Skip to Main content Skip to Navigation
Theses

Evénements métallogéniques à W-Bi (Au) à 305 Ma en Châtaigneraie du Cantal : apport d'une analyse multi-spectrométrique (micro PIXE-PIGE et Raman) des minéraux et des fluides occlus à l'identification des sources de fluides hydrothermaux.

Abstract : La Châtaigneraie is a vein-type W-district which includes two mines within the metamorphic contact aureoles of granites. We have undertaken PIXE-PIGE trace element analyses of individual fluid
inclusions and minerals associated with the primary W-ore stage. These were compared to trace element analyses of minerals and fluids from leucogranites and metamorphic schists. PIXE analysis
using a "funny filter" allows elements from K to U to be detected. This study shows that the method becomes absolute, providing that the geometry of the analytical apparatus is well-controlled. The W
primary paragenesis possesses a trace element pattern similar to that of leucogranites (F, Mn, Zn,Ga, As, Nb, Sn, Ta, W, Bi). Only arsenic is independant, and rather controlled by micaschists. It has been detected in barrovian metamorphic fluids (¡Ö340 Ma) and in fluids and minerals from the W-ore stage (¡Ö305 Ma). W-veins are affected by tensile fracturing, quartz dissolution and deposition of vuggy pyrite and muscovite. The secondary vein-stage consists of native bismuth, bismuthinite,molybdenite, halcopyrite, covellite, tennantite, waylandite, cannonite, siderite and chlorite. Massive unmineralized tourmalinites develop synchroneously in veins or as replacement. In the La Granière
massive tourmalinites, cataclastic quartz contains numerous microinclusions of biotite, muscovite, Kfeldspar,ilmenite, zircon, monazite and xenotime. The characteristic trace element pattern of the secondary ore-stage is Fe, Mn, Cu, Zn, Ti, Cr, Sc, V, Se, Zr, Ag, Cd, Ba, Sr, Sb, Hf, Y, La, Ce and Th. Associated fluids are H20-CO2-bearing, with trace amounts of K, Ca and base metals. Stage II fluids appear to be silica-undersaturated, K-, PO4- and Al-bearing, enriched in heavy and transition metals (including Sc and Cr) and REE, LILE and HFSE. They are similar to mantle metasomatic fluids. This is further confirmed by the geochemistry, mineralogy and microstructures of a W-vein and a lamprophyre crosscutting it, at the Enguialès mine. Mineral assemblages and fluid chemistry provide evidence for the generalized boiling of solutions in this district, in relation with the high heat flux
and the rapid uplifting of the area at the late Hercynian.
Document type :
Theses
Complete list of metadata

Cited literature [44 references]  Display  Hide  Download

https://tel.archives-ouvertes.fr/tel-00002404
Contributor : Nathalie Pothier <>
Submitted on : Monday, February 17, 2003 - 10:24:16 AM
Last modification on : Thursday, March 5, 2020 - 6:49:20 PM
Long-term archiving on: : Wednesday, March 29, 2017 - 10:32:35 AM

Identifiers

  • HAL Id : tel-00002404, version 1

Citation

Sophie Gama. Evénements métallogéniques à W-Bi (Au) à 305 Ma en Châtaigneraie du Cantal : apport d'une analyse multi-spectrométrique (micro PIXE-PIGE et Raman) des minéraux et des fluides occlus à l'identification des sources de fluides hydrothermaux.. Minéralogie. Université d'Orléans, 2000. Français. ⟨tel-00002404⟩

Share

Metrics

Record views

658

Files downloads

1844