Petrogeochemical Features of PGE-Bearing Metapicrites from Kulibinsky Potential Ore Territory (East Sayan)
The objects of the study are mafic-ultramafic complexes of Kulibinsk potential ore unit, including intrusive bodies of kingashsk complex and metavolcanic rocks of kuliginskaya and kuzinskaya series; studied objects are located at the north-west edge of Kansk greenstone belt in East Sayan. The relevance of the study is due to the appearance of new data on geological formations of the Kansk Greenstone Belt, which are the object of extensive discussions. Studied Kulibinst potential ore unit (POT) is a north-west part of Kansk greenstone belt. Its territory is composed of rocks from volcanic-sedimentary complexes, which are composed of orthoamfibolites, orthogneisses, and different metasedimentary rocks with mineral associations of epidote-amphybolic and amphybolic facies of metamorphism. Metavolcanic strata intruded with mafic-ultramafic bodies of magmatic kingash and restitic idarsk complexes. Based on the results of the study, it was established that prospects of the territory associated with low-sulfidic type of PGE (platinum-group elements) mineralization, which founded in mafic-ultramafic bodies of kingashsk dunite-verlite-picritic magmatic complex. The nature of the geochemical zonality and the position of platinum-mineralization are typical for known magmatic platinum-metal deposits in stratified mafic-ultramafic complexes, which were formed during the differentiation of the initial high-magnesian picritic melt in repeatedly occurring intermediate magmatic chambers. In the productive part of the ore-bearing bodies of metapicrites, the magnesia concentration is gradually growing down the section, which is reflected in the change of the mineral composition. At the top of the bodies, these rocks are close in chemical and mineral composition to picritic basalts, and in the bottom – to hi-Mg olivine picrites. The rocks of Kulibinsk POT are characterized by an increase of Pd concentrations with a decrease of MgO and an increase in the TiO2 content in rocks, but within the PGE-bearing picritic strata, an inverse regularity is observed: downward along the section MgO grows together with an increase in the concentrations of palladium. A direct correlation between the Cu and Pd concentrations is typical for all rocks, correlation between the Ni and Pd contents is not so clear and is noted only in the late differentiates. The criteria for the separation of productive horizons is the predominance of copper sulphides in the sulfide phase of the bottom parts from the picritic strata. Numerous dykes of plagiogranites, penetrating the productive strata of the Kulibinsky distribution substation, have a significant effect on the redistribution of Pd. In the exocontact parts of such dikes, there is an increase in the concentration of PGE. In some cases, metasomatites are formed on contacts with plagiogranites, containing ore sulphide-oxide mineralization up to 50 %. By the set of signs, PGE-metal deposits of Portimo complex (Finland) proposed as the object-analogue.
Babintsev Nikita Anatolyevich, Senior Geologist, Laboratory of Geochemical Methods, Krasnoyarsk Research Institute of Geology and Mineral Resourses, 55, Mir av., Krasnoyarsk, 660049, Russian Federation, Postgraduate, Departament of Petrography, National Research Tomsk State University, 36, Lenin av., Tomsk, 634050, Russian Federation, e-mail: firstname.lastname@example.org, tel.: (3822)52-94-45
Chernyshov Aleksey Ivanovich, Doctor of Sciences (Geology and Mineralogy), Professor, Head Petrography Departament, National Research Tomsk State University, 36, Lenin av., Tomsk, 634050, Russian Federation, e-mail: email@example.com, tel.: (3822)52-94-45
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