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1.
The tectonic scheme of the Siberian Craton proposed in this paper is compiled on the basis of a geological map of the craton prepared from numerous magnetometric maps and gravity measurements on various scales, the scheme of axes of magnetic anomalies, and the synthesis of geological information on the exposed territories. The shields and platform territories of the ancient Siberian Craton comprises Archean blocks and Paleoproterozoic foldbelts. The granite-greenstone terranes and granulite-gneiss domains were formed in the Meso- and Neoarchean. The granite-greenstone terranes exposed and overlapped by sedimentary cover are identical, although they generally differ in internal structure and rock compositions both at the infra- and supracrustal levels. The Archean granulite-gneiss domains are recognized either as special tectonic units or as deep sections of granite-greenstone terranes. Two groups of the Paleoproterozoic collisional belts that amalgamated separate Archean blocks of the Siberian Craton into a common stable structural unit evolved 2.1–1.9 and 1.9–1.8 Ga ago. Three types of deep faults arose in the Paleoproterozoic: (1) translithospheric fault zones as boundaries of tectonic blocks and collisional belts, (2) intracrustal fault zones that originated as a result of nonuniform uplift of particular segments of the common plate, and (3) transcrustal zones formed in a plate that overrode another, plunging plate.  相似文献   

2.
A new concept concerning the structure and stages of evolution of the Kas Block of the West Siberian Plate is stated in this paper. The Kas Block is traditionally considered to be a subsided western margin of the Siberian Platform. The new concept is based on the results of the interpretation of the geophysical data recently obtained along the reference and regional profiles in this territory. The geological interpretation of the deep dynamic sections obtained by reprocessing of the CDP seismic reflection records has been performed for the first time. The structural features of the Kas Block, as well as the character of its junction with the Siberian Platform and the Paleozoic framework, are discussed. The tectonic scheme of the territory and the scheme of the pre-Late Devonian surface of the Kas Block have been compiled. The Baikalian age of the basement of the Kas Block is substantiated. The Salairian allochthonous ophiolite-basalt tectonic nappe is localized for the first time within the sedimentary cover of the Kas Block. The available information allowed us to reconstruct the development of the western margin of the Siberian continent in the Riphean and Early Paleozoic before and after the Baikalian Orogeny, respectively. The informational background of the geological and geophysical interpretation involves the results of the CDP seismic reflection profiling, including the deep dynamic seismic sections and parameters of the P-wave velocities along the reference 1-SB seismic line and the regional Vostok 10, 12, 15, and 16 seismic lines; the results of the deep seismic and magnetotelluric soundings; the gravity measurements; the magnetic exploration; and the new coherent physical geological models.  相似文献   

3.
New data on the geology and tectonics of the main structural elements of the East Transbaikalian segment of the Central Asian Foldbelt are discussed. Correlation charts of the main stratified and igneous complexes are compiled. The rocks of the Baikal-Patom and Baikal-Muya belts, as well as the Barguzin-Vitim Superterrane, are characterized by new Nd isotopic data, which have allowed us to establish the sources of these rocks, to separate isotopic provinces, and to distinguish two stages of crust-forming processes: the Early Baikalian (1.0–0.8 Ga) and the Late Baikalian (0.70–0.62 Ga). The Early Baikalian crust was formed in relatively narrow and spatially isolated troughs of the Baikal-Muya Belt and probably in the Amalat Terrane, whereas the Late Baikalian continental crust was formed and reworked in the Karalon-Mamakan, Yana, and Katera-Uakit zones of the Baikal-Muya Belt. The Baikal-Patom Belt and most of the Anamakit-Muya Zone in the Baikal-Muya Belt are characterized by remobilization of the Early Precambrian continental crust and by a subordinate role of Late Riphean juvenile sources. Reworking of the mixed Late Riphean and Early Precambrian crustal sources is typical of the Barguzin-Vitim Superterrane. The origination and evolution of the continental crust in the studied region are considered in light of new data; alternative versions of paleogedynamic reconstructions are discussed.  相似文献   

4.
The petrogeochemical and geochronological correlations were carried out between boudined fragments of tonalitic rocks previously dated at Neoarchean, quartzite sandstones, and host amphibolites in the Yenisei Regional Shear Zone of the Yenisei Ridge in order to solve the problem of age of the Transangarian Yenisei Ridge basement. Detrital zircons in metasandstones can be derived from the Neoarchean–Paleoproterozoic crystalline rocks of the Angara–Kan block. Interpretation of available data does not confirm the inferred presence of the Early Precambrian basement of the Siberian Craton beneath the Transangarian Yenisei Ridge.  相似文献   

5.
The geometry and evolution of pre-existing basement in accretionary belts bordering supercontinents are often unclear. Integrative interpretation of long-wavelength potential field satellite data can image deep crust structure, improving our understanding of lithospheric processes that formed these margins bottom-up. Here, we present a multidisciplinary interpretation of the lithospheric architecture of the central southern Amazon Craton, a fragment of an accretionary belt at the southwestern Columbia supercontinent margin. Satellite-borne gravity and magnetic data, airborne magnetic data, passive seismic (Vp/Vs ratio, crustal thickness) and seismic tomography data reveals that basement terranes from the interior of the craton extend into the accretionary margin of Columbia. We demonstrate a vertically heterogeneous structure with an underlying strongly reworked pre-Columbia tectonic wedge that sustained prolonged modification during the supercontinent assembly as corroborated by Nd isotope and geochronology data. Nd isotope data suggest that the protracted orogenic wedge was influenced by subduction angle shifts over time, including addition of substantial juvenile material during slab retreat events. This interplay promoted Craton growth at the supercontinent margin while keeping a subtle record of the pre-existing framework. Our findings point to the possible misrepresentation of basement extension and geometry of supercontinent margins elsewhere.  相似文献   

6.
敦煌复合造山带前寒武纪地质体的组成和演化   总被引：3，自引：3，他引：0  
赵燕  孙勇 《岩石学报》2018,34(4):963-980
敦煌复合造山带位于塔里木克拉通东端,是连接塔里木克拉通和华北克拉通的重要纽带。近年来,敦煌基础地质研究取得了重大进展。本文简要回顾了敦煌基础地质研究历史和现状,系统归纳了区内前寒武纪地质单元时空分布特征及前寒武纪构造-热事件序列,初步讨论了前寒武纪大陆地壳形成和演化规律、前寒武纪结晶基底亲缘性及构造演化过程,提出:(1)敦煌造山带前寒武纪结晶基底形成于ca.3.1~1.6Ga,构造-热事件主要划分为新太古代(ca.2.7~2.6Ga和2.6~2.5Ga)、古元古代晚期(ca.2.0~1.8Ga)和中元古代早期(1.8~1.6Ga)三个阶段;(2)新太古代早期(ca.2.7~2.6Ga)和新太古代晚期(2.6~2.5Ga)是敦煌造山带大陆地壳形成的主要阶段;古元古代晚期(ca.2.0~1.8Ga)和中元古代早期(1.8~1.6Ga)主要是古老大陆地壳物质再循环阶段,也有少量新生陆壳物质的形成;(3)敦煌造山带前寒武纪结晶基底最初拼合事件可能发生在新太古代末期(~2.5Ga),之后经历了古元古代晚期(ca.2.0~1.8Ga)汇聚、碰撞造山过程,直到中元古代早期(1.8~1.6Ga),造山活动结束,前寒武纪结晶基底最终固结,进入稳定发展阶段;(4)前寒武纪结晶基底最终稳定固结之后,即～1.6Ga之后,敦煌前寒武纪结晶基底可能进入长达12亿年的静寂期,一直处于稳定状态,目前没有发现相关的岩浆-变质-沉积记录(类似于地盾状态),直至古生代志留纪开始活化(～440Ma),卷入古亚洲洋南缘俯冲、碰撞造山过程并被强烈改造。  相似文献   

7.
The New Siberian Islands terrane, represented on the Arctic shelf by the archipelagos of the New Siberian Islands and De Long Islands, is one of the key structures of the Arctic. However many questions of its structure, borders and formation history are under intense discussion. During the international expedition in 2011 we solved many problems concerning structural geology, paleontology, petrology and geochronology. A particular attention was given to obtaining paleomagnetic data for the sedimentary and igneous rocks of the archipelago. The primary objects of paleomagnetic studies were the Early Paleozoic sedimentary rocks of the Kotelny (Anzhu) and Bennett (De Long) islands. In this paper we present new paleontological data, including the first one for conodonts of the New Siberian Islands, which help us to specify the age of the Early Paleozoic deposits of the studied sections. In these sections we took a series of paleomagnetic samples. The match of the paleomagnetic directions we determined for Bennett Isl. and Kotelny Isl. indicates the tectonic unity between the territories of the Anzhu and De Long archipelagos. These first paleomagnetic data allow us to affirm that at least from the Early Ordovician the rocks of the Anzhu and De Long archipelagos formed within the same New Siberian Islands terrane, that is to say, on the same basement.  相似文献   

8.
This work presents the results of tectonophysical modeling of tectonic deformations in the crystalline basement of the Scythian Plate, including estimated deformation values and stress-field orientations. The morphostructural parameters of the Earth’s surface, which were calculated using the LESSA program, were compared. In addition, some parameters of modern geodynamic processes that occur in the Scythian Plate, such as the level of seismicity and heat flow value, were calculated. The similarity between ancient and modern geodynamic processes allows us to propose that deformational processes in the crystalline basement of the Scythian Plate play a significant role in the formation of the modern topography and makes it possible to use morphostructural parameters of the relief for studying the deep structure of platform covers.  相似文献   

9.
The geological, geochemical, and isotope-geochronological evidence of the events at the final stage of the Neoproterozoic history of the Yenisei Range is considered (beginning from the formation of fragments of the oceanic crust in the region and their accretion to the Siberian Craton until the postaccretionary stage of crustal tension and onset of the Caledonian orogeny). Based on an analysis of new data on the petrogeochemical composition, age, and geodynamic nature of the formation of contrasting rocks in the composition of tectonic mélange of the Near-Yenisei (Prieniseiskaya) regional shear zone, we have found the chronological sequence of events that marks the early stages of the Paleoasian Ocean evolution in the zone of its junction with the Siberian Craton. These events are documented by the continental marginal, ophiolitic, and island-arc geological complexes, each of which has different geochemical features. The most ancient structures are represented by fragments of oceanic crust and island arcs from the Isakovka terrane (700–620 Ma). The age of glaucophane-schist metamorphic units that formed in the paleosubduction zone corresponds to the time interval of 640–620 Ma. The formation of high-pressure tectonites in the suture zone, about 600 Ma in age, marks the finishing stage of accretion of the Isakovka block to the western margin of the Siberian Craton. The final events in the early history of the Asian Paleoocean were related to the formation of Late Vendian riftogenic amygdaloidal basalts (572 ± 6.5 Ma) and intrusion of postcollisional leucogranites of the Osinovka massif (550–540 Ma), which intruded earlier fragments of the oceanic crust in the Isakovka terrane. These data allow us to refine the Late Precambrian stratigraphic scheme in the northwestern Trans-Angarian part of the Yenisei Range and the evolutionary features of the Sayan–Yenisei accretionary belt. The revealed Late Neoproterozoic landmarks of the evolution of the Isakovka terrane are attributed to the terminal phase of the breakup of Rodinia, separation of the Siberian Craton, and opening of the Paleoasian Ocean.  相似文献   

10.
为了弄清楚龙首山地块的归属问题,对龙首山地块地壳结构和地层特征进行研究,发现龙首山地块具有由结晶基底和沉积盖层组成的双层地壳结构。该地块结晶基底由龙首山群组成,龙首山群岩性主要为一套条带状、眼球状混合岩夹斜长角闪岩、花岗质片麻岩、黑云斜长片麻岩等,普遍经历了角闪岩相区域变质作用。龙首山地块缺失长城系、青白口系和南华系,下部沉积盖层由蓟县系墩子沟群和震旦系顶部的烧火筒沟组构成。墩子沟群经历了埋藏变质作用,粉砂岩具千枚状构造,砂岩有一定程度的重结晶,地层层理保存完整。烧火筒沟组上部为含砾千枚岩、粉砂质千枚岩,下部为冰碛砾岩,冰碛砾岩总与寒武系含磷层相伴出现。地壳整体结构与华北克拉通基本特征相同,而扬子克拉通具有结晶基底、褶皱基底和沉积盖层3层地壳结构,与华北克拉通和龙首山地块迥异。因此,龙首山地块应归属于华北克拉通。  相似文献   

11.
Formation conditions of sedimentary successions in the Mezen Basin are considered on the basis of Cr, Th, Sc, Ni, Hf, and REE distribution and model Nd age of the Upper Vendian fine-grained terrigenous rocks. Geochemistry of mudstones and shales of the Lyamitsa, Verkhovka, Zimnie Gory, and Erga formations in the Belomorian-Kuloi Plateau, as well as the Ust-Pinega and Mezen formations in the Vychegda Trough, does not allow us to consider these stratigraphic units as erosion products of the primitive Archean basement of the Baltic Shield or the central segment of the East European Craton (EEC) basement. Taking into account sedimentological data on the direction of paleoflows in the basin and the model Nd age of the fine-grained terrigenous rocks, we suggest that the Mezen Basin was filled in the Late Vendian mainly with erosion products of the Riphean igneous and metasedimentary complexes of the Timan-Pechora region. These conclusions are consistent with the sequence-stratigraphic architecture of sediments in the basin. According to the new model proposed, the Late Vendian Mezen Basin was a foredeep formed as a result of subsidence of the northeastern margin of the EEC under the load of overthrusted rock masses of the Timan-Pechora Foldbelt. The clastic material was derived from the emerging orogen.  相似文献   

12.
合肥盆地基底构造属性   总被引：33，自引：4，他引：29       下载免费PDF全文
根据合肥盆地及周边地表地质、地震剖面、同位素测年及MT等新资料的综合研究,提出中-新生代合肥盆地的基底是一个不同构造类型基底的叠合与复合.上古生界以前的基底以六安断裂为界,其北为华北板块陆壳型-过渡壳型结晶基底及其上的华北克拉通-被动大陆边缘盆地沉积的上元古-下古生界基底;其南为大别型结晶基底及其上的北淮阳弧后盆地沉积的上元古-下古生界变质基底,而上古生界基底属于弧后前陆盆地型沉积.六安断裂是合肥盆地部位北大别弧、北淮阳晚元古-早古生代弧后盆地在早古生代晚期-晚古生代早期与华北板块的弧-陆碰撞缝合线.  相似文献   

13.
3D models of apparent magnetization and density of rocks allow us to provide insights into the deep structure of the Volga-Ural, Pericaspian, and Fore-Caucasus petroliferous basins. In the Volga-Ural Basin, some Riphean rifts reveal close spatial relations to Paleoproterozoic linear zones, presumably of the rift nature as well. The structure of the Paleoproterozoic Toropets-Serdobsk Belt is interpreted in detail. Rocks with petrophysical properties inherent to basic volcanics are established in the pre-Paleozoic basement of the marginal zone of the Pericaspian Basin. These rocks locally spread beyond the boundary escarpment and may be regarded as a part of the Riphean plume-related basaltic province. It is shown that the Pericaspian Basin was formed on the place of a triple junction of Riphean rifts: the Sarpa and Central Pericaspian oceanic branches and the continental branch of the Pachelma Aulacogen. The drastically different petrophysical properties of the basement beneath Baltica and the Astrakhan Arch indicate that this arch is an element of the large terrane that was attached to Baltica in the Vendian. The suture along which the Astrachan Terrane is conjugated with the basement of the central and southern segments of the Karpinsky Ridge is traced beneath the Paleozoic complex. A system of northwest-verging thrust faults formed during the collision between Scythia and Eurasia is mapped in the basement of the junction zone between the Karpinsky Ridge and Scythian Platform (Terrane). According to geological data, this event took place in the Early Paleozoic.  相似文献   

14.
This paper reports data on the structure of the central zone of the seismogenic fault in the originally deep segments of the fault zone. The isotopic analyses have made it possible to estimate the absolute age of the ancient coseismic faults at 673 ± 5 Ma, which is indicative of seismic activation of deep faults in the studied segment of the marginal suture of the Siberian Craton in the Neoproterozoic.  相似文献   

15.
The first data on the age of detrital zircons are given for Late Precambrian terrigenous rocks of the Baikal Group and Ushakovka Formation of the southern flank of the Siberian Craton. The ages obtained for 348 zircons cover the Paleoarchean to Late Ediacaran period, demonstrate the dynamics of change of sources of the clastic material in the sedimentation basin, and mark the changes of the Late Precambrian tectonic regimes. The age of the youngest group of detrital zircons extracted from the rocks of the Kachergat Formation allows us to restrict the upper age limit of accumulation of the rocks of the Baikal Group to the Late Ediacaran (Late Vendian).  相似文献   

16.
The Paleoproterozoic sedimentary and volcanic-sedimentary sequences of the Urik-Iya Graben at southern flank of the Siberian Craton have been studied. Based on the isotopic U-Pb LA-ICP-MS dating of detrital zircons contained in the clastic fraction of the studied rocks, three main extension stages accompanied by sedimentation are recognized; each stage is characterized by certain types of sediments and conditions of their accumulation. The oldest rocks (Ingashi Formation) mark early extension events (～1.91?1.87 Ga), which were caused by collapse of the orogen that arose due to collision of the Biryusa and Sharyzhalgai blocks. The basin formed as a result of extension is regarded as an aulacogen. Granitoids of the Sayan Complex were emplaced in the cratonic lithosphere at the final stage of the first extension stage. The second stage of extension started ～1.75 Ga ago as a response to the effect of the inferred mantle plume on the lithosphere of the Siberian Craton. It was accompanied by deposition of the Daldarma Formation. Stress inversion took place at the final stage (～1.70 Ga), and an intracratonic fold zone arose at the place of the paleoaulacogen. The third extension stage (1.65?1.60 Ga) corresponds to the time of molasse accumulation in pull-apart basins (Yermosokha Formation). The final stage of rifting was marked by emplacement of granitoids (Chernaya Zima Complex, 1.53 Ga), which completed the active tectonic events in the region. Afterward, the Urik-Iya Graben transformed into a stable intracratonic domain. The available data allow us to revise the tectonic history of the Urik-Iya Graben. In light of new evidence, this structural unit may be interpreted as a long-evolving paleoaulacogen. The series of revealed sedimentation settings reflects the formation of a consolidated continental lithosphere at the southern flank of the Siberian Craton.  相似文献   

17.
The U-Pb dating of detrital zircons from Carboniferous rocks in the northern frontal zone of the Verkhoyansk Fold-and-Thrust Belt (Kharaulakh Anticlinorium) at the boundary with the Siberian Platform is carried out for the first time. The age distribution of detrital zircons from the four dated samples has much in common, indicating that the same sources of clastic material were predominant. All of the samples are dominated by Precambrian zircons; the majority of them are Paleo- and Neoproterozoic grains. Early Ordovician and Late Devonian-Early Carboniferous detrital zircons are also numerous. The igneous rocks of the Taimyr-Severnaya Zemlya and/or Central Asian foldbelts extending along the northern, western, and southwestern margins of the Siberian continent probably were the main source areas of the studied sedimentary successions. The clastic material was transferred at a great distance by large river systems similar to the present-day Mississippi River and deposited in submarine fans at the passive margin of the Siberian continent. The occurrence of the detrital zircons whose age is synchronous to the time of sedimentation of the Carboniferous successions in the northern Verkhoyansk region (320–340 Ma) allows us to suggest that they were derived from the Taimyr-Severnaya Zemlya Foldbelt and that collision of the Kara Block with the Siberian continent began in the Early Carboniferous. The performed study shows the dating of detrital zircons is very helpful for the paleogeographic and tectonic reconstructions.  相似文献   

18.
The present study was undertaken with the objective of deriving constraints from available geological and geophysical data for understanding the tectonic setting and processes controlling the evolution of the southern margin of the East European Craton (EEC). The study area includes the inverted southernmost part of the intracratonic Dnieper-Donets Basin (DDB)–Donbas Foldbelt (DF), its southeastern prolongation along the margin of the EEC–the sedimentary succession of the Karpinsky Swell (KS), the southwestern part of the Peri-Caspian Basin (PCB), and the Scythian Plate (SP). These structures are adjacent to a zone, along which the crust was reworked and/or accreted to the EEC since the late Palaeozoic. In the Bouguer gravity field, the southern margin of the EEC is marked by an arc of gravity highs, correlating with uplifted Palaeozoic rocks covered by thin Mesozoic and younger sediments. A three-dimensional (3D) gravity analysis has been carried out to investigate further the crustal structure of this area. The sedimentary succession has been modelled as two heterogeneous layers—Mesozoic–Cenozoic and Palaeozoic—in the analysis. The base of the sedimentary succession (top of the crystalline Precambrian basement) lies at a depth up to 22 km in the PCB and DF–KS areas. The residual gravity field, obtained by subtracting the gravitational effect of the sedimentary succession from the observed gravity field, reveals a distinct elongate zone of positive anomalies along the axis of the DF–KS with amplitudes of 100–140 mGal and an anomaly of 180 mGal in the PCB. These anomalies are interpreted to reflect a heterogeneous lithosphere structure below the supracrustal, sedimentary layers: i.e., Moho topography and/or the existence of high-density material in the crystalline crust and uppermost mantle. Previously published data support the existence of a high-density body in the crystalline crust along the DDB axis, including the DF, caused by an intrusion of mafic and ultramafic rocks during Late Palaeozoic rifting. A reinterpretation of existing Deep Seismic Sounding (DSS) data on a profile crossing the central KS suggests that the nature of a high-velocity/density layer in the lower crust (crust–mantle transition zone) is not the same as that of below the DF. Rather than being a prolongation of the DDB–DF intracratonic rift zone, the present analysis suggests that the KS comprises, at least in part, an accretionary zone between the EEC and the SP formed after the Palaeozoic.  相似文献   

19.
The paper presents the results of paleomagnetic and geochronological studies of the Late Paleozoic granites of the Angara-Vitim batholith as well as Vendian-Early Cambrian sedimentary rocks and Late Devonian subvolcanic rocks of the Patom margin of the Siberian Platform. Primary and metachronous magnetization in the rocks of the study region was used to calculate an Early Permian (~ 290 Ma) paleomagnetic pole, which is proposed as a reference pole for the Siberian Platform in paleomagnetic reconstructions, plotting of the apparent polar-wander path curve, and other magnetotectonic studies. The published and obtained paleomagnetic data and analysis of the geological data confirm the Late Paleozoic age of the final folding in the Baikal-Patom area. Possible causes of Late Paleozoic deformations and large-scale granite formation in the Baikal-Patom area and Transbaikalia in the Late Paleozoic are discussed.  相似文献   

20.
渤海西南海域自中生代以来历经多期构造活动,记录了华北克拉通的破坏过程。为了明晰渤海西南海域中生代构造演化与区域构造间的关系,以研究区三维地震资料以及深层钻井资料为基础,结合区域构造背景,厘定了研究区中生代构造特征,恢复了中生代构造演化过程,并探讨了其动力学机制及其对华北克拉通破坏的响应。结果表明:(1)不同于渤海湾盆地陆上油区NEE向的构造面貌,渤海西南海域发育多走向、多类型构造,三维地震资料揭示中生代发育NWW向负反转裂陷、NEE向走滑逆冲、挤压褶皱等异于新生代伸展样式的特殊构造,其中尤以NWW向负反转构造占主导。(2)渤海西南海域中生代以来经历了印支期逆冲褶皱成山、燕山早期左旋逆冲改造、燕山中期裂陷反转以及燕山晚期褶皱等多期变形过程, 其中印支期逆冲褶皱是潜山形成的关键时期,而燕山中期反转是构造体制发生变革的关键时期。(3)NWW向构造的形成与印支期华南板块与华北板块的碰撞有关,燕山早期左旋走滑是太平洋板块NWW向俯冲于华北板块之下的结果,代表太平洋构造域接替古特提斯构造域控制华北板块变形;燕山中期的裂陷反转与区域大规模中基性岩浆活动相对应,是华北克拉通大规模破坏的浅层响应。印支期NWW向先存构造燕山中期反转裂陷模式的提出,丰富了传统华北克拉通破坏形成NEE向盆地的简单构造模式。  相似文献   

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