Geological structure and perspectives for mineralization of the Kichany structure, Tiksheozersky greenstone belt (Northern Karelia)

Abstract

2 Институт геологии и геохронологии докембрия РАН, 199034, г. Санкт-Петербург, наб. Макарова, 2 3 Всероссийский научно-исследовательский геологический институт, 199106, г. Санкт-Петербург, Средний просп., 74 4 Институт геологии и геохимии УрО РАН, 620016, г. Екатеринбург, ул. Акад. Вонсовского, 15 Поступила в редакцию 22.07.2016 г.; принята к печати 14.09.2016 г.В Кичанской структуре Тикшеозерского зеленокаменного пояса установлены типичные для зеленокаменных поя-сов мира проявления железистых кварцитов, колчеданных существенно пирротиновых руд, арсенопирита, молиб-денита и золота. Проявления молибденита, арсенопирита и золота имеют наложенный характер и связаны с па-леопротерозойскими свекофеннскими метаморфо-метасоматическими процессами во вмещающих породах нео-архейского возраста. Так, время формирования арсенопиритовой минерализации по составу монацита оценено значением 1789 ± 47 млн лет, а возраст золоторудной минерализации, установленный по титаниту с включения-ми самородного золота, составил 1739 ± 15 млн лет. Первоочередной поисковый интерес в Кичанской структуре могут представить рудопроявления золота, приуроченные к метасоматически измененным амфиболитам и гней-сам с пирротин-арсенопиритовой минерализацией в зонах надвиговых тектонических нарушений. Золото тонкое (<0.1 мм), высокопробное (890-913), чаще всего это ксеноморфные зерна, реже встречаются идиоморфные шести-гранные выделения. Золото образует включения и выделяется по трещинам в роговой обманке, плагиоклазе, тита-ните, кварце, часто оно приурочено к границе зерен арсенопирита и марказита с кварцем и силикатными минера-лами, а также отмечается в виде включений в пирротине и халькопирите. RAS, 184209, Fersman st., 14, Apatity, Russia, e-mail: kalinin@geoksc.apatity Mineral deposits in the Neoarchean greenstone belts in the Fennoscandian Shield, especially in its eastern (Russian) part, are not as numerous as in Archean belts of Canada, Australia, or Southern Africa. The goal of the present paper is to show with an example of Tiksheozersky belt, that Neoarchean greenstone belts in Northern Karelia and Kola Peninsula do contain ore occurrences, typical to greenstone belts in the world, therefore prospects of these geological structures for mineral deposits are not uncovered fully. Ore occurrences of jaspilite, massive sulfide pirrhotite ore, molybdenite with uranium and graphite, arsenopyrite, and gold were found in the Kichany structure of the Tiksheozersky belt. Jaspilites and massive sulfide ores were considered as syngenetic to volcanic-sedimentary host rocks. Occurrences of molybdenite, arsenopyrite, and gold are epigenetic, controlled by zones of alteration. Zonality in ore-bearing altered rocks, peculiar properties of their chemical and mineral composition, as well as composition of rock-forming and ore minerals, were studied in detail. Age of processes of alteration was estimated with different geochronological methods. Dating of zircon grains from the molybdenite occurrence with LA-ICP-MS method showed two events 2600-2700 Ma (...

Stages of Gold Deposits Formation in the Precambrian of the North-Eastern Fennoscandia

“…The deposits in the zones of amphibolite metamorphism formed under conditions of ductile deformations. The foliation of mineralized rocks was reported in the Porojarvi occurrences in the Pechenga belt [14], in the Sergozerskoe deposit (Strelninsky belt) [15], and in the Kichany occurrence (Tiksheozersky belt) [16].…”

“…[27] Olenegorsky, Olenegorsk group of BIF deposits 2784 ± 9 U-Pb, SHRIMP-II, zircon (central zone) from skarnoid-regional metamorphism? [31] 2644 ± 9 U-Pb, SHRIMP-II, zircon (marginal zone) from skarnoid [31] 1960 ± 30 U-Pb, apatite from the dyke aged 2740 ± 11 Ma [32] ± 11 U-Pb, dolerite [32] 2675 ± 3 U-Pb, SHRIMP-II, zircon (marginal zone) from skarnoid [31] Tiksheozersky, Kichany ± 20 U-Pb, zircon, metatuff [33] 1789 ± 47 U-Th-Pb, chemical estimating of the age, monazite from metasomatic rocks with arsenopyrite [16] No data 2720 ± 4 U-Pb, zircon, meta-andesite [34] 2674 ± 4 U-Pb, zircon, plagiomicrocline granite [35] 1739 ± 15 U-Pb, titanite from mineralized metasomatic rocks [16] Strelninsky, Sergozerskoe ± 14 U-Pb, zircon, the 1st generation, metavolcanics [36] 1739 ± 86 Rb-Sr, minerals and WR, mineralized metasomatic rock [15] No data ± 25 U-Pb, zircon, alkaline granite ± 13 U-Pb, zircon of the 2nd generation, metavolcanics, regional metamorphim [37] 1874 ± 3 U-Pb, zircon, diorite porphyry dyke [15] Perapohja, Rompas (Rm) and Rajapalot (Rp) 2050 ± 8 U-Pb, zircon, felsic porphyry [52] 1775 ± 12 U-Pb, zircon, Matalavaara tourmaline granite [53] No data 1973 ± U-Pb, zircon, metatuff [54] 1989 ± 8 U-Pb, zircon, Kierovaara granite [53] 1879 ± 3 U-Pb, titanite, Haaparanta inrusions [52] from to 1912 U-Pb, uraninite-1 (Rm) [55] 1819 ± 37 U-Pb, uraninite-3…”

Gold Prospects in the Western Segment of the Russian Arctic: Regional Metallogeny and Distribution of Mineralization

“…The Kichany occurrence (#7 in Figure 1) is located in the central part of the belt, in the Kichany synform (Figure 12) in a stratum of amphibolite (tholeiitic metabasalt) with interbeds of plagiogneiss-metatuffite. A series of thrusts at an angle of 30www.videleaf.com 40° splits the stratum to thin slabs, in the outcrops the thrusts reveal in intense jointing and schistosity of rocks [28].…”

Gold Prospects in the Western Segment of the Russian Arctic: Regional Metallogeny and Distribution of Mineralization

“…The Kichany occurrence (#7 in Figure 1) is located in the central part of the belt, in the Kichany synform ( Figure 12) in a stratum of amphibolite (tholeiitic metabasalt) with interbeds of plagiogneiss-metatuffite. A series of thrusts at an angle of 30-40 • splits the stratum to thin slabs, in the outcrops the thrusts reveal in intense jointing and schistosity of rocks [28].…”

“…Age of titanite (U-Pb method) from the silicified amphibolite with gold-arsenopyrite mineralization, which contains inclusions of gold (Figure 14c), is 1739 ± 15 Ma [28]. Mineralization either formed or was re-mobilized in the Paleoproterozoic during the Svecofennian metamorphic event.…”