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

Abstract

Location of the deposits and occurrences of gold mineralization in metamorphic complexes of the Kola region is controlled by tectonic zones at the regional scale at the boundaries of major segments of the Fennoscandian Shield. Three zones are the most important: (1) the system of Neoarchean greenstone belts Kolmozero–Voron’ya–Ura-guba along the southern boundary of the Murmansk craton; (2) the suture, delineating the core of the Lapland–Kola orogeny in the north; and (3) the series of overthrusts and faults at the eastern flank of the Salla–Kuolajarvi belt. Gold deposits and occurrences are located within greenstone belts of Neoarchean and Paleoproterozoic age, and hosted by rocks of different primary compositions (mafic metavolcanics, diorite porphyry, and metasedimentary terrigenous rocks). The grade of metamorphism varies from greenschist to upper amphibolite facies, but the mineralized rocks are mainly lower amphibolite metamorphosed, close to the transition from greenschist to amphibolite facies. Gold deposits and occurrences in the northeastern part of the Fennoscandian Shield formed during two periods: the Neoarchean 2.7–2.6 Ga and the Paleoproterozoic 1.9–1.7 Ga. According to paleo-geodynamic reconstructions, these were the periods of collisional and accretionary orogeny in the region. Those Archean greenstone belts, which were reworked in the Paleoproterozoic (e.g., Strel’na and Tiksheozero belts), can contain gold deposits of Paleoproterozoic age.

Porphyry-Related Metamorphosed Au-Ag and Cu-Mo Deposits in the Precambrian of the Fennoscandian Shield

“…The Oleninskoe Au-Ag deposit is located at the northwestern thinning of the Oleny Ridge amphibolite strata (Figure 1) in a shear zone of northwest strike [37][38][39]. The amphibolite and high-alumina metasedimentary schist host numerous granite porphyry sills with a thickness of 0.1-6.0 m (Figures 9 and 10).…”

“…The geochemical characteristics of the rocks correspond well to the composition of mineralization (Table 6). Arsenopyrite, pyrrhotite, and ilmenite are the most abundant ore minerals, which are present in all altered rocks [37,38]. Sporadic ore minerals in biotitizated and diopsidizated amphibolite are chalcopyrite and sphalerite; pentlandite and electrum are rare.…”

Mustard Gold in the Oleninskoe Gold Deposit, Kolmozero–Voronya Greenstone Belt, Kola Peninsula, Russia

“…The Oleninskoe is a small gold deposit (~10 t or 0.32 Moz @ 7.6 g/t Au [15,16]), located in the Neoarchean Kolmozero-Voronya greenstone belt, which separates two major tectonic units of the Fennoscandian Shield-the Murmansk craton and the Kola Province ( Figure 1A). The geological position and structure of the Oleninskoe deposit are described in [15][16][17][18], and here is a summary of the published data.…”

“…The location of the deposit is controlled by a shear zone of the NW strike in the amphibolite of the Oleny Ridge sequence ( Figure 1) [15,16]. The amphibolite and high-alumina metasedimentary schist in the area of the deposit contain numerous granodiorite quartz porphyry sills 0.1-6.0 m thick ( Figure 1).…”

“…Amphibolite and granodiorite porphyry are intensely altered, the alteration zone is~50 m thick and traced along the strike for 200-250 m. The whole zone of alteration is covered with early biotitization (potassium metasomatism) and formation of diopside-zoisite-carbonate mineral assemblage (calcium metasomatism) in the amphibolite [15,16]. Quartz-rich metasomatic rocks (quartz-muscovite-albite, quartz-tourmaline, and quartz rocks) formed later, replacing amphibolite and granodiorite porphyry as an echelon-like series of three lens bodies, cutting general schistosity in the host rocks at an acute angle of 10-15 • (Figure 1): We interpret the structure of the deposit [15] as a strike-slip fault bridge structure (this kind of structures is described in [20]).…”