The Ilmensky mountains
Lenin Illmensky state Reserve, Urals branch of Russian Ccademy of Sciences
Chelyabinskaya oblast, Miass
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The Ilmensky mountains are located in the Southern Urals between 54 58 - 55 21 northern latitude and 60 07 – 60 22 eastern longitude in the Chelyabiskaya oblast on the administrative territory of the Miass city in Chebarkulsky and Argayashsky districts. The nearest railway track is in Miass, and the nearest international airport is 100 km to the East, in Chelyabinsk.
Geo-mineralogical characteristics of the Ilmenogorsky complex
The Ilmensky mountains are a unique geological phenomenon famous for its semiprecious and rare-metal mineralisation of the pegmatite lodes and wine spread of the rare for the Urals alkaline rocks - nepheline syenites. Different metamorphic and plutonic rocks, to this or that degree modified by deformational and metasomatic processes, are host to them. The diversity of Ilmensky mountain rocks are known as the "Ilmenogorsky complex".
The Pegmatites of the Ilmenogorsky complex
The Pegmatites of the Ilmenogorsky complex are specific geological formations, which are coarse-grained or giant-grained rocks forming separate geological bodies. These bodies have specific shape, internal structure and mineral composition. As a rule they have contrasting borders with more fine-grained host rocks and can be clearly identified. Pegmatites present the greatest interest in the study of the Ilmenogorsky complex, since they contain the most interesting minerals and associations as well as the biggest and perfect mineral crystals. According the main rock-forming minerals, there are three main pegmatite types: granitic, miaskitic and syenitic. Granitic pegmatites contain the primary rock-forming quartz; the miaskitic pegmatites contain nepheline; the syenitic pegmatites do not contain neither quartz, nor nepheline, feldspar being the main mineral. The detailed studies of the pegmatites held in the 20th century helped to systematise them into the group of separate age groups and define their peculiarities of structure and mineral composition.
Group I is the earliest: p re-miaskitic granitic pegmatites. The pegmatites of this group are coarse-grained, their graphic structure and zoning are not clear-cut, deformation is well pronounced (boudinage, undulated textures, cataclasis, quartz granulation). The quantity and diversity of the accessory minerals is relatively small: magnetite, zircon, allanite, betafite, much less muscovite, fluorite, apatite and some other minerals.
Group II comprises alkaline pegmatites: miaskitic ans syenitic. Their formation is linked to the alkaline process in general. Due to the peculiarities of their composition and interrelations, they can be split into 3 subgroups identifying different phases of the alkaline process:
- IIa: f eldspatltic pegmntites nnd feldspatholites (syenitic) are linked to the early stages of the alkaline process. They have various bodies of very complex branchy form. The diversity of some accessory minerals is relatively small, but in certain lodes or their segments they are abundant and occasionally mineable (for example, molybdenite): magnetite, pyrochlore, aeschynite, zircon, allanite, titanite, apatite, molybdenite, ferrimolybdite, powellite, less frequently monazite and sarnarskite.
- IIb: miaskitic pegmatites (nepheline is the dominating mineral) are linked to the maximal stage of the alkaline process. They have bodies of various and often very complex form. They are peculiar for the cavities containing accessory minerals in the form of big and perfect crystals. They used to be produced originally for commercial purposes (collections and faceting) and later on for scientific studies. The main are cancrinite, sodalite, wischnewite, ilmenite and magnetite, zircon, pyrochlore, aeschynite, columbite, apatite and others.
- IIc: corundum- feldspathic pegmatites (syenitic, always contain corundum), are linked to the late phases of the alkaline process. The form of the pegmatite bodies and lodes is relatively simple, lens- or plate-like, sometimes zoning is well-pronounced. The corundum concentration and its quantities in some lodes are so big that in the 19Ih century it used to be produced as abrasive material. In some lodes corundum produces the asterism effect. The typical accessory minerals are zircon, columbite, samarskite, pyrochlore, aeschynite, monazite; spinel (pleonast- herzynite), garnet, chrysoberyl.
Group III: postmiaskitic granite pegmatites. They have quite thin bodies with simple plate-like form. Among the accessory minerals are zircon (malacon), fergusonite, betaphite chevkinite, apatite, thorite, titanite, ilmenite, helvite and others.
Group IV: amazonite pegmatites. This is the best-known type of pegmatites and one of the first to be produced and studied in the Ilmensky mountains. It was the main commercial attraction of these mountains in the 19th century: precious topaz, beryl (including aquamarine) and phenacite (for faceting) were produced here, as well as amazonite - beautiful perfect green microcline crystals - for collections. Amazonite pegmatites have simple plate-like bodies, but the inner structure of many is rather complex, with big cavities and perfect crystals inside. The mineral composition of this group of pegmatites is very diverse: in total there are more than 60 minerals. The most usual (besides rock-forming minerals) are topaz, beryl, phenacite, tourmaline, columbite, monazite and others. Alumo-fluorides are quite rare (cryolithionite, pachnolite, ralstonite, prosopite, cryolite, chiolite, gearksutite, thomsenolite), astrophyllite kupletskite and others.
Rock associations of the Ilmenogorsky complex
Rock associations of the Ilmenogorsky complex are numerous and feature up to 70 types of plutonic and metamorphic rocks. Alkoline rocks of the Ilmenogorsky complex are among the most recurrent. They possess a diverse mineral composition, forming numerous varieties. The forms of the geological bodies that they compose and the peculiarities of their relationships with the host rocks are also diverse. The biggest Ilmenogorsky massif of alkaline rocks is situated in the southern part of the Ilmensky ridge. It has a tear-shaped form with the dimensions 18x4,5 km stretching out in the submeridional direction. A series of relatively small and narrow alkaline rock bodies of the same type as the rocks of the Ilmenogorsky massif are submeridionally oriented to the north. The nepheline syenites, which produced a big group of alkaline rocks, were for the first time in the world science described in the beginning of the 19th century by I. Menge in the Ilmensky mountains and got the name of "ilmensky granite" due to the external similarity with granite which contains nepheline instead of quartz. Starting from the second half of the 19thcentury I.V.Mushketov set into use their present name "miaskite". The most wide spread types of alkaline rocks are biotite, biotite-amphibolite and amphibolite miaskites and syenites, miaskitic and syenitic migmatites, sandyites and fenites. The main rock-forming minerals are potassium-sodium feldspars (usually with perthite or antiperthite structure), nepheline (in miaskites), biotites and amphiboles. Among accessory minerals are titanites, zircon, apatite, les frequently pyrochlore and magnetite. The data of the last 5-7 years give grounds to relate the alkaline rocks of the complex with abyssal alkaline-ultrabasic magmatism. Associations of basic and ultra-basic rocks are mostly represented by small boudine like and lens-like bodies and less frequently by relatively big massifs (Nyashevsky, Bayksky and others), which are randomly placed in the blastomylonite matrix and concentrated in chains along the junction zones of the tectonic plates. The ultrabasic rocks are represented by meta- hyperbasites: serpentinites in big bodies, talc-carbonate, talc-antophillite, talc-tremolite- antophillite, olivine-enstatite, enstatite and other rocks, almost not containing the relicts of the primary minerals. The basic rocks are associated with meta-hyperbasites in tributary quantities, and are represented by gamet, zoisite, gamet- zoisite-corundum, cummingtonite and other amphibolites. Rarely do they display their primary magmatic structure (gabbro texture). According to the geochemical specificity these rocks are represented by Urazbaevskaya metabasite-peridotite association, which is formed by metasomatically transformed alkaline- ultrabasic rocks (from the ijolite-jacupirangitic series).
Associations of granitoids are spatially linked to the peripheral parts of the Ilmenogorsky complex, mostly to the eastern and southern ones. They formed between early Ordovician and Triassic periods. The main genetic groups are:
- basalt and alkaline-basalt magma derivatives (urazbaevsky, pustozerovsky, kundravinsky, uvildinsky complexes);
- ultrametamorphogenetic granitoids (chashkovsky complex);
- palingenetic crustal magma derivatives (sabanaysky complex).
In a number of complexes different types of migmatites have been identified (metasomatic, injection-metasomatic and injection types), reflexing the stages of their formation. All the granitoid associations go together with dyke complex. Metamorphic rocks are numerous and diverse. They compose a thick stratum, which can be split into 3 structural-substantial segments: selyankinsky block, ilmensky and saitovsky series.
They host plutonic rocks. The most recurrent are gneisses, amphibolites, schist, quartzites. The formation of the metamorphic rocks strata passed several stages over a long period of time: the most ancient are 2,2 bn years old, the youngest are 150 m years old. Metamorphism went on with brittle-ductile deformations, and its high level corresponds to the granulite and amphibolite factions.
The area around the Ilmensky mountains is one of the highest mountain ranges of the eastern foothill of the northern part of the Southern Urals. This mountain range runs meridian- wards up to lake Kundravinsky in the south, and in the north to the group of lakes: Silach, Irtyash, Kasli, Uvildy. The Southern part of the mountains situated between the lakes Kundravinsky and Ilmensky, is called the Chashkovsky mountains; to the north from them is the Ilmensky ridge and further to the north - the Vishnevy and Sysertsky mountains. The Chashkovsky and Ilmensky mountains are separated from the main chain of the Urals by the wide valley of the river Miass.
The Ilmensky mountains represent a system of ridges which go down from 754,1 m above the sea level in the South (mountain Ilmentau) to 364 m in the North. The central ridge runs 28 km from lake Ilmensky in the south to lake Ishkul in the north. The side western ridge 11 km long in the region of lake Ishkul is called the Ishkul ridge (mountain Ishkul, 661 m). In this region the Ilmensky ridge, crossed by rivers and springs, is scarcely pronounced. The average height of the ridge between lake Ishkul and lake Terenkul is about 400 m asl. In the northern part of the Ilmensky mountains between lake Terenkul and Argazinsky reservoir (14 km) there are 2 parallel ridges of low mountains.
The major part of the Ilmensky mountains belong to Lenin Ilmensky state Reserve, the Ural branch of Russian Academy of Sciences (the Reserve) with the area of 303,8 km2. The typical feature of the zonal-geographic position of the Reserve is its location in the transitional territory between the mountainous woodland of the Urals to the plain wooded steppe of the Zauralie and Western-Siberian lowland.
The climate is acutely continental with hot summer and cold winter. January with its average monthly temperature -20,8 C is the coldest month in the year, July with average monthly temperature +18,4 C is the warmest. Late frosts are quite common. The weather is unstable: dry and rainy summers can come in tums, as well as frosty winters with little snow and mild winters with much snow. The precipitation level fluctuates between 500-800mm per year, the maximum is reached in warm season. The depth of the snow cover reaches lm and can stay up to 195 days running. The frost-free period lasts 80-90 days, but morning frosts occur throughout the year.
There are more than 40 rivers on the territory of the Reserve, most of them flow from the Ilmensky ridge. The rivers are short, shallow, with steep falls in rocky shores and beds. In winter when the snow melts or after a strong rain the rivers tum into foamy streams. In summer they usually dry up, water remains only in the deepest holes, under the placers and in the strong springs feeding the rivers. The longest river is Bolshaya Cheremshanka (9,8 km). There are about 30 lakes on the territory which make part of the Kaslinsko-Kyshtymski lake system. There are 2 types of lakes: deep-water lakes with clear water in firm rocky shores, with scarce vegetation and little biomass stores (Bolshoy and Maly Kisegachi, Bolshoy Miassovo, Bolshoy Ishkul, Terenkul, Baraus, Savelkul, Karmakkul) and numerous shallow lakes with well-developed water and earth vegetation and big biomass reserves.
The territory of the Reserve makes part of the Vishnevogorsko-Ilmenogorsky geobotanical district of the pine-birch forest sub-zone. More than 82,3 % of the territory is covered with forests, 50 % are pine-woods, 44 % are birch woods, and the rest are deciduous aspen and alder forests. Pine dominates in the southern half of the Reserve, starting from the latitude at Selyankino-Miassovo and near lakes B. Ishkul, Karmakkul, Araktaban, Sharankul. On the rest of the forest territory birch prevails. Other species are mixed with these two or form there own massifs on small spots.
On the territory of the Reserve one can come across coniferous taiga forests and patches of herbal-poaceous steppes, northem sphagnous marshes and bushy steppes, light birch forests and shady riparian forests, tall-grass mountainous meadows, lowland ling marshes and stony placers with lichen stains.
The specific feature of the Reserve Bora is its mosaic character. There are no large areas of homogeneous forests; all of them feature numerous glades and meadows of different size.
The Reserve's flora counts about 927 vascular plants (50 relicts, 23 endemic species), about 140 moss species, 483 algae species and 566 mushroom species.
On the territory of the Reserve there are a number of species included into the Red Book of Russia: feather grass, downy-leaved feather grass, Zalessky feather grass, moccasin flower, ladies'-slipper, neottianthe cucullata, Baltic orchis, fen orchis, helmeted orchis, dark-winged orchis, Gelma sandwart, Krasheninnikov sandwart, Clare astragalus. Besides 35 plant species are included into the red Book of the Chelyabinkaya oblast.
The fauna of the vertebrate animals in the Reserve counts 19 fish, 5 amphibian, 5 reptile, 174 bird and 48 mammal species.
The territory is inhabited by elks, roe deer, boars, foxes, wolves, lynxes, badgers, common weasels, least weasels, forest ferrets, Siberian striped weasel, common marten, American mink. Squirrels, beavers, muskrats, hares, dibblers, moles, hedgehogs, voles are quite common, as well as chiropterans: pond bat, water bat, Brandt's bat, whiskered bat, northern bat, long-eared bat, parti-coloured bat, Nathusius' pipistrelle.
Bird species feature white-tailed eagles, honey hawks, boreal owls, gnome owls, hawk owls, tawny owls, common scoters, cuckoos, wookcocks, common grouses, wood grouses, hazel grouses, common partridges, shrikes, goldenmountain thrushes, black- throated loons and others.
Among the invertibrates the most diverse are the anthropoids (3389 species), rotifers - 166, Bat worms (1 25 species), ostraceans (24 species). In the Reserve there are insects included in the Red Book of Russia (Calosoma sycophanta, Rimn blue, Apollo butterfly, Bombus mastrucatus Gerstaecker and Bombus paradoxus); birds (eagle owls, peregrine falcons, ernes, lesser white-fronted geese). The regional Red Book counts 73 animal species.
Justification de la Valeur Universelle Exceptionnelle
In mineralogical sense the Ilmenogorsky complex is undoubtedly a unique geological object in the world. It is the mineral variety that gave the stimulus for the creation of the world's first mineralogical reserve here in 1920.
At present there are 277 mineral species (more than 360 including varieties) on the territory of the Reserve. Compare: 1109 mineral species are registered on the whole territory of the Urals, 120 of them were described in the Ilmensky mountains for the first time in the Urals. Besides 18 species, new for the global mineral taxonomy were discovered in the Ilmensky mountains: ilmenite (1827), aeschynite (1828), monazite (1829), cancrinite (1839), chevkinite (1840), chiolite (1846), samarskite (1847), ilmenorutile (1856), fergusonite-beta-(Ce) (1965), ushkovite (1983), svyazhinite (1984), makarochkinite (1986), fluororichterite (1993), fluor magnesiumarfedsonite (1998), potassic-sadanagaite (1999), polyakovite (2000), potassic- magnesiohastingsite (2005), ferriwinchite (2005).
The minerals of the basic systematic groups are widely represented in the Ilmenogorsky complex: feldspars, amphiboles, pyroxenes, mica, as well as minerals of rare, rare-earth and radioactive elements. In particular, it has been found out as a result of special research that the group of amphiboles which counts around 110 species in the world sistematics, is represented by 38 in the Ilmenogorsky complex (almost one third of all known amphiboles).
Déclarations d’authenticité et/ou d’intégrité
Lenin Ilmensky State Reserve of the Chelyabinsky scientific centre at the Ural branch of the Russian Academy of Sciences is the oldest research and development institution in this division and one of the first reserves in Russia. In 1935 by All-Russian Central Executive Commission and the USSR Council of Peoples' Commissioners regulation the Reserve was granted the status of a complex. The regulation says that "the former Ilmensky mineralogical Reserve...is to preserve and study the mineral riches, the flora and fauna of the Southern Urals". In 1936 a new regulation on the Ilmensky complex is issued which prescribes a more rigid regime. It bans all activity changing the natural conditions: mining and minerals collecting, lumbering, cutting and damaging trees and bushes, hunting, enticing animals and birds, nest ravaging, fishing, grass cutting, cattle pasturage, as well as damaging the flora by berry and mushroom gathering, staying on the Reserve territory with rifles, traps, snares, nets etc. Fires, littering and staying off the main routes without special approval of the administration are also banned.
By 2008 the staff of the Reserve counts 112 people. The scientific work is carried out by the 20 scientific employees of the biologic and geo-mineralogical departments of the museum (17 PhDs employees). The defence of the borders and the provision of the reserve regime is secured by 30 guards of the State Security division. The structure of the Reserve is made up of the scientific library, the archive, the developmental scientific basis for the student practice, information and publication centre. The Reserve museum of natural sciences (total area over 2000 sq m, 7 rooms) is the regional centre of ecological education, visited annually by more than 50000 people, including foreigners.
The territory is banned for visits, only some of the study routes for student practice are available in summer for the major higher institutions, such as Moscow State University, St Petersburg state University. But the Reserve can be visited virtually though an atomised information system "The Ilmensky reserve as a natural museum of geology and mineralogy", where one can find the description of the mines, the lists of the minerals and rocks, the bibliography of the Ilmenogorsky complex, take a video-excursion. The system is available through the web-site of the Reserve www.ilmeny.ac.ru.
Comparaison avec d’autres biens similaires
The geological composition and mineralogical diversity of the Ilmensky mountains is usually compared to such places as Vishnevy mountains (the Southem Urals), Sakharioksky massif (Kola Peninsula), Blue-Mountain (Canada, Ontario), ="esundfiord (Nonvay), Magnet- Cove (Arkansas, USA), Sri-Lanka, Madagascar.
A very peculiar type of complexes in geo-morphological and petrologic concern sets apart the Ilmenogorsky massif of alkaline rocks among other alkaline massifs in the world.
In the geo-morphological sense there are 5-10 types of alkaline massifs in the word (according to different authors): forces and laccoliths, intrusions of central type, circular, laminated etc. The Ilmenogorsky massif exemplifies the type "concordant bodies".
In the petrologic concern the world alkaline rocks form a class with over 80 varieties of intrusive rocks (and over 150 with effusive rocks) according to their chemical and mineral composition. The group of 20 main varieties is called "nepheline syenites". According to a number of structural features this group has a sub-group of "miaskitic nepheline syenites" (miaskite, laurdalite, litchfieldite etc) and a subgroup of "agpaite nepheline syenitesV(foyaite, lujaurite etc). There is a subgroup of transitional nepheline syenites (uvite, mariupolite, tinguaite etc.) between them. The alkaline rocks of the Ilmenogorsky massif exemplify the subgroup of "miaskite nepheline syenites", which are called nepheline syenites of the Ilmeny type in some publications.
Therefore, the Ilmenogorsky massif is typomorphic, and thus is includes in all the major geological guides and synoptic works in the world.