Investor Presentaiton

CONCLUSION 1. The geochemical features of the volcanic and ultramafic rocks are consistent with Supra-Subduction Zone 2. Chr-spinels rarely alteratied and can be used a reliable petrogenetic indicator. The primary chemistry of chr-spinels provides important information about the composition of the parental melt, magmatic processes (partial melting). Chr-spinels formed by participation of magmas of different composition and then changed in suprusubduction setting. Chr-spinels are localized into three fields: MORB, High-Al chromites from MORB-like tholeiitic magmas (in a back-arc setting), during melt/mantle interaction with a subsequent change to a subduction setting. High-Cr spineles are thought to form from boninitic magmas in an island arc environment (subduction setting) 3. Chr-spinels are localized in the fields MORB-type (the first group), Supra-subduction zone (Boninites) peridotites (the second and part of the first group), Alaskan type (the third group). The chromites falling into the field of the Uralo-Alaskan type could be formed during the partial melting of the fluid metasomatized mantle, with the interaction of andesitoid melts with the rocks of the overlying mantle wedge. 4. Chondrite-normalised PGE patterns of Ulan-Sar'dag chromitites display average (Os+Ir+Ru)/(Rh+Pt+Pd) ratios typical of Cr-rich chromitites formed in the mantle section of supra subduction zone ophiolites. The processes leading to extreme fractionation of PGE can be connected fluid-saturated supra-subduction. It is known that (Os-Ir) and solid solutions of laurite-erlichmanite are forming before or nearly simultaneously with the segregation of chrome - spinel in the upper mantle at T=1200°C and P= 5-10 kbar. We suppose there are two generation of sulphides in chromitites from Ulan-Sar'dag massive 1- PGM generation – magmatic solid solutions of laurite-erlichmanite. - 2 generation the newly formed laurite, with primary laurite-erlichmanite or intergrowths with chalcosine, and millerite is found in zones of chloritization. It has assotiation with serpentine, chlorite, irarsite, and BSE sulfides (Ni). The predominance of Os, Ru sulphides over the solid solutions of Os-Ir-Ru indicates a higher sulfur fugacity in the mantle source of Ulan-Sar'dag massive, than other ultrabasic massive of Dunzhugur ophiolites. Sulfo-arsenides and arsenides of Ru, Ir, Rh, Ni are formed from the residual fluid phase at post-magmatic Gargan microcontinent subduction subduction sediment oceanic crust subduction island arc Siberian continent eclogites and blue schists island arc accretion prism a Siberian continent: sedimentary cover (a), foundation (b) Microcontinents slab window Oceanic crust of the Paleo-Asiatic a lb ocean (a), its overlapping sediments (b) Ophiolites of back-arc spreading Siberian continent island arc back-arc basin HFSE+LILE+LREE spreading Pplum Island-arc formations of primitive island arcs Island-arc formations of mature island arcs Intrusive formations of mature island arcs Terrigenous-tufogenic rocks The paleoreconstruction of the formation of the Sayano-Baikal-Muya accretionary-collisional belt Olistostromes turbidites Amphibolites, Eclogites Alkaline volcanics Faults

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