Some Deep-Seated Features Of Platform Provinces Of The Soviet Union

Geophysical and deep-drilling data disclose the block nature of the faulting in both folded and platform provinces of the crust. System and morphology of deep-seated structures embraces two types of major elements: large angular crustal blocks bordered by intense crush zones on one or more sides,and narrow elongated graben rifts. On platforms, the sedimentary cover conceals the true identity of the deep-seated structures which reveal themselves as gentle flexures but seldom by thickening or thinning of the beds as a whole. Deep rifts of the Russian platforms (Russian, Scythian-Turanian, West Siberian, and East Siberian) are interpreted as parts of a planetary system of rifts. Associated with these major features are sub-systems of more localized faults and fold belts. The deep Russian rifts and structures of the platforms are analyzed by depth to basement measurements which collectively show the enormous amount of absolute crustal subsidence even on relatively elevated platforms. Combinations of platform and geosynclinal tectonic provinces are discussed with some interesting variations on the general pattern of geosynclinal evolution. - -B. N. Cooper.     

GEOLOGY OF THE ANGARA REGION

Industrial development of the Angara region has necessitated geological exploration for available resources. The Angara River flows north from Lake Baikal, intersecting the mountains surrounding it; passes through the 'Irkutsk Amphitheater, ' part of the central Siberian platform; and, near Bratsk, flows across a diabase intrusion, forming the Bratsk rapids (approximately 300 kilometers long). The Angara river basin is underlain by crystalline basement (the Siberian craton) composed of schists, gneisses, marble, and Archean and Proterozoic granites. These rocks dip sharply from the Sayan and Baikal ranges, where they outcrop, toward the Irkutsk Amphitheater, where they reach 3000 meters depth. The craton is covered by sediments ranging in age from Cambrian to Quaternary. Lower Cambrian rocks over 2500 meters thick are overlain by Middle Cambrian strata which are generally eroded. In the Irkutsk coal basin, north of Lake Baikal, Mesozoic rocks 600 meters thick are covered unconformably by Tertiary sediments. Quaternary deposits are known to occur; the Angara River terraces are probably pre-Quaternary. Regional tectonics involved fracturing within the Irkutsk Amphitheature and in the surrounding mountains. Geophysical survey and drilling revealed a wide horizontal protrusion (the 'Angara swell') in the Siberian craton; this protrusion divides the Irkutsk Amphitheater in the Pre-Baikal and Pre-Sayan depressions. Overlying Cambrian sediments are folded in conformity with these basement-complex dislocations. Jurassic deposits, generally horizontal, are disturbed only near the younger uplifts of Sayan and Baikal. The southwestern part of a large trap-rock intrusion crosses the Irkutsk Amphitheater; concordant intrusions, e. g. sills, entered lower Paleozoic sediments along with dikes, during late Permian and, principally, Triassic times. Mineral deposits are rich and varied: Precambrian rocks contain magnetic iron ore (of the Krivoy Rog type); talc; magnesite; pure crystalline limestone; and, possibly, phosphates. Paleozoic rocks contain large marine and lacustrine salt deposits, gypsum, phosphatized shell rock, and, possibly, oil: as well as carbonaceous rocks with lead and zinc minerals. Hydrogen-sulfide -saturated and saline mineral waters as well as subsurface water with high potassium content occur in Cambrian rocks. Siberian trap rocks are rich in magnesium and iron; magnesium-magnetite ores occur in volcanic necks as large veins of pure ore, associated with tuffs and aureoles. Trap rock (diabase) may be used in the new stone-melting industry. Jurassic deposits include saprolitic-bog and humus coals as well as extensive fire-clay and high-quality kaolin deposits. Cambrian fossils include trilobite and brachiopod remains, reefs, and molluscs; fish, insects, ostracods, and numerous fossil plant traces, are representative of the Mesozoic. The Angara River terraces, 25 to 30 meters thick, contain mammal remains, brackish-water molluscs, and, from the Middle Paleolithic, Azilian and Solutrean artifacts. -- D. D. Fisher     

Tectonic evolution of the Siberian paleocontinent from the Neoproterozoic to the Late Mesozoic: paleomagnetic record and reconstructions

In this paper we present the results of a generalization of paleomagnetic data for the territory of the Siberian craton and its folded framing that were obtained during the last fifteen years. We propose a new version of the apparent polar wander path for the Siberian continental plate, including the interval from the Mesoproterozoic–Neoproterozoic boundary up to the end of the Mesozoic. The constructed path forms the basis for new concepts on the tectonics of the Siberian paleocontinent and the paleooceans that surrounded it. We present a series of paleotectonic reconstructions based on paleomagnetic data, which not only displays the paleogeographic position of the Siberian continent, but also reveals the features of the tectonic evolution of its margins during the last billion years. In particular it has been established that large-scale strike-slip motions played an important role in the tectonic regime of the continental plate at all stages of its development.     

The Baikal system of rift valleys

The Baikal system of rift valleys has no evident structural connections with the World Rift System. The peculiar features of its structure, morphology and volcanicity reflect this isolation. The spatial position and major structural features of the system are determined where the central segment (the South Baikal depression) is confined to the junction of two major lithospheric plates, the Precambrian Siberian platform and the heterogenous folded framework of Sayan—Baikal. The contrasting structures and thermodynamic conditions of these two plates, and the deep nature of the suture zone developed between them, have been responsible for the location of crustal extension and proto-rift formation within the Baikal depression proper, first initiated not later than Eocene and then propagating to zones both west and northeastwards.     

关于古亚洲洋构造演化研究的几点思考

古亚洲洋不是西伯利亚陆台和华北地台间的一个简单洋盆,而是在不同时间、不同地区打开和封闭的多个大小不一的洋盆复杂活动(包括远距离运移)的综合体.其北部洋盆起始于新元古代末-寒武纪初(573~522Ma)冈瓦纳古陆裂解形成的寒武纪洋盆.寒武纪末-奥陶纪初(510~480Ma),冈瓦纳古陆裂解的碎块、寒武纪洋壳碎块和陆缘过渡壳碎块相互碰撞、联合形成原中亚-蒙古古陆.奥陶纪时,原中亚-蒙古古陆南边形成活动陆缘,志留纪形成稳定大陆.泥盆纪初原中亚-蒙古古陆裂解,裂解的碎块在新形成的泥盆纪洋内沿左旋断裂向北运动,于晚泥盆世末到达西伯利亚陆台南缘,重新联合形成现在的中亚-蒙古古陆.晚古生代时,在现在的中亚-蒙古古陆内发生晚石炭世(318~316Ma)和早二叠世(295~285Ma)裂谷岩浆活动,形成双峰式火山岩和碱性花岗岩类.蒙古-鄂霍次克带是西伯利亚古陆和中亚-蒙古古陆之间的泥盆纪洋盆,向东与古太平洋连通,洋盆发展到中晚侏罗世,与古太平洋同时结束,其洋壳移动到西伯利亚陆台边缘受阻而向陆台下俯冲,在陆台南缘形成广泛的陆缘岩浆岩带,从中泥盆世到晚侏罗世都非常活跃.古亚洲洋的南部洋盆始于晚寒武世.此时,华北古陆从冈瓦纳古陆裂解出来,在其北缘形成晚寒武世-早奥陶世的被动陆缘和中奥陶世-早志留世的沟弧盆系.志留纪腕足类生物群的分布表明,华北地台北缘洋盆与塔里木地台北缘、以及川西、云南、东澳大利亚有联系,而与上述的古亚洲洋北部洋盆没有关连,两洋盆之间有松嫩-图兰地块间隔.晚志留世-早泥盆世,华北地台北部发生弧-陆碰撞运动,泥盆纪时,在松嫩地块南缘形成陆缘火山岩带,晚二叠世-早三叠世华北地台与松嫩地块碰撞,至此古亚洲洋盆封闭.古亚洲洋的南、北洋盆最后的褶皱构造,以及与塔里木地台之间发生的直接关系,很可能是后期的构造运动所造成的.     

Geochemical,Isotopic, and SHRIMP Age Data for Precambrian Basement Rocks,Permian Volcanic Rocks,and Sedimentary Host Rocks to the Ore-bearing Intrusions,Noril'sk-Talnakh District,Siberian Russia

Petrographic, geochemical, and isotopic data have been obtained for 33 samples selected to provide constraints on contamination models for the volcanic and intrusive components of the Late Permian to Early Triassic, Siberian flood-volcanic province. Twenty-one of these samples were carried from great depth in an explosive diatreme of Triassic age, whereas 12 were collected from drill core from depths of tens to 2000 m. The studied diatreme xenoliths are: (1) fragments of the crystalline basement; and (2) fragments of a basaltic-to-rhyolitic volcanic suite.

Prompted by an unexpected, Late Paleozoic, Rb-Sr isochron age for this compositionally diverse volcanic suite, a SHRIMP U-Pb zircon age of ～270 Ma was obtained for a rhyodacite xenolith. Previously, a SHRIMP zircon U-Pb age of ～910 Ma had been determined for a leucogranite xenolith from the crystalline basement; this sample also contains substantial amounts of inherited, Early Proterozoic and Archean zircon.

The presence of this volcanic suite, only ～20 m.y. older than the 251 Ma, flood-volcanic sequence, is an extremely provocative result, inasmuch as hundreds of exploration drill holes in the Noril'sk area, and throughout the Siberian platform, have encountered only Tungusskaya Series coal-bearing sedimentary rocks in this stratigraphic/time interval. These data support arguments that subduction/underthrusting from the West Siberian Lowland under the northwest margin of the Siberian craton took place in Late Permian time.

The isotopic data obtained for the xenolith suite indicate that the upper part of the crystalline basement under the northwest margin of the Siberian craton is composed of Late Proterozoic (Riphean) rocks-alkaline granites, trondhjemites, crystalline schists, gneisses, and amphibolites-with much in common with rocks of the Central zone of the Taymyr folded area, which has been interpreted as an accretionary block formed and joined to Siberia in Late Riphean to Vendian time.

Measured isotopic characteristics for the Precambrian crystalline basement, and the Paleozoic sedimentary rocks that host the ore-bearing intrusions in the Noril'sk region, provide parameters for quantitative modeling of crustal contamination during evolution of the Siberian flood-volcanic rocks and related intrusions, both while en route to the surface and at the site of intrusion emplacement.     

华北地台北侧的古板块构造演化

在华北地台北侧原兴蒙华力西褶皱带内相继确立了加里东褶皱带和中晚元古代褶皱带,并划分了早、晚华力西褶皱带,探讨了定位于中亚—蒙古古大洋中的微大陆。本文概述了华北地台北侧古板块构造格局、各板块构造单元的地质构造特征以及华北地台北侧元古代—古生代岩石圈的形成与演化。     

Aspects of tectonics of Kamchatka

The tectonics of Kamchatka are reviewed in some detail and in several cases reinterpreted in light of recent geological and geophysical studies. Maps present major structural features and magnetic data, obtained by aerial survey. Recent work has confirmed four young phases of tectogenesis, accompanied by intrusions: 1) Late Cretaceous to early Paleogene (Laramian or Kamchatka phase), 2) early Miocene (Kuril phase), 3) late Miocene (Aleutian phase), and 4) late Pliocene (Sakhalin phase). These account for the young folded region that covers most of the Kamchatka Peninsula and the Koryak uplands to the northeast. Three structural-stratigraphic zones are recognized. The west zone is a marginal trough filled with coal- and oil-bearing strata, moderately folded. The central zone is an inner volcanic arc made up of volcanic rocks cut by granitoid rocks. The east zone consists of thick flysch with basic and ultrabasic igneous rocks characteristic of external folded arcs. In general, major synclinoria and anticlinoria have northeast strikes, and magnetic values in general correlate with the strike and composition of these belts. The meridionally oriented Central Massif of ancient rocks controlled the development of structures in nearby Tertiary and Cretaceous rocks. Deep faults also trend northeast and determined the position of volcanic and metallogenic zones, the ophiolite belts, and the chain of intrusive massifs. Geophysical work shows that the northern part of the Sea of Okhotsk is of platform type; it has recently been postulated that the Okhotsk massif is part of the Siberian platform.—W.D. Lowry     

BASIC FEATURES OF THE GEOLOGY OF THE SIBERIAN DIAMOND PROVINCE

The discovery of ultrabasic rocks and of diamonds in Upper Triassic-Lower Jurassic kimberlite pipes in the Siberian platform gave impetus to the search for diamond deposits in this area. Also, the discovery of diamond placers in Mesozoic and Cenozoic marine and nonmarine sediments in 1948 intensified the search. The geology of the area is characterized, as is that of the African diamond fields, by considerable faulting and heterogeneous composition of the basement, the development of large depressions, and a magmatic cycle dominated by basic and ultrabasic magmas. Many unexplored areas within the platform, undoubtedly having similar characteristics, are potential diamond producers. --G. E. Denegar.     

内蒙古阿拉善地块北缘的构造单元划分及各单元的基本特征

阿拉善地块北缘是一个多构造单元的结合部,可以划分出以下4个一级构造单元:①不成熟岛弧性质的雅干构造带;②早古生代被动大陆边缘,到晚古生代转化为活动大陆边缘的珠斯楞-杭乌拉构造带;③成熟岛弧性质的沙拉扎构造带;④元古代造山带,在古生代演化成拉张型过渡壳的诺尔公-狼山构造带。上述各构造单元在沉积建造、岩浆岩组合、变质作用以及地球化学特征等方面都有明显的差异,单元之间以断裂作为界线。     

ON THE BITUMINOSITY OF MESOZOIC SEDIMENTS IN THE TRANSBAIKAL REGION

Siberian prognostic reserves of oil and gas are now believed to constitute 40% and 25%, respectively, of U.S.S.R. totals. In the West-Siberian geosyneclise, thickness of hydrocarbon-bearing horizons increases toward the center, in the same direction as bituminosity and content of dispersed organic substance in marine Jurassic and Cretaceous sediments. Multi-layered oil pools are typical of the center; gas and oil pools occur on the periphery of the syneclise. In the Siberian platform, economic accumulations of oil and gas are found in sediments ranging in age from Riphean through Cretaceous. Lower Cambrian and the Underlying Riphean horizons are particularly promising. The Kolyma platfornnal massif, where first indications of oil were discovered in the Permian horizons, remains to be prospected. The close association of gas-petroliferous horizons with perfectly definite facies-zones and the rigorously sustained stratigraphic positions of the latter, as well as demonstrable associations of the hydrocarbon accumulations with their source rocks, leave no doubts as to the organic origins of the Siberian oils.--V. P. Sokoloff.     

EVOLUTION OF THE TAYMYR GEOSYNCLINE

The study of Taymyr has been difficult because of the poor accessibility of the region. Eight geotectonic zones have been identified. Six of these, from lower Proterozoic to Upper Paleozoic mark a geosynclinal development; the seventh, Triassic, is a post-inversion transition to the eighth, a Mesozoic-Cenozoic stage of young platform development. The geosynclinal cycle in Severnaya Zemlya was shorter than in Taymyr, with the inversion occurring at the close of the Silurian and the platform conditions initiated with the Devonian. The Taymyr geosyncline migrated southeast, advancing over the sinking margin of the Siberian platform, a distance of about 200 km, between early Proterozoic and the close of the Paleozoic. The post-geosynclinal structural stage is represented by Jurassic to Quaternary deposits, in the Taymyr low and in minor troughs. A Lower Cretaceous coal basin is present in Taymyr. Oil shows are associated with salt domes in the Khatanga and Ust-Yenisey troughs. A series of sulfide ore deposits are associated with traprocks in the Byrranga range. Hydrothermal ores are associated with minor subalkalic intrusions. --Scripta Technica, Inc.     

板块构造学说的过去和现在以及我国地质学家做出的贡献

<正> 科学领域中的任何一门学科在其发展的历史中,往往存在着以具有重大突破为标志的迅速发展阶段。板块构造学说就是现代地球科学取得最新进展的代表。所以,有人将其称为地球科学的一场革命。板块构造理论创建于六十年代后期,但与其有关的一些思想、概念则源远流长。     

Development of main structures of the siberian platform: history and dynamics

The location of the regions with maximum subsidence within the Siberian platform and the age volumes of the structural stages have been determined in relation to the location and periods of development of the adjacent geosynclines. The western and eastern parts of the platform differ in the character of the structures and magmatism, in the volume and age of the structural stages, as well as in the asynchronism of the main tectonic stages, which is connected with the boundary location of the platform between the Atlantic and Pacific Ocean segments of the earth's crust. The Siberian platform sharply differs from other ancient platforms of the northern hemisphere by the intensity of magmatism and style of tectonic deformation in the Meso-Cenozoic, and it is similar in this respect to the southern ancient platforms. The subcrustal processes in the adjacent geosynclines have played a leading role in the development of the platform structure; but the release of the stresses during the epochs of the magmatism and rift formation took place directly on the platform itself.     

Fragments of oceanic islands in accretion–collision areas of Gorny Altai and Salair, southern Siberia, Russia: early stages of continental crustal growth of the Siberian continent in Vendian–Early Cambrian time

The Altai-Salair area in southern Siberia is a Caledonian folded area containing fragments of Vendian–Early Cambrian island arcs. In the Vendian–Early Cambrian, an extended system of island arcs existed near the Paleo-Asian Ocean/Siberian continent boundary and was located in an open ocean realm. In the present-day structural pattern of southern Siberia, the fragments of Vendian–Early Cambrian ophiolites, island arcs and paleo-oceanic islands occur in the accretion–collision zones. We recognized that the accretion–collision zones were mainly composed of the rock units, which were formed within an island-arc system or were incorporated in it during the subduction of the Paleo-Asian Ocean under the island arc or the Siberian continent. This system consists of accretionary wedge, fore-arc basin, primitive island arc and normal island arc. The accretionary wedges contain the oceanic island fragments which consist of OIB basalts and siliceous—carbonate cover including top and slope facies sediments. Oceanic islands submerged into the subduction zone and, later were incorporated into an accretionary wedge. Collision of oceanic islands and island arcs in subduction zones resulted in reverse currents in the accretionary wedge and exhumation of high-pressure rocks. Our studies of the Gorny Altai and Salair accretionary wedges showed that the remnants of oceanic crust are mainly oceanic islands and ophiolites. Therefore, it is important to recognize paleo-islands in folded areas. The study of paleo- islands is important for understanding the evolution of accretionary wedges and exhumation of subducted high-pressure rocks.     

Formation and upwelling of mantle diapirs through the cratonic lithosphere: Numerical thermomechanical modeling

This paper reports the results of the numerical modeling of gravitationally instable processes in the lithospheric mantle of ancient cratons. The gravitational instability is considered as a result of melting at the lithosphere base owing to its local heating by anomalous mantle. Modeling was based on a finite element method in 2D formulation and took into account the geological structure and thermomechanical parameters of the lithosphere of the Siberian platform. Numerical results revealed the main tendencies in the mantle diapirisim of the mafic and ultramafic magma ascending through the “cold” high-viscosity lithosphere. It was shown that the shape of diapiric magmatic bodies is controlled by realistic visco-elastic-plastic rheology of lithosphere. The ascent of diapir in lithosphere was modeled for diverse regimes differing in duration, temperature field, and upwelling depth. It was concluded that the ascent of melt through lithosphere to the crust-mantle boundary is mainly controlled by rheology, and conditions of oscillatory diapirism with recurrent magma replenishments were modeled. Modeling results may shed light on some features related to the trap magmatism of the Siberian igneous province. The duration and rate of magma upwelling as well as the parameters of periodical magma upwelling were estimated and attempt was made to explain the high-velocity seismic anomalies that were recorded in the subcrustal regions of the Siberian platform.     

我国南方的古老动物群及有关问题的初步探讨

须腕动物门(Pogonophora)皱节虫科(Sabelliditidae)的化石(图版Ⅲ,图2)在前寒武纪和寒武纪沉积内均大量发现,最近此种化石还发现于苏联的中里菲界(约11亿年),被认为是一种可靠的最古老的后生动物化石。     

地球和月球起源的非传统模型(英文)

46亿年以来 ,地球的内力活动是由地球液体内核上升的富氢挥发物流所维持的。为了解释这些导致地球内核如此巨量氢集中的作用 ,文中提出了一个关于地球、其它行星及作为一个整体的太阳系 ,其起源与演化的非传统的岩石学模型。排氢脉冲导致洋壳扩张的增强 ,而此则与创造出造山带的地壳变动幕相关。随后大洋底板活动的减弱 ,则招致褶皱陆壳的剥蚀 ,并伴有广泛展布的玄武岩岩浆作用 ,以及大洋周边优地槽区的稳定化。地壳发展旋回的有规则重复 ,都与地球历史中岩浆作用、变质作用、成矿作用和全球灾变的特殊特点相关。在最大的地核排氢期间 ,氢流体达到了平流层 ,并在这里形成有高反射力的水冰云。它们增加了地球的反射率 ,并成为地球全球冰封的基础。平流层冰云促进了对臭氧辐射盾牌的破坏 ,从而导致继冰期之后的生物灾难。     

全球重油与油砂资源潜力、分布与勘探方向

基于对全球主要地质时期构造、沉积演化、盆地类型和主要成藏期的地质研究,评价全球重油和油砂资源潜力,进而指出有利勘探方向.据CNPC(2011)评价结果:全球重油地质资源量为42 712亿桶,可采资源量为7 147亿桶,油砂地质资源量为66 945亿桶,可采资源量为7 095亿桶;主要分布在北美、南美、俄罗斯和高加索地区,产区集中于北美和南美.以构造域进行划分,全球重油和油砂主要富集在科迪勒拉褶皱造山带、喜马拉雅阿尔卑斯褶皱造山带、西伯利亚地台周缘山系和乌拉尔山前四个大型构造带,盆地类型以克拉通和前陆为主,以斜坡降解、抬升破坏型两种模式成藏.未来重油和油砂勘探主要集中在3类地区:1)资源落实程度较高、勘探程度高的美洲地区;2)资源潜力大、勘探程度低的俄罗斯东西伯利亚盆地、伏尔加乌拉尔盆地;3)资源潜力大、尚未引起注意的中东地区.     

The Taimyr fold belt, Arctic Siberia: timing of prefold remagnetisation and regional tectonics

Late Precambrian and Palaeozoic platform sediments from the Central–South Taimyr Peninsula (Arctic Siberia) are all remagnetised. The remagnetisation is prefold and is related to thermal remagnetisation caused by Taimyr Trap magmatism. The remagnetisation age is estimated to 220–230 Ma and, hence, is considerably younger than the ca. 251 Ma age for the main body of Siberian Trap flood basalts. The folding that affected the Taimyr region platform sediments also included the Taimyr “Traps,” hence, relegating Taimyr deformation to post-Mid Triassic time, and most probably, to a Late Triassic age. This shows that whilst thrusting terminated in the Urals during the Permian, crustal shortening continued in Taimyr, Novaya–Zemlya and the South Barents Sea, well into the Mesozoic.