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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 (...

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The content of rare elements in zircon may vary significantly, although it typically does not exceed cer tain threshold values, which have been ascertained empirically. The so called hydrothermal/metasomatic zircons are notable for the highest content of these ele ments, which are almost always present as isomorphic impurities [1]. While zircons enriched in Hf, U, and Th are common [2, etc.], considerable deviations in the Y and REE contents have been less frequent. The Y content typically lies within the range from 10 to 5000 ppm; the total REE content varies from 100 to 2500 ppm [3]. The maximum REE content (98 200 ppm) was registered in zircons from metasomatites of the unique Oklo uranium deposit (Gabon, Equatorial Africa) [4]. For the Baltic shield, an anomalously high content of REE was ascertained in zircons from metabasites of the Kontokki dike complex in the Kos tomuksha structure (29 800 ppm [5]) and rocks of the Panozero sanukitoid complex in Central Karelia (55 300 ppm in lamproites [6] and 68 800 ppm in monzogabbro [7]). REEs are concentrated in local domains and zones of variation of zircon grains, which were of contrasting dark color in the BSE images. A high Y content (up to 5 wt % of Y 2 O 3 ) was revealed in metamict zircons from the metasediments of the Dal radian complex in Scotland, which associate with xenotime and are formed upon intensive low temper ature fluid processing of rocks [8].The anomality of the composition of the zircons considered in this article was revealed by performing U-Pb dating (SHRIMP II, Center of Isotopic Research, All Russia Research Institute of Geology), which was accompanied by studying the distribution of rare and rare earth elements (Cameca IMS 4f, Yaroslavl' Branch of the Physical Technical Institute) according to the procedure described in [9]. After sev eral months the zircon content in the same domains was measured again on an ion microprobe; the results were in a close agreement, and no analytical errors were ascertained. The features of the structure and composition of zircons with respect to the major ele ments were studied on a JEOL JSM 6510LA scanning electron microscope with a JED 2200 energy disper sive spectrometer (Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences); the analysis results were standardized to 100%. The presence of inclusions of foreign mineral phases was verified on an electron microscope upon the maxi mum possible magnification by composition contrast (BSE regime). The correctness of determination of the microelemental composition on an ion microprobe (with a locality of 15-20 µm) was regulated by analyz ing on an electron microprobe (which was less sensi tive, but was characterized by a locality of 1-2 µm only). No foreign mineral phases were revealed in zir cons. When plotting the spectra of REE distribution, the compositions of minerals were normalized to the composition of C1 chondrite [10].Zircons of anomalous composition were found in a thin (up to 20 cm) pegmatite vein (sample 101) cross ing the e...