The Russian and Poland Chapters collaborative field trip to Kola Region

The 5-days field trip to Kola Peninsula took place from September 14 to 20. The field trip was organized by North-West Russia Chapter, and in total 21 students of its, Siberian and Baltic Chapter participated (Figure 1). It is well known that Kola region has a long geological history, which come out in complex geological settings. As a result, the Kola region attracts many geologists of broad interests because it has a great resource potential, which is have not been fully studied yet. During the field trip, we tried to observe different examples of mineralization occurring in the region. Alkaline intrusions with rare-earth mineralization, carbonatites and mafic-ultramafic with sulfide mineralization were visited. Furthermore, we had one-day excursion in two geological museums located in Kola Science Centre of the Russian Academy of Sciences, where we were able to observe a numerous variety of magnificent specimens of mineralogical and petrological collection.

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Figure 1. A group picture of SGA students against a background of Khibiny Mountains.

All the geological objects visited are located in vicinity of Apatity. Therefore, it was the start point of our trip. The first day of excursion, we visited Khibiny Mountains, which are located in the central part of Kola Peninsula. Khibinky massif is a unique magmatic complex, which is famous by its rare types of rocks and minerals. The age according to the helium-lead method is defined as 290 ± 10 million years. A characteristic feature of the Khibiny massif is a lopolith structure, which includes of complex of alkaline rocks such as khibinite, foyaite, iolite, urtite and many other. Generally, this massif was used for the mining of apatite ores. However, in these host rocks more than 100 minerals were first discovered. We have visited one of the old mine (Figure 2), which disclosed a pegmatite vein with huge Nepheline, Aegirine crystals associated with rare Lamprophyllite and Eudialyte. Students were able to collect stunning samples of green Aegirine crystals embedded in a conic fan-like spray in alkalic matrix with pink Eudialyte crystals (Figure 3). Moreover, we climbed up to examine the outcrop of dyke, made up of rare rock type, named tinguaite, which is chemical analogue of iolite, but has very interesting extraordinary structure, called “turtle structure” because it looks like a tortoise shell.

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Figure 2. An old tunnel used for mining of apatite ores.

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Figure 3. Eudialyte crystals.

The second day we visited old excavation of pyrrhotite ores. The ores were prepared for transportation to the factory, but suddenly the works have been frozen due to financial problems and a huge amount of ore still lay on the slope. After collecting several samples of pyrrhotite ore, we went down to the valley where nice samples of Aegirine spherulites could be found in pebbles. Those Aegirine spherulites, named “Aegirine bombs” (Figure 4), can contain Analcim or Katapleite in the core.

The third day was devoted to visiting of Kovdor mining. First, we visited an office of EuroChem Mining Company, which exploits this deposit and then a Chief Geologists made a short excursion for our group. We visited a quarry, where we were able to observe all structural features. We were told about the geological settings of this deposit and about mining process. The Kovdor massif is a central-type oval caldera-like depression made up of multiphase igneous intrusion, which consists of ultrabasic alkaline rocks and carbonatites. It is one of the most interesting deposits not only in the Kola Peninsula, but also in the World. More than 180 mineral species have been found within the Kovdor massif, 13 of them first time discovered there and 9 of them are endemic minerals. Unfortunately, we did not have a lot of time to visit the entire part of open pit, but we had a chance to found nice samples of octahedral crystals of magnetite in carbonate matrix. The typical samples of Kovdor carbonatites. In addition, we visited dumps of the deposit and collected samples of apatite ore, Flogopite zonal crystals and giant crystals of green Diopside (Figure 5). 

The forth deposit we have visited is famous Monchegorsk intrusion. The Monchegorsk pluton is a typical representative of the Paleoproterozoic ore-bearing layered intrusions on the Fennoscandian Shield. The excursion route embraced four outcrops of different rock varieties of this deposit and was led by geologist from Kola Science Centre of the Russian Academy of Sciences. We were told about the genesis settings of Cu-Ni, Cr and PGE ore related to the layered mafic-ultramafic massifs. They are intruded into the supracrustal Archean complexes at the 2500-2400 Ma boundary and marked the productive phase of mantle plume activity at the Archean-Proterozoic boundary. The sulfide Cu-Ni mineralization makes up "hanging" bodies of disseminated ore in the layers of olivine-bearing rocks within the orthopyroxenites. Students were lucky to visit productive "Horizon 330" (Figure 6), which is in located in the upper part of the Monchepluton section. It consists of olivine pyroxenitesand monomineral pyroxenites with disseminated sulfide ore and characterized by the highest PGE content. Furthermore, we visited the outcrop of ore veins of the main ore field NKT in the northern part of Mt. Nittis. We were able to observe the outcrops of tectonic zones in pyroxenite, where oxidized sulfide veins occur. It was also possible to observe in detail the structure of the dislocations, cutting the ultramafic rocks and sample oxidized pentlandite-pyrrhotite ore. Moreover, participants were glad to visit a dump of layered dunite rocks and examine the nice banded texture of the Sopcheozero deposit chromite ores (Figure 7). The last point we visited were the outcrop with massive sulfides, which are confined to the norite and olivine norite complex.

The members of Siberian Student Chapter are grateful to SGA for providing such opportunities to visit famous and interesting from geological side places. We are also thankful to geologists of Kola Science Centre of the Russian Academy of Sciences and “EuroChem Mining Company”, who led us very informative excursions. 

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Figure 4. Aegirine “bomb”.

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Figure 5. Giand diopside crystals with aegirine rims.

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Figure 6. Students examine the “Horizon 330”.

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Figure 7. Layered chromite ore.