Trace element distribution among rock-forming minerals from metamorphosed to partially molten basic igneous rocks in a contact aureole (Fuerteventura, Canaries)

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Version: Final published version
Serval ID
serval:BIB_E88750E28174
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Trace element distribution among rock-forming minerals from metamorphosed to partially molten basic igneous rocks in a contact aureole (Fuerteventura, Canaries)
Journal
Lithos
Author(s)
Holloway M.I., Bussy F.
ISSN-L
0024-4937
Publication state
Published
Issued date
2008
Peer-reviewed
Oui
Volume
102
Pages
616-639
Language
english
Abstract
Low pressure partial melting of basanitic and ankaramitic dykes gave
rise to unusual, zebra-like migmatites, in the contact aureole of a
layered pyroxenite-gabbro intrusion, in the root zone of an ocean island
(Basal Complex, Fuerteventura, Canary Islands). These migmatites are
characterised by a dense network of closely spaced, millimetre-wide
leucocratic segregations. Their mineralogy consists of plagioclase
(An(32-36)), diopside, biotite, oxides (magnetite, ilmenite),
+/-amphibole, dominated by plagioclase in the leucosome and diopside in
the melanosome. The melanosome is almost completely recrystallised, with
the preservation of large, relict igneous diopside phenocrysts in dyke
centres. Comparison of whole-rock and mineral major- and trace-element
data allowed us to assess the redistribution of elements between
different mineral phases and generations during contact metamorphism and
partial melting.
Dykes within and outside the thermal aureole behaved like closed
chemical systems. Nevertheless, Zr, Hf, Y and REEs were internally
redistributed, as deduced by comparing the trace element contents of the
various diopside generations. Neocrystallised diopside - in the
melanosome, leucosome and as epitaxial phenocryst rims - from the
migmatite zone, are all enriched in Zr, Hf, Y and REEs compared to
relict phenocrysts. This has been assigned to the liberation of trace
elements on the breakdown of enriched primary minerals, kaersutite and
sphene, on entering the thermal aureole. Major and trace element
compositions of minerals in migmatite melanosomes and leucosomes are
almost identical, pointing to a syn- or post-solidus reequilibration on
the cooling of the migmatite terrain i.e. mineral-melt equilibria were
reset to mineral-mineral equilibria. (C) 2007 Elsevier B.V. All rights
reserved.
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01/10/2012 20:07
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20/08/2019 17:11
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