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Extensional deformation assisted by mineralised fluids within the brittle-ductile transition: Insights from the southwestern Massif Central, France

Abstract : Extensional deformation assisted by mineralized fluids within the brittle-ductile transition is inferred using structural, microstructural and textural investigations applied to the Sarlande shear zone of the southwestern Massif Central, France. The shear zone is a low-angle normal fault that bounds the Meuzac antiform to the south. These structures were formed during the NW-SE-trending synorogenic extension of Middle Carboniferous age. Pre-existing lithologies involved in the shear zone led to partitioning of behaviour and hydrothermal alteration in response to crustal extension and channelling of mineralising fluids. Intense fluid-rock interactions produce softening and weakening reactions induced by alteration of K-feldspar, remobilisation of graphite and rutile, and growth of white micas, chlorite and polymetallic sulphides. Extensional shear deformation and mineralization progressively and concomitantly developed within the brittle-ductile transitional crust (∼9–13 km depth). The derived crustal-scale model emphasises the importance of collision which led to the production of large quantities of granite-derived fluids, and the creation of a crustal permeability that drove these fluids near to the brittle-ductile transition. Late orogenic extension associated with fluid-rock interactions led to growth of mineralizing low-angle shear zones and footwall domes. The role of mineralising fluids (fluid pressure) appears to be essential in promoting deformation within the brittle-ductile transition of the extending crust.
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Soumis le : mercredi 20 avril 2022 - 13:51:46
Dernière modification le : mercredi 3 août 2022 - 04:06:09

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Jean-Philippe Bellot. Extensional deformation assisted by mineralised fluids within the brittle-ductile transition: Insights from the southwestern Massif Central, France. Journal of Structural Geology, Elsevier, 2007, 29 (2), pp.225-240. ⟨10.1016/j.jsg.2006.09.004⟩. ⟨hal-03647289⟩

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