This study employs Norman Fairclough’s Critical Discourse Analysis(CDA)three-dimensional model,using the Republic of Kazakhstan as a case study,to delve into the discourse construction of China’s Belt and Road Initi...This study employs Norman Fairclough’s Critical Discourse Analysis(CDA)three-dimensional model,using the Republic of Kazakhstan as a case study,to delve into the discourse construction of China’s Belt and Road Initiative(BRI)in Central Asian countries.Through detailed analysis of policy documents,media reports,and public discussions in Central Asian countries,this paper reveals how the BRI constructs specific social practices,discourse events,and textual meanings within these nations.The findings indicate that through this global development strategy,China has not only strengthened its economic ties with Central Asian countries but has also exerted profound influences on political,cultural,and social levels.展开更多
Central Asian Economies(CAEs)have diverse exchange rate policies.They have recorded higher volatility in the foreign exchange market since inception.High volatility of the transition era has drifted these economies to...Central Asian Economies(CAEs)have diverse exchange rate policies.They have recorded higher volatility in the foreign exchange market since inception.High volatility of the transition era has drifted these economies towards partial dollarization.Monetary authorities in CAEs,(already have a challenge of maintaining monetary policy autonomy)have a gigantic task of price stability and stopping the spread of dollarization.This study is directed towards assessing the drivers and the determinants of foreign exchange market pressure in CAEs.The results,based on panel data analysis and the System GMM model,have provided useful insights about the exchange market pressure determinants particularly USD,Euro,Ruble,and Renminbi.The results show that China and Russia exchange market pressure has a negative effect on the exchange market pressure of CAEs.While the dollar index shows a positive impact on the exchange market pressure of CAEs.Overall,the findings imply that China and Russia currency appreciation results in a trade deficit across CAEs.The policy implication suggests that the floating exchange rate regime(inflation targeting regime)is not in favor of CAEs,and they must use managed-float to reduce their trade deficits.展开更多
The Sidingheishan mafic-ultramafic intrusion is located in the eastern part of the Northern Tianshan Mountain, along the southern margin of the Central Asian Orogenic Belt in northern Xinjiang autonomous region of Chi...The Sidingheishan mafic-ultramafic intrusion is located in the eastern part of the Northern Tianshan Mountain, along the southern margin of the Central Asian Orogenic Belt in northern Xinjiang autonomous region of China. The Sidingheishan intrusion is mainly composed of wehrlite, olivine websterite, olivine gabbro, gabbro and hornblende gabbro. At least two pulses of magma were involved in the formation of the intrusion. The first pulse of magma produced an olivine-free unit and the second pulse produced an olivine-bearing unit. The magmas intruded the Devonian granites and granodiorites.An age of 351.4±5.8 Ma(Early Carboniferous) for the Sidingheishan intrusion has been determined by U-Pb SHRIMP analysis of zircon grains separated from the olivine gabbro unit. A U-Pb age of 359.2±6.4 Ma from the gabbro unit has been obtained by LA-ICP-MS. Olivine of the Sidingheishan intrusion reaches 82.52 mole% Fo and 1414 ppm Ni. On the basis of olivine-liquid equilibria, it has been calculated that the MgO and FeO included in the parental magma of a wehrlite sample were approximately10.43 wt% and 13.14 wt%, respectively. The Sidingheishan intrusive rocks are characterized by moderate enrichments in Th and Sm, slight enrichments in light REE, and depletions in Nb, Ta, Zr and Hf. The εNd(t) values in the rock units vary from +6.70 to +9.64, and initial87Sr/86Sr ratios range between 0.7035 and0.7042. Initial206Pb/204Pb,207Pb/204Pb and208Pb/204Pb values fall in the ranges of 17.23-17.91,15.45-15.54 and 37.54-38.09 respectively. These characteristics are collectively similar to the Heishan intrusion and the Early Carboniferous subduction related volcanic rocks in the Santanghu Basin, North Tianshan and Beishan area. The low(La/Gd)PMvalues between 0.26 and 1.77 indicate that the magma of the Sidingheishan intrusion was most likely derived from a depleted spinel-peridotite mantle.(Th/Nb)PMratios from 0.59 to 20.25 indicate contamination of the parental magma in the upper crust.Crystallization modeling methods suggest that the parental magma of the Sidingheishan intrusion was generated by flush melting of the asthenosphere and subsequently there was about 10 vol%contamination from a granitic melt. This was followed by about 5 vol% assimilation of upper crustal rocks. Thus, the high-Mg basaltic parental magma of Sidingheishan intrusion is interpreted to have formed from partial melting of the asthenosphere during the break-off of a subducted slab.展开更多
Objective The NE China is located in the eastern segment of the Central Asian Orogenic Belt(CAOB),which is a large accretionary orogen between the Siberian Craton and the North China Craton(NCC).Many researches ha...Objective The NE China is located in the eastern segment of the Central Asian Orogenic Belt(CAOB),which is a large accretionary orogen between the Siberian Craton and the North China Craton(NCC).Many researches have discussed about the evolution of the Paleo-Asian Ocean(PAO)in the eastern CAOB.However,展开更多
The eastern Central Asian Orogenic Belt(CAOB)in NE China is a key area for investigating continental growth.However,the complexity of its Paleozoic geological history has meant that the tectonic development of this be...The eastern Central Asian Orogenic Belt(CAOB)in NE China is a key area for investigating continental growth.However,the complexity of its Paleozoic geological history has meant that the tectonic development of this belt is not fully understood.NE China is composed of the Erguna and Jiamusi blocks in the northern and eastern parts and the Xing’an and Songliao-Xilinhot accretionary terranes in the central and southern parts.The Erguna and Jiamusi blocks have Precambrian basements with Siberia and Gondwana affinities,respectively.In contrast,the Xing’an and Songliao-Xilinhot accretionary terranes were formed via subduction and collision processes.These blocks and terranes were separated by the Xinlin-Xiguitu,Heilongjiang,Nenjiang,and Solonker oceans from north to south,and these oceans closed during the Cambrian(ca.500 Ma),Late Silurian(ca.420 Ma),early Late Carboniferous(ca.320 Ma),and Late Permian to Middle Triassic(260-240 Ma),respectively,forming the Xinlin-Xiguitu,Mudanjiang-Yilan,Hegenshan-Heihe,Solonker-Linxi,and Changchun-Yanji suture zones.Two oceanic tectonic cycles took place in the eastern Paleo-Asian Ocean(PAO),namely,the Early Paleozoic cycle involving the Xinlin-Xiguitu and Heilongjiang oceans and the late Paleozoic cycle involving the Nenjiang-Solonker oceans.The Paleozoic tectonic pattern of the eastern CAOB generally shows structural features that trend east-west.The timing of accretion and collision events of the eastern CAOB during the Paleozoic youngs progressively from north to south.The branch ocean basins of the eastern PAO closed from west to east in a scissor-like manner.A bi-directional subduction regime dominated during the narrowing and closure process of the eastern PAO,which led to“soft collision”of tectonic units on each side,forming huge accretionary orogenic belts in central Asia.展开更多
Objective The East Tianshan mafic-ultramafic rocks belt mainly produced in the eastern Jueluotage belt is an important part of the Central Asia Orogenic Belt (CAOB). The well- known deposits including Huangshan, Hu...Objective The East Tianshan mafic-ultramafic rocks belt mainly produced in the eastern Jueluotage belt is an important part of the Central Asia Orogenic Belt (CAOB). The well- known deposits including Huangshan, Huangshandong, Tulaergen, Hulu, Xiangshan were have been consecutively discovered in this belt (Duan Xingxing et al., 2016). The new discovery of the Lubei Cu-Ni sulfide deposit in recent years, which locates in the west of Jueluotage belt, has great significance to the westward extension of the East Tianshan Cu-Ni metallogenic belt. To determine whether the mineralization age of the Lubei Cu-Ni sulfide deposit is consistent with other typical deposits, this study conducted zircon U-Pb geochronology on the diorite from the Lubei Cu-Ni sulfide deposit in order to provide new information for further exploring direction of Cu-Ni prospecting in East Tianshan.展开更多
Continental reconstructions in Central Asia are represented by orogenesis along some large orogenic belts in the Altaid collage (Fig. 1 ) or Central Asian Orogenic Belt (CAOB), which separate the East European and...Continental reconstructions in Central Asia are represented by orogenesis along some large orogenic belts in the Altaid collage (Fig. 1 ) or Central Asian Orogenic Belt (CAOB), which separate the East European and Siberian cratons to the north from the Tarim and North China cratons to the south ($eng0r et al,, 1993; Jahn et al., 2004; Windley et al., 2007; Qu et al., 2008; Xiao et al., 2010; Xiao and Santosh, 2014). The Altaid Collage was characterized by complex long tectonic and structural evolution from at least ca. 1.0 Ga to late Paleozoic-early Mesozoic with considerable continental growth (Khain et al., 2002; Jahn et al., 2004; Xiao et al., 2009, 2014; KrOner et al., 2014), followed by Cenozoic intracontinental evolution related to far-field effect of the collision of the In- dian Plate to the Eurasian Accompanying with these complex world-class ore deposits developed 2001; Goldfarb et al., 2003, 2014). Plate (Cunningham, 2005). geodynamic evolutions, many (Qin, 2000; Yakubchuk et al,2001; Goldfarb et al., 2003, 2014).展开更多
The Wulungu Depression is the northernmost first-order tectonic unit in the Junggar Basin. It can be divided into three sub-units: the Hongyan step-fault zone, the Suosuoquan sag and the Wulungu south slope. The Ceno...The Wulungu Depression is the northernmost first-order tectonic unit in the Junggar Basin. It can be divided into three sub-units: the Hongyan step-fault zone, the Suosuoquan sag and the Wulungu south slope. The Cenozoic strata in the basin are intact and Mesozoic-Cenozoic deformation can be observed in the Wulungu step-fault zone, so this is an ideal place to study the Mesozoic-Cenozoic deformation. By integration of fault-related folding theories, regional geology and drilling data, the strata of the Cretaceous-Paleogene systems are divided into small layers which are selected as the subjects of this research. The combination of the developing unconformity with existing growth strata makes it conceivable that faults on the step-fault zone have experienced different degrees of reactivation of movement since the Cretaceous. Evolutionary analyses of the small layers using 2D-Move software showed certain differences in the reactivation of different segments of the Wulungu Depression such as the timing of reactivation of thrusting, for which the reactivity time of the eastern segment was late compared with those of the western and middle segments. In addition the resurrection strength was similarly slightly different, with the shortening rate being higher in the western segment than in the other segments. Moreover, the thrust fault mechanism is basement-involved combined with triangle shear fold, for which a forward evolution model was proposed.展开更多
Identifying the crust-mantle interactions in association with the evolution of the Precambrian microcontinents provides critical constraints on the accretionary evolution in the Central Asian Orogenic Belt(CAOB).The B...Identifying the crust-mantle interactions in association with the evolution of the Precambrian microcontinents provides critical constraints on the accretionary evolution in the Central Asian Orogenic Belt(CAOB).The Bainaimiao arc terrane(BAT)is one of the most important Precambrian microcontinents in southeastern CAOB,however,few studies have paid attention to the types and the evolving processes of the crust-mantle interactions that occurred before its final accretion onto the northern North China Craton.This study presents an integrated study of geochronology,zircon Hf isotope and whole-rock geochemistry on the latest Neoproterozoic diabases and the Early Paleozoic arc intrusions in the western BAT.The latest Neoproterozoic(ca.546 Ma)diabases display low SiO2(46.52-49.24 wt.%)with high MgO(8.23-14.41 wt.%),Cr(66-542 ppm)and Ni(50-129 ppm),consisting with mantle origin.Their highly negative zirconεHf(t)(-12.0 to-24.7)and high Fe/Mn ratios(62.1-81.7)further indicate a significantly enriched mantle source.Considering that the BAT maybe initially separated from the Tarim Craton with a thickened crustal root,we propose that these diabases were generated through partial melting of an enriched lithospheric mantle source that had been hybridized by lower-crustal eclogites during foundering of the BAT lower crust.The Early Paleozoic(ca.475-417 Ma)arc intrusions in western BAT can be divided into PeriodsⅠandⅡat approximately 450 Ma.The PeriodⅠ(>450 Ma)intrusions contain abundant mafic minerals like hornblende and pyroxene,and show positive zirconεHf(t)(+1.5 to+10.9).They are predominantly medium-K calc-alkaline with broad correlations of SiO2 versus various major and trace elements,which correlate well with the experimental melts produced by the fractional crystallization of primitive hydrous arc magmas at 7 kbar.We assume they were formed through mid-crustal differentiation of the mantle wedge-derived hydrous basaltic melts.By contrast,the PeriodⅡ(≤450 Ma)intrusions are characterized by variable zircon eHf(t)(-15.0 to+11.5)with irregular variations in most major and trace elements,which are more akin to the arc magmas generated in an open system.The general occurrence of elder inherited zircons,along with the relatively high Mg#(>45)of some samples,call upon a derivation from the reworking of the previously subduction-modified BAT lower crust with the input of mantle-derived mafic components.In combination with the Early Paleozoic tectonic melanges flanking western BAT,we infer that the compositional transition from PeriodⅠtoⅡcan be attributed to the tectonic transition from south-dipping subduction of Solonker ocean to north-dipping subduction of South Bainaimiao ocean in southeastern CAOB.The above results shed light not only on the latest Neoproterozoic to Early Paleozoic multiple crust-mantle interactions in western BAT,but also on the associated crustal construction processes before the final arc-continent accretion.展开更多
The tectonic setting of the northern Alxa region during the Late Paleozoic is highly controversial.The key to resolve this controversy is to recognize the Late Paleozoic magmatic processes in the northern Alxa.In this...The tectonic setting of the northern Alxa region during the Late Paleozoic is highly controversial.The key to resolve this controversy is to recognize the Late Paleozoic magmatic processes in the northern Alxa.In this paper,we present new zircon U-Pb ages,Hf-isotopic compositions and whole-rock geochemical data of four granitoids along the Zhusileng-Hangwula Tectonic Belt in the northern Alxa region that could provide critical information about the tectonic evolution of this region.The zircon U-Pb data could be grouped as two phases:Late Devonian granite and diorite(ca.373-360 Ma),and Late Carboniferous granodiorite(ca.318 Ma).The Late Devonian granites and diorites are metaluminous to slightly peraluminous,with A/CNK and A/NK ratios of 0.90-1.11 and0.95-2.19,respectively.The Late Devonian diorites are characterized by high MgO,Cr and Ni contents and MgO#values,together with variableεHf(t)values from-1.0 to+1.3 and old TDM2 ages varied from 1283 Ma to 1426 Ma,indicating the primary magma was potentially derived from magma mixing of depleted mantle with Mesoproterozoic continental crust.Even though the Late Devonian granites yielded most positive and minor negative eHf(t)values between-1.1 to+5.7(three grains are negative)with two-stage model ages(TDM2)of 1003-1438 Ma,they display low MgO,Cr and Ni contents and MgO#values,suggesting that they were mainly derived from juvenile crustal materials,mixed with a small amount of ancient crust.The Late Carboniferous granitoids are metaluminous and medium-K calc-alkaline series,with A/CNK and A/NK ratios ranging from 0.88 to 0.95 and1.75 to 1.90,respectively.These rocks were potentially derived from juvenile crustal materials mixed with depleted mantle,as evidenced by their highεHf(t)values(+11.6 to+14.1)and young TDM2 ages(427 Ma to 586 Ma),as well as high Mg#values,and MgO,Ni and Cr contents.Our data,along with available sedimentary evidence and previous researches,indicate that the Late Devonian and Late Carboniferous rocks are arc-related granitoids under the subduction setting.The identification of arc-related granitoids in the northern Alxa region not only reveals the Late Paleozoic magmatic process in response to the subduction of Paleo Asian Ocean,but also provide significant constrains to the tectonic evolution of the Central Asian Orogenic Belt.展开更多
The Chinese North Tianshan(CNTS)in the southern part of the Central Asian Orogenic Belt(CAOB)has undergone multistage accretion-collision processes during Paleozoic time,which remain controversial.This study addresses...The Chinese North Tianshan(CNTS)in the southern part of the Central Asian Orogenic Belt(CAOB)has undergone multistage accretion-collision processes during Paleozoic time,which remain controversial.This study addresses this issue by tracing the provenance of Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS through U-Pb dating and Lu-Hf isotopic analyses of detrital zircons.New detrital zircon U-Pb ages(N=519)from seven samples range from 261±4 Ma to 2827±32 Ma.The most prominent age peak is at 313 Ma and subordinate ages vary from 441 Ma to 601 Ma,with some Precambrian detrital zircon ages(~7%)lasting from 694 Ma to 1024 Ma.The youngest age components in each sample yielded weighted mean ages ranging from 272±9 Ma to 288±5 Ma,representing the maximum depositional ages.These and literature data indicate that some previously-assumed"Carboniferous"strata in the Bogda area were deposited in the Early Permian,including the Qijiaojing,Julideneng,Shaleisaierke,Yangbulake,Shamaershayi,Liushugou,Qijiagou,and Aoertu formations.The low maturity of the sandstones,zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East Junggar Arc and the Harlik-Dananhu Arc in the CNTS.The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc.Zircon EHf(t)values have increased since^408 Ma,probably reflecting a tectonic transition from regional compression to extension.This event might correspond to the opening of the Bogda intraarc/back arc rift basin,possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean.A decrease of zirconεHf(t)values at^300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision,which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous.展开更多
The late Paleozoic tectonic framework of the southeastern Central Asian Orogenic Belt is key to restricting the accretion orogeny between the Siberia Craton and the North China Craton. To clarify the framework, petrog...The late Paleozoic tectonic framework of the southeastern Central Asian Orogenic Belt is key to restricting the accretion orogeny between the Siberia Craton and the North China Craton. To clarify the framework, petrogenesis of early Permian intrusive rocks from southeastern Inner Mongolia was studied. Zircon U-Pb dating for bojite and syenogranite from Ar-Horqin indicate that they were emplaced at 288–285 Ma. Geochemical data reveal that the bojite is highly magnesian and low-K to middle-K calc-alkaline, with E-MORB-type REE and IAB-like trace element patterns. The syenogranite is a middle-K calc-alkaline fractionated A-type granite and shows oceanic-arc-like trace element patterns, with depleted Sr-Nd-Hf isotopes,(~(87)Sr/~(86)Sr)I = 0.7032–0.7042, ε_(Nd)(t) = +4.0 to +6.6 and zircon ε_(Hf)(t) = +11.14 to +14.99. This suggests that the bojite was derived from lithospheric mantle metasomatized by subducted slab melt, while the syenogranite originated from very juvenile arc-related lower crust. Usng data from coeval magmatic rocks from Linxi-Ar-Horqin, the Ar-Horqin intra-oceanic arc was reconstructed, i.e., initial transition in 290–280 Ma and mature after 278 Ma. Combined with regional geological and geophysical materials in southeastern Inner Mongolia, an early Permian tectonic framework as ‘one narrow ocean basin of the PAO', ‘two continental marginal arcs on its northern and southern' and ‘one intra-oceanic arc in its southern' is proposed.展开更多
The early Paleozoic tectonic framework and evolutionary history of the eastern Central Asian Orogenic Belt(CAOB)is poorly understood.Here we present zircon U-Pb geochronology,whole rock geochemistry,and Sr-NdHf isotop...The early Paleozoic tectonic framework and evolutionary history of the eastern Central Asian Orogenic Belt(CAOB)is poorly understood.Here we present zircon U-Pb geochronology,whole rock geochemistry,and Sr-NdHf isotope data of the early Paleozoic granitoids in eastern CAOB to investigate the petrogenesis and geodynamic implications.The early Paleozoic granitoids from the Songnen Block yield zircon U-Pb ages of 523-490 Ma,negative εNd(t)values of-6.7 to-0.8,and values of-8.6 to 7.1,indicating they were generated by partial melting of ancient crustal materials with various degrees of mantle contribution.They generally show affinities to A-type granites,implying their generation from an extensional environment after the collision between the Songnen and Jiamusi blocks.In comparison,the early Paleozoic granitoids from the Xing’an Block have zircon U-Pb ages of 480-465 Ma,εNd(t)values of-5.4 to 5.4,andεHf(t)values of-2.2 to 12.9,indicating a dominated juvenile crustal source with some input of ancient crustal components.They belong to I-type granites and were likely related to subduction of the Paleo-Asian Ocean.The statistics of TDM2 Hf model ages of the granitoids indicate that the Erguna and Jiamusi blocks contain a significant proportion of Mesoproterozoic crystalline basement,while the Xing’an Block is dominated by a Neoproterozoic basement.Based on these observations,the early Paleozoic evolutionary history of eastern GAOB can be divided into four stages:(1)before 540 Ma,the Erguna,Xing’an,Songnen,and Jiamusi blocks were discrete microcontinents separated by different branches of the Paleo-Asian Ocean;(2)540-523 Ma,the Jiamusi Block collided with the Songnen Block along the Mudanjiang suture;(3)ca.500 Ma,the Erguna Block accreted onto the Xing’an Block along the Xinlin-Xiguitu suture;(4)ca.480 Ma,the Paleo-Asian Ocean started a double-side subduction beneath the united Erguna-Xing’an and Songnen-Jiamusi blocks.展开更多
Objective The modem Earth is characterized by two types of orogens: collisional orogen and accretionary orogen. It is widely accepted that the Central Asian Orogenic Belt (CAOB) is made up of widespread multiple an...Objective The modem Earth is characterized by two types of orogens: collisional orogen and accretionary orogen. It is widely accepted that the Central Asian Orogenic Belt (CAOB) is made up of widespread multiple ancient archipelagos. It has been recognized as a non-collisional orogen, contrasting with the archetypical Alpine- Himalayan-type collisional orogens. Although the CAOB is traditionally compared to subduction-accretion systems that have been well studied, all accretionary orogens ultimately passed into a collisional phase at the end of the orogenic Wilson cycle due to ocean closure and termination of subduction, which will lead to subsequent crustal shortening, thickening and reworking. Therefore, the archipelago-type CAOB may also preserve a terminal collision record, although this is not a classic continental collision at all.展开更多
As an important tectonic unit in the middle part of the southern Central Asian Orogeny, the Alxa Block was affected by multiple deformational events occurring in the Central Asian tectonic regime during the Paleozoic ...As an important tectonic unit in the middle part of the southern Central Asian Orogeny, the Alxa Block was affected by multiple deformational events occurring in the Central Asian tectonic regime during the Paleozoic and Mesozoic. The record of deformation in the Alxa Block represents the entire evolutionary process from a continental margin to an intraplate setting. In the Langshan region of the northeastern Alxa Block, four important Paleozoic-early Mesozoic deformation events have been distinguished:(1) nearly north-south-striking ductile thrusting along the eastern Alxa Block in the Late Devonian;(2) nearly east-west-trending brittle top-to-the-south thrusting in the Mid-Late Permian;(3) nearly east-west-trending initially ductile then brittle dextral transtension with 30-40 km of displacement in the Late Permian;and(4) northeast-trending ductile sinistral shearing with 120-125 km of displacement in the Mid-Late Triassic. The ductile thrusting in the Late Devonian may have resulted from the interaction between the North China Craton and the Alxa Black, which was a peri-eastern Gondwana block. Parallel east-west-trending thrusts and related folds formed in the Neoproterozoic Langshan Group due to the closure of the PaleoAsian Ocean in the Mid-Late Permian. The Late Permian eastwest-trending and dextrally ductile transtension may have resulted from intraplate adjustment after the Central Asian Orogeny and the formation of the Ural Orogenic Belt to the west;this shear zone may have been part of a huge ductile tectonic belt developed along the whole southern Central Asian Orogenic Belt(CAOB). During the Early Triassic, the subduction of oceanic crust along the southern central CAOB terminated then the eastern Alxa Block was affected by the collision between the North China Craton and the Yangtze Craton to the south. Since the late Mesozoic, the Langshan region has experienced another five important deformation events, which were all far-field tectonic effects related to plate margin tectonic activities(e.g., the closure of the Mongolian-Okhotsk Ocean, the collision between the Qiangtang and Lhasa blocks and the India-Eurasia collision). The large-scale brittle and ductile strike-slip faults in the northeastern Alxa Block all formed in intraplate settings since the late Paleozoic in response to the collisional orogenies occurring along the plate margins or the intraplate adjustment following the closure of the Paleo-Asian Ocean.展开更多
Objective The Sidingheishan mafic-ultramafic intrusion is located in the eastern part of the North Tianshan Mountains. This work used zircon U-Pb age data, bulk rock major and trace elements, Sr-Nd-Pb isotope data to ...Objective The Sidingheishan mafic-ultramafic intrusion is located in the eastern part of the North Tianshan Mountains. This work used zircon U-Pb age data, bulk rock major and trace elements, Sr-Nd-Pb isotope data to assess mantle source characteristics and crustal assimilation of the parental magma of the Sidingheishan intrusion. We have also discussed the tectonic evolution of the southern margin of the Central Asian Orogenic belt in the Late Paleozoic.展开更多
The Central Asian Orogenic Belt(CAOB)is a huge tectonic mélange that lies between the North China Craton and the Siberian Block.It is composed of multiple orogenic belts,continental fragments,magmatic and metamor...The Central Asian Orogenic Belt(CAOB)is a huge tectonic mélange that lies between the North China Craton and the Siberian Block.It is composed of multiple orogenic belts,continental fragments,magmatic and metamorphic rocks,suture zones and discontinuous ophiolite belts.Although the Hegenshan and Sartohay ophiolites are separated by nearly 3000 km and lie in completely different parts of the CAOB,they are remarkably similar in many respects.Both are composed mainly of serpentinized peridotite and dunite,with minor gabbro and sparse basalt.They both host significant podiform chromitites that consist of high-Al,refractory magnesiochromite with Cr#s[100Cr/(Cr+Al)]averaging<60.The Sartohay ophiolite has a zircon U-Pb age of ca.300 Ma and has been intruded by granitic plutons of similar age,resulting in intense hydrothermal activity and the formation of gold-bearing listwanites.The age of the Hegenshan is not firmly established but is thought to have formed in the Carboniferous.Like many other ophiolites that we have investigated in other orogenic belts,the chromitites in these two bodieshave abundant diamonds,as well as numerous super-reduced and crustal minerals.The diamonds are mostly,colorless to pale yellow,200-300μm across and have euhedral to anhedral shapes.They all have low carbon isotopes(δ14C=-18 to-29)and some have visible inclusions.These are accompanied by numerous super-reduced minerals such as moissanite,native elements(Fe,Cr,Si,Al,Mn),and alloys(e.g.,Ni-Mn-Fe,Ni-Fe-Al,Ni-Mn-Co,Cr-Ni-Fe,Cr-Fe,Cr-Fe-Mn),as well as a wide range of oxides,sulfides and silicates.Grains of zircon are abundant in the chromitites of both ophiolites and range in age from Precambrian to Cretaceous,reflecting both incorporation of old zircons and modification of grains by hydrothermal alteration.Our investigation confirms that high-Al,refractory chromitites in these two ophiolites have the same range of exotic minerals as high-Cr metallurgical chromitites such as those in the Luobusa ophiolite of Tibet.These collections of exotic minerals in ophiolitic chromitites indicate complex,multi-stage recycling of oceanic and continental crustal material at least to the mantle transition zone,followed by uprise and emplacement of the peridotites into relatively shallow ophiolites.展开更多
This book consists of papers providing the geology of remote regions covering the boundary areas of Russia,Kazakhstan,Kyrgyzstan,Mongolia and China,which were inaccessible for a long time due to political and logistic...This book consists of papers providing the geology of remote regions covering the boundary areas of Russia,Kazakhstan,Kyrgyzstan,Mongolia and China,which were inaccessible for a long time due to political and logistical reasons.Consequently,these critical regions remained not well integrated in largescale geodynamic models of the Central Asian Orogenic Belt(CAOB).展开更多
Since the establishment of diplomatic relations between China and its western neighbors - the Central Asian countries, the friendly and good-neighborly relationship between the two sides has kept a sound momentum of d...Since the establishment of diplomatic relations between China and its western neighbors - the Central Asian countries, the friendly and good-neighborly relationship between the two sides has kept a sound momentum of development. China’s policy of creating an amicable, secure and展开更多
Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an ...Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andeantype active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two-mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U-Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two-mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean(PAO) and represents a suture between the North China craton(NCC) and Central Asian Orogenic Belt(CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400–420 Ma. Magmatism of the second stage in 380–390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes-type active continental margin of the CAOB has been proposed, including a development of the subduction-free PAO before 446 Ma, a subduction of the PAO and arc-related magmatism during 446–380 Ma, and formation of a molasse basin during 380–360 Ma.展开更多
基金supported by Teaching and Research Project of North China Institute of Aerospace Engineering(JY-2023-19)Humanities and Social Science Research Project of Hebei Education Department(SQ2024272).
文摘This study employs Norman Fairclough’s Critical Discourse Analysis(CDA)three-dimensional model,using the Republic of Kazakhstan as a case study,to delve into the discourse construction of China’s Belt and Road Initiative(BRI)in Central Asian countries.Through detailed analysis of policy documents,media reports,and public discussions in Central Asian countries,this paper reveals how the BRI constructs specific social practices,discourse events,and textual meanings within these nations.The findings indicate that through this global development strategy,China has not only strengthened its economic ties with Central Asian countries but has also exerted profound influences on political,cultural,and social levels.
文摘Central Asian Economies(CAEs)have diverse exchange rate policies.They have recorded higher volatility in the foreign exchange market since inception.High volatility of the transition era has drifted these economies towards partial dollarization.Monetary authorities in CAEs,(already have a challenge of maintaining monetary policy autonomy)have a gigantic task of price stability and stopping the spread of dollarization.This study is directed towards assessing the drivers and the determinants of foreign exchange market pressure in CAEs.The results,based on panel data analysis and the System GMM model,have provided useful insights about the exchange market pressure determinants particularly USD,Euro,Ruble,and Renminbi.The results show that China and Russia exchange market pressure has a negative effect on the exchange market pressure of CAEs.While the dollar index shows a positive impact on the exchange market pressure of CAEs.Overall,the findings imply that China and Russia currency appreciation results in a trade deficit across CAEs.The policy implication suggests that the floating exchange rate regime(inflation targeting regime)is not in favor of CAEs,and they must use managed-float to reduce their trade deficits.
基金financially supported by the National Science Foundation of China (41402070, 41602082, 4170021021)China Geological Survey (DD20160346)
文摘The Sidingheishan mafic-ultramafic intrusion is located in the eastern part of the Northern Tianshan Mountain, along the southern margin of the Central Asian Orogenic Belt in northern Xinjiang autonomous region of China. The Sidingheishan intrusion is mainly composed of wehrlite, olivine websterite, olivine gabbro, gabbro and hornblende gabbro. At least two pulses of magma were involved in the formation of the intrusion. The first pulse of magma produced an olivine-free unit and the second pulse produced an olivine-bearing unit. The magmas intruded the Devonian granites and granodiorites.An age of 351.4±5.8 Ma(Early Carboniferous) for the Sidingheishan intrusion has been determined by U-Pb SHRIMP analysis of zircon grains separated from the olivine gabbro unit. A U-Pb age of 359.2±6.4 Ma from the gabbro unit has been obtained by LA-ICP-MS. Olivine of the Sidingheishan intrusion reaches 82.52 mole% Fo and 1414 ppm Ni. On the basis of olivine-liquid equilibria, it has been calculated that the MgO and FeO included in the parental magma of a wehrlite sample were approximately10.43 wt% and 13.14 wt%, respectively. The Sidingheishan intrusive rocks are characterized by moderate enrichments in Th and Sm, slight enrichments in light REE, and depletions in Nb, Ta, Zr and Hf. The εNd(t) values in the rock units vary from +6.70 to +9.64, and initial87Sr/86Sr ratios range between 0.7035 and0.7042. Initial206Pb/204Pb,207Pb/204Pb and208Pb/204Pb values fall in the ranges of 17.23-17.91,15.45-15.54 and 37.54-38.09 respectively. These characteristics are collectively similar to the Heishan intrusion and the Early Carboniferous subduction related volcanic rocks in the Santanghu Basin, North Tianshan and Beishan area. The low(La/Gd)PMvalues between 0.26 and 1.77 indicate that the magma of the Sidingheishan intrusion was most likely derived from a depleted spinel-peridotite mantle.(Th/Nb)PMratios from 0.59 to 20.25 indicate contamination of the parental magma in the upper crust.Crystallization modeling methods suggest that the parental magma of the Sidingheishan intrusion was generated by flush melting of the asthenosphere and subsequently there was about 10 vol%contamination from a granitic melt. This was followed by about 5 vol% assimilation of upper crustal rocks. Thus, the high-Mg basaltic parental magma of Sidingheishan intrusion is interpreted to have formed from partial melting of the asthenosphere during the break-off of a subducted slab.
基金supported by the National Natural Science Foundation of China(grants No.41372108 and41602110)the Research Fund for the Doctoral Program of Higher Education of China(grant No.20133718130001)+1 种基金the Qingdao Postdoctoral Applied Research Project(grant No.2015193)the SDUST Research Fund(grant No.2015TDJH101)
文摘Objective The NE China is located in the eastern segment of the Central Asian Orogenic Belt(CAOB),which is a large accretionary orogen between the Siberian Craton and the North China Craton(NCC).Many researches have discussed about the evolution of the Paleo-Asian Ocean(PAO)in the eastern CAOB.However,
基金financially supported by the National Natural Science Foundation of China(42130305 and 42002227)project of the China Geological Survey(DD20190039-04,DD20179402,DD20190360 and DD20221632)+2 种基金National Key R&D Program of China(2017YFC0601300 and 2013CB429802)Taishan Scholars(ts20190918)Qingdao Leading Innovation Talents(19-3-2-19-zhc).
文摘The eastern Central Asian Orogenic Belt(CAOB)in NE China is a key area for investigating continental growth.However,the complexity of its Paleozoic geological history has meant that the tectonic development of this belt is not fully understood.NE China is composed of the Erguna and Jiamusi blocks in the northern and eastern parts and the Xing’an and Songliao-Xilinhot accretionary terranes in the central and southern parts.The Erguna and Jiamusi blocks have Precambrian basements with Siberia and Gondwana affinities,respectively.In contrast,the Xing’an and Songliao-Xilinhot accretionary terranes were formed via subduction and collision processes.These blocks and terranes were separated by the Xinlin-Xiguitu,Heilongjiang,Nenjiang,and Solonker oceans from north to south,and these oceans closed during the Cambrian(ca.500 Ma),Late Silurian(ca.420 Ma),early Late Carboniferous(ca.320 Ma),and Late Permian to Middle Triassic(260-240 Ma),respectively,forming the Xinlin-Xiguitu,Mudanjiang-Yilan,Hegenshan-Heihe,Solonker-Linxi,and Changchun-Yanji suture zones.Two oceanic tectonic cycles took place in the eastern Paleo-Asian Ocean(PAO),namely,the Early Paleozoic cycle involving the Xinlin-Xiguitu and Heilongjiang oceans and the late Paleozoic cycle involving the Nenjiang-Solonker oceans.The Paleozoic tectonic pattern of the eastern CAOB generally shows structural features that trend east-west.The timing of accretion and collision events of the eastern CAOB during the Paleozoic youngs progressively from north to south.The branch ocean basins of the eastern PAO closed from west to east in a scissor-like manner.A bi-directional subduction regime dominated during the narrowing and closure process of the eastern PAO,which led to“soft collision”of tectonic units on each side,forming huge accretionary orogenic belts in central Asia.
基金supported by the Geological Exploration Foundation Project of Xinjiang(grants No.Y15-1-LQ05 and No.T15-2-LQ13)Special Project of National Geological Mineral Investigation and Evaluation(grant No.DD20160345-04)
文摘Objective The East Tianshan mafic-ultramafic rocks belt mainly produced in the eastern Jueluotage belt is an important part of the Central Asia Orogenic Belt (CAOB). The well- known deposits including Huangshan, Huangshandong, Tulaergen, Hulu, Xiangshan were have been consecutively discovered in this belt (Duan Xingxing et al., 2016). The new discovery of the Lubei Cu-Ni sulfide deposit in recent years, which locates in the west of Jueluotage belt, has great significance to the westward extension of the East Tianshan Cu-Ni metallogenic belt. To determine whether the mineralization age of the Lubei Cu-Ni sulfide deposit is consistent with other typical deposits, this study conducted zircon U-Pb geochronology on the diorite from the Lubei Cu-Ni sulfide deposit in order to provide new information for further exploring direction of Cu-Ni prospecting in East Tianshan.
基金financially supported by the Natural National Science Foundation of China(Grant Nos.41230207,41202150, 41472192,41390441 and 41190075)
文摘Continental reconstructions in Central Asia are represented by orogenesis along some large orogenic belts in the Altaid collage (Fig. 1 ) or Central Asian Orogenic Belt (CAOB), which separate the East European and Siberian cratons to the north from the Tarim and North China cratons to the south ($eng0r et al,, 1993; Jahn et al., 2004; Windley et al., 2007; Qu et al., 2008; Xiao et al., 2010; Xiao and Santosh, 2014). The Altaid Collage was characterized by complex long tectonic and structural evolution from at least ca. 1.0 Ga to late Paleozoic-early Mesozoic with considerable continental growth (Khain et al., 2002; Jahn et al., 2004; Xiao et al., 2009, 2014; KrOner et al., 2014), followed by Cenozoic intracontinental evolution related to far-field effect of the collision of the In- dian Plate to the Eurasian Accompanying with these complex world-class ore deposits developed 2001; Goldfarb et al., 2003, 2014). Plate (Cunningham, 2005). geodynamic evolutions, many (Qin, 2000; Yakubchuk et al,2001; Goldfarb et al., 2003, 2014).
基金financially supported by the National Science and Technology Major Project (No.2011ZX05008-001)the Natural Science Foundation of China (No.40739906)the Chinese State 973 Project(No. 2011CB201100)
文摘The Wulungu Depression is the northernmost first-order tectonic unit in the Junggar Basin. It can be divided into three sub-units: the Hongyan step-fault zone, the Suosuoquan sag and the Wulungu south slope. The Cenozoic strata in the basin are intact and Mesozoic-Cenozoic deformation can be observed in the Wulungu step-fault zone, so this is an ideal place to study the Mesozoic-Cenozoic deformation. By integration of fault-related folding theories, regional geology and drilling data, the strata of the Cretaceous-Paleogene systems are divided into small layers which are selected as the subjects of this research. The combination of the developing unconformity with existing growth strata makes it conceivable that faults on the step-fault zone have experienced different degrees of reactivation of movement since the Cretaceous. Evolutionary analyses of the small layers using 2D-Move software showed certain differences in the reactivation of different segments of the Wulungu Depression such as the timing of reactivation of thrusting, for which the reactivity time of the eastern segment was late compared with those of the western and middle segments. In addition the resurrection strength was similarly slightly different, with the shortening rate being higher in the western segment than in the other segments. Moreover, the thrust fault mechanism is basement-involved combined with triangle shear fold, for which a forward evolution model was proposed.
基金financially supported by the China Geological Survey(1212011085490 and 1212011220465)the National Natural Science Foundation of China(41421002)。
文摘Identifying the crust-mantle interactions in association with the evolution of the Precambrian microcontinents provides critical constraints on the accretionary evolution in the Central Asian Orogenic Belt(CAOB).The Bainaimiao arc terrane(BAT)is one of the most important Precambrian microcontinents in southeastern CAOB,however,few studies have paid attention to the types and the evolving processes of the crust-mantle interactions that occurred before its final accretion onto the northern North China Craton.This study presents an integrated study of geochronology,zircon Hf isotope and whole-rock geochemistry on the latest Neoproterozoic diabases and the Early Paleozoic arc intrusions in the western BAT.The latest Neoproterozoic(ca.546 Ma)diabases display low SiO2(46.52-49.24 wt.%)with high MgO(8.23-14.41 wt.%),Cr(66-542 ppm)and Ni(50-129 ppm),consisting with mantle origin.Their highly negative zirconεHf(t)(-12.0 to-24.7)and high Fe/Mn ratios(62.1-81.7)further indicate a significantly enriched mantle source.Considering that the BAT maybe initially separated from the Tarim Craton with a thickened crustal root,we propose that these diabases were generated through partial melting of an enriched lithospheric mantle source that had been hybridized by lower-crustal eclogites during foundering of the BAT lower crust.The Early Paleozoic(ca.475-417 Ma)arc intrusions in western BAT can be divided into PeriodsⅠandⅡat approximately 450 Ma.The PeriodⅠ(>450 Ma)intrusions contain abundant mafic minerals like hornblende and pyroxene,and show positive zirconεHf(t)(+1.5 to+10.9).They are predominantly medium-K calc-alkaline with broad correlations of SiO2 versus various major and trace elements,which correlate well with the experimental melts produced by the fractional crystallization of primitive hydrous arc magmas at 7 kbar.We assume they were formed through mid-crustal differentiation of the mantle wedge-derived hydrous basaltic melts.By contrast,the PeriodⅡ(≤450 Ma)intrusions are characterized by variable zircon eHf(t)(-15.0 to+11.5)with irregular variations in most major and trace elements,which are more akin to the arc magmas generated in an open system.The general occurrence of elder inherited zircons,along with the relatively high Mg#(>45)of some samples,call upon a derivation from the reworking of the previously subduction-modified BAT lower crust with the input of mantle-derived mafic components.In combination with the Early Paleozoic tectonic melanges flanking western BAT,we infer that the compositional transition from PeriodⅠtoⅡcan be attributed to the tectonic transition from south-dipping subduction of Solonker ocean to north-dipping subduction of South Bainaimiao ocean in southeastern CAOB.The above results shed light not only on the latest Neoproterozoic to Early Paleozoic multiple crust-mantle interactions in western BAT,but also on the associated crustal construction processes before the final arc-continent accretion.
基金granted by the National Natural Science Foundation of China(Grant Nos.41802119 and 41330315)the Special Projects of China Geological Survey(Grant No.121201011000161111)Doctor’s Fund of Xi’an University of Science and Technology(Grant No.6310117052)。
文摘The tectonic setting of the northern Alxa region during the Late Paleozoic is highly controversial.The key to resolve this controversy is to recognize the Late Paleozoic magmatic processes in the northern Alxa.In this paper,we present new zircon U-Pb ages,Hf-isotopic compositions and whole-rock geochemical data of four granitoids along the Zhusileng-Hangwula Tectonic Belt in the northern Alxa region that could provide critical information about the tectonic evolution of this region.The zircon U-Pb data could be grouped as two phases:Late Devonian granite and diorite(ca.373-360 Ma),and Late Carboniferous granodiorite(ca.318 Ma).The Late Devonian granites and diorites are metaluminous to slightly peraluminous,with A/CNK and A/NK ratios of 0.90-1.11 and0.95-2.19,respectively.The Late Devonian diorites are characterized by high MgO,Cr and Ni contents and MgO#values,together with variableεHf(t)values from-1.0 to+1.3 and old TDM2 ages varied from 1283 Ma to 1426 Ma,indicating the primary magma was potentially derived from magma mixing of depleted mantle with Mesoproterozoic continental crust.Even though the Late Devonian granites yielded most positive and minor negative eHf(t)values between-1.1 to+5.7(three grains are negative)with two-stage model ages(TDM2)of 1003-1438 Ma,they display low MgO,Cr and Ni contents and MgO#values,suggesting that they were mainly derived from juvenile crustal materials,mixed with a small amount of ancient crust.The Late Carboniferous granitoids are metaluminous and medium-K calc-alkaline series,with A/CNK and A/NK ratios ranging from 0.88 to 0.95 and1.75 to 1.90,respectively.These rocks were potentially derived from juvenile crustal materials mixed with depleted mantle,as evidenced by their highεHf(t)values(+11.6 to+14.1)and young TDM2 ages(427 Ma to 586 Ma),as well as high Mg#values,and MgO,Ni and Cr contents.Our data,along with available sedimentary evidence and previous researches,indicate that the Late Devonian and Late Carboniferous rocks are arc-related granitoids under the subduction setting.The identification of arc-related granitoids in the northern Alxa region not only reveals the Late Paleozoic magmatic process in response to the subduction of Paleo Asian Ocean,but also provide significant constrains to the tectonic evolution of the Central Asian Orogenic Belt.
基金financially supported by the National Key R&D Program of China(2017YFC0601205)National Natural Science Foundation of China(41730213 and 41190075)+1 种基金the Hong Kong Research Grants Council General Research Fund(grants 17307918 and 17301915)the Youth Program of Shaanxi Natural Science Foundation(2020JQ589)。
文摘The Chinese North Tianshan(CNTS)in the southern part of the Central Asian Orogenic Belt(CAOB)has undergone multistage accretion-collision processes during Paleozoic time,which remain controversial.This study addresses this issue by tracing the provenance of Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS through U-Pb dating and Lu-Hf isotopic analyses of detrital zircons.New detrital zircon U-Pb ages(N=519)from seven samples range from 261±4 Ma to 2827±32 Ma.The most prominent age peak is at 313 Ma and subordinate ages vary from 441 Ma to 601 Ma,with some Precambrian detrital zircon ages(~7%)lasting from 694 Ma to 1024 Ma.The youngest age components in each sample yielded weighted mean ages ranging from 272±9 Ma to 288±5 Ma,representing the maximum depositional ages.These and literature data indicate that some previously-assumed"Carboniferous"strata in the Bogda area were deposited in the Early Permian,including the Qijiaojing,Julideneng,Shaleisaierke,Yangbulake,Shamaershayi,Liushugou,Qijiagou,and Aoertu formations.The low maturity of the sandstones,zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East Junggar Arc and the Harlik-Dananhu Arc in the CNTS.The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc.Zircon EHf(t)values have increased since^408 Ma,probably reflecting a tectonic transition from regional compression to extension.This event might correspond to the opening of the Bogda intraarc/back arc rift basin,possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean.A decrease of zirconεHf(t)values at^300 Ma was likely caused by the cessation of oceanic subduction and subsequent collision,which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous.
基金funded by project grants from the Chinese Geological Survey (Grants Nos. DD20190039, DD20160048–01, DD20160345–17, DD20190372, DD20190360 and 1212011220435)the Liaoning Education Department (Grant No. LQN201915)。
文摘The late Paleozoic tectonic framework of the southeastern Central Asian Orogenic Belt is key to restricting the accretion orogeny between the Siberia Craton and the North China Craton. To clarify the framework, petrogenesis of early Permian intrusive rocks from southeastern Inner Mongolia was studied. Zircon U-Pb dating for bojite and syenogranite from Ar-Horqin indicate that they were emplaced at 288–285 Ma. Geochemical data reveal that the bojite is highly magnesian and low-K to middle-K calc-alkaline, with E-MORB-type REE and IAB-like trace element patterns. The syenogranite is a middle-K calc-alkaline fractionated A-type granite and shows oceanic-arc-like trace element patterns, with depleted Sr-Nd-Hf isotopes,(~(87)Sr/~(86)Sr)I = 0.7032–0.7042, ε_(Nd)(t) = +4.0 to +6.6 and zircon ε_(Hf)(t) = +11.14 to +14.99. This suggests that the bojite was derived from lithospheric mantle metasomatized by subducted slab melt, while the syenogranite originated from very juvenile arc-related lower crust. Usng data from coeval magmatic rocks from Linxi-Ar-Horqin, the Ar-Horqin intra-oceanic arc was reconstructed, i.e., initial transition in 290–280 Ma and mature after 278 Ma. Combined with regional geological and geophysical materials in southeastern Inner Mongolia, an early Permian tectonic framework as ‘one narrow ocean basin of the PAO', ‘two continental marginal arcs on its northern and southern' and ‘one intra-oceanic arc in its southern' is proposed.
基金financially supported by the geological exploration fund of the Land and Resources Department in Heilongjiang Province(Grant No.201601)the Natural Science Foundation of China(Grant No.41602070)the Fundamental Research Funds for the Central Universities,China University of Geosciences。
文摘The early Paleozoic tectonic framework and evolutionary history of the eastern Central Asian Orogenic Belt(CAOB)is poorly understood.Here we present zircon U-Pb geochronology,whole rock geochemistry,and Sr-NdHf isotope data of the early Paleozoic granitoids in eastern CAOB to investigate the petrogenesis and geodynamic implications.The early Paleozoic granitoids from the Songnen Block yield zircon U-Pb ages of 523-490 Ma,negative εNd(t)values of-6.7 to-0.8,and values of-8.6 to 7.1,indicating they were generated by partial melting of ancient crustal materials with various degrees of mantle contribution.They generally show affinities to A-type granites,implying their generation from an extensional environment after the collision between the Songnen and Jiamusi blocks.In comparison,the early Paleozoic granitoids from the Xing’an Block have zircon U-Pb ages of 480-465 Ma,εNd(t)values of-5.4 to 5.4,andεHf(t)values of-2.2 to 12.9,indicating a dominated juvenile crustal source with some input of ancient crustal components.They belong to I-type granites and were likely related to subduction of the Paleo-Asian Ocean.The statistics of TDM2 Hf model ages of the granitoids indicate that the Erguna and Jiamusi blocks contain a significant proportion of Mesoproterozoic crystalline basement,while the Xing’an Block is dominated by a Neoproterozoic basement.Based on these observations,the early Paleozoic evolutionary history of eastern GAOB can be divided into four stages:(1)before 540 Ma,the Erguna,Xing’an,Songnen,and Jiamusi blocks were discrete microcontinents separated by different branches of the Paleo-Asian Ocean;(2)540-523 Ma,the Jiamusi Block collided with the Songnen Block along the Mudanjiang suture;(3)ca.500 Ma,the Erguna Block accreted onto the Xing’an Block along the Xinlin-Xiguitu suture;(4)ca.480 Ma,the Paleo-Asian Ocean started a double-side subduction beneath the united Erguna-Xing’an and Songnen-Jiamusi blocks.
基金supported by the National Natural Science Foundation of China(grants No.41402194, 41390441,41230207 and 41302177)
文摘Objective The modem Earth is characterized by two types of orogens: collisional orogen and accretionary orogen. It is widely accepted that the Central Asian Orogenic Belt (CAOB) is made up of widespread multiple ancient archipelagos. It has been recognized as a non-collisional orogen, contrasting with the archetypical Alpine- Himalayan-type collisional orogens. Although the CAOB is traditionally compared to subduction-accretion systems that have been well studied, all accretionary orogens ultimately passed into a collisional phase at the end of the orogenic Wilson cycle due to ocean closure and termination of subduction, which will lead to subsequent crustal shortening, thickening and reworking. Therefore, the archipelago-type CAOB may also preserve a terminal collision record, although this is not a classic continental collision at all.
基金funded by the National Key Research and Development Program of China from the Ministry of Science and Technology of China(No.2017YFC0601301)the National Natural Science Foundation of China(No.41572190)the China Geological Survey(Nos.12120115069601,121201102000150009)
文摘As an important tectonic unit in the middle part of the southern Central Asian Orogeny, the Alxa Block was affected by multiple deformational events occurring in the Central Asian tectonic regime during the Paleozoic and Mesozoic. The record of deformation in the Alxa Block represents the entire evolutionary process from a continental margin to an intraplate setting. In the Langshan region of the northeastern Alxa Block, four important Paleozoic-early Mesozoic deformation events have been distinguished:(1) nearly north-south-striking ductile thrusting along the eastern Alxa Block in the Late Devonian;(2) nearly east-west-trending brittle top-to-the-south thrusting in the Mid-Late Permian;(3) nearly east-west-trending initially ductile then brittle dextral transtension with 30-40 km of displacement in the Late Permian;and(4) northeast-trending ductile sinistral shearing with 120-125 km of displacement in the Mid-Late Triassic. The ductile thrusting in the Late Devonian may have resulted from the interaction between the North China Craton and the Alxa Black, which was a peri-eastern Gondwana block. Parallel east-west-trending thrusts and related folds formed in the Neoproterozoic Langshan Group due to the closure of the PaleoAsian Ocean in the Mid-Late Permian. The Late Permian eastwest-trending and dextrally ductile transtension may have resulted from intraplate adjustment after the Central Asian Orogeny and the formation of the Ural Orogenic Belt to the west;this shear zone may have been part of a huge ductile tectonic belt developed along the whole southern Central Asian Orogenic Belt(CAOB). During the Early Triassic, the subduction of oceanic crust along the southern central CAOB terminated then the eastern Alxa Block was affected by the collision between the North China Craton and the Yangtze Craton to the south. Since the late Mesozoic, the Langshan region has experienced another five important deformation events, which were all far-field tectonic effects related to plate margin tectonic activities(e.g., the closure of the Mongolian-Okhotsk Ocean, the collision between the Qiangtang and Lhasa blocks and the India-Eurasia collision). The large-scale brittle and ductile strike-slip faults in the northeastern Alxa Block all formed in intraplate settings since the late Paleozoic in response to the collisional orogenies occurring along the plate margins or the intraplate adjustment following the closure of the Paleo-Asian Ocean.
基金financially supported by the National Science Foundation of China(grants No.41402070, 41372101 and 41602082)China Geological Survey (grant No.DD20160346)
文摘Objective The Sidingheishan mafic-ultramafic intrusion is located in the eastern part of the North Tianshan Mountains. This work used zircon U-Pb age data, bulk rock major and trace elements, Sr-Nd-Pb isotope data to assess mantle source characteristics and crustal assimilation of the parental magma of the Sidingheishan intrusion. We have also discussed the tectonic evolution of the southern margin of the Central Asian Orogenic belt in the Late Paleozoic.
文摘The Central Asian Orogenic Belt(CAOB)is a huge tectonic mélange that lies between the North China Craton and the Siberian Block.It is composed of multiple orogenic belts,continental fragments,magmatic and metamorphic rocks,suture zones and discontinuous ophiolite belts.Although the Hegenshan and Sartohay ophiolites are separated by nearly 3000 km and lie in completely different parts of the CAOB,they are remarkably similar in many respects.Both are composed mainly of serpentinized peridotite and dunite,with minor gabbro and sparse basalt.They both host significant podiform chromitites that consist of high-Al,refractory magnesiochromite with Cr#s[100Cr/(Cr+Al)]averaging<60.The Sartohay ophiolite has a zircon U-Pb age of ca.300 Ma and has been intruded by granitic plutons of similar age,resulting in intense hydrothermal activity and the formation of gold-bearing listwanites.The age of the Hegenshan is not firmly established but is thought to have formed in the Carboniferous.Like many other ophiolites that we have investigated in other orogenic belts,the chromitites in these two bodieshave abundant diamonds,as well as numerous super-reduced and crustal minerals.The diamonds are mostly,colorless to pale yellow,200-300μm across and have euhedral to anhedral shapes.They all have low carbon isotopes(δ14C=-18 to-29)and some have visible inclusions.These are accompanied by numerous super-reduced minerals such as moissanite,native elements(Fe,Cr,Si,Al,Mn),and alloys(e.g.,Ni-Mn-Fe,Ni-Fe-Al,Ni-Mn-Co,Cr-Ni-Fe,Cr-Fe,Cr-Fe-Mn),as well as a wide range of oxides,sulfides and silicates.Grains of zircon are abundant in the chromitites of both ophiolites and range in age from Precambrian to Cretaceous,reflecting both incorporation of old zircons and modification of grains by hydrothermal alteration.Our investigation confirms that high-Al,refractory chromitites in these two ophiolites have the same range of exotic minerals as high-Cr metallurgical chromitites such as those in the Luobusa ophiolite of Tibet.These collections of exotic minerals in ophiolitic chromitites indicate complex,multi-stage recycling of oceanic and continental crustal material at least to the mantle transition zone,followed by uprise and emplacement of the peridotites into relatively shallow ophiolites.
文摘This book consists of papers providing the geology of remote regions covering the boundary areas of Russia,Kazakhstan,Kyrgyzstan,Mongolia and China,which were inaccessible for a long time due to political and logistical reasons.Consequently,these critical regions remained not well integrated in largescale geodynamic models of the Central Asian Orogenic Belt(CAOB).
文摘Since the establishment of diplomatic relations between China and its western neighbors - the Central Asian countries, the friendly and good-neighborly relationship between the two sides has kept a sound momentum of development. China’s policy of creating an amicable, secure and
基金supported by grants from National Key R&D Program of China (2017YFC0601302)the NSF of China (41672214)Geological Survey Project of China Geological Survey (DD20189612, DD20190004).
文摘Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andeantype active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two-mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U-Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two-mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean(PAO) and represents a suture between the North China craton(NCC) and Central Asian Orogenic Belt(CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400–420 Ma. Magmatism of the second stage in 380–390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes-type active continental margin of the CAOB has been proposed, including a development of the subduction-free PAO before 446 Ma, a subduction of the PAO and arc-related magmatism during 446–380 Ma, and formation of a molasse basin during 380–360 Ma.