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1.
Doklady Earth Sciences - The results of U–Pb geochronological studies of Early Paleozoic granitoids from the northern part of the Bureya continental massif are presented. It has been...  相似文献   

2.
This paper presents data on the geological position, geochemistry, age, and isotopic characteristics of the granitoids of the southern part of the Voznesenka terrane, Southern Primorye (Muraviev–Amursky Peninsula and its vicinities). All of the studied granitoids were formed in three stages: the Ordovician, Silurian, and Permian. The Silurian and Permian ages of the granitoid intrusions have been previously determined (Ostrovorussky Massif, 432–422 Ma, and 250 ± 4 Ma, early and late associations, respectively; Sedanka massif, 261 ± 3 Ma). The granites of the Artem and Nadezhdinsky massifs define an U–Pb zircon age of 481 ± 6 and 452 ± 4 Ma, respectively. The geochemical and isotope data show mainly the crustal nature of the granitoids. Their formation was related to melting of relatively immature rocks of the continental crust (mafic–intermediate volcanic rocks). The Nd isotope composition of the granitods (TNd(DM–2) = 1.3 Ga) indicates the absence of the mature ancient crust at the basement of the southern Voznesenka terrane. The maximum contribution of mantle sources to the granite formation is recorded in the Permian associations. A comparison of the peaks of intrusive magmatism in the southern part of the Voznesenka terrane and adjacent territories suggests that the formation of the granitoids of the Muraviev–Amursky Peninsula and its vicinities was caused by the interaction of continental blocks with two oceanic basins: the Paleoasian (and its fragments) and Paleopacific ones.  相似文献   

3.
A detailed study of a relatively well-exposed fragment of the Barabash Formation in the southern part of the Voznesenka terrane is carried out to specify the geodynamic settings of the Permian volcanogenic and volcanogenic-sedimentary complexes in South Primorye. It is established that the basaltic flows juxtaposed in the studied sequence originated from sharply different sources. The geochemical characteristics indicate that the basalts from the sequence base were presumably derived by melting of oceanic lithospheric mantle or asthenosphere, while the source of the overlying basalts was lithospheric mantle reworked by a subduction process. The basalts are subsequently overlain by tuffaceous–terrigenous and terrigenous rocks and limestones with remains of Capitanian (Middle Permian) fauna. Accessory zircons extracted from the tuffaceous–terrigenous rocks yield an U–Pb concordant age of 233.3 ± 3.3 Ma (Middle Triassic Ladinian Stage) for the youngest zircon population. The obtained data lead us to conclude that the Barabash Formation is a tectonostratigraphic rather than stratigraphic unit and may be a fragment of the Triassic accretionary wedge. The obtained data cast doubt on the accepted assignment of this unit to the Voznesenka terrane. It is more logical to include it in the Laoelin–Grodekov terrane, which represents a fragment of the Late Paleozoic active continental margin. This suggests that the boundary between these blocks should be specified and the timing of the final stage of amalgamation of the Laoelin–Grodekov terrane with the terranes of the Bureya–Khanka orogenic belt should be revised.  相似文献   

4.
The geochemical features of typical representatives of ferromanganese deposits are studied in the eastern Bureya and Khanka massifs (Russian Far East). Based on the major-, trace-, and rare-earth element distribution, the hydrothermal–sedimentary (with hydrogenic component) nature of their mineralization is established and the geodynamic setting and depth of ore formation are estimated. The differences in the depth and redox conditions of ore formation resulted in the metallogenic zonation of the Khingan block (Bureya Massif), which is expressed in a westward change in ore composition from the magnetite ores of the Kosten’ga–Kimkan zone to the hematite–magnetite and iron–manganese ores of the South Khingan zone. The conclusions about the participation of hydrothermal sources in the formation of ore mineralization of the studied deposits and the specifics of their localization require revision of the strategy of exploration and evaluation of ferromanganese ores in the southern Far East.  相似文献   

5.
A massif of porhyritic microcline biotite granites located in the southern part of the Bureya (Turan) terrane has an age of 185 ± 1 Ma. The granites are characterized by (K2O + Na2O) > 8%, a K2O predominance over Na2O, and a moderately differentiated REE distribution pattern ((La/Yb)n = 14.7–28.5). The obtained age indicates that at least one stage of the Early Mesozoic granitoid magmatism in the Bureya terrane occurred in the Early Jurassic. The formation of early Mesozoic granitoids was presumably related to collision between North Asian and Sino-Korean cratons, and the intervening Amur superterrane, although a subduction origin also cannot be completely ruled out.  相似文献   

6.
According to U–Pb dating, the granitoids of the Tyrma–Bureya complex in the northern Bureya–Jiamusi superterrane of the Central Asian fold belt are not of Paleozoic, as previously thought, but of Mesozoic age (Nizhnyaya Stoiba massif, 218 ± 2 Ma; Talakan and Ust’-Dikan massifs, 185 ± 1 Ma). They formed at the early stages of collision between the North Asian and Sino-Korean cratons and the intervening Amur superterrane.  相似文献   

7.
The results of geochemical and geochronological study of the Kengurak-Sergachi gabbroanorthosite massif in the Selenga-Stanovoi superterrane, southern frame of the Siberian craton, are presented. According to geochemical peculiarities, the massif rocks are close to the autonomous “massif-type anorthosite.” The massif age corresponds to 1866 ± 6 Ma based on the results of U-Pb zircon dating. The Kengurak-Sergachi massif was intruded most likely in post-collision epoch concurrently to formation of the South Siberian giant post-collision magmatic belt (1.87–1.84 Ga) extending along the southwestern flank of the Siberian craton.  相似文献   

8.
兴蒙造山系新元古代-古生代沉积盆地演化   总被引：5，自引：0，他引：5       下载免费PDF全文
在系统分析兴蒙造山系新元古代-古生代24个沉积盆地类型、沉积建造、生物地层与年代地层等特征的基础上,划分了6个沉积大地构造演化阶段并对其进行讨论:(1)新元古代-寒武纪早期陆缘增生阶段:额尔古纳地块向南增生并与兴安地块拼贴,形成环宇-新林蛇绿岩拼合带;(2)寒武纪纽芬兰世-第二世陆缘稳定沉积阶段:各地块边缘发育相对稳定的碎屑岩-碳酸盐岩沉积,佳木斯地块受晚泛非造山作用影响;(3)早-中奥陶世多岛弧盆系形成阶段:多宝山地区弧盆系发育,其他地块边缘均有不同强度陆间洋壳俯冲作用;(4)晚奥陶世-志留纪普里道利世多岛弧盆系发展阶段:各地块隆升遭受剥蚀;(5)早泥盆世-早石炭世多岛弧盆系消减阶段:早石炭世晚期额尔古纳-兴安地块与松嫩地块拼贴,佳木斯西缘由被动陆缘转为活动陆缘;(6)晚石炭世-二叠纪乐平世拼合后洋-陆转化阶段:从早石炭世晚期开始至二叠纪末,佳木斯地块分别与松嫩地块、兴凯地块拼贴,至此东北各地块拼贴完成.   相似文献   

9.
The Tagil structure representing a large fragment of the Paleozoic island arc on the eastern slope of the Urals has been sufficiently well studied in its southern part (Middle Urals). In contrast, reliable data on the age and geochemical properties of various, including granitoid, rock complexes available for its northern part are scarce. The first data on the U–Pb LA–ICP–MS age of zircons from quartz diorites of the Man’ya massif of the Petropavlovsk Complex (436 ± 3 Ma, MSWD = 1.3), tonalites of the same complex (439.4 ± 1.3 Ma, MSWD = 1.3), granites of the Yuzhno-Pomur massif of the Severorudnichnyi Complex (422.4 ± 3 Ma, MSWD = 1.5), and titanite of the same massif (423.4 ± 4.4 Ma, MSWD = 0.84) have been obtained. Based on these data combined with the geochemical properties of the host rocks, the conclusion that they were crystallized at the initial stages of the formation of comagmatic volcanic series is supported; by their composition, granitoids correspond to island arc igneous rocks.  相似文献   

10.
Early Paleozoic granitoids of autochthonous and allochthonous facies in the Baikal area (Ol’khon Island, Khamar-Daban Ridge) are in close spatial association with gneisses, migmatites, and plagiogranites and are usually confined to granite–gneiss domes. They are virtually not subjected to magmatic differentiation. Formation of granitoids of the Solzan massif and Sharanur complex lasted 26–28 Myr, which might be considered an indicator of collisional granitoid magmatism. Collisional granitoids of different provinces have a series of indicative features: They are peraluminous and highly potassic and are enriched in crustal elements (Rb, Pb, and Th) but sometimes have low contents of volatiles. In contrast to collisional magmatism, petrogenesis of intraplate granitoids does not depend on the composition and age of the enclosing rocks. The geochemical evolution of intraplate granitoid magmatism in the Baikal area is expressed as an increase in contents of F, Li, Rb, Cs, Sn, Be, Ta, Zr, and Pb and a decrease in contents of Ba, Sr, Zn, Th, and U during the differentiation of multiphase intrusions. The geochemical diversity of these granitoids formed both from crustal and from mantle sources and as a result of the mantle–crust interaction, might be due to the effect of plume on the geologic evolution of intraplate magmatism. The wide range of compositions and geochemical types of igneous rocks (from alkali and subalkalic to rare-metal granitoids) within the Late Paleozoic Baikal magmatism area suggests its high ore potential.  相似文献   

11.
This paper addresses the reasons for the evolution and genesis of the Early Paleozoic granitoids of the Munku-Sardyk Range, Eastern Sayan. It was established that the massif consists of three phases representing derivatives of mantle and crustal magmas. The major part of the massif is made up of mantle-derived granitoids, which are chemically similar to the exotic NEB-adakite association.The crustal granitoids of pluton were formed under the influence of the thermal field of primary magmas. The protoliths of these granitoids were presumably the metamorphic rocks of the Slyudyanka Group. In terms of geochemistry, they are ascribed to calc-alkaline rocks but bear some signatures of anorogenic granitoids.It was shown that the compositional variations of the granitoids were controlled by many factors, the most important of which are the compositions of primary magmas and their contaminant. The geochemical characteristics and mineral compositions of the granitoids distinctly reflect interaction with the host metamorphic sequences. Carbonate rocks played an important role in this process, causing an increase in the alkalinity and basicity of granitoid magmas. The abundance of carbonate rocks in the region was probably the main reason for the broad variations of alkalinity in coeval granitoids.Using the obtained data, a genetic model was proposed to explain all stages of the formation of the massif and compositional evolution of its rocks.  相似文献   

12.
Resulting from U-Pb geochronological study, it has been found that the gabbro-amphibolites composing the Bureya (Turan) Terrane in the eastern part of the Central Asian Fold Belt are Early Paleozoic (Early Ordovician; 455 ± 1.5 Ma) in age rather than Late Proterozoic as was believed earlier. The gabbro-amphibolites and associated metabasalts are close to tholeiites of the intraoceanic island arcs in terms of the geochemical properties. It is suggested that the tectonic block composed of these rocks was initially a seafloor fragment that divided the Bureya and Argun terranes in the Early Paleozoic and was later tectonically incorporated into the modern structure of the Bureya Terrane as a result of Late Paleozoic and Mesozoic events.  相似文献   

13.
The northern part of the western Kunlun (southern margin of the Tarim basin) represents a Sinian rifted margin. To the south of this margin, the Sinian to Paleozoic Proto-Tethys Ocean formed. South-directed subduction of this ocean, beneath the continental southern Kunlun block during the Paleozoic, resulted in the collision between the northern and southern Kunlun blocks during the Devonian. The northern part of the Paleo-Tethys Ocean, located to the south of the southern Kunlun, was subducted to the north beneath the southern Kunlun during the Late Paleozoic to Early Mesozoic. This caused the formation of a subduction-accretion complex, including a sizeable accretionary wedge to the south of the southern Kunlun. A microcontinent (or oceanic plateau?), which we refer to as “Uygur terrane,” collided with the subduction complex during the Late Triassic. Both elements together represent the Kara-Kunlun. Final closure of the Paleo-Tethys Ocean took place during the Early Jurassic when the next southerly located continental block collided with the Kara-Kunlun area. From at least the Late Paleozoic to the Early Jurassic, the Tarim basin must be considered a back-arc region. The Kengxiwar lineament, which “connects” the Karakorum fault in the west and the Ruogiang-Xingxingxia/Altyn-Tagh fault zone in the east, shows signs of a polyphase strike-slip fault along which dextral and sinistral shearing occurred.  相似文献   

14.
Overall petrologic and geochemical data indicate that the early Paleozoic magmatism in the Olkhon area of the Baikal Region exhibits diverse types of granitoids, whose time of formation is estimated at a narrow age interval of 500-465 Ma. This magmatism was responsible for the formation of both autochthonous gneiss-migmatite-granitoid suites (Sharanur complex) and multiphase intrusions (Aya complex) emplaced into the upper horizons of the continental crust. In major-element chemistry, K2O/Na2O values, and rare-element composition the migmatite-plagiogranites and calc-alkaline and subalkaline granitoids of the Sharanur complex are similar to the host gneisses and schists, as they were likely derived from melting of the ancient metamorphic substratum of the Olkhon series. In new isotope-geochemical characteristics (ICP MS method) the Sharanur granitoids are close to the first-phase biotite granites of the Aya massif, whose further geochemical evolution was governed mainly by intrachamber magmatic differentiation leading to the production of second-phase leucogranites enriched in HREE and HFSE (in particular, Ta and Nb) and depleted in Sr, Ba, Eu, Li, and LREE. The origin of the autochthonous and intrusive granitoids is related to early Paleozoic collision events within the Olkhon metamorphic terrane, while the formation of syncollisional granitoids is best explained by both melting of the crust protolith (Sharanur complex) and magmatic differentiation (multiphase Aya intrusion). All mineralogical and geochemical characteristics indicate that these granitoids are distinguished from rare-metal pegmatoid granites and Li-F and Rb-Be-Nb pegmatites, whose vein bodies crosscut the granitoids, and are regarded as middle Paleozoic rocks, which mark the transition to within-plate magmatism in the Baikal Region.  相似文献   

15.
We studied the geologic position, mineralogy, petrography, chemical composition, and age of granitoids of the Gamov batholith located in the Heilongjiang-Grodekovo terrane, southern Primorye (Russia). The studies have revealed four intrusive rock phases, from gabbro to leucogranites, in the massif. U-Pb zircon dating of tonalites of phase II and leucogranites of phase IV (254 ± 4 and 259 ± 2 Ma, respectively) shows that the intrusion of granitoids took place in the Late Permian without a significant gap in time. Structural investigations gave evidence for the intrusion in the E-W compression setting. Geochemical studies have revealed granitoids of strongly different compositional types in the intrusive massif: gabbroids, quartz diorites and tonalites with characteristics of low-alumina TTG, calc-alkalic granodiorites and I-type granites, and moderately alkaline leucogranites. The obtained data, together with the results of previous research into the Permo-Triassic granitoids of southern Primorye, reject their formation as a result of the evolution of the Solonker oceanic structures and suggest a more intricate tectonic scenario, which calls for additional study.  相似文献   

16.
何雨思  高福红  修铭  许文良 《地球科学》2019,44(10):3223-3236
前人对张广才岭福兴屯组研究程度较低,限制了对区域古生代构造演化的认识.福兴屯组凝灰岩锆石30个测点加权平均年龄为392±3 Ma,砂岩碎屑锆石最小一组年龄为393 Ma,指示福兴屯组形成于中泥盆世.Al2O3/TiO2平均值为19.58,稀土元素球粒陨石标准化曲线具有轻稀土富集、重稀土稳定和负Eu异常特征,结合碎屑锆石年龄峰值,确定福兴屯组物源主要为晚古生代中酸性火成岩和早古生代花岗质岩.地球化学和区域火山岩特征共同揭示福兴屯组形成于伸展构造环境.松嫩-张广才岭地块和佳木斯地块晚古生代早期地层均广泛分布有489~551 Ma的碎屑锆石,暗示两地块在福兴屯组沉积之前已完成拼合,为两地块于早古生代晚期拼合提供了新的证据.   相似文献   

17.
Early Proterozoic granitoids are of a limited occurrence in the Baikal fold area being confined here exclusively to an arcuate belt delineating the outer contour of Baikalides, where rocks of the Early Precambrian basement are exposed. Geochronological and geochemical study of the Kevakta granite massif and Nichatka complex showed that their origin was related with different stages of geological evolution of the Baikal fold area that progressed in diverse geodynamic environments. The Nichatka complex of syncollision granites was emplaced 1908 ± 5 Ma ago, when the Aldan-Olekma microplate collided with the Nechera terrane. Granites of the Kevakta massif (1846 ± 8 Ma) belong to the South Siberian postcollision magmatic belt that developed since ～1.9 Ga during successive accretion of microplates, continental blocks and island arcs to the Siberian craton. In age and other characteristics, these granites sharply differ from granitoids of the Chuya complex they have been formerly attributed to. Accordingly, it is suggested to divide the former association of granitoids into the Chuya complex proper of diorite-granodiorite association ～2.02 Ga old (Neymark et al., 1998) with geochemical characteristics of island-arc granitoids and the Chuya-Kodar complex of postcollision S-type granitoids 1.85 Ga old. The Early Proterozoic evolution of the Baikal fold area and junction zone with Aldan shield lasted about 170 m.y. that is comparable with development periods of analogous structures in other regions of the world.  相似文献   

18.
Iran is a mosaic of Ediacaran–Cambrian (Cadomian; 520–600 Ma) blocks, stitched together by Paleozoic and Mesozoic ophiolites. In this paper we summarize the Paleozoic ophiolites of Iran for the international geoscientific audience including field, chemical and geochronological data from the literature and our own unpublished data. We focus on the five best known examples of Middle to Late Paleozoic ophiolites which are remnants of Paleotethys, aligned in two main zones in northern Iran: Aghdarband, Mashhad and Rasht in the north and Jandagh–Anarak and Takab ophiolites to the south. Paleozoic ophiolites were emplaced when N-directed subduction resulted in collision of Gondwana fragment “Cimmeria” with Eurasia in Permo-Triassic time. Paleozoic ophiolites show both SSZ- and MORB-type mineralogical and geochemical signatures, perhaps reflecting formation in a marginal basin. Paleozoic ophiolites of Iran suggest a progression from oceanic crust formation above a subduction zone in Devonian time to accretionary convergence in Permian time. The Iranian Paleozoic ophiolites along with those of the Caucausus and Turkey in the west and Afghanistan, Turkmenistan and Tibet to the east, define a series of diachronous subduction-related marginal basins active from at least Early Devonian to Late Permian time.  相似文献   

19.
Geological, geochemical, and isotopic data (U-Pb for zircon and Sm-Nd for whole-rock samples) are summarized for Proterozoic and Early Paleozoic geological complexes known from various regions of East Antarctica. The main events of tectonothermal and magmatic activity are outlined and correlated in space and time. The Paleoproterozoic is characterized as a period of rifting in Archean blocks, their partial mobilization, and formation of a new crustal material over a vast area occupied by present-day East Antarctica. In most areas, this material was repeatedly reworked at the subsequent stages of evolution (1800–1700, 1100–1000, 550–500 Ma). Complexes of Mesoproterozoic juvenile rocks (1500, 1400–1200, 1150–1100 Ma) arising in convergent suprasubduction geodynamic settings are established in some areas (basalt-andesite and tonalite-granodiorite associations with characteristic geochemical signatures). The evolution of the Proterozoic regions in East Antarctica may be interpreted as a Wilson cycle with the destruction of the Archean megacontinent 2250 Ma ago and the ultimate closure of the secondary oceanic basins by 1000 Ma ago. The Mesoproterozoic regions make up a marginal volcanic-plutonic belt that combines three provinces of different ages corresponding to consecutive accretion of terranes 1500–1150, 1400–950, and 1150–1050 Ma ago. The Neoproterozoic and Early Paleozoic tectonomagmatic activity developed nonuniformly. In some regions, it is expressed in ductile deformation, granulite-facies metamorphism, and postcollision magmatism; in other regions, a weak thermal effect and anorogenic magmatism are noted. The evolution of metamorphic complexes in the regime of isothermal decompression and the intraplate character of granitoids testify to the collision nature of the Early Paleozoic tectonomagmatic activity.  相似文献   

20.
Geological, mineralogical, petrographic, geochemical, and geochronological data are reported for granitoids of the Aturkol Massif (Gorny Altai). It is shown that it was formed in within-plate setting in the Early Triassic, nearly simultaneously with flood basalts of the Kuznetsk Basin and alkalic basite and lampropyre dike swarms in the western Altai-Sayan Fold Region. At the same time, the mineralogical-petrographic, geochemical, and isotope characteristics of the considered granitoids are close to those of I-type granites. Intraplate signatures (elevated HFSE and REE) are recognized only in the least silicic rocks (granosyenites). Obtained data suggest mantle–crustal nature of the granitoids. They were formed by mixing of lamprophyre magmas with high pressure (>10 kbar) crustal melts derived from a mixed source consisting mainly of N-MORB-type metabasites with insignificant admixture of high-Ti basalts and metasedimentary rocks. The contribution of mantle component in the granitoids was insignificant (<20%). Proposed petrogenetic mechanism can provide the formation of large volumes of granitoid magmas with “crustal” geochemical and isotope signatures in an intraplate setting.  相似文献   

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