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GEOREF RECORD

P-V-T-X -fO (sub 2) evolution from wolframite to sulphide depositional stages in intragranitic W-veins; an example from the Spanish Central System

Elena Vindel, Jose Angel Lopez, Marie-Christine Boiron, Michel Cathelineau and Angel Carmelo Prieto
P-V-T-X -fO (sub 2) evolution from wolframite to sulphide depositional stages in intragranitic W-veins; an example from the Spanish Central System
European Journal of Mineralogy (June 1995) 7 (3): 675-688

Abstract

A detailed study of fluid inclusions in relation to the sequence of mineral deposition in this area has yielded significant constraints on the P-T-X conditions of ore deposition. The P-T path is characterized by a virtually isobaric evolution during the early stages dominated by the volatile-rich inclusions. The X-fO (sub 2) evolution indicates that fluid chemistry was controlled by graphite-fluid equilibrium, implying a source for fluids external to the granite and possibly also for W. The T changes and the dilution of the volatile-bearing fluids by cooler aqueous fluids is responsible for fluid disequilibrium with graphite and the subsequent CH (sub 4) -dominated low-density volatile component in the fluids. The sulphide stage is exemplified by W/S veins; it appears during the latest stage of hydrothermal circulation involving volatile-bearing fluids, and is related to the W mineralization. Dilution and cooling characterize the whole evolution of the volatile-rich fluid stages (main depositional stage). However, evidence for later fluid input is given by aqueous fluids trapped in healed cracks which are not related to the main depositional stage. - R.A.H.AG 95M/4370= volution of ore-forming fluids associated with late Hercynian antimony deposits in central/western Spain: case study of Mari Rosa and El Juncalon.These vein-type Sb deposits are hosted by late Precambrian metasedimentary rocks and are spatially related to late Carboniferous/early Permian granitic rocks. At Mari Rosa, the hydrothermal stages recognized are: 1) arsenopyrite-(pyrite), 2) stibnite-gold, 3) pyrite-(pyrrhotite-galena-sphalerite-chalcopyrite-tetrahedrite-boulangerite-berthierite-stibnite-ullmannite-cobaltite). Only the second stage is of economic importance, containing massive stibnite. El Juncalon has a simple paragenesis consisting of stibnite with very minor pyrite. Gold is associated with stibnite, which contains up to 30 ppm Au at Mari Rosa and up to 0.4 ppm at El Juncalon. Fluids associated with ore deposition lie in the H (sub 2) O-NaCl-CO (sub 2) -CH (sub 4) -N (sub 2) system, but CO (sub 2) is absent in the El Juncalon mineralized rocks. The fluids cooled progressively, from initial circulation T near 400 degrees C in the early stages to T approximately 150 degrees C in the late episodes. The evolution of the fluid composition is characterized by a progressive increase in the overall water content of the fluids and by an increase in the relative proportions of N (sub 2) with respect to CH (sub 4) and CO (sub 2) in the volatile fraction. At Mari Rosa, massive stibnite deposition resulted from boiling at 300 degrees C and 0.9-1 kbar ; unmixing of the fluid was induced by sudden drops in P associated with dilational jogs during low-angle fault movements. Cooling of the fluid is recognized as the driving mechanism for stibnite deposition at 250-270 degrees C and 50-300 bar at El Juncalon.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 7
Serial Issue: 3
Title: P-V-T-X -fO (sub 2) evolution from wolframite to sulphide depositional stages in intragranitic W-veins; an example from the Spanish Central System
Affiliation: Universidad Complutense, Departamento de Cristalografia y Mineralogia, Madrid, Spain
Pages: 675-688
Published: 199506
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 45
Accession Number: 1995-041708
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N36°00'00" - N43°45'00", W09°30'00" - E04°30'00"
Secondary Affiliation: CREGU CNRS, FRA, FranceUniversidad de Valladolid, ESP, Spain
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199515
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