Magma underplating of continental crust

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doi: 10.1016/0377-0273(92)90035-C
Authors:Fyfe, W. S.
Author Affiliations:Primary:
University of Western Ontario, Faculty of Science, London, ON, Canada
University of Leeds, United Kingdom
Volume Title:Essays on magmas and other earth fluids; a volume in appreciation of Prof. Peter G. Harris
Volume Authors:Cox, K. G., editor; Baker, P. E.
Source:Essays on magmas and other earth fluids; a volume in appreciation of Prof. Peter G. Harris, edited by K. G. Cox and P. E. Baker. Journal of Volcanology and Geothermal Research, 50(1-2), p.33-40. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-0273
Publication Date:1992
Note:In English. 53 refs.; illus.
Summary:Experiments have shown that common mantle melting products have densities at Moho P that exceed the density of average continental crust; in perfect gravitational equilibrium they would not rise to or near the surface. Their behaviour reflects the coupling of crust to the mantle: strong early in the magmatic cycle, but weak when crustal melting and degassing starts. Spreading of underplate magmas in rift zones, above subduction zones or even hot spots, may perturb the state of the crust over very large areas. Where dense magmas occur beneath normal 30-km continental crust they may crystallize to form gabbro-peridotite-anorthosite complexes. Dense crustal components may founder with melting, assimilation and degassing producing very high-T fluids rich in H2-CO2- CO and S-halogen species, depending on compositions. The process, which acts as a density filter cleaning the crust and lowering its mean density, must have been particularly efficient during the Archaean when komatiite magmas were common. Opportunities for magma contamination and mixing processes must abound in situations of large-scale underplating. When crust is overthickened underplate magmas may crystallize to products with eclogitic affinity with the possibility of their foundering in normal mantle. [R.E.S.]
Subjects:Anorthosite; Continental crust; Crust; Density; Geochemistry; Igneous rocks; Intrusions; Magmas; Melting; Peridotites; Plate tectonics; Plutonic rocks; Pressure; Subduction; Ultramafics; Underplating
Abstract Numbers:93M/1016
Record ID:1996025111
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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