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The nature and geological history of the deep crust under the Eifel, Germany
Author(s) -
Stosch H.G.,
Schmucker A.,
Reys Ch.
Publication year - 1992
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1992.tb00450.x
Subject(s) - geology , geochemistry , granulite , mafic , metamorphism , metamorphic facies , igneous rock , crust , orogeny , anatexis , petrology , partial melting , magma , facies , geomorphology , volcano , structural basin
The crust ≈ 10–20 km under the Eifel is composed of amphibolite‐facies metasediments and meta‐igneous rocks of tonalitic to granodioritic composition; mafic granulites occupy the base of the crust down to a Moho depth between about 29 and 34 km. The meta‐granodiorites and meta‐tonalites have I‐type chemical characteristics and appear to have formed approximately 400 Myr ago by partial melting of a lower crustal source. Amphibolite‐facies metamorphism probably followed within the same orogeny. During the Quaternary, many amphibolite‐facies rocks were subjected to contact heating in crustal magma chambers and/or during transport to the earth's surface. Contact heating is also recorded in radiogenic isotope compositions of minerals from one xenolith. A genetic link between meta‐igneous amphibolites and the deeper crustal mafic granulites can neither be proven nor discounted by the isotope data. If there is a genetic relationship, it requires fractionation of a mafic magma in the lower crust and assimilation of metasediments and separation of a highly evolved melt.