Carbonate alteration associated with talc-chlorite mineralization in the eastern Pyrenees, with emphasis on the St. Barthelemy Massif

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doi: 10.1007/s00710-006-0124-x
Authors:Boulvais, P.; de Parseval, P.; D'Hulst, A.; Paris, P.
Author Affiliations:Primary:
Université de Rennes I, Geosciences Rennes, Rennes, France
Other:
Observatoire Midi Pyrenees, France
Talc de Luzenac France, France
Volume Title:Mineralogy and Petrology
Source:Mineralogy and Petrology, 88(3-4), p.499-526. Publisher: Springer-Verlag, Vienna, Austria. ISSN: 0930-0708
Publication Date:2006
Note:In English. 65 refs.
Summary:The eastern Pyrenees host a large number of talc-chlorite mineralizations of Albian age (112-97 Ma), the largest of which occur in the St. Barthelemy massif. There talc develops by hydrothermal replacement of dolostones, which were formed by alteration of calcite marbles. This alteration is progressive. Unaltered calcite marbles have oxygen isotope composition of about 250/00 (V-SMOW). δ18O The values decrease down to values of 120/00 towards the contact with dolostones. This 18O depletion is accompanied by Mg enrichment, LREE fractionation and systematic shifts in the Sr isotope compositions, which vary from 87Sr/86Sr = 0.7087-0.7092 in unaltered calcite marbles to slightly more radiogenic compositions with 87Sr/86Sr = 0.7094 near dolomitization fronts. Dolostones have δ18O values (about 90/00) lower than calcitic marbles, higher REE content and more radiogenic Sr isotope composition (87Sr/86Sr = 0.7109 to 0.7130). Hydrothermal calcites have δ18O values close to dolostones but substantially lower δ13C values, down to -6.50/00, which is indicative of the contribution of organic matter. The REE content of hydrothermal calcite is one order of magnitude higher than that of calcitic marbles. Its highly radiogenic Sr composition with 87Sr/86Sr = 0.7091 to 0.7132 suggests that these elements were derived from silicate rocks, which experienced intense chlorite alteration during mineralization. The chemical and isotopic compositions of the calcite marbles, the dolostones and the hydrothermal calcites are interpreted as products of successive stages of fluid-rock interaction with increasing fluid-rock ratios. The hydrothermal quartz, calcite, talc and chlorite are in global mutual isotopic equilibrium. This allows the calculation of the O isotope composition of the infiltrating water at 300°C, which is in the δ18OH2O = 2-4.50/00 range. Hydrogen isotope compositions of talc and chlorite indicate a δDH2O= 0 to -200/00. This water probably derived from seawater, with minor contribution of evolved continental water. [H.P.B.]
Sections:Economic minerals and ore deposits
Subsections:Non-metallic deposits
Subjects:Albian; Alkaline earth metals; C-13/C-12; Calcite; Carbon; Carbonates; Chlorite; Chlorite group; Cretaceous; D/H; Deuterium; Dolomite; Hydrogen; Hydrothermal conditions; Isotope ratios; Isotopes; Lower Cretaceous; Marbles; Mesozoic; Metals; Metamorphic rocks; O-18/O-16; Oxygen; Sheet silicates; Silicates; Sr-87/Sr-86; Stable isotopes; Strontium; Talc; Water-rock interaction; Ariege France; Europe; France; French Pyrenees; Pyrenees; Western Europe; Saint Barthelemy Massif
Abstract Numbers:07M/624
Record ID:2011000147
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe
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