2011

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Geological structure and modern economic evaluation of Bolshoi Ihtegipahk and Pahkvaraka areas at Fedorova Tundra ore deposit (Kola Peninsula)

Mitrofanov A.F.

Vernadsky Institute of geochemistry and analytical chemistry, Moscow, Russia

mit-alex@ya.ru

Fedorova Tundra ore deposit belongs to the western part of the mafic-ultramafic layered intrusion, which is also known in the literature under the name of the Fedorova-Panskiy intrusion. From a geographical point of view, it is extended (80 km) and narrow (3-6 km) mountain range, which has the north-west strike. Intrusion is located in the northern contact zone of volcanic-sedimentary rocks of Proterozoic Imandra-Varzuga structure presented greenstone formations of rizhgubskaya and seydorechevskaya formations and Precambrian basement rocks represented by younger alkaline granites and Archean plagiogneiss-granites (Bayanova, 2004).

From east to west in the structure of the intrusion there are following main components: East Pansky block has a heterogeneous structure in lateral, it consist of gabbro and in the lower part of this block the presence of the Pt-Pd-low sulphide layered horizon (LH), presented by interbedded layers of gabbro-norite, anorthosite, norite and bronzitite was revealed. Next up is the West Pansky block, which is the thickest and most well-studied part of the intrusion. It consists of gabbro-norites (Schissel et al, 2002). Two main Pt-Pd-low sulphide layered horizons were also revealed there: upper (ULH) and lower (LLH). Most western is considered in this paper Fedorova Tundra block which consists of ultramafic and mafic rocks. From the West Pansky block it is separated by the large fault zone (Mitrofanov et al, 2004).

Fedorova Tundra layered intrusion, which containes the same name non-ferrous and precious metals ore deposit, consists of 90% basic rocks - from norite to gabbro. Ultramafic rocks are rare. All industrial Cu-Ni-PGE mineralization is confined to taxitic gabbro-norite zone. The latter zone got its name because of the significant heterogeneity of mineral grains, which compose it.

Sulphide Cu-Ni mineralization is the most prevalent within deposit. It tends to taxitic gabbro-norite zone rocks and noritic plagioamfibolites endocontact zones. Total thickness of mineralized rocks varies from 80 to 200 m. The sulphide mineralization is represented by three mineral types: p pyrrotine, pyrrotine-chalcopyrite and pentlandite-chalcopyrite-pyrrotine. The first is most common in Maliy, Sredniy and Bolshoi Ihtegipahk areas. Pyrrotine-chalcopyrite type is the second most common after pyrrotine and occurs mainly in the middle and upper parts of the mineralized zone within Bolshoi Ihtegipahk and Pahkvaraka areas. Pentlandite-chalcopyrite-pyrrotine type is at the bottom part of the same areas. Complex mineralization is closely associated with sulphide copper-nickel type, tending mainly to its pentlandite-chalcopyrite-pyrrotine mineral type, although in rare cases, high amounts of PGE were observed in sulphideless rocks.

As a part of this work there was studying the contents of platinum group elements in sulfide minerals (PGM), which showed that even in spite of the high detection threshold of microlog CAMECA-100 (0.1% PGE), some grains of pentlandite contain significant amounts of palladium (up to 0.2 %).

In addition to pentlandite, the main PGE and Au concentrators in ores are their own minerals. There were found 29 kinds of PGE and gold minerals, as well as the 8 phases of PGE that did not yet have the status of independent minerals. All of them are diagnosed on the basis of a quantitative study of their chemical composition by electron microscopy studies of polished sections in the Geological Institute KSC RAS. The main concentrators of palladium in the ore, along with pentlandite are kotulskit, merenskiit, braggite, stillwaterite, vysotskite and sobolevskite; platinum – braggite, moncheite, vysotskite, merenskiite and sperrylite; gold - gold-silver alloys (Balabonin et al, 1998).

By 2008 exploration work on the field have been completed, ore reserves were counted and approved by the State Reserves Committee.

In order to update the economic data for 2011 in this work there was full economic assessment and reserves calculation in the light of new data, which include the price of metals, the values of capital and operating costs.

The first step was ore deposit delineation within the prospecting profiles, and combining them into a single three-dimensional closed wireframe model. Then the model was filled with elementary blocks, which size was chosen based on the parameters of exploration network and prospected pit benches (Kaputin, 2007).

For the grade interpolation to the elementary blocks several experimental variogram were built, which allowed to pick up variogram palladium conditional distribution model which is required for the subsequent kriging.

После проведения необходимых расчетов и интерполяции производился подсчет запасов и ресурсов модели как по российской, так и по зарубежной классификации.

After the necessary calculations and interpolation was carried out calculation of reserves and resources for Russian and foreign classification was made.

The final stage of the work were the calculation the ultimate pit contour in the program NPV Scheduler, evaluation of reserves and all economic calculations, which included the analysis of the project’s economic sustainability, confirmed the high profitability and rapid return on investment (ROI) in the deposit.

References:

D. Schissel, F. Mitrofanov, A. Korchagin, A. Cvetkov, «Basal Platinium-Group Element Mineralization in the Fedorov Pansky Layered Mafic Intrusion, Kola Peninsula, Russia», Economic Geology, 2002, №97, p. 1657-1677.

Balabonin, N.L. Forms of finding and the distribution balance of precious metals in the ores of the Fedorova-Pansky intrusion (Kola Peninsula)/ Subbotin V.V., Skiba V.I., Voytehovskiy U.A., Savchenko E.E., Pahomovskiy Y.A. // Ore-dressing journal. – 1998. - №6. – p.24-30.

Bayanova T. B. Age of reference geological complexes of the Kola region and the duration of magmatic. St. Petersburg: Science, 2004.

Kaputin Y.E., «Modeling the ore deposit and evaluation of mineral resources using the Studio 3. Training course», St. Petersburg, 2007.

Mitrofanov F.P., Korchagin A.U., Rundkvist T.V., «Fedorova-Pansky layered mafic intrusion: Geology and platinum mineralization», ed. KSC RAS, Apatity, 2004.