DEPTH STRUCTURE AND ORE-FORMING SYSTEMS OF THE PECHENGA ORE REGION (RUSSIAN ARCTIC ZONE)

The integral depth model of the Pechenga ore region was created via computer simulation on the basis of the results of geophysical studies and ultra-deep drilling. The integral depth model simulates the Pechenga ore region as a horizontal section of a mantle volcano-plutonic ore-forming system of the central type. The model defines the North wing of the Pechenga structure as a volcanic caldera fragment, and its southern part describes as a scaly monocline, combined with the domes of rheomorphicgranitoids. Subsequently, they underwent intense compression and metamorphism. Then, in conditions of stretching, steeply dipping zones of cataclasites and retrograde metamorphism were formed. Thus, the Pechenga Cu-Ni deposit can be referred to the volcano-plutonic type and the corresponding ore-forming system of the mantle-crust type.

Using geophysical methods, the Vp/Vs anomaly at a depth of 20-25 km and the rise of the Moho boundary, reaching a maximum height of 34 km under the Pechenga structure, were identified. This can be interpreted as a relic mantle plume that determined geological events in the Paleoproterozoic.

The compilation of structural, petrological, mineralogical and geochemical data suggests that at the upper levels of the Cu-Ni ore-forming system was evolving in two stages: 1) the introduction mantle gabbro-wehrlite sills in heterogeneous Productive strata, their differentiation and the formation of magmatic Cu-Ni ores; 2) shear deformations and metamorphism of gabbro-wehrlite sills and the deposition of remobilized Cu-Ni ores in the synmetamorphic shear zones.

Drilling and studies of the SG-3 well have proven high saturation of the Precambrian crust with a variety of ore mineralization cross the whole section, including gold ore one in the range of 9800-11000 meters. The gold mineralization spatially coincides with the zones of regressive changes, which indicates its structural control. The question of the gold mineralization position in the SG-3section in the overall sequence of endogenous processes remains debatable.

Based on the integral geodynamic model of the deep structure of the Pechenga ore region, a new interpretation of the deposits’ localization is proposed. According to these views, the Pechenga ore field with nickel-bearing intrusions is a paleo-analogue of the Norilsk ore region, but has undergone intensive tectonic-metamorphic transformations. Given that the horizons of low-sulfide PGE mineralization in gabbro-wehrlite stratified intrusions were identified in the Norilsk area, an attempt was made to study the same mineralization in the Pechenga ore region.

1. Kazanskii V. I., Kuznetsov O. L., Kuznetsov A. V. et al. Glubinnoe stroenie i geodinamika Pechengskogo rudnogo raiona: opyt issledovaniya Kol’skoi sverkhglubokoi skvazhiny. [Deep structure and geodynamics of the Pechenga ore district: the experience of study of the Kola superdeep borehole]. Geologiya rud. mestorozhdenii, 1994,vol. 36, no. 6, pp. 500—519. (In Russian).

2. Lobanov K. V., Kazanskii V. I., Kuznetsov A. V., Zharikov A. V. Integral’naya geodinamicheskaya model’ Pechengskogo rudnogo raiona na osnove korrelyatsii geologicheskikh, petrologicheskikh i petrofizicheskikh dannykh po Kol’skoi sverkhglubokoi skvazhine i opornomu profilyu na poverkhnosti. [Integrated geodynamic model of Pechenga ore region on the basis of correlation of geological, petrological and petrophysical data on Kola superdeep borehole and reference profile on the surface]. Sovremennye problem rudnoi geologii, petrologii, mineralogii i geokhimii. IGEM RAN. Moscow, 2010, pp. 258—300. (In Russian).

3. Kazansky V. I., Lobanov K. V., Isanina E. V., Sharov N. V. The Paleoproterozoic Pechenga Cu-Ni ore field (Fennoscandian Shield): a fault-bound volcanic center. Izvestiya Earth Sciences section Russian academy of Natural Sciences 33 International Geological Congress, 2008,no. 17: Special Iss., pp. 43—46.

4. Lobanov K. V., Kazansky V. I. The mantle-crustal ore-forming Cu-Ni system of the Pechenga ore district (Fennoscandian shield).Proceedings of 6 European Congress on Regional Geoscientific Cartography and Information Systems EUREGEO, 2009,vol. 2,pp. 201—205.

5. Kazanskii V. I., Lobanov K. V. Strukturno-geofizicheskaya pozitsiya, glubinnoe stroenie i usloviya lokalizatsii unikal’nogo Pechengskogo rudnogo polya (Baltiiskii shchit). [Structural and geophysical position, deep structure and localization conditions of the unique Pechenga ore field (Baltic shield)]. Krupnye i superkrupnye mestorozhdeniya: zakonomernosti razmeshcheniya i usloviya obrazovaniya. IGEM RAN. Moscow, 2004, pp. 187—205. (In Russian).

6. Stroenie litosfery rossiiskoi chasti Barents-regiona. [Structure of the lithosphere of the Russian part of the Barents region].Pod red. N. V. Sharova, F. P. Mitrofanova, M. L. Verby, K. Gillena. Moscow, Petrozavodsk: Karel. nauch. tsentr RAN, 2005, 318 p. (In Russian).

7. Lobanov K. V., Kazanskii V. I., Chicherov M. V. Zolotaya mineralizatsiya v razreze Kol’skoi sverkhglubokoi skvazhiny i na poverkhnosti v Pechengskom rudnom raione. [Gold mineralization in the section of the Kola superdeep borehole and on the surface of the Pechenga ore district]. Materialy mezhdunarodnoi konferentsii “Zoloto Fennoskandinavskogo shchita”. Petrozavodsk 1—5.10.2013. Karel. NTs RAN. Petrozavodsk, 2013, pp. 121—125. (In Russian).

8. Kozlovskii E. A., Guberman D. M., Kazanskii V. I. Rudonosnost’ glubinnykh zon drevnei kontinental’noi zemnoi kory (po materialam Kol’skoi sverkhglubokoi skvazhiny) .[The ore bearing of the deep zones of the ancient continental crust (based on the materials of the Kola superdeep borehole)]. Sovet. geologiya, 1988, no. 9,pp. 3—11. (In Russian).

9. Kazanskii V. I., Novgorodova M. I., Smirnov Yu. P., Boronikhin V. A. Neobychnye mineral’nye assotsiatsii na nizhnikh gorizontakh Kol’skoi sverkhglubokoi skvazhiny. [Unusual mineral associations on the lower horizons of the Kola superdeep borehole]. Geologiya rud. mestorozhdenii, 1989, vol. 31, no. 6, pp. 75—82. (In Russian).

10. Kalinin A. A., Bayanova T. B., Lyalina L. M., Serov P. A., Elizarov D. V. Proyavleniya zolota Yuzhno-Pechengskoi strukturnoi zony: novye izotopno-geokhimicheskie dannye. [Manifestations of gold in the South Pechenga structural zone: new isotope-geochemical data]. Materialy Vserossiiskoi (c mezhdunarodnym uchastiem) konferentsii “Geologiya i geokhronologiya porodoobrazuyushchikh i rudnykh protsessov v kristallicheskikh shchitakh”. KNTs RAN. Apatity, 2013, pp. 69—71. (In Russian).

11. Gorbunov G. N. Astaf’ev Yu. A., Goncharov Yu. V., Korchagin A. U., Neradovskii Yu. N., Smol’kin V. F., Sokolov S. V., Sharov N. V., Yakovlev Yu. N. Medno-nikelevye mestorozhdeniya Pechengi. [Copper-nickel deposits of the Pechenga]. Otv. red. N. P. Laverov. Moscow, GEOS, 1999, 236 p. (In Russian).