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1.
It draws much attention of scientists how early hu- mans occupy and adapt to the rigorous climate and environment at high northern latitudes in East Asia after they stepped out of Africa, passed West Asia and finally arrived in East Asia[1-4]. Reliable age determi- nations of Paleolithic sites from northeastern Asia not only help to find out the earliest occupation of early humans in this region, but also relate to the founda- tion of the overall framework of human origin and migration[1-8]…  相似文献   

2.
Paleo-earthquake studies on the eastern section of the Kunlun fault   总被引：1，自引：0，他引：1  
Introduction East Kunlun active fault is one of the largest sinistral slip fault zones in northern Tibetan Pla-teau. The fault tails primarily after the ancient eastern Kunlun suture zone, which was reactivatedby the northward subduction of the Indian plate beneath the Eurasian plate. The western end of thefault starts near the western flank of the Buxedaban peak in Qinghai Province. The fault then ex-tends eastwards through the Kusai Lake, Xidatan, Dongdatan, Alag Lake, Tuosuo Lak…  相似文献   

3.
Uplift of the Tibetan Plateau, inversion of eastern and western geomorphology, eastward flowing of large rivers, and run-through of the Changjiang River exert great influence on sedimentation and environ-mental variations in the East China Sea. Provenance discrimination of Tibetan-Plateau-originated sediments in the river-mouth areas and marginal seas is key to figure out these issues.In the past, most studies of the run-through time of the Changjiang and the Yellow rivers focused on geomo…  相似文献   

4.
The selection of high-resolution loess sections is needed in order to determine the climatic variability of the East Asian Monsoon during the last interglacial. Two sequences of S1 on the eastern and west-ern sides of the Liupan Mountain were both composed of five paleosol layers and four loess layers,indicating that there were five strong summer monsoon events and four strong winter monsoon events in MIS5. This corresponds with other records of the East Asian Monsoon,along with NGRIP and the North Atlantic records,implying that the climate of the Northern Hemisphere was very instable during the last interglacial. Two layers of paleosols and one layer of loess had developed during MIS5a and MIS5c. Compared with MIS5e,the climate in MIS5a and MIS5c fluctuated more intensively on a millen-nial scale,whereas the climate was relatively stable in MIS5e.  相似文献   

5.
Using annual precipitation and discharge data measured in the past five decades,this paper analyzed the regional differences over west China in terms of climate and discharge variations,and investigated the relationship between the regional characteristics and the activities of South and East Asian sum-mer monsoon. Results revealed that the precipitation and discharge in the upper reaches of the Yellow River (Central West China) have a negative correlation with those in Xinjiang (northwest China) and the Yarlung Zangbo River (the upper reaches of the Brahmaputra Rive,southwest China) regions. The geographical patterns of precipitation and discharge variations are different over west China,i.e. the regional climate displays the alteration of dry-wet-dry or wet-dry-wet from north to south in west China. The negative correlation of annual discharges between Xinjiang and the upper reaches of the Yellow River is found statistically significant in the decadal scale,and that between the Yarlung Zangbo River and the upper reaches of the Yellow River is found active in the interannual scale. The regional char-acteristics indicate that the discharge/precipitation variations in the upper reaches of the Yellow River are dominated by the East Asian summer monsoon while their variations in Xinjiang are affected by both the west wind and East Asian summer monsoon.  相似文献   

6.
Early in the1970s,Madden and Julian[1,2]first re-vealed the existence of eastward propagation of the intraseasonal(or30-60-day)oscillation(ISO)in the zonal wind fields over the tropics.Later on,the northward propagation of the ISO activities over the Indian Ocean was discovered by Yasunari[3,4],which accounts for the seasonal variations of the Indian summer monsoon.Similar studies were carried out on the low-frequency oscillation activities related to the ENSO and the East Asian summer …  相似文献   

7.
INTRODUCTIONThe Kokoxili earthquake,which ruptured the East Kunlun fault in northern Tibet on November14,2001,is the largest earthquake that has occurred on the Chinese continent in the past50yearsever since the Moto,TibetM8.0earthquake of August15,1950.The macro hypocenter of thisearthquake is located in the north of Bukadaban Peak at36.2°N,90.9°E,MS=8.1(ChineseSeismological Network),or the west of Bukadaban Peak at36.01°N,90.49°E,MW=7.9(USGSNEIC),or near the Kusai Lake …  相似文献   

8.
The Yanshan movement/orogeny has been proposed for 90 years, which is of special significance in the history of geological research in China. This study conducted a review by synthesizing major achievements regarding episodic deformation features, sedimentary and magmatic records of the Yanshan orogeny in China, and clarified the episodic tectono-magmatism and its geodynamic origins. The tectonic implications of the Yanshan orogeny are discussed in the context of global plate tectonics and supercontinent reconstruction. Lines of evidence from structural, sedimentary and magmatic data suggest that the Yanshan orogeny represents a regional-scale tectonic event that affected the entire China continent in late Mesozoic period. Numerous age and structural constraints consistently indicate that the Yanshan orogeny was initiated in the Jurassic(at ～170±5 Ma). and was characterized by alternating stages of crustal shortening at ～170–136 Ma, crustal extension at ～135–90 Ma, and weak shortening at ～80 Ma. The 170–136 Ma crustal shortening was reflected in the generation of two regional stratigraphic unconformities(the Tiaojishan and Zhangjiakou unconformities), which were initially named the A and B episodes of "the Yanshan Orogeny" by Mr.Wong Wenhao in 1928. Geodynamically, the Yanshan orogeny in East Asia was associated with nearly coeval oceanic subduction and continental convergence in the Paleo-Pacific, Neo-Tethys, and Mongol-Okhotsk tectonic domains. As a consequence, three giant accretionary-collisional tectonic systems were formed along the continental margins of East Asia, i.e., the Mongol-Okhotsk, Bangonghu-Nujiang, and SE China subduction-and collision-related accretionary systems. The Yanshan orogeny induced widespread crustal-scale folding and thrusting, tectonic reactivation of long-lived zones of crustal weakness,and extensive magmatism and mineralization in intraplate regions. Based on the time principle of supercontinent assembly and break-up, we propose that the mid-Late Jurassic multi-plate convergence in East Asia might represent the initiation of the assembly of the Amasia supercontinent, and the Yanshan orogeny might be the first "stirrings" that is a prerequisite for the birth of the Amasia supercontinent.  相似文献   

9.
INTRODUCTIONQuanzhou Citylocates on the southeast coast of Fujian Province .Tectonically,it locates in thevolcanic fault depression zone in East Fujian betweenthe Wuyi-Daiyunfolded doming-upregion of theSouth China block and the depression zone of the Taiwan Straits . Being on the north segment of thesoutheast seismic belt of China , many destructive earthquakes inthe history affected the area and theregional seismicityis closelyrelated withfaulting.Inthe Quanzhou basin,large-scalelo…  相似文献   

10.
The Nihewan (Nihowan) Basin is well known in the world for producing abundant mammal fossils and paleoliths. As one issue of the program 搕he early hominid evolution and environmental background in East Asia?a biostratigraphic survey was made in July 2001, and a large number of mammal fossils were un-earthed and 5 lithic artifacts were recognized from the Majuangou gully in the Nihewan Basin, Hebei Prov-ince, North China. 1 Stratigraphic section The new site is located on the south bank…  相似文献   

11.
Geology of the Grove Mountains in East Antarctica   总被引：2，自引：0，他引：2  
Grove Mountains consists mainly of a series of high-grade (upper amphibolite to granulite facies) metamorphic rocks, including felsic granulite, granitic gneiss, mafic granulite lenses and charnockite, intruded by late tectonic gneissic granite and post-tectonic granodioritic veins. Geochemical analysis demonstrates that the charnockite, granitic gneiss and granite belonged to aluminous A type plutonic rocks, whereas the felsic and mafic granulite were from supracrustal materials as island-arc, oceanic island and middle oceanic ridge basalt. A few high-strained shear zones disperse in regional stable sub-horizontal foliated metamorphic rocks. Three generations of ductile deformation were identified, in which D1 is related to the event before Pan-African age, D2 corresponds to the regional granulite peak metamorphism, whereas D3 reflects ductile extension in late Pan-African orogenic period. The metamorphic reactions from granitic gneiss indicate a single granulite facies event, but 3 steps from mafic granulite, with P-T condition of M1 800°C, 9.3×105 Pa; M2 800–810°C, 6.4 × 105 Pa; and M3 650°C have been recognized. The U-Pb age data from representative granitic gneiss indicate (529±14) Ma of peak metamorphism, (534±5) Ma of granite emplacement, and (501±7) Ma of post-tectonic granodioritic veins. All these evidences suggest that a huge Pan-African aged mobile belt exists in the East Antarctic Shield extending from Prydz Bay via Grove Mountains to the southern Prince Charles Mountains. This orogenic belt could be the final suture during the Gondwana Land assemblage.  相似文献   

12.
Granulites in the Dabie Mountains are mainly ob-served in northern Dabie complex zone. Huangtuling intermediate-acid granulites and Huilanshan mafic granulites in the Luotian dome are two famous out-crops (Fig. 1)[1]. It is important to know the genesis and metamorphic age of these granulites for under-standing tectonic evolution and exhumation history of the Dabie Mountains. Previous geochemical and geo-chronological work[2―8]1) on the Huangtuling granu-lites indicates that their protoli…  相似文献   

13.
Ion microprobe UThPb ages of zircons from granulite facies lower crustal xenoliths from north Queensland, Australia, correlate well with the ages of major orogenic episodes manifest at the earth's surface. About half of the xenoliths contain Proterozoic zircons which are similar in age to the episodes of high-grade metamorphism of the older surface rocks. All the xenoliths contain late Paleozoic zircons which show a real 100 Ma range in206Pb238/U ages (from 320 to 220 Ma), which is attributed to granulite facies metamorphism followed by slow cooling in the deep crust. The Paleozoic zircon ages coincide in time with the prolonged episode of eruption of voluminous felsic ash-flows and intrusion of high-level granites in this region (320-270 Ma). Mineral and melt inclusions in the zircons provide clues to the origin of some of the xenoliths, and coupled with the age information, can be used to infer the geological processes operating in the lower crust. The zircons from two mafic xenoliths contain felsic and intermediate melt inclusions implying at least a two-stage history for these rocks, involving either partial melting of a more felsic protolith or crystal accumulation from an evolved melt. Some of the zircons from the felsic xenoliths contain CO2-rich fluid inclusions, indicating that those zircons grew during high-grade metamorphism. The isotopic and chemical data for the whole rock xenoliths show that they originate from a segment of the lower crust which is a heterogeneous mixture of supracrustal and mafic, mantle-derived, lithologies. The major orogenic event responsible for the formation of that crust occurred in the late Paleozoic, when Proterozoic supracrustal rocks were emplaced into the lower crust, possibly along thin-skinned thrust slices. This was accompanied by intrusion of high-temperature, mantle-derived melts which caused partial melting of pre-existing crust. The most likely setting for such tectonism is a continental margin subduction zone.  相似文献   

14.
冀东陆壳结构的岩石学模型   总被引：7，自引：4，他引：7       下载免费PDF全文
吴宗絮  郭才华 《地震地质》1991,13(4):369-376
冀东地区的古老变质岩系是一个出露的大陆地壳断面。根据变质岩系的变质相、亚相的研究和地质温压计计算的结果推定的深度,并结合地球物理测深资料,以及笔者测定和前人的岩石高压下波速实验资料提出了本区大陆地壳结构的岩石学模型。下地壳由麻粒岩相岩石组成,上部为角闪石麻粒岩亚相的中性成分的麻粒岩,下部为辉石麻粒岩亚相的基性成分的麻粒岩构成,底部夹有透镜状蛇纹石化橄榄岩以及紫苏花岗岩。中地壳主要由高角闪岩相的中性-中酸性成分的片麻岩、片岩构成,顶部为低角闪岩相的片麻岩、片岩,广泛发育英云闪长岩和花岗闪长岩岩体,含隙间高温流体相(fluid phase),形成高导-低速层。上地壳主要为绿片岩相(部分低角闪岩相)的板岩、千枚岩、片岩、变粒岩以及花岗岩组成,顶部为沉积盖层  相似文献   

15.
There are five major geological events in Precambrian complex, Taihangshan region determined by researching into geology and isotopic chronology of the complex. Basaltic magma erupted and quartz-dioritic to tonalitic magma intruded in earlier neo-Archaean, which formed hornblende-plagiogneiss of Fuping gneiss complex and metamorphic mafic rock enclaves in TTG gneiss complex. Granulite facies metamorphism and emplacement of biotite-plagiogneiss occurred in late neo-Archaean. Extension and uplifting from the end of neo-Archaean to Paleoproterozoic era formed Chengnanzhuang large extensional deformation zones and metamorphic mafic veins emplaced into the deformation zones. Remobilization of Precambrian complex and tectonic uplifting in late Paleoproterozoic era formed Longquanguan ductile shear zone and emplacement of Nanying gneiss. Occurrence of regional granite pegmatite at the end of Paleoproterozoic era means the end of the Lliang movement.  相似文献   

16.
The Hidaka Metamorphic Belt is a well-known example of island-arc crustal section, in which metamorphic grade increases westwards from unmetamorphosed sediment up to granulite facies. It is divided into lower (granulite to amphibolite facies) and upper (amphibolite to greenschist facies) metamorphic sequences. The metamorphic age of the belt was considered to be ~55 Ma, based on Rb – Sr whole-rock isochron ages for granulites and related S-type tonalities. However, zircons from the granulites in the lower sequence yield U – Pb ages of ~21 – 19 Ma, and a preliminary report on zircons from pelitic gneiss in the upper sequence gives a U – Pb age of ~40 Ma. In this paper we provide new zircon U – Pb ages from two pelitic gneisses in the upper sequence to assess the metamorphic age and also the maximum depositional age of the sedimentary protolith. The weighted mean 206Pb/238U ages from a biotite gneiss in the central area of the belt yield 39.6 ± 0.9 Ma for newly grown metamorphic rims and 53.1 ± 0.9 Ma for the youngest detrital cores. The ages of zircons from a cordierite–biotite gneiss in the southern area are 35.9 ± 0.7 Ma for metamorphic rims and 46.5 ± 2.8 Ma for the youngest detrital cores. These results indicate that metamorphism of the upper sequence took place at ~40 – 36 Ma, and that the sedimentary protolith was deposited after ~53 – 47 Ma. These metamorphic ages are consistent with the reported ages of ~37–36 Ma plutonic rocks in the upper sequence, but contrast with the ~21–19 Ma ages of metamorphic and plutonic rocks in the lower sequence. Therefore, we conclude that the upper and lower metamorphic sequences developed independently but coupled with each other before ~19 Ma as a result of dextral reverse tectonic movement.  相似文献   

17.
Cong  Bolin  Wang  Qingchen  Zhai  Mingguo  Zhang  Ruyuan  Zhao  Zhongyan Ye  Kai 《Island Arc》1994,3(3):135-150
Abstract Based on petrological, structural, geological and geochronological research, the authors summarize the progress of ultra-high pressure (UHP) metamorphic rock study since 1989 by Chinese geoscientists and foreign geoscientists in the Dabie-Su-Lu region. The authors introduce and discuss a two-stage exhumation process for the UHP metamorphic rocks that have various lithologies; eclogite, ultramafics, jadeitic quartzite, gneiss, schist and marble. The metamorphic history of UHP metamorphic rocks is divided into three stages, that is, the pre-eclogite stage, coesite eclogite stage, and retrograde stage. Prior to UHP metamorphism, the ultramafics had a high temperature environment assemblage of mantle and others had blueschist facies assemblages. The granulite facies assemblages, which have recorded a temperature increase event with decompression, have developed locally in the Weihai basaltic rocks. Isotopic ages show a long range from > 700 Ma to 200 Ma. The diversity in protoliths of UHP metamorphic rocks may be related to the variation of isotopic ages older than 400 Ma. The Sm-Nd dating of ~ 220 Ma could reflect the initial exhumation stage after the peak UHP metamorphism in relation to the collision between the Sino-Korean and Yangtze blocks and subsequent events. Petrological and structural evidence imply a two-stage exhumation process. During the initial exhumation, the UHP metamorphic rocks were sheared and squeezed up in a high P/T regime. In the second exhumation stage the UHP metamorphic rocks were uplifted and eventually exposed with middle crustal rocks.  相似文献   

18.
The Yushugou terrane of deepcrustal granulite facies in southern Tianshan consists of two parts, granulite and metaperidotite. The whole terrane is a metamorphism of (high-pressure) grunulite facies, and typical mineral associations are: Gt-Cpx-P1-Tit-Ilm (±Qz) (silica-saturated and oversaturated mafic rocks), Gt-Ky (pseudomorph)-P1-Ru-Ilm± Qz (metapelitic rocks) and Spi-Opx-Cpx-01 (meta-ultramafic rocks). The peak-stage P-T conditions are 795— 964°, 0.97—1.42 GPa, which are obtained with mineral chemistry, assemblage analyses and P-T estimation. The Sm-Nd isochron age of peak-stage metamorphic minerals is (315 ± 3.62) Ma. All of these indicate that the terrane is a deep-crustal body, which subducts to the depth of 40—50 km in the middle late-Paleozoic, undergoing metamorphism of (high-pressure) granulite facies, and exhumed again to the surface by tectonic uplifting. Project supported hy the National Natural Science Foundation of China (Grant No. 49472135).  相似文献   

19.
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20.
This proposed model is based on geological, geophysical and geochemical data. Previous models suggested for the lower continental crust consisted of basalt, gabbro, or charnockitic rocks; however, experimental and field petrological data indicate that the bulk of crustal rocks are metamorphic. A lower crust of heterogeneous metamorphic rocks also agrees with seismic reflection results which show numerous reflections from “layering”. Geothermal conditions favor a “dry” charnockitic or gabbroic lower crust rather than an amphibolitic lower crust because heat production data imply that wet amphibolitic rocks would have a higher heat production than their dry metamorphic equivalents. Relatively high velocities from field and laboratory measurements in such low-density rocks as granite, syenite, anorthosite and granulitic rocks in general imply that the composition of the lower crust is more felsic than gabbro. Variation in seismic velocity and depths from crustal refraction studies and numerous seismic reflections all indicate a highly heterogeneous lower crust. The lower crust, which has traditionally been described as gabbroic or mafic, may consist of such diverse rocks as granite gneiss, syenite gneiss, anorthosite, pyroxene granulite, and amphibolite, interlayered on a small scale, deformed, and intruded by granite and gabbro. Interlayering of these rocks explains the presence and character of seismic reflections. Abrupt changes in dip, tight folding, disruption of layers, intrusion, and changes in layer thickness explain the characteristic discontinuity of deep reflections. Igneous intrusions may be floored by metamorphic rocks. The lower crust consists of a complex series of igneous and metamorphic rock of approximate intermediate composition.  相似文献   

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