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The variable role of slab-derived fluids in the generation of a suite of primitive calc-alkaline lavas from the southernmost Cascades, California

Lars E. Borg, Michael A. Clynne and Thomas D. Bullen
The variable role of slab-derived fluids in the generation of a suite of primitive calc-alkaline lavas from the southernmost Cascades, California (in Nature and origin of primitive magmas at subduction zones, G. T. Nixon (editor), A. D. Johnston (editor) and R. F. Martin (editor))
The Canadian Mineralogist (April 1997) 35, Part 2: 425-452

Abstract

The geochemical signatures found in primitive lavas erupted from small centres across the southernmost Cascade arc are considered to be produced by the varied contribution of slab-derived fluids to the mantle wedge, and not by differentiation processes. All these lavas have a prominent sediment-contributed signature, which does not correlate with the modern subduction signature, and is interpreted to reflect enrichment of the mantle wedge in an older subduction regime. The addition of fluid to the mantle wedge beneath the forearc stabilizes amphibole, produces enrichment in unradiogenic Sr and Pb, and depletions in Ta and Nb. Higher concentrations of Sr and Pb in the fluid allow it to control the Sr and Pb isotopic signatures of magmas derived from the fluid-rich sources. The lavas with a limited fluid-contributed geochemical signature are derived from peridotites that are compositionally similar to an OIB-source, whereas lavas with a more prominent fluid-contributed geochemical signature are derived from peridotites more similar to a MORB-source.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 35, Part 2
Title: The variable role of slab-derived fluids in the generation of a suite of primitive calc-alkaline lavas from the southernmost Cascades, California
Title: Nature and origin of primitive magmas at subduction zones
Author(s): Borg, Lars E.Clynne, Michael A.Bullen, Thomas D.
Author(s): Nixon, G. T.editor
Author(s): Johnston, A. D.editor
Author(s): Martin, R. F.editor
Affiliation: University of Texas at Austin, Department of Geological Sciences, Austin, TX, United States
Affiliation: British Columbia Geological Survey, Victoria, BC, Canada
Pages: 425-452
Published: 199704
Text Language: English
Summary Language: French
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
Meeting name: Joint annual meeting of the Geological Association of Canada and the Mineralogical Association of Canada
Meeting location: Victoria, BC, CAN, Canada
Meeting date: 199505May 1995
References: 109
Accession Number: 1999-052477
Categories: Igneous and metamorphic petrologySolid-earth geophysics
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables, sketch map
N40°00'00" - N41°00'00", W122°00'00" - W120°00'00"
Secondary Affiliation: University of Oregon, USA, United StatesU. S. Geological Survey, USA, United States
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199918
Program Name: USGSOPNon-USGS publications with USGS authors
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