Ecology/6. Ecologic monitoring

D.V. Ulrich, Cand.Sc. (Engineering); G.O. Zhbankov, postgraduate student; S.E. Denisov, Dr.Sc. (Engineering)

South Ural State University, Russia

Stratigraphy and petrography of Karabash syncline.

The characterized region is composed of volcanic sedimentary rocks of the lower and middle Paleozoic era metamorphosed in terms of the greenschist facies and breached by the linear intrusions. To the west and east along regional tectonic dislocation greenstone bodies come into contact with highly metamorphosed rock units of Uraltauskiy and Ilmenskiy solid masses correspondingly. The above mentioned units are partially eluviated and overlapped by thin sedimentary cover of blanket quaternary deposits of various genesis and composition.

Upper volcanic sedimentary formation (S₁ ln-w): deposits with the name of upper volcanic sedimentary formation crop out to the day in the central part of Karabash syncline, the region where they build up western roots of Sidorkiniy mountains, western slopes of Berezovskiy and Konniy ridges; and can be visible along eastern slopes of Lysaya, Zolotaya and Karabash mountains to the south beyond the characterized area.

There is no a complete uninterrupted section of formation within this area.

The composition of the characterized formation consist of three steeply pitching to the east benches (65º - 80º), they are lower volcanogenic (traprocks, porphyrite and calc sinters with interbedded tuff sandstone); middle sandstone (tufaceous sandstones of mafic composition with siliceous tuffites interbedded at the base, rarely of a mixed composition with quartzite shale rocks interbedded at the top); and upper schist ones (phyllitic clayed, topsoil and quartzite schists).

There are mutual transitions between these benches. Visible thickness of formation is 800-1000 meters.

Sedimentary volcanogenic formation (S₂ld-D₁c): It is composed with deposits united in the stratum and developed within Miassko-Sugomakskiy and Saimonovo-Sharabrinskiy blocks.

In terms of lithological composition the formation can be divided into two sub-formations, they are the lower (sedimentary) and the upper (volcanogenic) ones.

Lower (sedimentary) sub-formation represents conformable clayed, sandy clayed and quartzite schists and tufaceous and shaly sandstones. We can observe relatively thin interbedded small-grained crystalline limestone (10-15 m) and rarely pyroxene porphyrites. The thickness of a sub-formation is 300-350 m.

Upper (volcanogenic) sub-formation is much more popular and represents pyroxene, plagioclase and pyroxene, basaltic, andesite-basaltic porphyrites and their sinters. In a sub-formation thin interbedded tufaceous sandstones are developed.

Middle volcanogenic formation (D₁c-D₂e): the formation is composed of a great number of rocks. It has the following stones metamorphosed to a variable degree: they are traprocks, diabase porphyrites, and their sinters and tufaceous sandstones. There are heavy lenses of marmorized limestones (up to 250 m) in separate blocks of the formation. The thickness of formation is unfixed and is increasing from north to south.

Upper volcanogenic formation (D₂е-gv): the composition of rocks built up the formation is of a variable and unbalanced character: there are felsic and mafic porphyrites and sinters, alteration of clay shale, carbon siliceous, quartz sericite and other schists; tufaceous sandstones; rarely banded iron formations. In the area of Karabash town in the lower part of the section at volcanogenic formation bedding there are siliceous, carbon and siliceous, clay shale rocks and tuffites. In the middle part of the formation a heavy unit of marmoized limestones (up to 300 m) is logged.

Intrusive rocks: intrusive rocks are expanding in the characterized region. They present a wide range of ultramafic, mafic and felsic rocks. Intrusive rocks of the region are dated to lower Middle Devonian and Middle Upper Devonian Cycles.

Lower-Middle-Upper Devonian Cycle: corniferous apopyroxenite rocks and grey gabbro amphibolites dismanteled in the valley of the Olkhovka River, to the north-west of the region in the Ufaleiskiy metamorphic aureole with greenstone units of Tagilo-Magnitogork mountain trench belong to the cycle. From west along the tectonic deformation they come into contact with sedimentary rocks of the Curtin suite composed by garnet mica schists. Residuals of the schists can be seen in the eastern aureole of pyroxenites with later gabbro intrusions (D_2-3) as well as inside the intrusions. From south gabbro pyroxenites intrusion is outlined by gabbro serpentinites of Middle Upper Devonian era which is the northern end of the Talovskie mountains group.

Gabbro amphibolites are massive medium granular and slightly interstratified rocks of a dark or dark grey color. There can be banded varieties, deformed into minor folds and presented by interdigitation of dark bands consisting of protobase with interbeds enriched by plagioclase.

Middle Upper Devonian Intrusive Cycle: basic number of solid masses within described region composed of serpentinites and intrusions which are difficult to differentiate from pyroxenites to plagiogranites belongs to this cycle.

Intrusions of the cycle transect the whole unit of greenstone rocks, which are dated to from the Upper Ordovician period till the Givetian age of Middle Devonian.

In the formation of intrusions we may identify two stages that seem to be divided by a small period of time.

Serpentine belts confined to the zones of deep-seated faults belong to the first intrusive stage. In the described region from north-east to south-west Sidorkinskaya branch of Sidorkinsko-Karabash serpentine belt, which is in its turn divided into two chains: western and eastern ones, is traced.

The exposure of serpentinites is not the same. They usually give rocky outcrop and heavy block rocky debris on the top of the mountains and hills. Bed-rock outcrops occur less frequently in the upper parts of the slopes and mountain roots where there are usually heavy deluvial block masses of serpentinites of brown sandy loams and sit loams.

Steady serpentinites are green grey or blue grey, have scaly, micrograting, acicular, sheaf-like and radial fibrous structure. The texture is cryptocrystalline, massive, sheeted or brecciated. The processes of talc formation and carbonization considerably confined to the west endomorphosed part of the units are highly developed in serpentinites.

In the south-western part of the described region there is East-Barninskiy serpentine belt. Serpentinite building up this belt can be traced in north-north-eastern direction from the southern end of Karabash town to the Olkhovka River, building up Bogorodskaya, Zavodskie and Krestovaya mountains. Maximum belt width is marked in the southern region of Bogorodskaya mountain (up to 600 m). The belt is built up with antigorytos difference of serpentinites carbonated and talcose of various degrees.

Apart from characterized belts separate tiny bodies of serpentinites metamorphosed in various degrees are recorded.

The complex of rocks of mafic and alkali structure intruded by the intrusions of the first stage belongs to the second stage of Middle Upper Devonian intrusion cycle. In most cases they are restricted to the western junctions of serpentine belts. Massive intrusive bodies of gabbro and diorites are marked in the south-western part of the region.

Hydrothermal metasomatic rocks: numerous manifestations of intrusive and accompanying it hydrothermal activity have determined development of metasomatic and hydrothermal rocks of a complex structure, among which ore-bearing shale rocks are mainly developed.

Ore-bearing schists (hsz-gh): Hydrothermal metasomatic units which accompany the process of sulphide salinity belong to this group. They are basically distributed in deposits of upper volcanogenic formation of Soimanovsko-Sharabrinskiy block (D₂e-gv) building up north-north-eastern extension zone traced from the south boarder up to Sharabrin stream. This zone consists of echelon folding with the range of a few to tens meters. In its majority these rocks are rudaceous and middle fragmentary calc-sinters of a dacitic, andesite-dacitic structure and plagiogranites. Schist formations of tufaceous sandstones of a mixed and mafic structure are less frequent as well as the formations of traprocks and other mafic volcanogenic rocks.

In the expansion of described schists we can observe the following regularity. Central parts of schistic zones are formed by quartzite serictic or quartzite chlorite seritic schists and marginal parts are formed by quartzite chlorite schists.

Paleozoic deposits are considerably topped off by sedentary deposits and deposits of Quaternary period. In terms of genesis they can be divided into alluvial, colluvial, eluvial, diluvial and technogenic mineral formations.

Alluvial deposits (aQ): Alluvial deposits expanding along the valley of the Miass River and the lower course of the Sak-Elga River are composed by sandy-pebbled material. The expansion of pebble material is incoherent. Fragmentary material is basically quartzite one. In the mass of terrigenous material interbed of grey clay, clay loam and fine sandy loam can be observed. Thin decayed peat bog (up to 40 cm) of a woody-fen type can be traced in microdepression. The width of alluvium is from 3.2 m up to 17.7 m.

Colluvial and proluvial deposits (proQ): On the steep slope of side-hills we can see loosened rocks and debris which are of a colluvial deposit origin. Lithological peculiarities of colluvium are entirely determined by the structure of enduring Paleozoic rocks. Colluvium is introduced by block masses, breakstones as well as clay with breakstones.

Colluvial deposits are closely connected with proluvial deposits forming cones and alluvial piedmont plains on the mountain slopes. They are characterized by flattened blocks of Paleozoic rocks concrete-bound by silt loams and fine sandy loams. The width of deposits is in direct relation with land forms and is not balanced.

Eluvial deposits (eMz): Eluvial deposits cover smooth hillsides and flat tops. The width of covering is different: it can be up to 1-3 m. Eluvium is usually represented by block masses, breakstone, rotted rocks and sand-clay aggregates. At ultrabasites the width of eluvium is insignificant which is not more than 0.5; eluvium is formed by serpentinite chips which are partially silicified and carbonated and enclosed in brown clay mixture. Eluvium of carbon silicious schists is of 3 m and represented by brown, yellow and green clay with chlorite lamels and quartzite rubbles.

Deluvial deposits (dQ): Deluvial deposits are the products of eluvium sheet flood down the slope and are characterized by some assortment of the material. They are represented by brown, greyish brown, brownish grey clay loams, clay with breakstones of bedding rocks and scree quartz debris. The width of deposits is from 0.1 up to 12 m.