In situ Re-Os analysis of sulfide inclusions in kimberlitic olivine: New constraints on depletion events in the Siberian lithospheric mantle

摘要: [1] Os and other highly siderophile elements in mantle-derived peridotites are strongly concentrated into trace amounts of sulfide minerals. We have used a laser-ablation microprobe coupled to multicollector ICPMS (LAM-MC-ICPMS) determine the Os isotope composition, Re/Os Pt/Os 92 inclusions olivine macrocrysts, derived from mantle peridotites, Udachnaya kimberlite Siberian craton. 26 these also been analyzed for Platinum Group Elements by LAM-ICPMS. The sulfides mixtures Ni-rich Fe-rich monosulfide solid solutions (MSS), pentlandite chalcopyrite, exsolved MSS bulk compositions. They can be divided five populations (1, 2, 3A–3C) on basis content, Os/Pt Re/Os. genetic relationships groups constrained comparison with published experimental data element partitioning between melts. 1 modeled as residual after low degrees melting primitive source, under sulfur-saturated conditions. 2 best alloy phases, formed at sulfur-undersaturated conditions; many contain Pt-rich micronuggets. 3C liquids, or crystallized very evolved liquids. Sulfides Groups 3A 3B interpreted products reaction liquids 3C. Inclusions different may occur within single grains, suggesting repeated introduction melts, followed annealing grain growth. some sulfides, give model ages (TMA) that geologically reasonable (0–4 Ga). Most 3 unsupported 187Os, implying two-stage history. A negative correlation TMA is consistent mixing (3C) source high Re/Os, such ca 3.0 Ga eclogites described Udachnnaya [Pearson et al., 1995c]. Our modeling suggests 187Re/188Os 2.8 Ga. suggest most lithospheric beneath Daldyn field during period 3–3.5 Ga, lithosphere formation culminated major event 2.9 which involved remelting older eclogites. There little evidence Re-Os significant additions this time. In situ analysis removes ambiguity whole rock peridotite samples (or even separated grains), where several generations present. analysis, combined careful petrographic chemical study populations, thus provide more precise temporal constraints evolution mantle.