Co-Pd-Ag AND Th-REE MINERALIZATION OF HOST ROCKS FROM THE EXOCONTACT ZONE OF TASHLY-TAU MASSIF, KHUDOLAZ COMPLEX (SOUTH URALS): ORE SOURCES AND FLUID INCLUSIONS DATA

• Published in: Izvestiâ Tomskogo politehničeskogo universiteta. Inžiniring georesursov Vol. 331; no. 8; pp. 77 - 91
• Main Authors: Ildar R. Rakhimov, Natalia N. Ankusheva, Vladimir V. Kholodnov
• Format: Journal Article
• Language: Russian
• Published: Tomsk Polytechnic University 01.08.2020
• Subjects: calcite; cobaltite-gersdorffite solid solution; exocontact zone; fluid inclusions; lithochemistry; lithology; mineralogy; monazite; quartz
• ISSN: 2500-1019; 2413-1830
• DOI: 10.18799/24131830/2020/7/2770

The relevance of the research is caused by the absence of research of geochemical peculiarities and ore mineralization of exocontact rocks of ore-bearing massifs belonging to Khudolaz layered complex. The aim of the research is mineralogical and geochemical characteristics of exocontact zone of Tashly-Tau massif and salt composition and PT-parameters of ore-forming fluid. Analytical methods: geological field works, optical and electronic microscopy, EDS and WDS analyses of minerals compositions, XRF and ICP MS analyses of chemical compositions of rocks. Results. Co-Pd-Ag и Th-REE mineralization consisted of Fe-Ni-cobaltite, Fe-Co-gersdorffite, michenerite, hessite, and Th-monazite was found in exocontact rocks of Khudolaz complex massifs. We subdivided the far and near exocontact zones of ore-bearing Tashly-Tau massif varying in the grade of sandstones metamorphism and metasomatism. In near exocontact zone, quartz-calcite veins with Co-Pd-Ag mineralization are identified. Sulfoarsenides contain Pd admixture up to 0,44 % correlating with nickel content. Quartz and quartz-chlorite-feldspar veins from near and far exocontacts zones contain disseminated Th-REE mineralization. Also, in late quartz veins, we detected goethite-hematite grains with impurity of Pd (up to 0,17–0,32 %) and Rh (up to 0,03 %). It is determined that the source of Co-Pd-Ag mineralization in host rocks is Tashly-Tau massif which rocks and ores were altered by hydrothermal fluid during the post-magmatic stage. We suppose that the source of Th-REE mineralization of exocontact zone are the rocks of Byagoda Suit (sandstones with clayey cement). According to fluid inclusion data, the earlier sulfide-quartz and late sulfide-quartz-carbonate veins are formed from the same hydrothermal Na-K-Mg-chloride fluid at temperatures from 370–320 up to 280–250 °С diluted from 10,6 up to 6 wt %, respectively.