Résumé
The S-isotopic composition of the Earth's mantle (delta 34S=0+ or -2ppm) has been found to be chondritic [1,2]. Such composition satisfies the paradigm that chemical composition of the whole Earth should be "chondritic" and provide support to the late veneer hypothesis which is otherwise supported by a broadly chondritic abundances of the highly siderophile (HSE: Os, Ir, Ru, Rh, Pt, Pd, Au, Re) and chalcogenides elements (S, Se, Te) and 187Os/188Os. However in details, mantle data show large variability (-7< or = delta 34S <10ppm) and a strong dichotomy between in one hand peridotite xenolith showing mostly delta 34S>0 [4] and on the other hand sulfide from orogenic massifs showing delta 34S<0ppm [2]. These differences could be related to: (i) sampling processes (magmatic vs. tectonic); (ii) sulfide weathering; (iii) the strong contrast between sulfide mineralogy (mss vs. pn); (iv) mantle heterogeneities; or (v) analytical techniques. Coupling EMP, SIMS, LA-ICPMS and LA-MC-ICPMS, major elements, delta 34S, siderophile and chalcophile trace elements, and Os isotopes have been obtained in-situ on 200 sulfide grains from > or =30 mantle samples. Almost all sulfides from xenoliths or orogenic massifs have delta 34S<0 (-7< or = delta 34S < or = 0.5ppm). These results do not support a contrasted composition between massif and xenoliths, but still indicate a significant level of heterogeneity within the SCLM. Preliminary results unfold broad correlations between delta 34S and HSE and/or chalcogenides abundances and fractionations and/or 187Os/188Os. Thus, as for Os isotopes and HSE abundances [4,5], delta 34S is fractionated during mantle processes. These results are in agreement with recent data obatined on lavas [6,7] and sugget alltogether that S isotopic composition of the modern earh mantle is not chondritic.