Geodynamic significance of the Raspas Metamorphic Complex (SW Ecuador): geochemical and isotopic constraints
| Autor: | Delphine Bosch, Jean-Louis Malfere, Henriette Lapierre, Etienne Jaillard, Piercarlo Gabriele |
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| Rok vydání: | 2002 |
| Předmět: |
biology
Metamorphic rock Continental crust Geochemistry Oceanic plateau ROCHE METAMORPHIQUE biology.organism_classification OPHIOLITE ELEMENT EN TRACE Geophysics SUBDUCTION GEOCHIMIE Ultramafic rock GEODYNAMIQUE ANALYSE ISOTOPIQUE METAMORPHISME ROCHE BASIQUE ACCRETION Mafic Eclogite ROCHE ULTRABASIQUE Metamorphic facies Geology Lile Earth-Surface Processes |
| Zdroj: | Tectonophysics. 345:83-102 |
| ISSN: | 0040-1951 |
| DOI: | 10.1016/s0040-1951(01)00207-4 |
| Popis: | The Raspas Metamorphic Complex of southwestern Ecuador is regarded as the southernmost remnant of oceanic and continental terranes accreted in the latest Jurassic–Early Cretaceous. It consists of variably metamorphosed rock types. (1) Mafic and ultramafic rocks metamorphosed under high-pressure (HP) conditions (eclogite facies) show oceanic plateau affinities with flat REE chondrite-normalized patterns, eNd150 Ma ranging from +4.6 to 9.8 and initial Pb isotopic ratios intermediate between MORB and OIB. (2) Sedimentary rocks metamorphosed under eclogitic conditions exhibit LREE enriched patterns, strong negative Eu anomalies, Rb, Nb, U, Th, Pb enrichments, low eNd150 Ma values (from � 6.4 to � 9.5), and high initial 87 Sr/ 86 Sr and 206,207,208 Pb/ 204 Pb isotopic ratios suggesting they were originally sediments derived from the erosion of an old continental crust. (3) Epidote-bearing amphibolites show N-MORB affinities with LREE depleted patterns, LILE, Zr, Hf and Th depletion, high eNd150 Ma (>+10) and low initial Pb isotopic ratios. The present-day well defined internal structure of the Raspas Metamorphic Complex seems to be inconsistent with the formerly proposed |
| Databáze: | OpenAIRE |
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