RT Journal Article
T1 P-V-T-X -f02 evolution from wolframite to sulphidedepositional stages in intragranitic W-veins.An example from the Spanish Central System
A1 Vindel Catena, Elena
A1 López García, José Ángel
A1 Boiron, Marie Christine
A1 Cathelineau, Michel
A1 Prieto Colorado, Ángel Carmelo
AB The relative P-T-X conditions of the deposition of wolframite and sulphides in quartz veins has beeninvestigated using representative W-polymetallic sulphide veins hosted by peraluminous granites in the centraldomain of the Spanish Central System. Ore-bearing quartz veins fall into two groups : W-veins (wolframite-bearingquartz veins with minor amounts of sulphides) and sulphide (S) dominated veins (wolframite free). The two veintypes (S and W) have similar orientation, silicate and sulphide mineralogy. A multidisciplinary approach based ona detailed fluid-inclusion analysis in relation with a paragenetic reconstruction of vein fillings suggests a similargenesis and fluid history, as follows :(i) an early fluid stage, lacking in S-veins, characterized by CO2-H20-NaCl rich vapours is at the origin of a strongK-mica alteration of the granite wall-rock, and of vein filling by milky quartz (QI) - phengite I - (wolframite), ataround 130 ± 20 MPa and 525 ± 25°C ;(ii) a second stage characterized by H2O-CO2-CH4-NaCl fluids with a low volatile-phase density, at the originof the deposition of : a) saccharoidal quartz (QII) (+ phengite II and minor amounts of scheelite in W-veins),and then, b) a chlorite-sulphide (pyrrhotite, sphalerite and galena) assemblage. A progressive decrease of the CO2content in fluids is recorded, CH4 being the major volatile species in the latest inclusions spatially associated withsulphides. Pressure is around 130 ± 30 MPa, and temperature decreases from 380° to 330°C throughout the courseof the fluid trapping.iii) later fluid inputs in the veins are shown by two types of secondary aqueous fluid inclusions in healed microfissures,which display moderate Th (160°-220°C) and salinities.The two main stages (wolframite, then sulphides) are characterized by a nearly isobaric cooling and dilutionof volatile rich fluids. The X-fO2 evolution indicates that fluid chemistry was probably controlled during the firststage by graphite-fluid equilibrium, implying a fluid source external to the granite (surrounding metamorphicseries). The sulphide stage, which is ubiquitous in most W deposits, appears clearly in this example as the lateststage of a primary hydrothermal cycle involving volatile bearing fluids, and is not disconnected from the W stages.
PB E. Schweizerbart'sche Verlagsbuchhandlung
SN 0935-1221
YR 1995
FD 1995
LK https://hdl.handle.net/20.500.14352/58321
UL https://hdl.handle.net/20.500.14352/58321
LA eng
DS Docta Complutense
RD 7 abr 2025