An explosive seismic sounding profile across the transition zone between west Kunlun Mts. and Tarim Basin

The explosive seismic sounding profile across the transition zone from the west Kunlun Mts. to the Tarim Basin revealed the complex deep structure formed by continent-continent collision on the northern margin of the Tibetan Plateau. The profile shows that the attitude of the Moho is in agreement with that of the crystalline basement in the Tarim Basin and the whole crust dips as a thick slate southwards with an angle from 5° to 7°. Meanwhile, the Moho depth increases from 40 km to 57 km within a distance of 150 km in the southern Tarim region, depicting the subduction of the crust of this region towards the west Kunlun Mts. The crust of the northern slope of the west Kunlun Mts. shows an evident compressed and shortened feature, that is, the basement is uplifted, the interface dips northwards and the Moho rises abruptly to become flat, so that the lower crust is as thick as 20 km.

Surface Processes Driving Intracontinental Basin Subsidence in the Context of India–Eurasia Collision:Evidence from Flexural Subsidence Modeling of the Cenozoic Southern Tarim Basin along the West Kunlun Foreland,NW Tibetan Plateau

The India–Eurasia collision has produced a number of Cenozoic deep intracontinental basins,which bear important information for revealing the far-afield responses to the remote collision.Despite their significance,their subsiding mechanism remains the subject of debate,with end-member models attributing it to either orogenic or sedimentary load.In this study,we conduct flexural subsidence modeling with a two-dimensional finite elastic plate model on the Hotan-Mazatagh section along the southern Tarim Basin,which defines a key region in the foreland of the West Kunlun Orogen,along the NW margin of the Tibetan Plateau.The modeling results indicate that the orogenic load of West Kunlun triggers the southern Tarim Basin to subside by up to less than ~6 km,with its impact weakening towards the basin interiors until ~230 km north from the Karakax fault.The sedimentary load,consisting of Cenozoic strata,forces the basin to subside by ~2 to~7 km.In combination with the retreat of the proto-Paratethys Sea and the paleogeographic reorganization of the Tarim Basin,we propose that surface processes,in particular a shift from an exorheic to an endorheic drainage system associated with the consequent thick sedimentary load,played a decisive role in forming deep intracontinental basins in the context of the India-Eurasia collision.

An Early Aged Ophiolite in the Western Kunlun Mts., NW Tibetan Plateau and Its Tectonic Implications

The early aged ophiolites have attracted attention of many geologists in recent decades, because the early aged ophiolites can provide the information about the ancient oceanic processes relevant to the evolution of plate tectonics in the early period of the earth, and also concern such problems as whether there existed a ＂Proto-Tethys＂ and the break-up and convergence of the Rodinian Supercontinent. This paper reveals a definite complete ophiolite of Neoproterozoic-Early Paleozoic, named Kuda ophiolite in the western Kunlun Mrs., NW Tibetan Plateau, and reports the recent reasonable SHRIMP zircon U-Pb ages of 510±4 Ma, and 502±13 Ma for the cumulates of the Kuda ophiolite, using the most powerful dating tool, the SHRIMP-Ⅱ. The geochemical and geochronology data integrating with the geological setting suggest that the Kuda ophiolite might have formed in an archipelago oceanic basin, not in a vast ocean, the so-called ＂Proto-Tethys＂, and was tectonically emplaced during the Early Paleozoic.

Tectonic evolution of the West Kunlun Orogenic Belt along the northern margin of the Tibetan Plateau:Implications for the assembly of the Tarim terrane to Gondwana

The West Kunlun orogenic belt(WKOB) along the northern margin of the Tibetan Plateau is important for understanding the evolution of the Proto-and Paleo-Tethys oceans. Previous investigations have focused on the igneous rocks and ophiolites distributed mostly along the Xinjiang-Tibet road and the China-Pakistan road, and have constructed a preliminary tectonic model for this orogenic belt. However, few studies have focused on the so-called Precambrian basement in this area. As a result, the tectonic affinity of the individual terranes of the WKOB and their detailed evolution process are uncertain. Here we report new field observations, zircon and monazite U-Pb ages of the "Precambrian basement" of the South Kunlun terrane(SKT) and the Tianshuihai terrane(TSHT), two major terranes in the WKOB. Based on new zircon U-Pb age data, the amphibolite-facies metamorphosed volcanosedimentary sequence within SKT was deposited during the late Neoproterozoic to Cambrian(600-500 Ma), and the flysch-affinity Tianshuihai Group, as the basement of the TSHT, was deposited during the late Neoproterozoic rather than Mesoproterozoic. The rock association of the volcano-sedimentary sequence within SKT suggests a large early Paleozoic accretionary wedge formed by the long-term lowangle southward subduction of the Proto-Tethys Ocean between Tarim and TSHT. The amphibolitefacies metamorphism in SKT occurred at ca. 440 Ma. This ca. 440 Ma metamorphism is genetically related to the closure of the Proto-Tethys Ocean between Tarim and the Tianshuihai terrane, which led to the assembly of Tarim to Eastern Gondwana and the final formation of the Gondwana. Since the late Paleozoic to early Mesozoic, the northward subduction of the Paleo-Tethys Ocean along the HongshihuQiaoertianshan belt produced the voluminous early Mesozoic arc-signature granites along the southern part of NKT-TSHT. The Paleo-Tethys ocean between TSHT and Karakorum closed at ca. 200 Ma, as demonstrated by the monazite age of the paragneiss in the Kangxiwa Group. Our study does not favor the existence of a Precambrian basement in SKT.

Geochemistry of the Cenozoic Potassic Volcanic Rocks in the West Kunlun Mountains and Constraints on Their Sources

The geochemical characteristics of the Cenozoic volcanic rocks from the north Pulu, east Pulu and Dahongliutan regions in the west Kunlun Mountains are somewhat similar as a whole. However, the volcanic rocks from the Dahongliutan region in the south belt are geochemically distinguished from those in the Pulu region (including the north and east Pulu) of the north belt. The volcanic rocks of the Dahongliutan region are characterized by relatively low TiO2 abundance, but more enrichment in alkali, much more enrichment in light rare earth elements and large ion lithosphile elements than those from the Pulu region. Compared with the Pulu region, volcanic rocks from the Dahongliutan region have relatively low 87Sr/86Sr ratios, and high εNd, 207Pb/204Pb and 208Pb/204Pb. Their trace elements and isotopic data suggest that they were derived from lithospheric mantle, consisting of biotite- and hornblende-bearing garnet lherzolite, which had undertaken metasomatism and enrichment. On the primitive mantle-normalized patterns, they display remarkably negative Nb and Ta anomalies, indicating the presence of early-stage subducted oceanic crust. The metasomatism and enrichment resulted from the fluid released from the crustal materials enclosed in the source region in response to the uplift of asthenospheric mantle. Based on the previous experiments it can be inferred that the thickness of the lithosphere ranges from 75 to 100 km prior to the generation of the magmas. However, the south belt differs from the north one by its thicker lithosphere and lower degree of partial melting. The different thickness of the lithosphere gives rise to corresponding variation of the degree of crustal contamination. The volcanic rocks in the south belt are much more influenced by crustal contamination. In view of the tectonic setting, the generation of potassic magmas is linked with the uplift of asthenosphere resulted from large-scale thinning of the lithosphere after the collision of Indian and Eurasian plates, whereas the thinning of the lithosphere may result from delamination. The potassic magmas mainly resulted from partial melting of lithosphere mantle caused by the uplift of asthenosphere.

Glacier Changes during the Past 40 Years in the West Kunlun Shan

Recent studies on glaciers in the West Kunlun Shan, northwest Tibetan Plateau, have shown that they may be stable or retreating slightly. Here, we assess changes in the mass of the glaciers in the West Kunlun Shan(WKS) in an attempt to understand the processes that control their behavior. Glaciers over the recent 40 years(1970-2010) have shrunk 3.4±3.1%in area, based on a comparison between two Chinese glacier inventories. Variations of surface elevations, derived from ICESat-GLAS(Ice, Cloud, and Land Elevation Satellite-Geoscience Laser Altimeter System) elevation products(GLA14 data) using the robust linear-fit method, indicate that the glaciers have been gaining mass at a rate of 0.23±0.24 m w.e./a since 2003. The annual mass budget for the whole WKS range from 2003 to 2009 is estimated to be 0.71±0.62 Gt/a. This gain trend is confirmed by MOD10A1 albedo for the WKS region which shows a descent of the mean snowline altitude from 2003 to 2009.

Isotope Geochronologic and Geochemical Constraints on the Magmatic Associations of the Collisional Orogenic Zone in the West Kunlun Orogen, China

The Jiajiwaxi pluton in the southern portion of the West Kunlun Range can be divided into two collision-related intrusive rock series, i.e., a gabbro-quartz diorite-granodiorite series that formed at 224±2.0 Ma and a monzonitic granite-syenogranite series that formed at 222±2.0 Ma. The systematic analysis of zircon U-Pb geochronology and bulk geochemistry is used to discuss the magmatic origin （material source and thermal source）, tectonic setting, genesis and geotectonic implications of these rocks. The results of this analysis indicate that the parent magma of the first series, representing a transition from I-type to S-type granites, formed from thermally triggered partial melting of deep crustal components in an early island-arc-type igneous complex, similar to an I-type granite, during the continental collision orogenic stage. The parent magma of the second series, corresponding to an S-type granite, formed from the partial melting of forearc accretionary wedge sediments in a subduction zone in the late Palaeozoic-Triassic. During continued collision, the second series magma was emplaced into the first series pluton along a central fault zone in the original island arc region, forming an immiscible puncture-type complex. The deep tectonothermal events associated with the continent-continent collision during the orogenic cycle are constrained by the compositions and origins of the two series. The new information provided by this paper will aid in future research into the dynamic mechanisms affecting magmatic evolution in the West Kunlun orogenic belt.

Geochronology, petrogenesis and tectonic significance of Dahongliutan pluton in Western Kunlun orogenic belt, NW China

The Dahongliutan granitic pluton,in the eastern part of the West Kunlun orogenic belt,provides significant insights for studying the tectonic evolution of West Kunlun.This paper presents a systematic study of LA-ICP-MS zircon U Pb age,major and trace elements,Sr-Nd-Hf isotopes,and the first detailed Li isotope analysis of the Dahongliutan pluton.LA-ICP-MS zircon U Pb dating shows that the Dahongliutan granites were emplaced in the Late Triassic((213±2.1)Ma).Geochemical data show relatively high SiO2 contents(68.45 wt%73.62 wt%)and aluminum saturation index(A/CNK=1.111.21)indicates peraluminous high-K calc-alkaline granite.The Dahongliutan granites are relatively high in light rare earth elements(LREE)and large ion lithophile elements(LILEs)(e.g.,Rb,K,Th),and relatively depleted in high field strength elements(HFSEs)(e.g.,Nb,Ta,P,Ti).TheεNd(t)values range from 8.71 to 4.73,and(87Sr/86Sr)i=0.70870.71574.Zircons from the pluton yield 176Hf/177Hf values of 0.2826181 to 0.2827683,andεHf(t)values are around 0;the two-stage Hf model ages range from 0.974 to 1.307 Ga.Theδ7Li values are 0.76‰3.25‰,with an average of 2.53‰.Isotopic compositions of the pluton suggest a mixed trend between the partial melting of the Middle Proterozoic ancient crustal material and a juvenile mantle-derived material.This study infers that the Dahongliutan rock mass is formed in the post-collisional extension environment,when the collision between South Kunlun and the Tianshuihai terranes results in the closure of the Palaeo-Tethys.The mantle-derived magma results in partial melting of the lower crust.

Ore-forming Conditions and Prospecting in the West Kunlun Area,Xinjiang, China

The West Kunlun ore-forming belt is located between the northwestern Qinghai-Tibet Plateau and southwestern Tarim Basin. It situated between the Paleo-Asian Tectonic Domain and Tethyan Tectonic Domain. It is an important component of the giant tectonic belt in central China (the Kunlun-Qilian-Qinling Tectonic Belt or the Central Orogenic Belt). Many known ore-forming belts such as the Kunlun-Qilian Qinling ore-forming zone, Sanjiang (or Three river) ore-forming zone, Central Asian ore-forming zone, etc. pass through the West Kunlun area. Three ore-forming zones and seven ore-forming subzones were classified, and eighteen mineralization areas were marked. It is indicated that the West Kunlun area is one of the most favorable region for finding out large and superlarge ore deposits.

WHEN THE KUNLUN MTS.PASS AREA UPLIFTED TO PRESENT ELEVATION

Introduction There are big disputes on the uplift of the Tibetan Plateau. Some scientists believe the plateau uplifted to its highest elevation by 14Ma BP,and it decreased in elevation afterward. The second idea about the uplift of the plateau was similar to the first one in tectonic theory, but they consider the time of C3 plant change to C4 in the South Asia, as the time when the plateau reached its highest elevation. This time is 8Ma BP. The third idea, the most Chinese scientists believed, the nearest uplift of the plateau took place since 3 4Ma BP. The occurrence of fault depression and gravel deposit with large thickness in the inner and the marge of the plateau represented the speed uplift. After the collision of the India plate and the Eurasia plateau by the 36Ma, the Tibetean area uplifted several times, but it had been planed to lower area. The plateau with 4500m elevation formed in the Quaternary. While our recent research in the Kunlun Pass area suggest , the nearest uplift occurred at the border of the Early and Middle Pleistocene, and before that time, the elevation of this area was no more than 1500 m.

Discovery of Enclaves from Cenozoic PuluVolcanic Rocks in West Kunlun Mountains and ItsGeological Implications

In this paper, we present the occurrence and mineral components of the enclaves firstly discovered in the Cenozoic Pulu volcanic rocks in west Kunlun Mountains, and propose that the enclave is accumulated by fractional crystallization within high-level magma chamber. In addition, the chemical compositions of its primary magma are calculated. The calculated compositions are similar to those of the Kangxiwa volcanic rocks that belong to the same volcanic belt in the Pulu volcanic region, suggesting their origin from the same source region. However, the temperatures and oxygen fugacity of magmas at high-level magma chamber decreased along with fractional crystallization.

The Sachakou Deposit in West Kunlun of Xinjiang: A Pb-Zn Polymetallic Deposit Associated with Magmatic Metasomatism of Carbonate Rock

Objective The Sachakou Pb-Zn polymetallic deposit is located in Hetian County, Xinjiang （geographical coordinates of E78° 57＇ 54.30＂-78°59＇ 53.63＂, N34° 39＇ 27.50＂-34° 40＇ 57.21＂）. It belongs to the West Kunlun orogenic belt on the northwest edge of the Qinghai-Tibet Plateau and is connected to the Sanjiang orogenic belt to the south （Spurlin et al., 2005）. In recent years, a series of Pb-Zn mineralized spots and deposits have been discovered in this area one after another, which is called the Huoshaoyun ore concentration area. Among them, the Sachakou Pb-Zn deposit has reserves up to140 Mt, which has reached a large scale. However, the study on the genesis of deposits in this area has only just begun. This work studied the genesis ofthis Pb-Zn deposit in order to provide new ideas for the genesis of regional deposits and regional prospecting.

DEEP SEISMIC SOUNDING EVIDENCE FOR TECTONIC INTERACTION BETWEEN TARIM AND WEST KUNLUN MT

The Tarim basin, located in the northern margin of Tibet, plays a key role in comprehending Tibetan plateau rapid uplift process. Focuses have been on the contribution of basin block to create high mountain (e.g.,Chen and Molnar,1977, Molnar et al.,1993, Ph. Matte, Tapponnier et al.,1996) since 1970. The models, which mainly depend on result of geological survey and other geophysical observation in the region excepted Deep Seismic Sounding, remained unsure because of blank(or absence ) of DSS data until our experiment was performed. How Tarim and west Kunlun to contact in depth ? What different is in crust structure between Tarim and west Kunlun Mt.? This is what we will reply to in our program.We finished the program in 1997. A total of 120 set seismograms (with 3\|component sensors) and 18000kg (AT and TNT) dynamos were used for the DSS field project. 6 shot in Tarim basin and 1 shot in west Kunlun Mt. (Quanshuigou) had been shoot successfully. One shot (Pishan shot) is used as fan\|shape observation (offset is from 150km to 220km) in 6 shots located in Tarim basin. The survey line is along Hotan river across the Tarim basin from the north to the south. In particular, we carried 20 set seismic recorders to Kunlun Mt. to make a short line about 60 km as the southern tendency of our line. The seismic recorders were placed in an interval of 3km from one stations to the next and covered a distance of more than 300km. The stations have to be moved their location per 2\|shotting to form a meeting system or a tracing system (layout). Fig.1 showed our survey line and location of shot as well as recorder stations. Finally we gained 625 cassettes with original seismic record (include cassettes of shooting time recorder et al.). After data process total 1147 quite high\|quality three\|component digital records have been used to analyze. Here, only results of analyzing P wave data is given.

TECTONIC EVOLUTION OF THE WESTERN KUNLUN AND KARAKORAM MOUNTAINS—SOME NEW OBSERVATIONS FROM A MULTI-DISCIPLINARY GEOSCIENTIFIC TRANSECT (MGT) IN NW TIBET

New results from deep seismic sounding reveal that the Tarim block (basin) was subducted, with gently dipping, to the W.Kunlun Mts. The depths of Moho from north to south are 50km in S.Tarim to 65km in the W. Kunlun Mts. A low velocity and low resistivity layer occurs at the depth of 15～30km, which may be the decollement in the upper crust. A “delamination Crack" might have been formed in the lower crust\|mantle lid, causing the intrusion of alkaline magma along the southern margin of the W. Kunlun Mts. A detailed research for forming and evolving of the Kudi ophiolite in the central part of the W. Kunlun Mts.,which has been given the age of 700～450Ma by using the Re\|Os isotopic dating, and the Radiolarits in chert intercalated with pillow lava are determined to be the late Ordovician to Silurian. Until now we did not find any complete ophiolite suite except Kudi ophiolite. So we suggest that there was no “vast protero\|ocean", and a “limited oceanic basin" exists only during the late Proterozoic to Early Paleozoic, which might have been subducted in Silurian\|Devonian and formed the oldest suture in the north of the Tibet plateau.A suture zone consisting of H. P/T metamorphic blueschist, ophiolitic melange and olistostrome in the north\|western Tibet has been revealed recently, which may extend to NW. connecting with MKT in N. Pakistan.A study of the Fission track thermochronology indicates that the W.Kunlun Mts. has been undergone a pulsatory uplift since 20～18Ma,and a rapid uplift after 3Ma.A model of collision between the Indo\|Pakistan subcontinent\|N.Tibet and the Eurasian blocks of Tarim has been illustrated.

GRANITOIDS AND TETONIC EVOLUTION OF THE WEST KUNLUN OROGENIC BELT

The West Kunlun orogenic belt, one of the least studied areas in China, is located at the junction between the Qinghai—Tibetan Plateau and Tarim Basin and has undergone intense tectonic action and frequent magmatism.The West Kunlun orogenic belt can be divided into five tectonic\|magmatic evolution stages according to the character of the igneous rocks, metamorphic rocks, sedimentation mode, tectonic phases and isotopic ages(Fig 1).Active stages have dominated with only short intervening stable stages. This kind of evolution is not simply repeated but that a later stage is elevation and development of its former stage.Space\|time distribution of granitoids varies with each different tectonic\| magmatic stage as well as within different periods of the same tectonic\| magmatism stage. Take time into condition , It is an important turning movement of tectonics\|magmatism evolution during the Indo\|Sinian movement, as space the middle fault (Jiang Chunfa 1982) of the West Kunlun orogenic belt is a significant border o f tectonics\|magmatism evolution. Granitoids formed before Indo\|Sinian movement are mainly distributed to the north of the middle fault of West Kunlun. These granitoids are mostly granites of early and middle Proterozoic, Caledonian and Hercynian ages. A unique control on the granitoid evolution is that they become younger from NE to SW, crossing the regional structure line. Granitoids formed after Indo\|Sinian movement are mainly distributed to the south of the middle fault. But distribution of granitoids of early Yanshan cycle cut across the middle fault of West Kunlun Mountain. Their age distribution shows a bidirectional control with the granitoids becoming younger across the regional structural lines from NE and SW boundary fault to the interior of the fracture belts.

Caledonian Low-Temperature Granulite-Facies Metamorphism in the West Kunlun Orogenic Belt-SHRIMP Chronological Evidence from Zircon

The West Kunlun orogenic belt is located at the conjunction of the paleo\|Asian tectonic system and the Tethys tectonic system. Petrological and mineralogical studies of the Early Cambrian metamorphic surface crust in this region have shown that in case the metamorphism reached low\|temperature granulate facies, the typical mineral assemblage is biotite\|garnet\|silimanite\|K feldspar\|plagioclase\|quartz. The peak metamorphic temperatures are within the range of 720-740℃ and the pressure is \{0.6\} GPa±. Three types of metamorphic zircon have been detected in the metamorphic rocks: the complex inclusion\|bearing type; the early relic zircon inclusion\|bearing type; and the inclusion\|free type. SHRIMP age determination of these three types of metamorphic zircon have revealed that these zircons were formed principally during 400-460 Ma, indicating that pre\|Cambrian metamorphic surface crust rocks underwent low\|temperature granulite facies metamorphism during the Caledonian. In combination with the geological characteristics of this region, it is considered that when the oceanic basin was closed, there occurred intense intracontinental subduction (type A), bringing part of the Early Cambrian metamorphic basement in this region downwards to the lower crust. Meanwhile, there were accompanied with tectonic deformation at deep levels and medium\| to high\|grade metamorphism. This study provided important chronological and mineralogical evidence for the exploration of the evolutionary mechanism and process of the West Kunlun Early Paleozoic.

TECTONIC SIGNIFICANCE OF THE WEST KUNLUN FOLD-THRUST-BELT AND THE TARIM SOUTHWEST DEPRESSION

The evolution of the Tarim southwest depression lying at the piedmont of the West Kunlun orogen differs completely from the evolution of the main part of Tarim basin after Later Palaeozoic because the former strongly subsides many times.. Subsidence is related closely to the West Kunlun fold thrust\|belt, thus the evolution of the Depression and the fold\|thrust\|belt reflects clearly the formation and evolution of the West Kunlun and even the Tibet.1 Evolution of the West Kunlun fold\|thrust\|belt\;Thrusting of the fold\|thrust\|belt can be classified into three stages:(1) Devonian thrusting:This is the oldest thrusting distinguished in the northern margin of the West Kunlun while the Silurian—Devonian thrusting was discriminated a few years ago by seismic data in the northern part of the East Kunlun. The Devonian thrusting is proved by the Upper Devonian dynamometamorphic rocks outcropping at the core of the anticline in the Sangzhu lying at the fold\|thrust\|belt. The rocks consist of slightly metamorphic clastic rock and have always been regarded as the Mid\|Proterozoic strata. But they are actually Upper Devonian strata according to the amount of perfect plant fossils that we found recently in the metamorphic rock, and they are overburdened `with an angular unconformity by another reliable Upper\|Devonian conglomerate in the core of the Aqike anticline. A possible explanation for this and its limited lined distribution parallel to the West Kunlun orogen is that they are subjected to metamorphism during the Later Devonian thrusting.

PERSISTENCES IN THE δ^(13)C AND δ^(18)O FROM TS95, A LAKE CORE AT THE SOUTH FRANK OF WEST KUNLUN MOUNTAIN

Tibet Plateau has uplifted greatly in the Late Cenozoic era (Li Jijun et al., 1979; Sun Honglie, 1996; Shi Yafeng et al., 1998). The uplift will unquestionably influence the environment and climate of the plateau in the same time (such as resulting in the decrease of temperature) and leave some footprint on the contemporary sediments on or around the plateau. So, there must be some persistence component in the environmental and climatic evolution reflected by the geochemical information in the contemporary sediments. TS95, namely Tianshuihai Lake core is at the south frank of West Kunlun Mountain of Tibet Plateau and is suitable for the investigation of the persistence component. Using R/S analysis, Zhou Houyun et al. (1999) have previously calculated the Hurst index H of the three ferric indexes, FeO, Fe\-2O\-3 and ratio of FeO/ Fe\-2O\-3, from TS95. It is found that all these indexes satisfy Hurst law and they all are greater than 0 5, which means that there are some long run dependencies\|persistence component in the climatic and environmental evolution around Tianshuihai Lake area. This is in accordance with previous work by Yu Suhua et al. (1996). In this paper, the authors use the same method to do some R/S analysis on the other two climatic proxies of TS95, δ 13 C and δ 18 O, which are more suitable than the three ferric indexes to be climatic and environmental proxies. It is found that both the δ 13 C and δ 18 O satisfy Hurst law very well with H δ 13 C =0 875 and H δ 18 O =894, which suggests stronger persistence than the three ferric indexes.

THE EVOLUTIONARY HISTORY OF THE WEST KUNLUN MOUNTAINS: A TECTONIC RECONSTRUCTION BASED ON STUDIES OF MAGMATISM

The Kunlun Mountains is situated in the north margin of the Tibetan plateau and is one of crucial areas for unraveling the tectonic evolutionary history of the plateau and Eurasia. However, there is no widely accepted model for this area. One of the reasons is that some basic issues for the tectonic reconstruction have not been well settled, they are: (1) Is the Kunlun Mountains an ancient accretion prism, or a mini continent with old basement?(2) What is the age of the Kudi ophiolite, early Paleozoic or late Paleozoic?(3) When did the South Kunlun Block accrete to the Tarim Block?(4) Do the fifth and the forth sutures represent different oceans, or they are just the chronologically different relics of the same ocean?(5) Did the Kunlun Mountains experience continuous subduction since Neoproterozoic?(6) When did the Paleo\|Tethys closed in the West Kunlun range?

CHARACTERISTICS OF NATURAL CONTENTS OF CHEMICAL ELEMENTS IN SOILS OF KARAKORUM-WEST KUNLUN MOUNTAIN REGION

Natural contents of 23 elements in soils of Karakorum-West Kunlun Mts are studied. By comparison of natural contents andcalculation of regional differentiation coefficients, similarity anddchrence of elemental contents between soils of the region and thatof China and of the world are discussed. Through main componentanalysis, relation of intergrowth and realignment among elementsin soils and characteristics of cluster expressed in soil types are alsodiscussed. Coherence of elements in soi1s and characteristics ofregional dtherence of the elements are clarified. The concernedregion is abound in natural resources. Research on natural contentsof chemical elements in soils of the region is significant forstudying elemental chemical geography and environmentalgeochemistry. Besides, it also offers necessary data for explorationand development of this region.