Detailed information about the course
Title | Late-orogenic Au-bearing magmatic-hydrothermal systems of the Cévennes area (South French Massif Central) |
Dates | June 5-9th 2017 |
Organizer(s) | |
Speakers | Dr. Alain Chauvet, Directeur de recherche CNRS, UMR 5243 – Géosciences Montpellier, Université de Montpellier 2 |
Description | The late-hercynian evolution of the French Massif Central is synchronous with the emplacement of numerous calc-alkaline granites around 300 Ma. This magmatism has been intensively studied and most models argue for a magmatic activity related to the late-orogenic extension, postdating the main compressional event at 340 Ma. During this event, large-scale magmatic hydrothermal fluid circulation occurred in the crust, generating various hydrothermal ore manifestations, the latest event being associated with the formation of gold-bearing quartz veins. The main objective of the field trip is to characterize and understand field relations between tectonic, magmatic, and hydrothermal features in order to construct a geological model of the mineralized system. The three days of intensive field work will include: First day: Characterization of the deformation in the Cévennes micashists (host for magma emplacement and mineralization) and distinction between hydrothermal features related to compression and those related to the late magmato-tectonic extensional events and relationship between fluid circulations, fluid trapping and shearing structures. Second day: Characterisation of the magmatic system - observations on several outcrops of the Mont-Lozère porphyritic granite and distinction between sub-solidus and magmatic foliation; defining the tectonic context that prevailed during magma emplacement and characterization of syn-tectonic late-magmatic features (aplite and pegmatite veins) along the borders of the granitic intrusion. Third day: Work on the link between magmatic and hydrothermal events using structural analysis on magmatic bodies and hydrothermal veins at the "Le Travers" outcrop; detailed geological mapping in an old gallery, with arsenopyrite mineralization containing invisible gold (the Le Gal lode). General discussion about the global tectono-magmatic and metallogenic model, including the available geochronological and geochemical data and potential consequences for exploration programs in similar terrains. |
Location |
Massif des Cévennes, France |
Information | |
Places | 11 |
Deadline for registration | 28.05.2017 |