Unravelling the effects of melt depletion and secondary infiltration on mantle re-os isotopes beneath the french massif central

(2010). Unravelling the effects of melt depletion and secondary infiltration on mantle re-os isotopes beneath the french Massif Central. Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online's data policy on reuse of materials please consult the policies page. Unravelling the effects of melt depletion and secondary infiltration on mantle re-os isotopes beneath the french massif central the effects of melt depletion and secondary infiltration on mantle re-os isotopes beneath the french massif central, This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ABSTRACT 26 27 Spinel lherzolite xenoliths from Mont Briançon, French Massif Central, retain 28 evidence for multiple episodes of melt depletion and melt / fluid infiltration 29 (metasomatism). Evidence for primary melt depletion is still preserved in the co-30 variation of bulk-rock major elements (MgO 38.7–46.1 weight %; CaO 0.9–3.6 31 weight %), and many samples yield unradiogenic bulk-rock Os isotope ratios 32 (187 Os/ 188 Os = 0.11541-0.12626). However, many individual xenoliths contain 33 interstitial glasses and melt inclusions that are not in equilibrium with the major 34 primary minerals. Incompatible trace element mass balance calculations demonstrate 35 that metasomatic components comprise a significant proportion of the bulk-rock 36 budget for these elements in some rocks, ranging to as much as 25% of Nd and 40% 37 of Sr Critically, for Re-Os geochronology, melt / fluid infiltration is accompanied by 38 the mobilisation of sulfide. Consequently, bulk-rock isotope measurements, whether 39 using lithophile (e.g. Rb-Sr, Sm-Nd) or siderophile (Re-Os) based isotope systems, 40 may only yield a perturbed and / or homogenised average of these multiple events. 41 Osmium mass balance calculations demonstrate that bulk-rock Os in peridotite 42 is dominated by contributions from 2 populations of sulfide grain: (i) interstitial, 43 metasomatic sulfide with low [Os] and radiogenic 187 Os/ 188 Os, and (ii) primary 44 sulfides with high [Os] and unradiogenic 187 Os/ 188 Os, which have been preserved …