Crystallization conditions of dunites in the Konder platiniferous alkaline-ultramafic massif of the southeastern Aldan Shield |
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Authors: | V A Simonov V S Prikhod’ko S V Kovyazin A V Tarnavsky |
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Institution: | 1.Institute of Geology and Mineralogy, Siberian Branch,Russian Academy of Sciences,Novosibirsk,Russia;2.Institute of Tectonics and Geophysics, Far East Division,Russian Academy of Sciences,Khabarovsk,Russia |
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Abstract: | The investigation of melt inclusions in Cr spinels yielded direct information on the physicochemical parameters of the magmatic
processes responsible for the formation of the Konder platiniferous alkaline-ultrabasic massif (southeastern Aldan Shield).
The comparative analysis of the composition of the chromites containing the inclusions revealed that the Cr spinels from the
Konder dunites differ significantly from their counterparts in the ultrabasic complexes of ophiolites and the modern oceanic
crust. In terms of their composition and REE distribution, the clinopyroxene microcrystals from the Konder chromites are significantly
different from the pyroxenes in the basic-ultrabasic ophiolite complexes of associations and identical to the minerals from
the Kytlym platiniferous massif (the Urals). With respect to the distribution of the major components, the high-magnesian
inclusions are identical to alkaline biotite-pyroxene picrites, testifying to the active participation of ultrabasic (picritic)
alkaline magmatic systems in the formation of the dunites in the Konder Massif. The results of the ion probe investigation
of the inclusions indicate a high water content (up to 0.54 wt %) in the melts. The data on the distribution of the rare and
rare-earth elements in the inclusions suggest that the dunites of the Konder Massif crystallized with the involvement of water-saturated
magmas at minimal temperatures of about 1230°C. Such temperatures are consistent with the earlier estimates for the melt inclusions
in the olivine of the Konder Massif. |
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