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Shaybekov R.I.

Coloradoite from the silicification zones  of the Uchastok Krutoy gold ocur-rence, Pay-Khoy, Russia  

РЕФЕРАТ

Приводятся данные о минерале колорадоите, который был впервые установлен (на основе электронно-микроскопических исследований) в областях окварцевания и кварцевых прожилках рудопроявления «участок Крутой» в пределах хенгурского габбро-долеритового комплекса Пай-Хоя, и имеющий поздний низко- среднетемпературный гидротермальный генезис.

Ore occurence “uchastok Krutoy” is located in the central part of the hengursky (Zaborin, 1972), tsentralnopaykhoysky (Ostaschenko, 1979; Yushkin et al, 1972) complex, on the right riverside of Hengur-u in 500 m southeastwards from the outlet of the creek stream Krutoy and has been allocated in 1969 during the geological exploration of Nyalpeyskaya geological party (Zhukov et al, 1969). The occurence is represented by elongated in north-west direction reservoir body of gabbro-dolerite, concordant to middle ordovician shales. The length of the deposits is about 1.5 km, in plan the body forms number of upswells and crimps, so its apparent thickness ranges from 60 to 200 m. Intrusion inclination is south-east at an angle of 60-70°. Dolerites in plan clearly show zonal structure. The boundary of the deposit are composed of crystallitic pale-greenish-gray glomerogranular dolerites that in the central part of the intrusion through the porphyraceous differences are replaced by coarse-grained quartz amphibolized gabbro-dolerites which, in turn, are spatially and genetically related to zone of evenly disseminated (1-2 mm) chalcopyrite-pyrite-pyrrhotite mineralization that is the properly magmatic and formed on the final stages of intrusion crystallization. Vermiform concretions of sulfides are associated with quartz-albite myrmekite performing interstices between randomly distributed prismatic grains of plagioclase and sometimes form a discontinuous margin along their borders. Also accessory minerals such as apatite, often forming accretion with sulfides, are common, more rarely – tourmaline, zircon. Sulphide content varies from 5 to 20% (average about 7-10%). Chalcopyrite is extremely rare, it doesn’t exceed 0.5-1.0%, sometimes forming a thin crosscutting quartz-sulfide veins! As a result of mining activities ore zone has been traced by trenches, traversed from each other by approximately 80-120 m, for a distance of 1.2 km, by its width within 2-20 m (Zhukov et al, 1969).

According to the predecessors, gold-telluride mineralization was previously met in the gabbro-dolerite bodies of hengursk complex in the Pay-Khoy only at the “uchastok First” and “uchastok Savabeysky” as part of copper-nickel sulfide ores (Shaybekov, 2011). The studied sulfide (significantly chalcopyrite) mineralization in quartz veins from “uchastok Krutoy” has been set previously unmarked on the Pay-Khoy сoloradoite (according to available data, Yushkin and others, 2007). Its description is below.

Сoloradoite (fig. 1) is noted only in close association with chalcopyrite and is found for the fist time in the Pay-Khoy. It forms inclusion of isometric shape, measuring up to 1 micron. Mineral composition differs slightly from the source (Hg-61.12 and Te-38.88%), for example, the mercury content in two phases is 58.35% and 58.41, tellurium – 40.65 and 41.59% respectively. Accordingly, it should be noted that minor variations ay be related primarily to the small size of analyzed grains. Сoloradoite contains the impurities of silver up to 25.35%, nickel up to 2.06% and lead up to 17.96%, the latter is classic. Presence of elements such as silver and nickel can be completely natural and is caused by regional mineralization characteristics (such as in the presence of copper-nickel studied occurrences, quartz veins and silicification in basites etc.). As a result of the above can be identified lead-silver and silver varieties of koloradoite. The average crystal-chemical formula is Hg0.91Te (table 1).

Besides the above mineral phases in quartz veinlets met chalcopyrite (from 1-4 mm to 2 cm, the average formula– Cu0.88Fe1.00S2), covellite (20×100 mm, often replaced by silver (50% volume), crystal-chemical formula is (Cu0.64Fe0.06)0.7S)), wurtzite (a rare mineral of size up to 1 mm, associated with gold), gold and electrum (from 0.1 to 0.5 microns, contains the impurities of silver up to 17.6%, the crystal-chemical formulas are Ag0.08Au and Ag0.32Au respectively). Also marked native phase Pb (up to 1.5 microns, often mixed with tin to 14.5%), Sn (up to 3 microns in cataclastic areas) that have submicron dimensions and usually irregular angular shape.

Based on these data we can draw the following conclusion. Сoloradoite directly associated with chalcopyrite and is characterized by slight deviations of its composition (as comparison with the empirical composition), which is the result of mineral formation features and small grain sizes. In koloradoite the impurities of silver and lead are noted in significant amounts, which allowed to distinguish two varieties – lead-silver and silver. The formation of this mineralization type occurred in the conditions of low-, medium temperature hydrothermal process in quartz-chalcopyrite veinlets.

The author would like to thank Astakhova I.S., Shevchuk S.S. for their assistance with preparation of the work.

The work was supported by the program presidium RAS № 27 (12-P-5-1027), project 12-5-6-016-ARCTIC.

 

 

REFERENCES

  1. Zaborin O.V. Diabase formation Pay-Khoy // Magmatism, metamorphism and metallogeny of the North Urals and Pay-Khoy. Syktyvkar. 1972. pp. 41-42.
  2. Zhukov Y.V., Zaborin O.V., Kostyukova L.A. et al Geological structure sheets R-41-115-A,B; R-41-116-A,B. (Report Sopchinsk GPSP on the results of geological prospecting surveying at a scale of 1:50.000 for 1966-1968 yrs). Vorkuta. 1969. 261 p. Komi TGF.
  3. Ostaschenko B.A. Petrology and ore tsentralnopaykhoysky basaltic complex. Leningrad: Nauka. 1979. 113 p.
  4. Shaybekov R.I. Mineral associations and genesis of platinum sulfide mineralization in the gabbro-dolerite Pay-Khoy (Russia, Nenets Autonomous District) // Notes RMO, 2011. №6, pp. 70-86.
  5. Yushkin N.P., Davydov V.P., Ostaschenko B.A. Igneous rocks of the Central Pay-Khoy and their metallogenic features // Problems of Petrology of the Northern Urals and Timan. (Proceedings IG Komi SC UB AS of the USSR. Vol. 17). Syktyvkar. 1972. pp. 3-34.
  6. Yushkin N.P., Kunz A.F., Timonin N.I. Minerageny Pay-Khoy. Yekaterinburg: UB RAS, 2007, 292 p.