thrust. During this episode, meteoric fluids (¿18O fluid = -6.4 to -0.3 ¿VSMOW), heated at depth (temperatures between 56 and 98 ºC) and interacted with basement rocks (87Sr/86Sr ratio > 0.71) before ascending through the fault zone. These ascending fluids progressively increased the fluidrock interaction from the thrust plane towards the hanging wall. During the Neogene extension, the Estamariu thrust was reactivated and normal faults and shear fractures developed. During this period, hydrothermal fluids (temperatures up to 208 ºC), derived from the basement (¿18 Ofluid up to +12 ¿VSMOW and 87Sr/86Sr ratio > 0.71), migrated upwards through reactivated and newly formed fault zones. Finally, during the latest to post stages of extension and uplift of the structure, the fluid regime changed to percolation of low temperature meteoric fluids migrating from the surface through small shear fractures. Neogene extensional faults are still conduits of current hydrothermal springs in the study area. Thus, these structures have probably been acting as conduits for hydrothermal fluids from Neogene times to present in the Pyrenean Axial Zone. |
| Databáze: | OpenAIRE |
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