High field strength element anomalies in arc lavas; source or process?

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Authors:Thirlwall, M. F.; Smith, T. E.; Graham, A. M.; Theodorou, N.; Hollings, P.; Davidson, J. P.; Arculus, R. J.
Author Affiliations:Primary:
University of London, Royal Holloway, Department of Geology, Egham, Surrey, United Kingdom
University of Windsor, Canada
BP Exploration Operation Company, United Kingdom
University of California at Los Angeles, United States
University of New England, Australia
Volume Title:Journal of Petrology
Source:Journal of Petrology, 35(3), p.819-838. Publisher: Clarendon Press, Oxford, United Kingdom. ISSN: 0022-3530
Publication Date:1994
Note:In English. 38 refs.; illus. incl. 1 table, sketch maps
Summary:The common presence of high-MgO lavas in the S Lesser Antilles, with their chemistry essentially unmodified since derivation from the mantle, provides an opportunity to test models for both magma genesis in arcs and for the relationship between arc magmatism and growth of the continental crust. Depletion (relative to REE) in the HFSE, Ti, Zr and Nb is shown to exist in the mantle wedge before melting, and is probably produced by an REE-rich slab flux. In contrast to many other arcs, there is evidence that the Lesser Antilles mantle source is more depleted in HFSE than the source of MORB. Relative to REE, Ti depletion in melts is enhanced during melting, requiring a Ti-rich phase in the residue at low melt fractions; Ti depletion is also enhanced during fractionation of magnetite and amphibole, whereas relative Zr depletion is reduced during fractionation. In most arc magmas (usually << 6% MgO), fractionation is probably a major control on the extent of Ti and Zr depletion. In the Lesser Antilles, the extent of Nb depletion relative to La is largely unaffected by melting or crystal fractionation process. [R.A.H.]
Subjects:Basalts; Continental crust; Crust; Crystal fractionation; Depletion; Geochemical anomalies; Geochemistry; Igneous rocks; Island arcs; Lava; Magmas; Melts; Metals; Mid-ocean ridge basalts; Niobium; Rare earths; Subduction zones; Titanium; Trace elements; Volcanic rocks; Zirconium; Antilles; Caribbean region; Lesser Antilles; West Indies
Abstract Numbers:95M/618
Record ID:1994056087
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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