Microstructures of epidote-prehnite bearing damaged granitoids (northern Victoria Land, Antarctica): clues for the interaction between faulting and hydrothermal fluids

International audience Exhumed faults in granitoids along the Lanterman Fault-Rennick Graben Fault system (northern Victoria Land, Antarctica) show superposed ductile to brittle deformation and pervasive hydrothermal fluid-rock interaction. These processes triggered multiple brittle slip events prod...

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Bibliographic Details
Published in:Journal of Structural Geology
Main Authors: Malatesta, Cristina, Crispini, Laura, Ildefonse, Benoit, Federico, Laura, Lisker, Frank, Läufer, Andreas
Other Authors: Department of Earth, Environmental and Life Sciences (DISTAV), Universita degli studi di Genova, Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Universität Bremen, Federal Institute for Geosciences and Natural Resources (BGR)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 2021
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Online Access:https://hal.archives-ouvertes.fr/hal-03206964
https://hal.archives-ouvertes.fr/hal-03206964/document
https://hal.archives-ouvertes.fr/hal-03206964/file/Malatesta_JSG_2021.pdf
https://doi.org/10.1016/j.jsg.2021.104350
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Summary:International audience Exhumed faults in granitoids along the Lanterman Fault-Rennick Graben Fault system (northern Victoria Land, Antarctica) show superposed ductile to brittle deformation and pervasive hydrothermal fluid-rock interaction. These processes triggered multiple brittle slip events producing crosscutting epidote and prehnite-rich fault veins, ultracataclasites and pseudotachylytes of crushing origin. Combined microstructural and minerochemical investigations on fault damage zones show three types of alteration: (i) albitization of K-feldspar and Caplagioclase; (ii) crystallization of prehnite and calcite in veins; (iii) alteration of magmatic phases by secondary hydrous minerals (e.g. chlorite, white mica, epidote and prehnite). The fault experienced various episodes of strain weakening and hardening, due to alteration of minerals and precipitation of epidote and prehnite within ultracataclastic intervals, at decreasing temperature conditions (200 < T • C < 450) and varying CO 2 fugacity of the fluids. Cyclic crystallization of epidote/prehnite within the fault cores caused cementation and locking of faults, concentration of deformation at weaker horizons and a progressive broadening of the fault zone. Our results indicate that multiple co-seismic slip and syntectonic fluid flow very likely occurred prior to the Cenozoic brittle reactivation of inherited anisotropies in the northern Victoria Land crust along the Lanterman Fault-Rennick Graben Fault system and underlines its high potential for polyphasicity.