Title
The granite hosted gold deposit of Moulin de Chéni (Saint-Yrieix district, Massif Central, France): Petrographic, structural, fluid inclusion and oxygen isotope constraints
Date Issued
01 May 2004
Access level
open access
Resource Type
journal article
Author(s)
Boiron M.C.
Cathelineau M.
Fourcade S.
Varlet M.
Marignac C.
Section des Sciences de la Terre
Abstract
The Moulin de Chéni orogenic gold deposit is the only granite-hosted deposit of the Saint-Yrieix district, French Massif Central. It occurs in 338 ± 1.5 Maold peraluminous leucogranites and is characterized by intense microfracturing and bleaching of the granite in relation to pervasive sulfide crystallization. Formation of quartz veins and gold deposition occurred in two successive stages: an early "mesozonal" stage of quartz-sulfide (Fe-As-S) deposition, usually devoid of gold and a late "epizonal" stage of base metal and gold deposition. Both stages postdate peak metamorphism and granite intrusion. The genesis of the deposit is the result of four successive fluid events: (1) Percolation of aqueous-carbonic metamorphic fluids under an assumed lithostatic regime of 400-450 °C, at a maximum depth of 13 km; (2) Formation of the main quartz lodes with coeval K-alteration and introduction of As and S from aqueous-carbonic fluids percolating along regional faults. Arsenopyrite and pyrite deposition was linked to the alteration of Fe-silicates into K-feldspar and phengite at near-constant iron content in the bulk granite. Temperature was similar to that of the preceding stage, but pressure decreased to 100-50 MPa, suggesting rapid uplift of the basement up to 7.5 km depth; (3) The resulting extensional tectonic leads to the deposition of gold, boulangerite, galena and sphalerite in brecciated arsenopyrite and pyrite from aqueous fluids during a mixing process. Temperature and salinity decrease from 280 to 140 °C and 8.1 wt% eq. NaCl to 1.6 wt% eq. NaCl, respectively; (4) Sealing of the late fault system by barren comb quartz which precipitated from dilute meteoric aqueous fluids (1.6 wt% eq. NaCl to 0.9 wt% eq. NaCl) under hydrostatic conditions at 200-150 °C. © Springer-Verlag 2004.
Start page
265
End page
281
Volume
39
Issue
3
Language
English
OCDE Knowledge area
Mineralogía Geología
Scopus EID
2-s2.0-2942557036
Source
Mineralium Deposita
ISSN of the container
00264598
Sponsor(s)
Acknowledgements Funding for this research was provided by grants from the GeoFrance 3D program and the regional project ‘‘Massif Central 3D Mapping and Metallogeny’’ and the French Research group on Ore deposits ‘‘TRANSMET’’ (GDR CNRS-n°2458). The company ‘‘Société des Mines du Bourneix’’ is thanked for having permitted sampling in the mine. Juliette Nicaud is especially acknowledged for her technical and scientific assistance during field work. The authors are grateful to Susanne Schmidt for improving the manuscript. This paper has significantly benefited from the constructive reviews of Odin Christensen, Bernd Lehmann and Eric Marcoux.
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