Центральный Сихотэ-Алинский разлом

В работе подробно описан Центральный Сихотэ-Алинский разлом - главная разрывная структура региона. Он геологически прослежен более чем на 700 км по простиранию на северо-восток (20-25 градусов) от берега моря до верховья р. Хор. Вероятно его продолжение и далее, где геологическая изученность территории хуже. Зона разлома хорошо выражена морфологически, к ней во многих местах приурочены долины рек, отличающиеся прямолинейностью н располагающиеся одна на простирании другой; на водоразделах и склонах наблюдаются небольшие уступы или впадины. Разлом характеризуется геологической контрастностью соприкасающихся по нему блоков, особенно отчетливой на юге. В строении Западного блока значительное участие принимают палеозойские, в том числе наиболее древние силур-девонские породы. Восточный блок в большей части сложен мезозойскими отложениями, на поверхности преимущественно представленными нижним мелом. Контрастность блоков объясняется не влиянием разлома на осадконакопление и не вертикальными перемещениями, а большим левосторонним горизонтальным смещением, в результате которого контактирующими между собой оказались разновременные или разнофациальные формации. Возникновение разлома, по-видимому, связано еще с раннемезозойскими деформациями, но главные смещения произошли в позднем мелу. Левый сдвиг доказывается анализом структур. Амплитуда определена предположительно по косвенным признакам, но с учетом деталей геологического строения, главным образом по смещению фациальных зон нижнемеловых отложений и рассеченных разломом частей позднемеловых гранитоидных массивов. В первом случае она равна 150-200 км, во втором - 60-100 км. Металлогеническое значение разлома заключается в том, что связанными с ним движениями были подготовлены рудопроводящие и рудоконтролирующие структуры, осуществлена связь с глубокими частями земной коры, вызвано гранитоидное магмообразование, которым в значительной степени обусловлены извлечение, захват, концентрация и вынос металлов. Окончательное формирование месторождений, однако, во многих случаях зависело от более молодых деформаций, магматической и гидротермальной деятельности, с которыми связаны и самостоятельные месторождения. Центральный Сихотэ-Алинский разлом является одним из основных и вполне закономерным элементом зоны контакта континентальных и океанического блоков литосферы, структура которой создана субмеридиональным горизонтальным сжатием и относительным движением океанического блока к северу. = Ответственный редактор издания Н.И. Лаврик.

The Central Sikhote-Alin fault (CF) trending through the Sikhote-Alin folded region, and has been traced geologically striking north 20-25 degree at east for at least 700 km; it extends far northeastward probably to the edge of the continent,
The relief of CF zone is typical - the river valleys confined to it with unusual straight-linear directions. On the divides or slopes the fault is marked by slight ledges or hollows. The altitude main line of CF varies from 0 to 705 m. The nearest summits are higher than hundred meters but somewhere a thousand meters above the CF trench and more. There are menv places with the sharp differences in the relief to the east and west from the CF. Oil both sides of the CF there are relatively high-mountain sectors, but the difference in altitudes does not indicate the difference of vertical movements. Complicated tectonics of the CF zone is expressed in (he fanciful relief. The latter arises in the places of development of the numerous feather faults hounding the blocks of the different rocks.
The CF sprang up in the Jurassic or Early Cretaceous. The first volcanic rocks distinctly related with the CF are established in the north of Maritime Province. These rocks are referred to Lower Cretaceous. Also on the north the earlier fault-side coarse-fragmental formations were found. They are represented by Valanginian large pebble and bolder conglomerate with Aucetla. In other areas of the CF zone only Upper Cretaceous volcanic and-faultside sedimentary deposits are known. The Senonian-to-and-Paleocene volcanic and tuffaceous rocks were disturbed with the CF, but their upper layers were not everywhere touched by considerable displacements. The Eocene-Oligocene continental deposits show no evidence of lateral movements, that is evident in the Yanmutliousa depression.
The CF is a narrow zone and includes many simple and complex high-angled, gentle, straight, curved, branched fault planes, among which can always be distinguished a principal one that is strictly straight and linear within its entire length. This principal plane is approximately vertical and just divides two different blocks.
Very large displacement of the blocks along the CF is doubtless. In the southern part it is demonstrated by the contrast of their construction. On the west side of the CF at interval 40 km there is the Silurian-Devonian terrain (which is the earliest For Sikhote-Alin), but on the east side there ure mainly the Mesozoic sedimentary deposits. Northwardly the CF cuts one of the largest and best studied structures - the Sandagou-Okrainsky Mesozoic sinclinorium. The CF clearly cuts the boundaries of the distribution of the facieses of the Cretaceous marine sediments.
Left lateral movement along the CF is proved with its specific influence upon the adjoined structures which are formed a regular arched bends of the fold axes and the unsymmetrical and overturned folds. There are direct observations over the outcrops of the main fault plane and numerous subparallel planes. These observations also indicate the above mentioned displacement by the typical slickensides with the striations and grooves oriented nearly horizontally or under low angle in (he most cases.
The amplitude of displacement may be determined only provisory by indirect evidences. The disposition of the facial boundaries of the Cretaceous terrain is the main evidence, showing that this displacement is equal 150-200 km. The exact value of displacement cannot be established because the facial boundaries approach the CF at acute angles. The granitoid masses are cut and shifted in many cases. Looking at the geological maps attentively one can see a certain regularity in their quantity of the displacement. To the north of the Meridional fault (that joins the CF in the west at a small angle) granitoid masses are shifted for 60 km approximately, by the Meridional fault - 40 km, and by the CF to the south of the Meridional fault these values are summed and total displacement along CF is equals 100 km. There is some reason to suppose that first the East block had been moved mostly to the north, and then the West block was moved along the Meridional fault and southern part of the CF.
The theoretical premises and geological and geophysical data at the present time permit us to build a model with relatively larger thickening of the crust within the frontal parts of moving blocks, where pressure, folding and thrusting were intensive. It is here the most advantageous conditions for the origin of some magma chambers were formed. Such a model is agrees with new data about crustal thickness. The whole model seems necessary to be oriented not horizontally but under low angle northward.
The importance of the CF for metallogeny is the following: the first - the movements connected with CF, to some extent, have prepared the ore-bearing and ore-controlling structures; the second - communication with deep levels of the crust and perhaps with the upper mantle was reached; the third - the origin of the granitoid magma (with all consequences) was provoked. The magma to a great extent promoted the metals to be extracted, seized, concentrated and carried out to the high level of the crust. The scale of these processes can be appreciated by the capacity of granitoid masses with metallic elements more than dark, and by the size of the deposits, which were formed under favorable conditions. Final formation of the deposits, however, in many cases was dependent upon the younger deformations, magmatic and hydrothermal activity. The latter caused the formation of the independent deposits as well. There is a clear zonality in the distribution of mineral deposits which shows the regular changes in deposits composition and their genetic types from the CF to the edge of the continent. This regularity depends upon the following cardinal factors: the distance from CF and its granitoids, the thickness of the crust, the lithology of rocks, the originality of the tectonic structures, the young magmatism, the depth of erosion.
The Asiatic and American sides of the north half of the Pacific are the glassy reflection, although distinguished with some typical features. There are very long stretched and large amplitude wrench faults on both sides. It is known, that faults with north-east trends and left-lateral displacement are typical for the Asiatic side, on the contrary, the faults with north-west trends and right lateral displacement arc characteristic for the American side. The folded structures are intersected with the faults at acute angle, but also the greatest part of them trending north-east on the Asiatic, and north-west on the American sides.
The wrench faults are easily formed on the fringe of the continents, because the sialic sheet within the ocean is absent and the continental crust blocks may move to this direction. It is here the largest and well proved wrench faults are known. Inland, due to the wrench faulting, there is no free place for spreading of the crust athwart direction and the blocks must move upward or thrust over one another. The structural features of the wrench fault zones are also different. For example, the CF is rather more similar to the wrench faults of the west continental margin of North America, than with the inner continental wrench faults.
The shifts on the Asiatic and American borderlands give evidence of the general relative movement of the oceanic block to the north. The displacement along the faults continued in the same direction during a long time-since Mesozoic, somewhere since Paleozoic, till Cenozoic, and for (he certain faults to the present.
The regular trend of the faults on the Asiatic and American continental margins and direction of the movements along them, give us the opportunity to suppose, that they were formed by the forces arising from submeridional horizontal pressure. Left lateral displacement along the north-east faults and right-lateral one on the north-west faults is possible only at that orientation of pressure. Some divergences (rom that regular trend of the faults are distinguish for faults investigated on the islands, but (his phenomenon may be explained by the displacement and curve of the island arcs.
In the first stages of deformation due to the meridional maximum tan-gential stress and relative movements of the oceanic block (or its peripheral parts) to the north, on the continental margins the folded structures have been formed according to deformation of a simple shear or its combination with pure shear (an echelon systems, a drag folds etc.). Perhaps at the same time significant deforming forces have acted from the Ocean towards the continent. After the compression and the consolidation had lean achieved to a certain degree, the system of regular shear planes with large lateral displacement arose. The CF is one of the principal members of that system. The folded structures then continued their development and were formed again according to the type of drag folds, oriented at acute angle to the faults.
For explanation of the origin of all borderland structures in the north part of the Pacific block of lithosphere, in addition to the main cause - the submeridional horizontal pressure, it is perhaps necessary to take into account the convection, gravitational-convection current of the upper mantle, the ocean floor spreading or the continental drift. But the latter contradicts to the large wrench faults, which are straight-linear (in the great part), regularly oriented and long-lived. Therefore, providing the continents moved, they did not transfer over those faults, did not bend them, we must speak about displacement of the blocks of lithosphere, probably at the level of asthenospheric layers, along great fault zones, but not about continental drift.

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Это первое монографическое описание Центрального Сихотэ-Алинского разлома (левого сдвига) и сопряженных с ним деформаций. Уникальная по своему уровню работа, предвосхитившая на десятилетия многие последующие результаты как по сдвиговой тектонике Приморья и Сихотэ-Алиня в частности, так и всей Азиатско-Тихоокеанской зоны перехода в целом. Ее полноценными аналогами по охвату фактического материала и теоретических наработок в англоязычной литературе являются только обобщающие работы регионального уровня по разлому (правому сдвигу) Сан-Андреас.

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