Origin of the Dashuigou independent tellurium deposit at Qinghai–Xizang Plateau: constraints from the light stable isotopes C, O, and H

By studying the light isotopic compositions of carbon,oxygen,and hydrogen,combined with previous research results on the ore-forming source of the deposit,the authors try to uncover its metallogenic origin.The δ^(18)O and δ^(13)C isotope signatures of dolomite samples vary between 10.2 and 13.0‰,and between−7.2 and−5.2‰,respectively,implying that the carbon derives from the upper mantle.δD and δ^(18) O of quartz,biotite,and muscovite from diff erent ore veins of the deposit vary between−82 and−59‰,and between 11.6 and 12.4‰,respectively,implying that the metallogenic solutions are mainly magmatic.According to the relevant research results of many isotope geologists,the fractionation degree of hydrogen isotopes increases as the depth to the Earth’s core increases,and the more diff erentiated the hydrogen isotopes are,the lower their values will be.In other words,mantle-derived solutions can have extremely low hydrogen isotope values.This means that the δD‰ value−134 of the pyrrhotite sample numbered SD-34 in this article may indicate mantle-derived oreforming fl uid of the deposit.The formation of the Dashuigou tellurium deposit occurred between 91.71 and 80.19 Ma.

Quantification of the concrete freeze–thaw environment across the Qinghai–Tibet Plateau based on machine learning algorithms

The reasonable quantification of the concrete freezing environment on the Qinghai–Tibet Plateau(QTP) is the primary issue in frost resistant concrete design, which is one of the challenges that the QTP engineering managers should take into account. In this paper, we propose a more realistic method to calculate the number of concrete freeze–thaw cycles(NFTCs) on the QTP. The calculated results show that the NFTCs increase as the altitude of the meteorological station increases with the average NFTCs being 208.7. Four machine learning methods, i.e., the random forest(RF) model, generalized boosting method(GBM), generalized linear model(GLM), and generalized additive model(GAM), are used to fit the NFTCs. The root mean square error(RMSE) values of the RF, GBM, GLM, and GAM are 32.3, 4.3, 247.9, and 161.3, respectively. The R^(2) values of the RF, GBM, GLM, and GAM are 0.93, 0.99, 0.48, and 0.66, respectively. The GBM method performs the best compared to the other three methods, which was shown by the results of RMSE and R^(2) values. The quantitative results from the GBM method indicate that the lowest, medium, and highest NFTC values are distributed in the northern, central, and southern parts of the QTP, respectively. The annual NFTCs in the QTP region are mainly concentrated at 160 and above, and the average NFTCs is 200 across the QTP. Our results can provide scientific guidance and a theoretical basis for the freezing resistance design of concrete in various projects on the QTP.

Petrogenesis of the Cenozoic Volcanic Rocks from the Northern Part of Qinghai-Xizang (Tibet) Plateau

Based on electron probe analyses of the minerals and bulk composition of the Cenozoic volcanic rocks from Yumen and Hoh Xil lithodistricts, Qinghai\|Xizang plateau, the forming conditions including the temperature and pressure of those rocks are studied in this paper. According to the thermodynamic calculation results of mineral\|melt equilibrium, the depth of the asthenosphere superface (about 75-130 km) for the northern part of the Qinghai\|Xizang plateau during the Cenozoic is suggested. Finally, this paper indicates that the Cenozoic volcanic rocks in the northern part of the Qinghai\|Xizang plateau mainly consist of shoshonite series. Their forming temperature is 630-1039℃ and forming pressure is between 2.3-4.0 GPa. The rocks were formed in the intracontinental orogenic belt, of which the primary magma was originated from a particular enrichment upper mantle and accreted crust\|mantle belt or directly from asthenospheric superface as a result of partial melting of pyrolite.

LAST GLACIATION AND MAXIMUM GLACIATION IN THE QINGHAI-XIZANG (TIBET) PLATEAU: A CONTROVERSY TO M. KUHLE,S ICE SHEET HYPOTHESIS

Since the late 1950’s, many Chinese scientists have explored the remains of the Quaternary glaciation in the Qinghai-Xizang (Tibet) Plateau and its surrounding mountains. In the main, 3-4 glaciations have been recognized. The largest one occurred in the Late Middle Pleistocene with piedmont glaciers, ice caps and trellis valley glaciers in many high peak regions. But here is no evidence of a unified ice sheet covering the whole plateau as described by M. Kuhle. Due to the further uplifting of the Himalayas and Qinghai-Xizang Plateau the climate became progressively drier, diminishing the extension of glaciers during the Late Pleistocene. The elevation of the snow line during the Last Glaciation was about 4,000 m on the south, east and northeast edges of the plateau and ascended to 5500 m on the hinder northwest of the plateau. The thermal effect of the big plateau massif, the sharp increase of aridity from the southeast rim to the northwest inland area and the abrupt decrease of precipitation during

A NEW INTERPRETATION OF THE EVOLUTION OF THE TETHYS CRUSTOBODY AND THE PETROLEUM POTENTIAL OF THE QINGHAI-XIZANG (TIBET) PLATEAU

Although large amounts of data have been collected during the past 30 yesrs in the study of the formation, evolution and dynamics of the Tethys Sea by the use of the theory of plate tectonics, a large volume of geological and geophysical information has also been accumulated which cannot be explained by the plate tectonic hypothesis. For example, the Qinghai-Xizang Plateau is underlain by many thousands of meters of Ordovician through Eocene, gently-dipping, essentially undeformed, stable platform sequences. Stratigraphic and tectonic investigations reveal that the plateau-wide east-west fracture zones, interpreted as "sutures" in a plate-tectonic model, are not sutures at all. On the other hand, from the Late Carboniferous to the beginning of the Early Permian, it was impossible for the Tethys ocean with a width of several thousand kilometers to."open" and "close" (the speed could not be so great). The east-west fracture zones, with very sharp angles, exerted no control over deposition. Stress analysis of magmatic activity indicates that the Himalayan zone is presently under compression, the Gangdise zone under interwoven comprepsion and tension, and the Qinghai and Deccan Plateaus under weak tension. Lateral compression caused by weak tension at the northern and southern terminations was not enough for Xizang and its surroundings between India and Qinghai Province of China with an area of 2,400,000 km2 to rise to a height of 4,000 m above mean sea level. The authors believe that surge tectonics is the force driving the evolution of the Tethys Sea and the rising of the Qinghai-Xizang Plateau. G. G. T. demonstrates that two surge channels, an upper and a lower, exist in the Yadong-Anduo litho sphere, and the upper mantle in the southern part is uplifted. During the Eocene, as a result of tectogenesis, molten magma poured out from the channel along the Yarlung Zangbo River,forming ophiolites and melanges, and earthquakes and terrestrial heat are also distributed along the fracture zone. Likewise, at an earlier time the Banggong Co-Nujiang and Longmu Co-Yushu Jinshajiang surge channels and their fracture zones formed. During the Miocene, the three surge channels merged laterally, and then the unified rise of the Qinghai-Xizang Plateau took place. The formation and evolution of the surge channels resulted in a variety of worthy Paleozoic, Mesozoic and Cenozoic exploration targets and a series of sedimentary basins with the largest Qamdo Basin occupying 120, 000 km2 with sediments attaining a thickness of 15, 000 m. These basins contain multiple source-beds, reservoirs, traps and seals of different ages, showing oil and gas every-where. In the northern part lithology and facies are more stable than in the southern, and subsequent tectonic overprinting and volcanic activity are relatively weak. At present commercial oil flow has been penetrated by drilling in the Tertiary Lunpola Basin.

A PRELIMINARY STUDY ON TRE ZONE OF ALPINE SCRUB AND MEADOW OF QINGHAI-XIZANG (TIBETAN) PLATEAU

The zone of alpine scrub and meadow, characterized by highlandsubpolar humid/subhumid climate, is a transitional area from deep gorges to theplateau proper.The natural zone is unique in physical environments and naturalecosystems, and could not be found at the lowlands elsewhere on the earth.Thepredominant type of vegeation is alpine meadow, including Kobresia meadow,herbaceous meadow and swampy meadow. It is an important pasturelands ofanimal husbandry for Tibetan on the plateau. Main vegetion types, animal groups,characteristics of alpine meadow soils, the altitudinal belt and the horizontalzonality of the natural zone, as well as utilization and management of the grasslandsare discussed in the present paper.

Contribution of external forcing to summer precipitation trends over the Qinghai-Tibet Plateau and Southwest China

在过去的60年中,全球气候经历了快速变暖和短暂的变暖停滞,而中国的区域降水也经历了多样而复杂的变化.本文分析了1961年至2014年外强迫因子对青藏高原和中国西南地区夏季降水趋势的影响.观测数据显示,青藏高原的夏季降水呈增加趋势,而中国西南地区的夏季降水呈减少趋势,这两个相邻地区的夏季降水变化趋势相反.利用CMIP6数据,本文研究了不同外强迫因子对两个区域夏季降水趋势的影响.结果表明,温室气体对青藏高原夏季降水的增加具有显著影响,而气溶胶在中国西南地区夏季降水减少中起主要作用。

Present-day tectonic movement in the northeastern margin of the Qinghai-Xizang (Tibetan) plateau as revealed by earthquake activity

Characteristics of present-day tectonic movement in the northeastern margin of Qinghai-Xizang plateau (Tibetan) are studied based on earthquake data. Evidence of earthquake activity shows that junctures between blocks in this area consist of complicated deformation zones. Between the Gansu-Qinghai block and Alxa block there is a broad compressive deformation zone, which turns essentially to be a network-like deformation region to the southeast. The Liupanshan region, where the Gansu-Qinghai block contacts the Ordos block, is suffering from NE-SW compressive deformation. Junction zone between the Ordos and Alxa block is a shear zone with sections of variable trend. The northwestern and southeastern marginal region of the Ordos is under NNW-SSE extension. The above characteristics of present-day tectonic deformation of the northeastern Qinghai-Xizang plateau may be attributed to the northeastward squeezing of the plateau and the resistance of the Ordos block, as well as the southeastward extrusion of the plateau materials.

Cu-Ni-PGES MINERALIZATION OF MELANOCRATIC ROCKS IN SOUTHEAST MARGIN OF THE QINGHAI-XIZANG(TIBET) PLATEAU, HKT

The Panxi Rift Zone is a famous metallogenic province in Southwest China. Continental rifting developed in Hercynian period (P 2, 260～250Ma) accompany with a series of basic\|ultrabasic rocks. Various in lithologies, such as layered intrusions (V\|Ti\|Fe formation), small\|sized mafic\|ultramafic bodies (stocks) and large\|scale basalt (Emeishan Basalt) are constituted of a complete melanocratic rock system.Most of Cu\|Ni\|PGE sulfide deposits are related to small\|sized ultramafic rock bodies. It is a perfect possibility for them to be an affinity of basic eruptive lava and for the neck facies. But in ① Panzhihua\|Center Yunnan Province, the Gaojiacun, also Jinbaoshan, as large stratiform basic\|ultrabasic complex used to be thought that is older one intruded to basement rocks in Precambrian. However, new evidences suggest it is similar with the small\|sized ultramafic rock bodies containing Cu\|Ni\|PGE, and also the both are affinity of the Emeishan Basalt; ② Miyi district, Cu\|Pt mineralization was discovered in the Xinjie bedded basic complex, and in where ophitic olivine\|pyroxenite\|peridotite facies are exactly Pt\|bearing layers; ③ Longzhoushan district, we have recently researched basic\|ultrabasic clusters which intruded into fracture zones, and Cu\|Ni\|Pt, Pd mineralization developed at the salbands.Generally, the basalt is poor in PGE and rich in Cu. It is suggested as the result of PGE dispersion\|concentration processing in the melanocratic rock system when rifting happened.

Critical Approach to Methods of Glacier Reconstruction in High Asia and Discussion of the Probability of a Qinghai-Xizang (Tibetan) Inland Ice

This overview discusses old and new results as to the controversy on the past glacier extension in High Asia, which has been debated for 35 years now. This paper makes an attempt to come closer to a solution. H.v. Wissmann's interpretation (1959) of a small-scale glaciation contrasts with M. Kuhle's reconstruction (1974) of a large-scale glaciation with a 2.4 million km2 extended Qinghai-Xizang (Tibetan) inland glaciation and a Himalaya-Karakorum icestream network. Both opinions find support but also contradiction in the International and Chinese literature (Academia Sinica). The solution of this question is of supraregional importance because of the subtropical position of the concerned areas. In case of large albedo-intensive ice surfaces, a global cooling would be the energetical consequence and, furthermore, a breakdown of the summer monsoon. The current and interglacial heat-low above the very effective heating panel of the Qinghai-Xizang (Tibetan) Plateau exceeding 4000 m, which gives rise to this monsoon circulation, would be replaced by the cold-high of an inland ice. In addition, the plate-tectonically created Pleistocene history of the uplift of High Asia — should the occasion arise up to beyond the snowline (ELA) —would attain a paleoclimatically great, perhaps global importance. In case of a heavy superimposed ice load, the question would come up as to the glacio-isostatic interruption of this primary uplift. The production of the loesses sedimentated in NE-China and their very probable glacial genesis as well as an eustatic lowering of the sea-level by 5 to 7 m in the maximum case of glaciation are immediately tied up with the question of glaciation we want to discuss. Not the least, the problems of biotopes of the sanctuary-centres of flora and fauna, i.e., interglacial re-settlement, are also dependent on it. On the basis of this Quaternary- geomorphological-glaciological connection, future contributions are requested on the past glaciation, the current and glacial permafrost table and periglacial development, the history of uplift, and the development of Ice Age lakes and loess, but also on the development of vegetation and fauna in High Asia.

EVOLUTION AND DIFFERENTIATION OF THE PHYSICO-EOGRAPHICALENVIRONMENT OF THE QINGHAI-XIZANG (TIBETAN) PLATEAU

The intense uplift of the Qinghai-Xizang Plateau givesrise to drastic changes of natural environment and distinctdifferentiation of the Plateau proper. This paper focuses on theevolution of subtropical environment at low altitude to frigidenvironment at high altitude of the region since Pliocene and thechanges effected by cold-warm amplitude bf global change. Bycomparative study on the structure-type of the altitudinal belt, adistributional model diagram with close relevance to highlanduplift effect has been generalized. Based on regjonaldifferentiation of the Qinghai-Xizang Plateau, a number ofstriking geo-ecological phenomena such as moisture corridor, dryvalleys and high cold-arid core area are investigated anddiscussed.

Study on the Anomaly of Small Earthquake Activity Before Moderate-strong Earthquake in the Northeast Margin of the Qinghai-Xizang (Tibet) Block

26 earthquakes with MS ≥5. 0 have been recorded in the northeast margin of the Qinghai- Xizang (Tibet) block since 1980,22 of which were relatively independent of other moderate- strong earthquakes. Research on the increase of small earthquake activity before the 22 moderate-strong earthquakes has indicated that small earthquake activity was enhanced before 17 of the moderate-strong earthquakes. Though the increased seismicity is a common phenomenon in the northeast margin of the Qinghai-Xizang ( Tibet ) block,we have difficulty in predicting the moderate-strong earthquakes by this phenomenon. In order to predict the moderate-strong earthquakes through the increased seismicity of small earthquakes,this paper attempts to propose a new method, which calculates small earthquake frequency through the change of distribution pattern of small earthquakes, based on the characteristics of small earthquake activity in the northeastern Qinghai-Xizang (Tibet) block,and then make primary applications. The result shows that we are able to obtain obvious anomalies in the frequency of small earthquakes before moderate strong earthquakes through the new method,with little spatial range effect on the amplitude of this small earthquake frequency anomaly. We can obtain mid to short-term anomaly indices for moderate-strong earthquakes in the northeast margin of the Qinghai-Xizang (Tibet) block.

Study on Statistical Features About Weak Earthquake Activity Before Moderately Strong Earthquakes in the Middle Northern Part of the Qinghai-Xizang (Tibet) Block

In regards to the earthquakes recording M≥5.0 that occurred in middle northern part of the Qinghai-Xizang (Tibet) Block from 1970～2003, in this study we describe the temporal and spatial centralization features of the weak earthquakes and the enhancement and anomalous quiescence of their seismic activity before main shocks through 4 parameters, which are basically not correlated: earthquake time centralization degree parameter C_t, earthquake space centralization degree parameter C_d, η value and weak earthquake frequency and so on. On the basis of calculation results, it has been seen that before earthquakes with M≥5.0 took place in the middle northern part of the Qinghai-Xizang (Tibet) Block, the frequency of weak earthquakes often shows ascent and drop, their strength shows an obvious enhancement and the centralization distribution with time and space is evident.

Earthquake Activity Features Before Earthquakes with M_S≥7.0 in the Central-Northern Qinghai-Xizang(Tibet) Block

We have studied the seismicity features of M_S≥5.0 earthquakes two years before strong earthquakes with M_S≥7.0 occurred in the central-northern Qinghai-Xizang (Tibet) block since 1920. The results have showed that there is an obvious gap or quiescence of M_S5.0～6.9 earthquakes near epicenters. We have also studied statistical seismicity parameters of M_S5.0～6.9 earthquakes in the same region since 1950. The results have showed that earthquakes with M_S≥7.0 occurred when earthquake frequency is relatively high and earthquake time, space accumulation degrees are rising. And the prediction effect R value scores are between 0.4～0.7. We have concluded that, before earthquakes with M_S≥7.0 in the central-northern Qinghai-Xizang (Tibet) block, M_S5.0～6.0 earthquake activity in the whole area increased and accumulated in time and space, but earthquakes with M_S≥7.0 occurred where M_S5.0～6.0 earthquake activity was relatively quiet.

The Present Space-Time Motion and Deformation Features of the Northeastern Margin of the Qinghai-Xizang(Tibet) Block and Its Adjacent Area

On the basis of Discontinuous Deformation Analysis (DDA), and considering the moderate intrusion of specific block boundaries to different extents, the first-order block motion model is established for the northeastern margin of Qinghai-Xizang(Tibet) block and the kinematical model for depicting deformation of small regions as well by using GPS observations of three periods (1991, 1999 and 2001). By simulating, we obtained the motion features of the first-order blocks between the large WWN faults on the sides of the studied region, the distribution features of the principal strain rate field and the inhomogeneous motion features with space-time of the faults in the northern boundary of the Qinghai-Xizang (Tibet) block.

Modeling the Dynamic Gravity Variations of Northeastern Margin of Qinghai-Xizang (Tibet) Plateau by Using Bicubic Spline Interpolation Function

In this paper, the spatial-temporal gravity variation patterns of the northeastern margin of Qinghai-Xizang (Tibet) Plateau in 1992～2001 are modeled using bicubic spline interpolation functions and the relations of gravity change with seismicity and tectonic movement are discussed preliminarily. The results show as follows: ① Regional gravitational field changes regularly and the gravity abnormity zone or gravity concentration zone appears in the earthquake preparation process; ② In the significant time period, the gravity variation shows different features in the northwest, southeast and northeast parts of the surveyed region respectively, with Lanzhou as its boundary; ③ The gravity variation distribution is basically identical to the strike of tectonic fault zone of the region, and the contour of gravity variation is closely related to the fault distribution.

RATIONAL UTILIZATION OF MOUNTAIN SOILS IN SOUTHEAST QINGHAI-XIZANG (TIBETAN) PLATEAU

The southeast Qinghaicozang (Tibetan) Plateau is a physcal mpon ofvery complicated eco-envirorunent with optimum hydrothermal conditions. Thisregon conains not ouly vast expanse of alpine soils but also abounds in mosttypes of Chinese forest soils. The distributon and tallization of soils presents avery evident horizontal-vertical zonality. At present, panial soil resources arebeing damaged and the mountain ecology also tends to be instable. So rationalcuttin and forest conservation, barren mountain afferestation, retuming thecultivated land on stop slopes to forest, controlled graking, and soil ameliorationconstitute importan means for rational use of soil resources and improvement andstabilization of mountain ecology in tyis region

MECHANISM AND HISTORICAL BACKGROUND OF THE UPLIFT OF THE QINGHAI-XIZANG(TIBET) PLATEAU

The uplift of the Qinghai-Xizang (Tibet) Plateau happened in a different crustal movementsand different time from those of the collision of Asia continent with the allochthonous India crusto-body, and the uplift occurred very long after the finish of the collision. In fact, there are no direct-ly causationic relationships in time and dynamics, as well as in crustobody movement nature be-tween the uplift and collision. According to its temporal evolution, the uplift happened in anotheractive stage of the mantle creep flow after the active stage resulting in the collision and the inter-ruption of the 140 Ma’s quiet stage-particularly noticeably after this interruption of quiet stage-resulting in the universal Qinghai-Xizang (Tibet) ancient platform. On the basis of the dynamicanalysis, the uplift resulted from the multiple compressing stresses in the reactivation stage afterweakening of the colliding stress and the following compressing stress, and after the interruptionof the stable stage dominating the vertical movements and represented by fomation of the universalQinghai-Xizang (Tibet) ancient platform. It was the production of another stress field existing inanother crustobody evolution stage and growth age. In the light of the nature of the orogeny, theuplift was caused by the intracontinental diwa (geodepression)-type orogeny after converging con-nection of the Centra1 Asia Crustobody and the India Crustobody.Because of the big temporal difference between the uplift and collision events, the so-calleddouble-crust hypothesis of the Qinghai-Xizang (Tibet) Plateau may not be realistic.

“Tibet”或“Xizang”——关于“西藏”英译的讨论

西藏英文翻译采用汉语拼音Xizang取代Tibet,能够更准确地表达西藏作为地名的真实含义,符合国家地名翻译的规范标准,获得国际上中国的文化话语权,抵制十四世达赖分裂集团提出"大藏区"分裂祖国的图谋。

Review of numerical simulation on the dy-namics of Qinghai-Xizang plateau

In recent twenty years, much numerical simulation work has been done on the evolution of Qinghai-Xizang (Tibetan) plateau. In this paper some principal numerical models and results are reviewed and analyzed. The earlier plane stress or plane strain model has much discrepancy with the actual deformation of Qinghai-Xizang plateau, such as the thickening of Tibetan crust and the lateral extrusion of Tibet along strike-slip faults. The thin viscous sheet model and the thin-plate model may simulate the change of the crustal thickness and the deformation pro-duced by gravitational force. It is suitable for studying the large-scale and long-time deformation. The influence of faults on the deformation of Tibetan plateau should be further studied.