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1.
This paper presents the results of Sm-Nd isotopic-geochemical and U-Pb geochronological studies of metamorphic (Ilikan Sequence) and associated igneous rocks from the Ilikan lithotectonic zone (terrane) located in the Dzhugdzhur-Stanovoi Superterrane from the Central Asian Foldbelt. The Nd model age, T Nd(DM), of metamorphic rocks from the Ilikan Sequence is 2.6–3.2 Ga pointing to the likelihood that the lower boundary of their protolith formation probably does not exceed 2.6 Ga. The age of detrital zircons from metasedimentary rocks of the Ilikan Sequence is 2700–2900 Ma, which absolutely agrees with Sm-Nd isotopic-geochemical results. The U-Pb zircon age of metagabbro that intruded the rocks of the Ilikan Sequence and underwent high-temperature amphibolite metamophism with subsequent structural transformations is 2635 ± 4 Ma. The obtained results allow us to conclude that the age of the Ilikan Sequence is 2630–2700 Ma. All this gives grounds to state that the Dzhugdzhur-Stanovoi Superterrane in the Central Asian Foldbelt was formed due to amalgamation of non-Siberian terranes as is assumed for the Argun, Bureya, and Mamynskii terranes of the Amur Superterrane from the Central Asian Foldbelt.  相似文献   

2.
Geochemical Sm–Nd isotope and U–Th–Pb geochronological (LA-ICP-MS) studies have demonstrated that the Zeya Group of the Stanovoy Complex of the Dzhugdzhur–Stanovoy Superterrane (Central Asian fold belt) is not Paleoarchean, as was previously thought, but Paleoproterozoic in age.  相似文献   

3.
U–Pb ID–TIMS zircon analyses of the Dzhigda gabbro–gabbrodiorite Massif (Ilikan block in the southwestern part of the Dzhugdzhur–Stanovoi superterrane) have been carried out. The results demonstrate that the formation of the massif at 244 ± 5 Ma corresponds to one of the stages of formation of the Selenga–Vitim volcano–plutonic belt. The latter stretches along the southeastern margin of the North Asian Craton along its border with the Mongol–Okhotsk fold belt. This indicates that the Selenga–Vitim volcano–plutonic belt along with granitoids and volcanics comprises Permian–Triassic massifs and that this belt is superimposed onto structures of not only the Selenga–Stanovoi terrane but also the Dzhugdzhur–Stanovoi terrane.  相似文献   

4.
In this paper, we report U-Pb geochronological, Sm-Nd isotopic, and geochemical data for the basic schists of the Bryanta sequence of the Stanovoi complex of the Dzhugdzhur-Stanovoi superterrane of the Central Asian fold belt. It was shown that the protolith of the schists was composed of island-arc subalkali basalts, which crystallized at 1933 ± 4 Ma; the age of the earliest metamorphic processes is approximately 1890?C1910 Ma. This metamorphic event could be related to the collision of the Aldan and Stanovoi continental plates or accretion-collision processes at the boundary of the Ilikan and Kupurin lithotectonic zones during the formation of the latter.  相似文献   

5.
Complex mineralogical, geochemical, and geochronological studies of the gabbroids from the Dzhigdinskii Massif located in the western part of the Dzhugdzhur–Stanovoy Superterrane are performed. It is established that the age of the rocks from the Dzhigdinskii Massif is Middle Triassic (244 ± 5 Ma), rather than Early Archean, as was previously assumed. The age of the Dzhigdinskii Massif is close to the age of the formation of the other Triassic gabbroid massifs, such as the Amnunaktinskii (~240 Ma), Lukindinskii (~250 Ma), and Luchinskii (~248 Ma) in the southeastern environ of the North Asian Craton. One of the stages in the formation of the Selenga–Vitim volcanoplutonic belt falls in this period as well. This indicates that the Selenga–Vitim volcanoplutonic belt, along with the granitoids and volcanic rocks, is composed of ultrabasic–basic and basic massifs and that this belt is superposed on the structures of the Selenga–Stanovoy Superterrane, as well as on the western part of the Dzhugdzhur–Stanovoy Superterrane. The gabbro, gabbro–diorite, and series of gabbro and gabbro–diorite with high sodic alkalinity from the Dzhigdinskii Massif show obvious geochemical features of duality, including combination of intraplate and super-subduction origin. In this relation, we can assume that the origin of the gabbroids of the Dzhigdinskii Massif is related to the detachment of the oceanic lithosphere and its subduction into the mantle with the formation of an “asthenospheric window.”  相似文献   

6.
The results of Sm–Nb isotopic–geochemical studies of metasedimentary and metavolcanic rocks of the Dzheltulak Group of the central part of the Dzheltulak suture, as well as geochronological U–Th–Pb (LA ICP MS) studies of detrital zircons from metasedimentary rocks, which are considered as Paleoproterozoic in current stratigraphic schemes, are presented. The age of the youngest zircons is 170–190 Ma, whereas the age of the last stage of regional metamorphism is 140–150 Ma. Thus, the Dzheltulak Group hosts metasedimentary rocks, the age of the protolith of which ranges from 140–150 to 170–190 Ma. The detrital zircons derived from intrusive and metamorphic rocks of the Selenga–Stanovoi and Dzhugdzhur–Stanovoi superterranes.  相似文献   

7.
As follows from the results of a structural study and available geochronological constraints, the Gonzha Block located in the northeastern Argun-Idermeg Superterrane of the Central Asian Foldbelt is similar to Late Mesozoic (133?119 Ma) Cordilleran-type metamorphic cores of western Transbaikalia. Exhumation of metamorphic rocks of the Gonzha Block resulted from a collapse of the Late Mesozoic orogen after accrecionary and collisional events related to closure of the Mongolia-Okhotsk paleooceanic basin. The structural elements that determine the main geological features of this block formed over the course of at least three deformation stages. By the onset of the third stage responsible for exhumation of metamorphic rocks pertaining to the Gonzha Group, they had already undergone complex structural transformation and metamorphism related to growth of the Amur microcontinent and its subsequent collision with the Dzhugzur-Stanovoi and Selenga-Stanovoi supperterranes of the Central Asian Foldbelt. This distinguishes the Gonzha Block from complexes of metamorphic cores in western Transbaikalia, whose structural transformation and metamorphism are directly related to their origin.  相似文献   

8.
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   

9.
The U-Pb geochronological studies showed that metarhyolites from the Turan Group of the Bureya (Turan) Terrane to the east of the Central Asian Foldbelt are Middle Cambrian (504 ± 8 Ma), not Neoproterozoic in age, as was suggested before. Metarhyolites are younger than the Early Cambrian terrigenous-carbonate sediments from this terrane characterized by the Atdabanian archaeochyatid. Considering that volcanic rocks have features of intraplate origin, it may be assumed that their formation corresponds to the breakup of the Early Paleozoic passive continental margin.  相似文献   

10.
The Gilyui Complex includes sedimentary and volcanic rocks metamorphosed to amphibolite and epidote–amphibolite facies, which constitute blocks confined to the main structural sutures of the Dzhugdzhur–Stanovoi superterrane in the Central Asian fold belt. In recent stratigraphic scales, they are considered as being Neoarchean in age with Nd model age values of 1.5–3.0 Ga. The youngest detrital zircons from metamorphosed mudstone of the Gilyui Complex yield a date of 285 ± 4 Ma, which determines the lower age limit for the formation of its protolith. The age of crystallization of rhyolites from the Gilyui Complex is determined to be 231 ± 4 Ma. If the rhyolites form volcanic flow units or sills, the Gilyui Complex is approximately 230 Ma or 231 ± 4 to 285 ± 4 Ma old, respectively.  相似文献   

11.
The first results on current movements are presented for the western part of the Dzhugdzhur–Stanovoi Terrane based on GPS geodesy of a geodynamic survey area of the Upper Amur region. Processing of the GPS data resulted in a vector field of the displacement rates of points of the geodynamic survey area with zones of intense deformations. It was concluded from a comprehensive analysis of geological–geophysical data and estimates of the displacement rates that the terrane is characterized by kinematic integrity and was subjected to a complex of tectonic factors related to the evolution of the eastern segment of Baikal Rift Zone in the area of transpression interaction of the Eurasian and Amur plates.  相似文献   

12.
The Dotulur alkalic granite and Usugli Depression volcanics (West Stanovoi Superterrane of the Central Asia Fold Belt) have been dated by the U–Pb method, and their geochemistry has been analyzed. The geochemistry of the rocks suggests their intraplate nature. The alkalic granite and volcanics have similar ages of 142 ± 1 Ma and 138 ± 3 Ma, respectively. Considering the Usugli Depression structural position as an upper fault slice of the Elikan metamorphic core, the obtained dates allow the formation of the mentioned core and, accordingly, the collapse of central part of the Mongol–Okhotsk orogeny to have occurred not prior to 140 Ma.  相似文献   

13.
The Yili Block is one of the major Precambrian microcontinents of the Central Asian Orogenic Belt (CAOB). Detrital zircon U-Pb ages and Hf isotopic data of the Meso-Neoproterozoic (meta)-sedimentary units within the Yili Block constrain the tectonic affinity and early history of the block. Detrital zircon U-Pb ages, in combination with related magmatic age data, indicate that the Tekesi and Kusitai groups were deposited during the latest Mesoproterozoic-earliest Neoproterozoic (1040–960 Ma) and early Neoproterozoic (<926 Ma), respectively. Zircons from the Kusitai Group yield major age groups at 941–910 Ma and 1887–1122 Ma, whereas the Tekesi Group have a dominant age group at ca. 2.0–1.1 Ga with age peaks at ca. 1.9 Ga, 1.8 Ga, 1.75–1.70 Ga, 1.58 Ga, 1.5 Ga, 1.47–1.43 Ga and 1.27–1.20 Ga. A minor age peak of ca. 2.5 Ga is also recognized in the middle part of the Tekesi Group. Early Neoproterozoic detrital zircons with relatively uniform εHf(t) values (+0.7 to +3.2) were mainly derived from contemporaneous magmatic rocks in the Yili Block. The Central Tianshan Block provides a likely source for detritus with ages of ca. 1.7–1.4 and 2.5 Ga. The predominant late Paleoproterozoic to latest Mesoproterozoic detrital zircons with positive εHf(t) values (+0.5 to +12.0) in the Yili Block were probably derived primarily from regions exhumed during collisional assembly of Rodinia. These populations are consistent with those from the late Mesoproterozoic-early Neoproterozoic (meta)-sedimentary successions in the Central Tianshan, Kokchetav-North Tianshan and Erementau-Niyaz blocks, and Southeast Siberia and northeastern Laurentia cratons. The Yili Block, together with the Precambrian microcontinents in the southwestern Central Asian Orogenic Belt, was likely located at the margin of Rodinia supercontinent, between the southeast Siberia and northeast Laurentia during the early Neoproterozoic.  相似文献   

14.
华北克拉通古老大陆地壳组成及演化   总被引：1，自引：1，他引：0       下载免费PDF全文
对鞍本、冀东、鲁西、阴山等早前寒武纪典型地区和深部物质进行了深入研究,总结了华北克拉通早期地壳形成演化历史。揭示出鄂尔多斯地块本身强烈卷入了古元古代晚期构造热事件。首次在华北克拉通划分出3个>2.6 Ga古陆块。  相似文献   

15.
胡波  翟明国  郭敬辉  彭澎  刘富  刘爽 《岩石学报》2009,25(1):193-211
化德群出露地区位于华北克拉通北缘中部,紧邻中亚造山带南缘,呈近东西向展布。在它的西边是早-中元古代的白云鄂博裂谷和渣尔泰—狼山裂谷,东南面是由长城系、蓟县系和青白口系组成的早-新元古代的燕辽裂陷槽,南边分布着1.9~1.8Ga麻粒岩相变质的丰镇群（孔兹岩系）,北边出露有代表中亚造山带的古生代岩石。化德群由一套浅变质和未变质的沉积岩组成,无火山岩夹层。地层序列包含多个沉积旋回,每个旋回自下而上为含砾砂岩、砂岩、碳酸盐岩和泥质岩。岩石组合反映了从河流—滨海—浅海相的沉积环境。化德群的地层序列可以和白云鄂博群及渣尔泰群相对比。本文对化德群四个变质砂岩样品中的碎屑锆石进行了LA-ICP-MS U-Pb年龄测定,年龄主要集中在1800±50Ma和1850±50Ma,另外还有~2500Ma和~2000Ma的次要峰值。化德群底部变质含砾云母长石石英砂岩中碎屑锆石的最小谐和年龄是1758±7Ma,限定了化德群沉积时代的下限。碎屑锆石的CL图像显示,1800±50Ma和1850±50Ma的锆石主要是变质成因,少量岩浆成因,说明化德群的源区主要是古元古代的变质岩,少量岩浆岩。~2500Ma和~2000Ma的碎屑锆石代表了更为古老的源区。碎屑锆石的U-Pb年龄限制了化德群的沉积时代为古元古代晚期—中元古代,年龄峰值对应华北克拉通的重要构造热事件,而无与中亚造山带地质事件相关的年龄信息。沉积组合特征表明化德群属于稳定的浅水—半深水沉积盆地。化德盆地、渣尔泰—狼山盆地和白云鄂博盆地共同构成华北克拉通北缘的被动陆缘裂谷系,该裂谷系的形成可能与燕辽及熊耳裂陷槽的打开是同时期的。因此,华北克拉通的北界应该置于化德群出露区域以北。基于锆石特征的详细分析及对比,我们认为化德群以南的孔兹岩系可能是化德群的主要源区。  相似文献   

16.
碧口地块北缘下中泥盆统踏坡组的物源长期被认为来自碧口地块新元古界基底——碧口岩群,但一直缺少碎屑锆石物源数据的支持。本文对略阳地区泥盆系踏坡组不同层位的3个碎屑岩样品开展了系统的岩石学、锆石岩相学及其U-Pb定年和微量元素组成研究。锆石晶体特征对比分析显示,研究样品存在两种类型的锆石:普遍发育变质增生边的碎屑锆石(剖面北段样品)和不发育变质增生边的典型岩浆成因的碎屑锆石(剖面南、中段样品)。前者显示2个年龄峰值(～2.5 Ga主峰、～2.0 Ga次峰),还形成了2473±24 Ma的上交点年龄和359±84 Ma的下交点年龄,而后者两个样品有着一致的年龄峰值(～2.0 Ga主峰、～2.5 Ga次峰和～1.39 Ga微小峰值)。3个样品的谐和年龄均大于1.3 Ga,并不能限定踏坡组的沉积时代,且均不支持其物源主要来自碧口岩群的传统认识。碎屑锆石地球化学判别图解指示它们的源岩主要为形成于造山带环境中的花岗岩类(花岗闪长岩和英云闪长岩)、基性岩和钾镁煌斑岩。基于样品中的岩屑类型,结合区域地质、古流向、锆石年龄对比和源岩判别,认为踏坡组的原始物源来自位于扬子板块北缘的太古宙—古元古代基底(鱼洞子杂岩和崆岭杂岩),并且鱼洞子杂岩在踏坡组沉积后期曾大面积出露/抬升。同时表明碧口地块可能至少在早中泥盆世就与扬子板块拼合在一起了。  相似文献   

17.
This work presents the results of geological, geochemical, Sm–Nd isotope-geochemical studies of metasedimentary rocks of the Teploklyuchevskaya, Garmakan, and Algaja formations of the Tukuringra Terrane of the eastern part of the Mongol–Okhotsk fold belt, as well as U–Th–Pb geochronological (LA-ICP-MS) studies of detrital zircons from these rocks. It is established that the lower age boundary of formation of the protolith of metasedimentary rocks of the Teploklyuchevskaya Formation is about 243 Ma (Middle Triassic); those of the Garmakan and Algaja formations are ~175 Ma (Lower–Middle Jurassic boundary) and ~192 Ma (Lower Jurassic), respectively. This makes it possible to correlate the Teploklyuchevskaya, Garmakan, and Algaja formations with the youngest sedimentary complexes of the eastern part of the Mongol–Okhotsk fold belt. In terms of geochemistry, the protoliths of metasedimentary rocks of the above-mentioned formations are the most similar to sedimentary rocks of island arcs and active continental margins. The source terrigenous material was transported from the southern frame of the Mongol–Okhotsk fold belt. It is not improbable that Lower Mesozoic deposits of the western part of the Tukuringra Terrane, in particular, and the eastern part of the Mongol–Okhotsk fold belt, as a whole, are relics of residual basins, preserved in “gaps” in the collision zone between the southern margin of plates of the North Asian Craton and the Amur Superterrane.  相似文献   

18.
A summary of original Nd isotopic data on granitoids, silicic volcanics, and metasediments of the Baikal Fold Region is presented. The available Nd isotopic data, in combination with new geological and geochronological evidence, allowed recognition of the Early Baikalian (1000 ± 100 to 720 ± 20 Ma) and Late Baikalian (700 ± 10 to 590 ± 5 Ma) tectonic cycles in the geological evolution. The tectonic stacking, deformation, metamorphism, and granite formation are related to orogenic events that occurred 0.80–0.78 Ga and 0.61–0.59 Ga ago. The crust-forming events dated at 1.0–0.8 Ga and 0.70–0.62 Ga pertain to each cycle. The Early Baikalian crust formation developed largely in the relatively narrow and spatially separated Kichera and Param-Shamansky zones of troughs in the Baikal-Muya Belt. The formation and reworking of the Late Baikalian continental crust played the leading role in the Karalon-Mamakan, Yana, and Kater-Uakit zones and in the Svetlinsky Subzone of the Anamakit-Muya Zone in the Baikal-Muya Belt. In general, three large historical periods are recognized in the evolution of the Baikal Fold Region. The Early Baikalian period was characterized by prevalence of reworking of the older continental crust. The Late Baikalian-Early Caledonian period is distinguished by more extensive formation and transformation of the juvenile crust. The third, Late Paleozoic period was marked by reworking of the continental crust with juxtaposition of all older crustal protoliths. Two models of paleogeodynamic evolution of the Baikalian fold complexes are considered: (1) the autochthonous model that corresponds to the formation of suboceanic crust in rift-related basins of the Red Sea type and its subsequent reworking in the course of collision-related squeezing of paleorifts and intertrough basins and (2) the allochthonous model that implies the formation of fragments of the Baikal-Muya Belt at the shelf of the Rodinia supercontinent, their subsequent participation in the evolution of the Paleoasian ocean, and their eventual juxtaposition during Late Baikalian and Early Caledonian events in the structure of the Caledonian Siberian Superterrane of the Central Asian Foldbelt.  相似文献   

19.
Late Neoarchean metavolcanic rocks are widely distributed in the Western Shandong Terrane (WST). They are classified as ~2590–2580 Ma tholeiites (Group MB-1), ~2550–2530 Ma tholeiites (Group MB-2), calc-alkaline basalts (Group MB-3), high-Si adakites (Group MAD) and ~2520–2500 Ma tholeiites (Group MB-4) based on zircon U-Pb chronological and geochemical data. Their parental magmas have complex origins and were derived from a depleted mantle wedge enriched by slab-derived melts or fluids (Group MB-1); an unaltered depleted mantle (Group MB-2); the delaminated lower crustal materials (Group MAD); a strongly melt- and fluid-metasomatized depleted mantle (Group MB-3); and a fluid- and sediment-metasomatized asthenospheric mantle (Group MB-4). The late Neoarchean geodynamic evolution of the WST revealed by these multi-genetic volcanic rocks can be summarized as follows: (1) an ~2.62–2.53 Ga eastward subduction operated along the ancient continental margin, followed by delamination of unstable continental lithosphere in the back-arc region during ~2.60–2.53 Ga; and (2) delamination-derived mantle magmas ascended and caused the regional extension, further inducing the asthenosphere to passively rise and the back-arc basin to open during ~2.52–2.50 Ga. The above intense mantle magmatism and crust-mantle interactions have consumed abundant mantle energy and facilitated the continental stratification and final cratonization of the WST.  相似文献   

20.
尚义杂岩是冀西北地区有代表性的变质地质体,由变质表壳岩和侵入岩组成。其中的变质表壳岩曾认为是新太古代晚期蛇绿岩洋壳残片。该区也有红旗营子群存在。我们对尚义黄土窑地区尚义杂岩和红旗营子群不同类型岩石进行了锆石SHRIMP U-Pb定年。含石榴黑云斜长片麻岩(HB1410)核部锆石年龄为310~2500Ma,边部变质锆石年龄为255Ma左右。黑云片麻岩(HB1411)和石英岩(HB1415)碎屑锆石年龄都为2.5Ga左右。辉长岩(HB1518)和石英闪长岩(HB1519)岩浆锆石年龄为278~279Ma。根据这些资料和前人研究,该地区的原红旗营子群和尚义杂岩变质表壳岩主体可能不是新太古代地质作用产物,而是形成于晚古生代,由不同时代地质体组成的构造杂岩。不存在所谓的太古宙蛇绿岩残片。晚古生代时期,中亚造山带对华北克拉通北缘的影响十分强烈。  相似文献   

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