Stable isotope constraints on the origin and depth of penetration of hydrothermal fluids associated with Hercynian regional metamorphism and crustal anatexis in the Pyrenees

Saved in:
Authors:Wickham, Stephen M.; Taylor, H. P., Jr.
Author Affiliations:Primary:
Div. Geol. Planet. Sci., Calif. Inst. Technol., Pasadena, CA 91125, United States
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 95(3), p.255-268. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1987
Note:In English. 61 refs.; illus. incl. 49 anal., 1 table, charts, geol. sketch maps, sect.
Summary:Late Carboniferous (Hercynian) tectonism in this area generated steep thermal gradients at 8-14 km depth in the continental crust, producing andalusite- and sillimanite-grade metamorphism and partial melting of lower Palaeozoic metasediments under water-rich conditions. At the same time, amphibolite- and granulite-facies basal gneisses were equilibrated under drier conditions at 4-7 kbar (14-25 km depth), beneath these higher-level rocks. New oxygen isotopic analyses (95) of samples from the Agly, St. Barthelemy, Castillon and Trois Seigneurs massifs highlight contrasting 18O/16O systematics at different structural levels in the Hercynian crust. The inferred fluid circulation systems operating during Hercynian low-P regional metamorphism in the Pyrenees may operate in other regions of the Earth, if the thermal and lithological structure and tectonic setting are appropriate. In the Pyrenees, a good case can be made that these effects were produced within a rift-zone environment, which provided a focused thermal flux from the upper mantle. The large-scale anatexis of pelitic rocks towards the base of the H2O-rich Palaeozoic supracrustal pile contrasts with the smaller (or negligible) amounts of melting that occurred at the same time in the deeper and hotter environment occupied by the relatively dry basal gneisses. [P.Br.]
Subjects:Amphibolites; Anatexis; C-13/C-12; Calcite; Carbon; Carbonate rocks; Carbonates; Clastic rocks; Geochemistry; Gneisses; Hydrology; Infiltration; Interpretation; Isotopes; Metamorphic belts; Metamorphic rocks; Metamorphism; Minerals; O-18/O-16; Oxygen; Paleozoic; Petrology; Regional metamorphism; Schists; Sedimentary petrology; Sedimentary rocks; Shale; Silicates; Stable isotopes; Stratigraphy; Surface water; Agly Massif; Ariege France; Castillon Massif; Europe; France; French Pyrenees; Pyrenees; Pyrenees-Orientales France; Western Europe; Agly-Massiv, Castillon-Massiv, St-Barthelemy-Massiv; Isotope geochemistry; Ratios; Saint Barthelemy Massif
Abstract Numbers:87M/6337
Record ID:1988009292
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
Tags: Add Tag
No Tags, Be the first to tag this record!
Be the first to leave a comment!
You must be logged in first