The Tuerkubantao ophiolite melange in Xinjiang, NW China： New evidence for the Erqis suture zone   总被引：1，自引：0，他引：1  

Yuwang Wang  Jingbin Wang  Lijuan Wang  Lingli Long  Pingzhi Tang  Zhen Liao  Huiqiong Zhang  Yu Shi 《地学前缘(英文版)》2012,3(5):587-602

The extension of the suture zone between the Siberian and Kazakhstan continents in China has been a matter of debate because few outcrops of ophiolitic melange have been found so far.The recently found Tuerkubantao ophiolitic melange,which is located east of the Kekesentao Mt.in the Buerjin County of the Chinese Altay,provides an important clue for this problem.This paper presents the results of field investigation,petrology,U-Pb isotope dating of zircons and bulk-rock geochemistry of the Tuerkubantao melange rocks.The melange consists of fault-contacted ultramafic rocks,gabbro, diabase,basalt,flysch and granitoids.The ultramafic-mafic rocks are Mg-rich（Mg^#=4.25—6.35） and w（SiO₂） spans 38.8%—46.8%.Basalt and gabbro are geochemically similar and are characterized by low w（FeO^t）（10.9%）,total alkali w（Na₂O+K₂O）=2.58%) and w（TiO₂）（1.17%） and affinity to the Mg-rich tholeiite series.The flat REE and trace-element patterns of the ultramafic-mafic rocks are indicative of their ophiolite origin,i.e.,formation in a mid-oceanic ridge setting.The fragments of low-K gneissic granite formed in suprasubduction or syn-collisional setting.Zircons from gabbro and gneissic granite yielded U-Pb ages of 363 and 355 Ma.respectively,suggesting Late Devonian mid-oceanic spreading and oceanic subduction accompanied by suprasubduction magmatism.The Tiierkubantao ophiolite together with the Qiaoxiahala and Buergen ophiolites of the Kekesentao belt define an ophiolitic melange belt extending along the Erqis fault.This belt probably belongs to the Ural-Zaisan -South Mongolian suture-shear zone formed during the subduction of the Paleo-Asian Ocean and subsequent collision of the Siberian and Kazakhstan continents.  相似文献   

Dynamics of India-Asia Collision from 2-D and 3-D Numerical Modeling     

LI Zhonghai  XU Zhiqin  GERYA Taras  BURG Jean-Pierre 《《地质学报》英文版》2013,87(Z1):142-142

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Geology and metamorphism of the Ladakh Terrane and Shyok Suture Zone in the Chogo Lungma – Turmik area (northern Pakistan)     

Franco Rolfo  Bruno Lombardo  Roberto Compagnoni  Patrick Le Fort  Yves Lemennicier  Arnaud Pêcher 《Geodinamica Acta》2013,26(5):251-270

Abstract

Metamorphism of the Askore Amphibolite, metabasaltic and metasedimentary medium-grade hornblendebearing schists at the northernmost portion of the Ladakh Terrane and of the Shyok Suture Zone, mainly a low-grade volcano-sedimentary series, has been studied in the area between the Chogo Lungma glacier and the Indus river halfway between Skardu and Rondu.

In the Askore Amphibolite the peak assemblage in the amphibolite facies defines the regional metamorphic foliation, and is overprinted by a later static recrystallization at comparable P-T conditions. In spite of similar peak temperatures (630–650°C), geobarometry based on amphibole composition reveals a marked difference between garnet – epidote – andesine amphibolites exposed just above the Main Mantle Thrust at the head of Turmik valley, which equilibrated at high pressures (about 10 kbar) in late Miocene (Tortonian), and biotite – epidote – oligoclase amphibolites outcropping at the mouth of Turmik valley, which equilibrated at pressures of c. 6 kbar before late Eocene (Priabonian).

The Dasu Ultramafite and other smaller lens-shaped bodies of low- to medium-grade metaperidotite separate the Ladakh Terrane from the Shyok Suture Zone. They are antigorite serpentinites, often with talc and magnesite, in which relict cumulitic structures are locally recognisable. The ultramafites may represent remnants of oceanic lithosphere separating the Ladakh-Kohistan island arc from the Asian plate, or they may be deep crustal rocks stripped from the basement of the arc.

The mostly greenschist-facies Shyok Suture Zone shows the lithology of a calc-alkaline volcano-sedimentary series. It is supposed to be a remnant of a back arc basin of early Cretaceous age, separating the arc from the southern margin of Asia. Chloritoid, kyanite and biotite have been found in individual thrust sheets occurring at different structural levels and totally subordinate in volume to very low- and low-grade rocks. Such sharp differences in mineral paragenesis, together with field evidence of local shear, suggest a complex internal structure for the Shyok Suture Zone. From the head of Chogo Lungma glacier to the Basha valley, close to the contact with the Karakorum Metamorphic Complex, the rocks of the Shyok Suture Zone record a late Miocene metamorphic event at medium pressures and temperatures. Thermobarometric and geochronological evidence suggests that this event can be related to the exhumation and thrusting of the Karakorum metamorphic core over the Shyok Suture Zone.  相似文献   

扬子地块与南秦岭造山带的盆山系统与构造耦合   总被引：12，自引：3，他引：9  

肖安成  魏国齐  沈中延  王亮  杨威  钱俊锋 《岩石学报》2011,27(3):601-611

本文重新厘定了扬子地块西北缘晚古生代至早中生代沉积盆地的原型,在综合分析南秦岭造山带和勉略缝合带形成规律的基础上,对于南秦岭造山带与扬子地块北缘的拼合演化历史以及盆山耦合关系进行了研究。指出在晚二叠世晚期(长兴组沉积上段)和早三叠世早期(飞仙关组沉积下段)发生点式碰撞,在两个不同的大地构造单元之间形成了与碰撞相关的裂谷盆地群(包括开江-梁平裂谷、城口-鄂西裂谷和东部的当阳裂谷等),碰撞裂谷群的持续演化时间为5~6Ma,这一阶段典型的沉积标志为水下早期阶段形成的海相磨拉石层序。至早三叠世的嘉陵江二段沉积时期,两个不同地块的持续拼合导致大巴山和米苍山地区与周缘前陆盆地相关的古冲断带的形成,该阶段在缝合带接触部位发育角度不整合和河流相沉积,扬子地块其余大部仍然是保持连续的海相碳酸盐岩沉积。晚三叠世南秦岭造山带与扬子北缘之间的残余大洋消失,为整体闭合的碰撞后期阶段,沉积了须家河组开始的陆相碎屑岩系,大巴山和米苍山地区进入到了以陆相磨拉石为主的前陆盆地阶段,在扬子北缘形成了神农架-黄陵隆起和米苍山隆起。晚三叠世以后大巴山和米苍山地区进入了比较复杂的后期改造阶段,产生了多期的收缩性构造活动,包括以形成区域性的假整合和小角度不整合为特征的晚侏罗世-早白垩世早期(J₃-K₁)的低幅度活动期;以大巴山和米苍山冲断带的强烈改造为主,形成薄皮冲断构造系统的早白垩世晚期变形和以形成大巴山弧形冲断带和米苍山基底卷入的冲断带为特征的新生代晚期变形。  相似文献   

U–Pb dating of detrital zircon grains in the Paleocene Stumpata Formation,Tethyan Himalaya,Zanskar, India     

《Journal of Asian Earth Sciences》2014

The sediments deposited on the northern margin of Greater India during the Paleocene allow the timing of collision with the Spontang Ophiolite, the oceanic Kohistan–Dras Arc and Eurasia to be constrained. U–Pb dating of detrital zircon grains from the Danian (61–65 Ma) Stumpata Formation shows a provenance that is typical of the Tethyan Himalaya, but with a significant population of grains from 129 ± 7 Ma also accounting for ∼15% of the total, similar to the synchronous Jidula Formation of south central Tibet. Derivation of these grains from north of the Indus Suture can be ruled out, precluding India’s collision with either Eurasia or the Kohistan–Dras before 61 Ma. Despite the immediate superposition of the Spontang Ophiolite, there are no grains in the Stumpata Formation consistent with erosion from this unit. Either Spontang obduction is younger than previously proposed, or the ophiolite remained submerged and/or uneroded until into the Eocene. The Mesozoic grains correlate well with the timing of ∼130 Ma volcanism in central Tibet, suggesting that this phase of activity is linked to extension across the whole margin of northern India linked to the separation of India from Australia and Antarctica at that time. Mesozoic zircons in younger sedimentary rocks in Tibet suggest a rapid change in provenance, with strong erosion from within or north of the suture zone starting in the Early Eocene following collision. We find no evidence for strongly diachronous collision from central Tibet to the western Himalaya.  相似文献   

Subsurface imaging,TAIGER experiments and tectonic models of Taiwan     

《Journal of Asian Earth Sciences》2014

The seismicity, deformation rates and associated erosion in the Taiwan region clearly demonstrate that plate tectonic and orogenic activities are at a high level. Major geologic units can be neatly placed in the plate tectonic context, albeit critical mapping in specific areas is still needed, but the key processes involved in the building of the island remain under discussion. Of the two plates in the vicinity of Taiwan, the Philippine Sea Plate (PSP) is oceanic in its origin while the Eurasian Plate (EUP) is comprised partly of the Asian continental lithosphere and partly of the transitional lithosphere of the South China Sea basin. It is unanimously agreed that the collision of PSP and EU is the cause of the Taiwan orogeny, but several models of the underlying geological processes have been proposed, each with its own evolutionary history and implied subsurface tectonics.TAIGER (TAiwan Integrated GEodynamics Research) crustal- and mantle-imaging experiments recently made possible a new round of testing and elucidation. The new seismic tomography resolved structures under and offshore of Taiwan to a depth of about 200 km. In the upper mantle, the steeply east-dipping high velocity anomalies from southern to central Taiwan are clear, but only the extreme southern part is associated with seismicity; toward the north the seismicity disappears. The crustal root under the Central Range is strongly asymmetrical; using 7.5 km/s as a guide, the steep west-dipping face on the east stands in sharp contrast to a gradual east-dipping face on the west. A smaller root exists under the Coastal Range or slightly to the east of it. Between these two roots lies a well delineated high velocity rise spanning the length from Hualien to Taitung. The 3-D variations in crustal and mantle structures parallel to the trend of the island are closely correlated with the plate tectonic framework of Taiwan. The crust is thickest in the central Taiwan collision zone, and although it thins toward the south, the crust is over 30 km thick over the subduction in the south; in northern Taiwan, the northward subducting PSP collides with Taiwan and the crust thins under northern Taiwan where the subducting indenter reaches 50 km in depth. The low Vp/Vs ratio of around 1.6 at a mid-crustal depth of 25 km in the Central Range indicates that current temperatures could exceed 700 °C. The remarkable thickening of the crust under the Central Range, its rapid uplift without significant seismicity, its deep exhumation and its thermal state contribute to make it the core of orogenic activities on Taiwan Island.The expanded network during the TAIGER deployment captured broadband seismic data yielding enhanced S-splitting results with mainly SKS/SKKS data. The polarization directions of the fast S-waves follow very closely the structural trends of the island, supporting the concept of a vertically coherent Taiwan orogeny in the outer few hundred kilometers of the Earth.  相似文献   

Possible detachment zone in Precambrian rocks of Kanjamalai Hills,Cauvery Suture Zone,Southern India: Implications to accretionary tectonics     

《Journal of Asian Earth Sciences》2014

Existence of a possible detachment zone at Elampillai region, NW margin of Kanjamalai Hills, located in the northern part of Cauvery Suture Zone (CSZ), Southern India, is reported here for the first time. Detailed structural mapping provides anatomy of the zone, which are rarely preserved in Precambrian high grade terranes. The detachment surface separates two distinct rock units of contrasting lithological and structural characters: the upper and lower units. The detachment zone is characterized by a variety of fold styles with the predominance of tight isoclinal folds with varied plunge directions, limb rotations and the hinge line variations often leading to lift-off fold like geometries and deformed sheath folds. Presence of parasitic folding and associated penetrative strains seem to be controlled by differences in mechanical stratigraphy, relative thicknesses of the competent and incompetent units, and the structural relief of the underlying basement. Our present study in conjunction with other available geological, geochemical and geochronological data from the region indicates that the structures of the detachment zone are genetically related to thrust tectonics forming a part of subduction–accretion–collision tectonic history of the Neoproterozoic Gondwana suture.  相似文献   

Aeromagnetic signatures of Precambrian shield and suture zones of Peninsular India   总被引：2，自引：1，他引：1  

Mita Rajaram  S.P.Anand 《地学前缘(英文版)》2014,5(1):3-15

In many Precambrian provinces the understanding of the tectonic history is constrained by limited exposure and aeromagnetic data provide information below the surface cover of sediments,water,etc.and help build a tectonic model of the region.The advantage of using the aeromagnetic data is that the data set has uniform coverage and is independent of the accessibility of the region.In the present study,available reconnaissance scale aeromagnetic data over Peninsular India are analyzed to understand the magnetic signatures of the Precambrian shield and suture zones thereby throwing light on the tectonics of the region.Utilizing a combination of differential reduction to pole map,analytic signal,vertical and tilt derivative and upward continuation maps we are able to identify magnetic source distribution,tectonic elements,terrane boundaries,suture zones and metamorphic history of the region.The magnetic sources in the region are mainly related to charnockites,iron ore and alkaline intrusives.Our analysis suggests that the Chitradurga boundary shear and Sileru shear are terrane boundaries while we interpret the signatures of Palghat Cauvery and Achankovil shears to represent suture zones.Processes like metamorphism leave their signatures on the magnetic data:prograde granulites(charnockites)and retrograde eclogites are known to have high susceptibility.We fnd that charnockites intruded by alkali plutons have higher magnetization compared to the retrogressed charnockites.We interpret that the Dharwar craton to the north of isograd representing greenschist to amphibolite facies transition,has been subjected to metamorphism under low geothermal conditions.Some recent studies suggest a plate tectonic model of subductionecollisioneaccretion tectonics around the Palghat Cauvery shear zone(PCSZ).Our analysis is able to identify several west to east trending high amplitude magnetic anomalies with deep sources in the region from Palghat Cauvery shear to Achankovil shear.The magnetic high associated with PCSZ may represent the extruded high pressureeultra high temperature metamorphic belt(granulites at shallow levels and retrogressed eclogites at deeper levels)formed as a result of subduction process.The EW highs within the Madurai block can be related to the metamorphosed clastic sediments,BIF and mafc/ultramafc bodies resulting from the process of accretion.  相似文献   

桐柏—大别山碰撞造山带的大地构造演化   总被引：1，自引：0，他引：1  

徐贵忠  王艺芬  张稳胜 《地球科学与环境学报》1993,(1)

桐柏—大别山碰撞造山带是华北板块南部大陆边缘和扬子板块北部大陆边缘长期演化和碰撞的结果。造山带主要由北淮阳加里东构造带、桐柏—大别山古老断块隆起带和随广加里东构造带组成。根据现今查明的三条蛇绿混杂岩带和不同时代岩系的原岩建造及区域构造特征,重建了其碰撞期前的古地理-古构造格局。在加里东末期,华北板块与扬子板块发生碰撞,形成了桐柏—大别山造山带。在碰撞期及碰撞期后曾发生了大规模的滑脱-推覆构造。  相似文献   

巴尔喀什-准噶尔构造单元划分及特征   总被引：3，自引：0，他引：3  

成守德  祁世军  陈川  高鹏  黄诚  刘通  王世伟 《新疆地质》2009,27(Z1)

以板块构造观点讨论了构造单元的划分原则.研究区包括西伯利亚、哈萨克斯坦-准噶尔和塔里木三大板块,以哈萨克斯坦.准噶尔板块为主体.该板块进一步划分为两个微板块,东北为巴尔喀什.准噶尔微板块,以古生代洋盆为主体,古老陆壳残片少量;西南称科克切塔夫-伊塞克-伊犁-中天山微板块,以古老的陆壳基底为主体,古生代洋盆次之.在此基础上对各微板块作了进一步划分,对各次级单元主要特征分别进行了描述.  相似文献