Investor Presentaiton
PGE mineralization are represented by Os-Ir-(Ru) solid solutions, native Os, Ru, laurite-erlichmanite (Ru,Os)S2, laurite (RuS2), irarsite
(IrAsS), zakarinit (RhNiAs).
Diagram of composition Os-Ir-Ru alloys
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Sulfides of PGE are the predominant phases in the chromitites of the Ulan-Sar'dag ophiolite. They occur as
idiomorphic inclusions in chrom-spineles. Solid solutions of Os-Ir-(Ru) were found as idiomorphic inclusions in
spinel, and in xenomorphic grains in intergrowths with laurite. Solid-solution laurite-erlichmanite and Os-Ir
correspond to early high-temperature magmatic stage.
The phases (Os, Ir, Ru) of varying composition are common as numerous micro- and nano-size inclusions in
laurite-erlichmanite. Native Os (Os> 80 wt.%) and Ru (Ru=93 wt.%) occur in polyphase aggregates, together
with chalcocite, laurite, laurite-erlichmanite, heazlewoodite, zakarinite, Os-Ir-Ru solid solutions.
Laurite and laurite-erlichmanite RuS2-(Ru,Os)S2 are represented most widely. There are two groups: 1) laurite-
erlichmanite (Ru,Os)S2; 2) laurite RuS2 - phase of variable composition (Ru,Os)S2 occurring in multi-
component aggregates of heterogeneous composition and containing a large number of rounded and rectangular
micro-inclusions of native Os, (Os-Ir), and Ru. Laurite has homogeneous microstructure and composition
consistent with the stoichiometric composition. It forms individual grains in chlorite and serpentine. It is known
that (Os-Ir) and solid solutions of laurit-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.
Sulfo-arsenides and arsenides of Ru, Ir, Rh, Ni are formed from the residual fluid phase at post-magmatic stage,
together with heazlewoodite. It is possible that in chromitites from Ulan-Sar'dag ophiolite there are two
generations of sulphides:
The first generation - magmatic solid solutions of laurite-erlichmanite.
The second stage- the newly formed laurite, with primary laurite-erlichmanite or intergrowths with chalcosine,
and millerite confined to zones of chloritization.
Os
Ru
individual grains
inclusion in RuS2
*
inclusion in Crsp
A poliphase agregates
Diagram of composition PGE sulfides
(Ru+Rh)S,
■individual grains
▲ poliphase agregates
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 ophiolite
OSS
LAURITE
ERLICHMANITE
Ir
(Ir+Pt+Pd)S₂View entire presentation