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PRODID:-//Columba Systems Ltd//NONSGML CPNG/SpringViewer/ICal Output/3.3-
 M3//EN
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20180928T143507Z
DTSTART:20181107T130000Z
DTEND:20181107T140000Z
SUMMARY:Tracing fluid transfer across subduction zones using iron and zin
 c stable isotopes 
UID:{http://www.columbasystems.com/customers/uom/gpp/eventid/}p18z-jmm1xq
 y3-wew5va
DESCRIPTION:Our speaker is Dr Helen Williams from the Department of Earth
  Sciences at the University of Cambridge. \n\nSubduction zones are the m
 ain site of volatile element transfer between the downgoing plate\, the 
 overriding mantle \nwedge and the Earth’s deep interior. The breakdown o
 f serpentine minerals within the downgoing slab and the fluids \nrelease
 d play a fundamental role in volatile cycling as well as the redox evolu
 tion of the sub-arc mantle. Constraining \nsubduction-related serpentini
 te devolatilisation is essential in order to better understand of the na
 ture and composition\nof slab-derived fluids and fluid/rock interactions
 .  Iron and Zn stable isotopes are recently-established geochemical trac
 ers \ncan trace fluid composition and speciation as isotope partitioning
  is driven by changes in oxidation state\, coordination\, and \nbonding 
 environment. In the case of serpentinite devolatilisation\, Fe isotope f
 ractionation should reflect changes in Fe \nredox state and the formatio
 n of chloride and sulfide complexes\; Zn isotope fractionation should be
  sensitive to complexation \nwith carbonate\, sulfide and sulfate anions
 . This study involved targeting samples from Western Alps ophiolite comp
 lexes\, \ninterpreted as remnants of serpentinized oceanic lithosphere m
 etamorphosed and devolatilized during subduction. A striking \nnegative 
 correlation is present between bulk serpentinite Fe isotope composition 
 and proportion of ferric iron\, with the \nhighest grade samples display
 ing the heaviest Fe isotope compositions and proportion of oxidised iron
 . The same samples \nalso display a corresponding variation in Zn isotop
 es\, with the highest grade samples displaying isotopically light compos
 itions. \nThe negative correlation between Fe and Zn isotopes and decrea
 se in ferric iron content can explained by serpentinite sulphide \nbreak
 down and the release of fluids enriched in isotopically light Fe and hea
 vy Zn sulphate complexes. The migration of these \nhighly oxidizing sulf
 ate-bearing fluids from the slab to the slab-mantle interface or mantle 
 wedge has important implications \nfor the redox evolution of the sub-ar
 c mantle and the transport of metals from the subducting slab.\n\n\nCoff
 ee and tea will be available after the seminar in the first floor foyer 
 of the Williamson Building.\n\n \n
STATUS:TENTATIVE
TRANSP:TRANSPARENT
CLASS:PUBLIC
LOCATION:G.03\, Williamson Building\, Manchester
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