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Experimental study of trace element release during ultrahigh-pressure serpentinite dehydration

Spandler, Carl; Hermann, Joerg; Pettke, Thomas

Description

Subduction of serpentinite is envisaged to play a key role in volatile and element recycling at convergent plate margins, but there is currently little known about the composition of the fluid phase(s) released by devolatilisation of deeply subducted serpentinite. We have performed a series of ultrahigh pressure experiments to examine the phase relations and fluid compositions produced by reaction of a natural serpentinite under sub-arc conditions. We employ a novel technique of forming...[Show more]

dc.contributor.authorSpandler, Carl
dc.contributor.authorHermann, Joerg
dc.contributor.authorPettke, Thomas
dc.date.accessioned2015-12-10T23:33:16Z
dc.identifier.issn0012-821X
dc.identifier.urihttp://hdl.handle.net/1885/69207
dc.description.abstractSubduction of serpentinite is envisaged to play a key role in volatile and element recycling at convergent plate margins, but there is currently little known about the composition of the fluid phase(s) released by devolatilisation of deeply subducted serpentinite. We have performed a series of ultrahigh pressure experiments to examine the phase relations and fluid compositions produced by reaction of a natural serpentinite under sub-arc conditions. We employ a novel technique of forming synthetic fluid inclusions in olivine at run conditions to preserve samples of experimental fluids for subsequent analysis. Our experiments confirm that the breakdown of antigorite and chlorite are the most important fluid-producing reactions from serpentinite at sub-arc depths. For our low CaO/Al2O3 peridotitic composition at 3.5 to 4.0 GPa we find that clinopyroxene reacts out below 750°C and chlorite breaks down progressively between 700 and 800°C to form garnet harzburgite.Raman analysis of synthetic fluid inclusions indicates that all experiments contained a single aqueous fluid phase, which - together with a lack of textural or mineralogical evidence for hydrous melting - indicates that the water-saturated solidus for our starting composition is above 900°C at 4.0 GPa. Element concentrations in the fluid for three experiments were determined in situ via laser ablation ICP-MS of individual fluid inclusions. In general, the fluids are enriched in trace elements compared to the bulk starting material, but particularly so for Li, B, LILE, LREE, and U. Chlorite dehydration fluids have high Li/B, LREE/HREE and Ce/Y due to retention of some B in olivine, and retention of Y and HREE in garnet. Our results indicate that fluids produced by serpentinite dehydration at sub-arc depths may carry some of the slab-derived trace elements required for arc magmatism, and may fractionate key trace element ratios in the dehydrated residues, which in turn may ultimately contribute to the geochemical heterogeneity of mantle-derived magmas.
dc.publisherElsevier
dc.sourceEarth and Planetary Science Letters
dc.titleExperimental study of trace element release during ultrahigh-pressure serpentinite dehydration
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume391
dc.date.issued2014
local.identifier.absfor040304 - Igneous and Metamorphic Petrology
local.identifier.ariespublicationU3488905xPUB1954
local.type.statusPublished Version
local.contributor.affiliationSpandler, Carl, James Cook University
local.contributor.affiliationHermann, Joerg, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationPettke, Thomas, University of Bern
local.description.embargo2037-12-31
local.bibliographicCitation.startpage296
local.bibliographicCitation.lastpage306
local.identifier.doi10.1016/j.epsl.2014.02.010
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2015-12-10T11:26:04Z
local.identifier.scopusID2-s2.0-84894302646
local.identifier.thomsonID000333998700033
CollectionsANU Research Publications

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