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1.
Late Paleozoic and Early Mesozoic epochs in the formation history of the Central Asian Foldbelt are distinguished by high rare-metal productivity. A number of large REE, Ta, Nb, Zr, Be, Sn, Li, Mo, Re, and other deposits were formed at that time. As a rule, they are of the magmatic origin and related to the intrusions of highly evolved igneous rocks varying in composition from alkaline ultramafic with carbonatites to alkali and Li-F granites. In general, the occurrences of rare-metal magmatism are related to the rift zones of the Central Asian Rift System formed 310?C190 Ma ago and conjugated with a consecutive series of the Barguzin, Hangay, and Hentiy zonal igneous provinces characterized by the large batholiths in their centers and rift zones in the framework. Such a structure indicates that these provinces were formed above isometric mantle sources or plumes with participation of large-scale crustal anatexis. The evident links of rare-metal deposits to occurrences of mantle magmatism within the zonal igneous provinces show that plume sources played an important role in their formation.  相似文献   

2.
The phanerozoic within-plate magmatism of Siberia is reviewed. The large igneous provinces (LIPs) consecutively arising in the Siberian Craton are outlined: the Altai-Sayan LIP, which operated most actively 400–375 Ma ago, the Vilyui LIP, which was formed from the Middle Devonian to the Early Carboniferous, included; the Barguzin-Vitim LIP (305–275 Ma); the Late Paleozoic Rift System of Central Asia (318–250 Ma); the Siberian flood basalt (trap) province and the West Siberian rift system (250–247 Ma); and the East Mongolian-West Transbaikal LIP (230–195 Ma), as well as a number of Late-Mesozoic and Cenozoic rift zones and autonomous volcanic fields formed over the last 160 Ma. The trace-element and isotopic characteristics of the igneous rocks of the above provinces are reviewed; their mantle origin is substantiated and the prevalence of PREMA, EM2, and EM1 mantle magma sources are shown. The paleogeographic reconstructions based on paleomagnetic data assume that the Iceland hot spot was situated beneath the Siberian flood basalts 250 Ma ago and that the mantle plumes retained a relatively stable position irrespective of the movements of the lithospheric plates. At present, the Iceland hot spot occurs near the northern boundary of the African large low shear velocity province (LLSVP). It is suggested that the within-plate Phanerozoic magmatism of Siberia was related to the drift of the continent above the hot spots of the African LLSVP.  相似文献   

3.
亚洲3个大火成岩省(峨眉山、西伯利亚、德干)对比研究   总被引：1，自引：0，他引：1  
峨眉山(～260 Ma)、西伯利亚(～250 Ma)和德干(～66 Ma)大陆溢流玄武岩是世界上3个重要的大火成岩省.大火成岩省至少具有4个通常被用于识别古地幔柱的标志:(1)先于岩浆作用的地表隆升;(2)与大陆裂谷化和裂解事件相伴;(3)与生物灭绝事件联系密切;(4)地幔柱源玄武岩的化学特征.虽然这3个大火成岩省都是来源于原始地幔柱,但是它们的地球化学特征有本质上的差异,反映其地幔柱曾与不同的上地幔库相互作用.(1)峨眉山和西伯利亚大陆溢流玄武岩的母岩浆,在上升过程中经受了与地球化学上和古老克拉通岩石圈地幔相同的上地幔库(EM1型幔源)的相互作用;(2)而德干大火成岩省没有受到地壳(或岩石圈)混染的原生玄武岩则显示地幔柱和EM2之间的Sr-Nd同位素变化.这种差异有可能制约了3个大火成岩省的成矿潜力.峨眉山和西伯利亚大火成岩省含有世界级岩浆矿床,而德干大火成岩省则不含矿.  相似文献   

4.
A number of large areas of igneous provinces produced in North Asia in the Late Paleozoic and Early Mesozoic include Siberian and Tarim traps and giant rift systems. Among them, the Central Asian Rift System (CARS) has the most complicated structure, evolved during the longest time, and is a large (3000 × 600 km) latitudinally oriented belt of rift zones extending from Transbaikalia and Mongolia to Middle Asia and including the Tarim traps in western China. CARS was produced in the Late Carboniferous, and its further evolution was associated with the lateral migration of rifting zones; it ended in the Early Jurassic and lasted for approximately 110 Ma. CARS was produced on an active continental margin of the Siberian continent and is noted for largest batholiths, which were emplaced simultaneously with rifting. The batholiths are surrounded by rift zones and compose, together with them, concentrically zoned magmatic areas, with crustal (granitoid) magmatism focused within their central portions, whereas mantle (rift-related) magmatism is predominant in troughs and grabens in peripheral zones. The batholiths show geological and isotopic geochemical evidence that their granitoids were produced by the anatexis of the host rocks at active involvement of mantle magmas. Zonal magmatic areas of the type are viewed as analogues of large igneous provinces formed in the environments characteristic of active continental margins. Large within-plate magmatic provinces in North Asia are thought to have been generated in relation to the overlap of at least two mantle plumes by the Siberian continent during its movement above the hot mantle field. In the continental lithosphere, mantle plumes initiated within-plate magmatic activity and facilitated rifting and the generation of traps and alkaline basite and alkali-salic magmatic associations. Because of the stressed states during collision of various type in the continental margin, the mantle melts did not ascend higher than the lowest crustal levels. The thermal effect of these melts on the crustal rocks induced anatexis and eventually predetermined the generation of the batholiths.  相似文献   

5.
The paper systematizes and integrates the results of geological, isotopic geochronological, and geochemical studies of the igneous rocks that make up the Ulkan-Dzhugdzhur anorthosite-rapakivi granite-peralkaline granite association and related mineralization. This association is a typical example of anorogenic igneous rocks that formed in the within-plate geodynamic setting most likely under effect of the mantle superplume, which was active in the territory of the Siberian Craton 1.75–1.70 Ga ago. The igneous rock association formed in a discrete regime that reflected the pulsatory evolution of a sublithospheric mantle source. The prerift (1736–1727 Ma) and rift proper (1722–1705 Ma) stages and a number of substages are distinguished. All igneous rocks pertaining to this association have mixed mantle-crustal origin. Basic rocks crystallized from the OIB-type basaltic magma, which underwent crustal contamination at various depths. Felsic rocks are products of mantle and crustal magma mixing. The contribution of mantle component progressively increased in a time-dependent sequence: moderately alkaline subsolvus granite → moderately alkaline and alkaline hypersolvus granites → peralkaline hypersolvus granite. All endogenic deposits in the studied district are related to a single source represented by the mantle plume and its derivatives. The Fe-Ti-apatite deposits hosted in anorthosite formed as a result of intense lower crustal contamination of basaltic magma near the Moho discontinuity and two stages of fractional crystallization at lower and upper crustal depth levels. The rare-metal deposits are genetically related to peralkaline granite. Formation of uranium deposits was most likely caused by Middle Riphean rejuvenation of the region, which also involved rocks of the Ulkan-Dzhugdzhur association.  相似文献   

6.
The Central Asian Orogenic Belt (CAOB) was produced as a consequence of the successive closure of the Paleoasian Ocean and the accretion of structures formed within it (island arcs, oceanic islands, and backarc basins) to the Siberian continent. The belt started developing in the latest Late Neoproterozoic, and this process terminated in the latest Permian in response to the collision of the Siberian and North China continents that resulted in closure of the Paleoasian ocean (Metcalfe, 2006; Li et al., 2014; Liu et al., 2009; Xiao et al., 2010; Didenko et al., 2010). Throughout the whole evolutionary history of this Orogenic Belt, a leading role in its evolution was played by convergent processes. Along with these processes, an important contribution to the evolution of the composition and structure of the crust in the belt was made by deep geodynamic processes related to the activity of mantle plumes.Indicator complexes of the activity of mantle plumes are identified, and their major distribution patterns in CAOB structures are determined. A number of epochs and areas of intraplate magmatism are distinguished, including the Neoproterozoic one (Rodinia breakup and the origin of alkaline rock belt in the marginal part of the Siberian craton); Neoproterozoic–Early Cambrian (origin of oceanic islands in the Paleoasian Ocean); Late Cambrian–Early Ordovician (origin of LIP within the region of Early Caledonian structures in CAOB); Middle Paleozoic (origin of LIP in the Altai–Sayan rift system); Late Paleozoic–Early Mesozoic (origin of the Tarim flood-basalt province, Central Asian rift system, and a number of related zonal magmatic areas); Late Mesozoic–Cenozoic (origin of continental volcanic areas in Central Asia).Geochemical and isotopic characteristics are determined for magmatic complexes that are indicator complexes for areas of intraplate magmatism of various age, and their major evolutionary trends are discussed. Available data indicate that mantle plumes practically did not cease to affect crustal growth and transformations in CAOB in relation to the migration of the Siberian continent throughout the whole time span when the belt was formed above a cluster of hotspots, which is compared with the African superplume.  相似文献   

7.
The Phanerozoic history of mafic magmatism in the southern Siberian craton included three major events. The earliest event (～500 Ma) recorded in dolerite dikes occurred during accretion and collision at the early stage of the Central Asian orogen. Injection of mafic melts into the upper crust was possible in zones of diffuse extension within the southern Siberian craton which acted as an indenter. The Late Paleozoic event (～275 Ma) produced dikes that intruded in a setting of subduction-related extension at the back of the active continental margin of Siberia during closure of the Mongolia–Okhotsk ocean, as well as slightly older volcanics (290 Ma) in the Transbaikalian segment of the Central Asian orogen. Early Mesozoic magmatism in the southern Siberian craton resulted in numerous 240–250 Ma mafic intrusions in the Angara–Taseeva basin. The intrusions (Siberian traps) appeared as the subducting slab of the Mongolia–Okhotsk ocean interacted with a lower mantle plume. The post-Late Paleozoic ages of flood basalts (290–275 Ma) correspond to progressive northwestward (in present coordinates) motion of the slab beneath the southern craton margin which likely ceased after the slab had reached the zone of the Siberian superplume. Since its consolidation after the Early Mesozoic activity, the crust in the area has no longer experienced extension favorable for intrusion of basaltic magma.  相似文献   

8.
Data on the composition, inner structure, and magma sources of giant batholith in the Central Asian Orogenic Belt are analyzed with reference to the Khangai batholith. The Khangai batholith was emplaced in the Late Permian–Early Triassic (270–240 Ma) and is the largest accumulations (>150000 km2) of granite plutons in central Mongolia. The plutons are dominated by granites of normal alkalinity and contain subalkaline granites and more rare alkaline granites. The batholith is hosted in the Khangai zonal magmatic area, which consists of the batholith itself and surrounding rift zones. The zones are made up of bimodal basalt–trachyte–comendite (pantellerite) or basalt-dominated (alkaline basalt) volcanic associations, whose intrusive rocks are dominated by syenite and granite, granosyenite, and leucogranite. Both the batholith and the rift zones were produced within the time span of 270–240 Ma. Although the rocks composing the batholith and its rift surroundings are different, they are related through a broad spectrum of transitional varieties, which suggests that that the mantle and crustal melts could interact at various scale when the magmatic area was produced. A model is suggested to explain how the geological structure of the magmatic area and the composition of the magmatic associations that make up its various zones were controlled by the interaction between a mantle plume and the lithospheric folded area. The mantle melts emplaced into the lower crust are thought to not only have been heat sources and thus induced melting but also have predetermined the variable geochemical and isotopic characteristics of the granitoids. In the marginal portions of the zonal area, the activity of the mantle plume triggered rifting associated with bimodal and alkaline granite magmatism. The formation of giant batholiths was typical of the evolution of the active continental margin of the Siberian paleocontinent in the Late Paleozoic and Early Mesozoic: the Khangai, Angara–Vitim, and Khentei batholiths were formed in this area within a relatively brief time span between 300 and 190Ma. The batholiths share certain features: they consist of granitoids of a broad compositional range, from tonalite and plagiogranite to granosyenite and rare-metal granites; and the batholiths were produced in relation to rifting processes that also formed rift magmatic zones in the surroundings of the batholiths. The large-scale and unusual batholith-forming processes are thought to have occurred when the active continental margin of the Late Paleozoic Siberian continent overlapped a number of hotspots in the Paleo- Asian Ocean. This resulted in the origin of a giant anorogenic magmatic province, which included batholiths, flood-basalt areas in Tarim and Junggar, and the Central Asian Rift System. The batholiths are structural elements of the latter and components of the zonal magmatic areas.  相似文献   

9.
地幔柱构造是基于全地慢对流模式、主要依据热点火山活动提出的新的全球构造理论。它的主要表现形式和产物是地幔柱头上部地壳抬升、岩浆活动形成大火成岩省、大型放射状岩墙群，并导致大陆裂解、板块运动和大规模成矿，是生物灭绝、磁极倒转的诱因。中国大陆的地质演化历史中保存了多期地幔柱活动印记，它们主要是华南新元古代Rodinia地幔柱、古生代古特提斯和峨眉山地幔柱和中一新生代中国东部地慢柱构造事件。上述地幔柱活动产生了地壳抬升、强烈岩浆活动、大陆伸展与裂解、岩石圈剧烈减薄和大规模成矿等重要地质事件。  相似文献   

10.
Supercontinent evolution and the Proterozoic metallogeny of South America   总被引：2，自引：1，他引：2  
The cratonic blocks of South America have been accreted from 2.2 to 1.9 Ga, and all of these blocks have been previously involved in the assembly and breakup of the Paleoproterozoic Atlantica, the Mesoproterozoic to Neoproterozoic Rodinia, and the Neoproterozoic to Phanerozoic West Gondwana continents. Several mineralization phases have sequentially taken place during Atlantica evolution, involving Au, U, Cr, W, and Sn. During Rodinia assembly and breakup and Gondwana formation, the crust-dominated metallogenic processes have been overriding, responsible for several mineral deposits, including Au, Pd, Sn, Ni, Cu, Zn, Mn, Fe, Pb, U, P2O5, Ta, W, Li, Be and precious stones. During Rodinia breakup, epicontinental carbonate-siliciclastic basins were deposited, which host important non-ferrous base metal deposits of Cu–Co and Pb–Zn–Ag in Africa and South America. Isotope Pb–Pb analyses of sulfides from the non-ferrous deposits unambiguously indicate an upper crustal source for the metals. A genetic model for these deposits involves extensional faults driving the circulation of hydrothermal mineralizing fluids from the Archean/Paleoproterozoic basement to the Neoproterozoic sedimentary cover. These relations demonstrate the individuality of metal associations of every sediment-hosted Neoproterozoic base-metal deposit of West Gondwana has been highly influenced by the mineralogical and chemical composition of the underlying igneous and metaigneous rocks.  相似文献   

11.
S.  M.  D.   《Gondwana Research》2007,11(1-2):7
The Western Pacific Triangular Zone (WPTZ) is the frontier of a future supercontinent to be formed at 250 Ma after present. The WPTZ is characterized by double-sided subduction zones to the east and south, and is a region dominated by extensive refrigeration and water supply into the mantle wedge since at least 200 Ma. Long stagnant slabs extending over 1200 km are present in the mid-Mantle Boundary Layer (MBL, 410–660 km) under the WPTZ, whereas on the Core–Mantle Boundary (CMB, 2700–2900 km depth), there is a thick high-V anomaly, presumably representing a slab graveyard. To explain the D″ layer cold anomaly, catastrophic collapse of once stagnant slabs in MBL is necessary, which could have occurred at 30–20 Ma, acting as a trigger to open a series of back-arc basins, hot regions, small ocean basins, and presumably formation of a series of microplates in both ocean and continent. These events were the result of replacement of upper mantle by hotter and more fertile materials from the lower mantle.The thermal structure of the solid Earth was estimated by the phase diagrams of Mid Oceanic Ridge Basalt (MORB) and pyrolite combined with seismic discontinuity planes at 410–660 km, thickness of the D″ layers, and distribution of the ultra-low velocity zone (ULVZ). The result clearly shows the presence of two major superplumes and one downwelling. Thermal structure of the Earth seems to be controlled by the subduction history back to 180 Ma, except in the D″ layer. The thermal structure of the D″ layer seems to be controlled by older slab-graveyards, as expected by paleogeographic reconstructions for Laurasia, Gondwana and Rodinia back to 700 Ma.Comparison of mantle tomography between the Pacific superplume and underneath the WPTZ suggests the transformation of a cold slab graveyard to a large-scale mantle upwelling with time. The Pacific superplume was born from the coldest CMB underneath the 1.0–0.75 Ga supercontinent Rodinia where huge amounts of cold slabs had accumulated through collision-amalgamation of more than 12 continents. A high velocity P-wave anomaly on a whole-mantle scale shows stagnant slabs restricted to the MBL of circum-Pacific and Tethyan regions. The high velocity zones can be clearly identified within the Pacific domain, suggesting the presence of slab graveyards formed at geological periods much older than the breakup of Rodinia. We speculate that the predominant subduction occurred through the formation period of Gondwana, presumably very active during 600 to 540 Ma period, and again from 400 to 300 Ma during the formation of the northern half of Pangea (Laurasia). We correlate the three dominant slab graveyards with three major orogenies in earth history, with the emerging picture suggesting that the present-day Pacific superplume is located at the center of the Rodinian slab graveyard.We speculate the mechanism of superplume formation through a comparison of the thermal structure of the mantle combined with seismic tomography under the Western Pacific Triangular Zone (WPTZ), Laurasia (Asia), Gondwana (Africa), and Rodinia (Pacific). The coldest mantle formed by extensive subduction to generate a supercontinent, changes with time of the order of several hundreds of million years to the hottest mantle underneath the supercontinent. The Pacific superplume is tightly defined by a steep velocity gradient on the margin, particularly well documented by S-wave velocity. The outermost region of the superplume is characterized by the Rodinia slab graveyard forming a donut-shape. We develop a petrologic model for the Pacific superplume and show how larger plumes are generated at shallower depths in the mantle. We link the mechanism of formation of the superplume to the presence of the mineral post-perovskite, the phase transformation of which to perovskite is exothermic, and thus aids in transporting core heat to mantle, and finally to planetary space by plumes.We summarize the characteristics of tectonic processes operating at the CMB to propose the existence of an “anti-crust” generated through “anti-plate tectonics” at the bottom of the mantle. The chemistry of the anti-crust markedly contrasts with that of the continental crust overlying the mantle. Both the crust and the anti-crust must have increased in volume through geologic time, in close relation with the geochemical reservoirs of the Earth. The process of formation of a new superplume closely accompanies the process of development of anti-crust at the bottom of mantle, through the production of dense melt from the partial melting of recycled MORB, observed now as the ULVZ. When CMB temperature is recovered to near 4000 K through phase transformation, the recycled MORB is partially melted imparting chemical buoyancy of the andesitic residual solid which rises up from CMB, leaving behind the dense melt to sink to CMB and thus increase the mass of anti-crust. These small-scale plumes develop to a large-scale superplume through collision and amalgamation with time. When all recycled MORBs are consumed, it is the time of demise of superplume. Immediately above the CMB, anti-plate tectonics operates to develop anti-crust through the horizontal movement of accumulated slab and their partial melting. Thus, we speculate that another continent, or even a supercontinent, has developed through geologic time at the bottom of the mantle.We also evaluate the heating vs. cooling models in relation to mantle dynamics. Rising plumes control not only the rifting of supercontinents and continents, but also the Atlantic stage as seen by anchored ridge by hotspots in the last 200 Ma in the Atlantic. Therefore, we propose that the major driving force for the mantle dynamics is the heat supplied from the high-T core, and not the slab pull force by cooling. The best analogy for this is the atmospheric circulation driven by the energy from Sun.  相似文献   

12.
Giant sedimentary rock-hosted stratiform copper (SSC) deposits commonly occur in rift environments, temporally coincident with the breakup of the Rodinia and Pangea supercontinents. However, whether or not such deposits have also formed during the breakup of the Paleoproterozoic Columbia supercontinent is not well known. A group of dolostone-hosted Cu deposits in late Paleoproterozoic rift-related sedimentary sequences of the Dongchuan Group, South China, form one of the largest SSC districts in the world. Being one of the largest SSC deposits in the region, the Yinmin deposit has stratiform Cu orebodies intruded by dolerite dykes. One dyke has a SIMS zircon U–Pb age of 1,701?±?28 Ma, slightly younger than the ore-hosting strata with a zircon U–Pb age of 1,742?±?13 Ma for a tuff unit. Six chalcopyrite and bornite separates from stratiform orebodies contain highly radiogenic Os and extremely low common Os and yield a weighted mean Re–Os model age of 1,666?±?82 Ma and a 187Os–187Re errorchron age of 1,585?±?100 Ma. The present zircon U–Pb and sulfide Re–Os ages thus constrain the timing of the mineralization at ~1,700 Ma. The Yinmin deposit and, by inference, other SSC deposits in the region, arguably represent a large-scale SSC mineralization event during the late Paleoproterozoic. The formation of these deposits was coeval with the initial breakup/fragmentation of the Columbia supercontinent. This study highlights the temporal and likely genetic links between large-sized SSC deposits and the supercontinent cycle.  相似文献   

13.
The intraplate activity within the Siberian Craton in the Phanerozoic is related to continental migration above the hot spot agglomeration compared to the African superplume. The continuity of intraplate activity within this superplume testifies to its age identity to the antipodal to the Rodinian superplume that destroyed the Rodinia supercontinent. This allowed us to conclude that the African superplume has existed for no less than 1 Ga. Because the Rodinian and Pacific superplumes are compared, it may be gathered that superplumes are the most long-lived deep-seated structures of the Earth. Their relation to the formation of supercontinents probably reflects the antiphased activity caused by the thermostating effect and energy accumulation by superplumes when being overlapped by supercontinents. When analyzing the evolution and generation of modern continents, it is necessary to consider both processes related to the plate boundaries and the activity of superplumes determining the intraplate magmatism therein.  相似文献   

14.
稀有金属成矿全球时空分布与大陆演化   总被引：1，自引：0，他引：1  
王汝成  邬斌  谢磊  车旭东  向路  刘晨 《地质学报》2021,95(1):182-193
花岗岩是大陆地壳的主要组成,是陆壳的特征性物质。花岗岩的形成及演化往往伴随着金属元素的不断富集和广泛的成矿作用,进而形成与之相关的大陆成矿体系。稀有金属成矿是大陆成矿体系的重要内容,毫无疑问,与花岗岩有关的稀有金属成矿作用是大陆演化的直接产物,因此,稀有金属成矿学是大陆动力学的研究内容之一。花岗伟晶岩是锂、铍、钽最重要的成矿母岩,碱性岩(花岗岩、伟晶岩和碳酸岩)与铌、锆等成矿作用有关。全球稀有金属成矿时代集中在太古代3.0~2.6Ga、古元古代1.8Ga、新元古代1.0~0.9Ga、古生代450~400Ma、早中生代250~200Ma、晚中生代160~130Ma和新生代中新世35~10Ma,直接反映了稀有金属成矿与超大陆演化重大事件具有密切的成因关系。最古老的稀有金属成矿作用始于乌尔-诺基兰超大陆,形成了现今分布于北美、非洲南部、西澳等地的重要钽成矿带,其它时期成矿作用相继对应于哥伦比亚超大陆、罗迪尼亚超大陆、冈瓦纳超大陆和潘吉亚超大陆聚合、裂解作用,并终结于新生代发生的印度板块与亚洲板块的碰撞作用。值得关注的是,稀有金属矿物与稀有金属成矿总是共演化,锂辉石、锂电气石、绿柱石和铌铁矿-钽铁矿等几种重要的稀有金属矿物最早出现的时代都在太古代3.0~2.6Ga。  相似文献   

15.
中国金矿床成矿构造背景探讨   总被引：1，自引：0，他引：1  
罗镇宽  关康  沈明星 《矿床地质》1991,10(4):325-332
本文试图采用板块构造观点来探讨金矿床成矿构造背景。板块的消减带及消减带一侧的大陆边缘活动带和岛弧活动带是有利于金矿化的位置。显生宙以来,中国地块周边发生了3次大规模的板块运动,并伴随有3次大的金矿化。据此将中国划分为海西、特提斯—喜马拉雅、燕山3大构造成矿域。由于受板块构造的控制,导致中国金矿时、空分布规律和成因上的一些重要特征。时间上,前寒武纪金矿不是特别重要,显生宙的金矿占了主导地位;空间上,金矿床常分布在古消减带及其附近的古大陆边缘活动带;成因上,许多矿床具有多期矿化复成因的特征。  相似文献   

16.
The study of the Mesoproterozoic (1473 ± 24 Ma) dolerites of the Olenek uplift of the Siberian craton basement has shown their petrologic and geochemical similarity to typical OIB produced with participation of a mantle plume. The dolerites are characterized by variations in the geochemical composition explained by different degrees of melting of the same source. A conclusion is drawn that the parental melts of the rocks were slightly modified by crustal contamination, as evidenced from their Nd isotope composition (£Nd(T) = + 0.6 to − 0.8) and the presence of inherited zircons of four ages (2564, 2111, 2053, and 1865 Ma). Since the Siberian craton in the structure of the Nuna supercontinent (Columbia) was located relatively close to the Baltic continent and the Congo and Sao Francisco cratons, we assume that the Early Mesoproterozoic mafic intrusions (1500–1470 Ma) of all these cratons belong to the same large igneous province (LIP). The province formation was related to the activity of superplume (or mantle hot field), which supplied mantle matter to the lithosphere basement. The superplume core was probably located beneath the northern part of the Siberian craton, where basites are compositionally most similar to the primary mantle source.  相似文献   

17.
We investigate extension events in the southern Siberian craton between 1.8 and 0.7 Ga. Signature of Late Paleoproterozoic within-plate extension in the Northern Baikal region is found in 167 4± 29 Ma dike swarms. A Mesoproterozoic extension event was associated with intrusion of the 1535 ± 14 Ma Chernaya Zima granitoids into the Urik-Iya graben deposits. Neoproterozoic extension recorded in the Sayan-Baikal dike belt (740-780 Ma dike complexes) was concurrent with the breakup of the Rodinia supercontinent and the initiation of the Paleoasian passive margin along the southern edge of the Siberian craton. The scale of rifting-related magmatism and the features of the coeval sedimentary complexes in the southern Siberian craton indicate that Late Paleoproterozoic and Early Mesoproterozoic extension did not cause ocean opening, and the Paleoasian Ocean opened as a result of Neoproterozoic rifting.  相似文献   

18.
The involvement of the North China Craton (NCC) in the assembly or breakup of Rodinia has long been debated. Studies of palaeomagnetism, mafic sills (dikes), igneous events, and sedimentary records have led to contrasting opinions on this topic. No igneous events related to the late Mesoproterozoic assembly of Rodinia have been reported in the NCC. However, the authors found numerous late Mesoproterozoic zircons in the Tonian system on the northern margin of the NCC. The Tonian Zhulazhagamaodao formation is composed of meta-sandstone, siltstone, slate, carbonate, and dolomine of the littoral to neritic facies and occurs mainly in the western part of the Bayan Obo–Zhaertai–Langshan rift. U–Pb dating of detrital zircons from the Tonian system reveals age peaks at 1079 ± 23 Ma, 1092 ± 22 Ma, 1175 ± 50 Ma, 1175 ± 18 Ma, 1260 ± 45 Ma, 1266 ± 16 Ma, and 1270 ± 26 Ma, which correspond to the timing of Rodinia assembly. Considering that coeval igneous rocks and orogenic belts developed mostly in the Laurentia–Baltica cratons, we propose that these cratons supplied clastic material to the northern margin of the NCC and that they had a close spatial relationship between each other during the Tonian.  相似文献   

19.
The ore deposits of the Mesozoic age in South China can be divided into three groups, each with different metal associations and spatial distributions and each related to major magmatic events. The first event occurred in the Late Triassic (230–210 Ma), the second in the Mid–Late Jurassic (170–150 Ma), and the third in the Early–Mid Cretaceous (120–80 Ma). The Late Triassic magmatic event and associated mineralization is characterized by peraluminous granite-related W–Sn–Nb–Ta mineral deposits. The Triassic ore deposits are considerably disturbed or overprinted by the later Jurassic and Cretaceous tectono-thermal episodes. The Mid–Late Jurassic magmatic and mineralization events consist of 170–160 Ma porphyry–skarn Cu and Pb–Zn–Ag vein deposits associated with I-type granites and 160–150 Ma metaluminous granite-related polymetallic W–Sn deposits. The Late Jurassic metaluminous granite-related W–Sn deposits occur in a NE-trending cluster in the interior of South China, such as in the Nanling area. In the Early–Mid Cretaceous, from about 120 to 80 Ma, but peaking at 100–90 Ma, subvolcanic-related Fe deposits developed and I-type calc-alkaline granitic intrusions formed porphyry Cu–Mo and porphyry-epithermal Cu–Au–Ag mineral systems, whereas S-type peraluminous and/or metaluminous granitic intrusions formed polymetallic Sn deposits. These Cretaceous mineral deposits cluster in distinct areas and are controlled by pull-apart basins along the South China continental margin. Based on mineral assemblage, age, and space–time distribution of these mineral systems, integrated with regional geological data and field observations, we suggest that the three magmatic–mineralization episodes are the result of distinct geodynamic regimes. The Triassic peraluminous granites and associated W–Sn–Nb–Ta mineralization formed during post-collisional processes involving the South China Block, the North China Craton, and the Indo-China Block, mostly along the Dabie-Sulu and Songma sutures. Jurassic events were initially related to the shallow oblique subduction of the Izanagi plate beneath the Eurasian continent at about 175 Ma, but I-type granitoids with porphyry Cu and vein-type Pb–Zn–Ag deposits only began to form as a result of the breakup of the subducted plate at 170–160 Ma, along the NNE-trending Qinzhou-Hangzhou belt (also referred to as Qin-Hang or Shi-Hang belt), which is the Neoproterozoic suture that amalgamates the Yangtze Craton and Cathaysia Block. A large subduction slab window is assumed to have formed in the Nanling and adjacent areas in the interior of South China, triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic W–Sn mineralization. A relatively tectonically quiet period followed between 150 and 135 Ma in South China. From 135 Ma onward, the angle of convergence of the Izanagi plate changed from oblique to parallel to the coastline, resulting in continental extensional tectonics and reactivation of regional-scale NE-trending faults, such as the Tan-Lu fault. This widespread extension also promoted the development of NE-trending pull-apart basins and metamorphic core complexes, accompanied by volcanism and the formation of epithermal Cu–Au deposits, granite-related polymetallic Sn–(W) deposits and hydrothermal U deposits between 120 and 80 Ma (with a peak activity at 100–90 Ma).  相似文献   

20.
The Kuznetsk Basin is located in the northern part of the Altai–Sayan Folded Area (ASFA), southwestern Siberia. Its Late Permian–Middle Triassic section includes basaltic stratum-like bodies, sills, formed at 250–248 Ma. The basalts are medium-high-Ti tholeiites enriched in La. Compositionally they are close to the Early Triassic basalts of the Syverma Formation in the Siberian Flood basalt large igneous province, basalts of the Urengoi Rift in the West Siberian Basin and to the Triassic basalts of the North-Mongolian rift system. The basalts probably formed in relation to mantle plume activity: they are enriched in light rare-earth elements (LREE; Lan = 90–115, La/Smn = 2.4–2.6) but relatively depleted in Nb (Nb/LaPM = 0.34–0.48). Low to medium differentiation of heavy rare-earth elements (HREE; Gd/Ybn = 1.4–1.7) suggests a spinel facies mantle source for basaltic melts. Our obtained data on the composition and age of the Kuznetsk basalts support the previous idea about their genetic and structural links with the Permian–Triassic continental flood basalts of the Siberian Platform (Siberian Traps) possibly related to the activity of the Siberian superplume which peaked at 252–248 Ma. The abruptly changing thickness of the Kuznetsk Late Permian–Middle Triassic units suggests their formation within an extensional regime similar to the exposed rifts of Southern Urals and northern Mongolia and buried rifts of the West Siberian Basin.  相似文献   

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