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Open AccessArticle

Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)

1
Géosciences Environnement Toulouse (GET), CNRS, IRD, UPS, CNES. Université de Toulouse, 31400 Toulouse, France
2
Bureau de Recherches Géologiques et Minières (BRGM), 3 Avenue Claude Guillemin, 45000 Orléans, France
*
Author to whom correspondence should be addressed.
Minerals 2019, 9(10), 637; https://doi.org/10.3390/min9100637
Received: 4 September 2019 / Revised: 2 October 2019 / Accepted: 14 October 2019 / Published: 17 October 2019
The Echassières district in central France contains complex rare-element ore deposits, whose formation is related to exotic igneous events and several hydrothermal episodes that are not entirely understood to date. Tungsten mineralization consists of three generations of wolframite, characterized by distinct Fe/Mn ratios (8.4; 3.5 and 0.3, for wolframite a, b and c, respectively), formed during three separate hydrothermal episodes related to the Variscan orogeny. Wolframite a occurs in quartz veins of the La Bosse stockwork where it crystallized before the Barrovian metamorphism that affected these veins and the host rock. After metamorphism, before intrusion of the Beauvoir and Colettes granites, wolframite b crystallized in the stockwork during massive topazification. High concentrations of wolframite c occur in the proximal quartz veins in the Mazet area, while only scant amounts are found in the La Bosse stockwork. In both settings, wolframite c precipitated from the fluid responsible for greisen alteration that massively affected the Beauvoir granite. In the La Bosse stockwork, greisen alteration is characterized by hydrothermal topaz that is texturally and chemically distinct from that precipitated during topazification. Supergene alteration responsible for kaolinization of Beauvoir and Colettes granites caused remobilization of a non-negligible amount of tungsten (W) during replacement of wolframite by W-rich goethite in all units of the Echassières district. This model for multiple W mineralizing events is novel and can prove essential in distinguishing potential economic deposits worldwide. View Full-Text
Keywords: wolframite; W mineralization; greisen; beauvoir granite; topaz; W-rich goethite; hydrothermal alteration wolframite; W mineralization; greisen; beauvoir granite; topaz; W-rich goethite; hydrothermal alteration
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MDPI and ACS Style

Monnier, L.; Salvi, S.; Melleton, J.; Bailly, L.; Béziat, D.; de Parseval, P.; Gouy, S.; Lach, P. Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France). Minerals 2019, 9, 637.

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