“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。

Zircon U-Pb Age,Geochemical Data:Constraints on the Origin and Tectonic Evolution of the Metamafic Rocks from Longmuco-Shuanghu-Lancang Suture Zone,Tibet

Bulk-rock major and trace elements and zircon U-Pb data are reported for Permian metamafic rocks from Guoganjianan, in the western part of Longmuco-Shuanghu-Lancang suture zone. These results offer new insights into mantle source characteristics and geodynamic setting of Permian ophiolitic fragments. U-Pb isotopic dating using SHRIMP II method reveals that the metamafic rocks were formed at 274.7± 3.9 and 279.8± 3.6 Ma. The metamafic rocks mostly show N-MORB-typed rare earth element patterns and are enrichment in large-ion lithophile elements, indicating that they are probably derived from partial melting of a depleted mantle in a back-arc basin. Our new data, together with recent studied results on Paleozoic ophiolitic fragments suggest the Paleo-Tethys Ocean in Central Qiangtang opened at Cambrian and widened between Ordovician and Devonian. Northward subduction started in the Late Devonian–Early Carboniferous and a back-arc basin developed during Permian.

Tempo-spatial rupture process of the 1997Mani, Xizang(Tibet), China earthquake of Ms=7.9

An earthquake of Ms=7.4 occurred in Mani, Xizang (Tibet), China on November 8, 1997. The moment tensor ofthis earthquake was inverted using the long period body wave form data from China Digital Seismograph Network(CDSN). The apparent source time functions (AS TFs) were retrieved from P and S waves, respectively, using thedeconvolution technique in frequency domain, and the tempo-spatial rupture process on the fault plane was imagedby inverting the azimuth dependent AS TFs from different stations. The result of the moment tensor inversionindicates that the P and T axes of earthquake-generating stress field were nearly horizontal, with the P axis in theNNE direction (29), the T axis in the SEE direction (122) and that the NEE-SWW striking nodal plane andNNW-SSE striking nodal plane are mainly left-lateral and right-lateral strike-slip, respectively; that this earthquakehad a scalar seismic moment of 3.4xl02o N. .m, and a moment magnitude of Mw=7.6. Taking the aftershock distribution into account, we proposed that the earthquake rupture occurred in the fault plane with the strike of 250,the dip of 88 and the rake of 19. On the basis of the result of the moment tensor inversion, the theoretical seismograms were synthesized, and then the AS T Fs were retrieved by deconvoving the synthetic seismograms fromthe observed seismograms. The A S T Fs retrieved from the P and S waves of different stations identically suggestedthat this earthquake was of a simple time history, whose ASTF can be approximated with a sine function with thehalf period of about 10 s. Inverting the azimuth dependent A S T Fs from P and S waveforms led to the imageshowing the tempo-spatial distribution of the rupture on the fault plane. From the 'remembering' snap-shots, therupture initiated at the western end of the fault, and then propagated eastward and downward, indicating an overallunilateral rupture. However, the slip distribution is non-uniform, being made up of three sub-areas, one in thewestern end, about 10 km deep ('western area'), another about 55 kin away from the western end and about 35 Iondeep ('eastern area'), the third about 30 km away from the western end and around 40 km deep ('central area').The total rupture area was around 70 km long and 60 km wide. From the 'forgetting' snap-shots, the rupturingappeared quite complex, with the slip occurring in different position at different time, and the earthquake being ofthe characteristics of 'healing pulse'. Another point we have to stress is that the locations in which the ruptureinitiated and terminated were not where the main rupture took place. Eventually, the static slip distribution wascalculated, and the largest slip values of the three sub-areas were 956 cm, 743 cm and 1 060 cm, for the western.eastern and central areas, respectively. From the slip distribution, the rupture mainly distributed in the fault about70 km eastern to the epicenter; from the aftershock distribution. however, the aftershocks were very sparse in thewest to the epicenter while densely clustered in the east to the epicenter It indicated that the Maul Ms=7.9 earthquake was resulted from the nearly eastward extension of the NEE-SWW to nearly E-W striking fault in thenorthwestern Tibetan plateau.

Zircon U-Pb Geochronological Constraints on Rapid Exhumation of the Mantle Peridotite of the Xigaze Ophiolite, Southern Xizang(Tibet)

The Xigaze ophiolite crops out in the central segment of the Yarlung Zangbo suture zone,southern Tibet(Fig.1).It is characterized by large amounts of ultramafic units with minor mafic rocks.The mafic rocks consist of gabbros,

Climatic changes have led to significant expansion of endorheic lakes in Xizang (Tibet) since 1995

Robust climate warming has led to significant expansion of lakes in the central Tibetan Plateau. Using remote sensing data, our quantitative analysis indicates that Siling Co, a saline lake in a characteristic endorheic basin in the central region of the Plateau, has expanded more than 600 km2 in area since 1976. Particularly since 1995, the lake has signif- icantly expanded in response to increasing precipitation, decreasing water surface evaporation caused by weaker winds and less solar radiation, and increased glacier meltwater draining to the lake. Glacie^lake interactions are important in governing lake expansion and are also part of a feedback loop that influences the local climate. Worsening climatic conditions （decreased precipitation and increased temperatures） that could have caused the lake to shrink during 1976-1994 were offset by increasing glacier meltwater feeding the lake, which made the lake nearly stable. We demonstrate that this pattern changed during 1995-2009, when glacier meltwater actually decreased but participation runoff increased and evaporation decreased, leading to expansion of the lake. If climatic conditions became suitable for further lake development, which would be indicated by expansion in lake area, glacier meltwater could be saved in a stable reservoir.

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.

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.

Application of tensor CSAMT with high-power orthogonal signal sources in Jiama porphyry copper deposit,South Tibet

The Jiama porphyry copper deposit in Tibet is one of the proven supergiant copper deposits in the Qinghai-Tibet Plateau at present,with the reserves of geological resources equivalent to nearly 20×10^(6) t.However,it features wavy and steep terrain,leading to extremely difficult field operation and heavy interference.This study attempts to determine the effects of the tensor controlled-source audiomagnetotellurics(CSAMT)with high-power orthogonal signal sources(also referred to as the high-power tensor CSAMT)when it is applied to the deep geophysical exploration in plateaus with complex terrain and mining areas with strong interference.The test results show that the high current provided by the highpower tensor CSAMT not only greatly improved the signal-to-noise ratio but also guaranteed that effective signals were received in the case of a long transmitter-receiver distance.Meanwhile,the tensor data better described the anisotropy of deep geologic bodies.In addition,the tests also show that when the transmitting current reaches 60 A,it is still guaranteed that strong enough signals can be received in the case of the transmitter-receiver distance of about 25 km,sounding curves show no near field effect,and effective exploration depth can reach 3 km.The 2D inversion results are roughly consistent with drilling results,indicating that the high-power tensor CSAMT can be used to achieve nearly actual characteristics of underground electrical structures.Therefore,this method has great potential for application in deep geophysical exploration in plateaus and mining areas with complex terrain and strong interference,respectively.This study not only serves as important guidance on the prospecting in the Qinghai-Tibet Plateau but also can be used as positive references for deep mineral exploration in other areas.

Depositional features and sedimentary model of Buqu Stage in Mid-Jurassic in Qangtang Basin, Xizang (Tibet), China

The largest Mesozoic northward transgression in Qangtang Basin of Qinghai-Xizang (Tibet) Plateau occurred during the Buqu Stage, Middle Jurassic. Mainly filled with carbonate rocks, the whole basin is composed of transgression-regression sedimentary cycle. Field outcrops and indoor analysis revealed 8 types of sedimentary facies markers in this region. 4 types of sedimentary facies have been recognized: platform facies, platform marginal facies, foreslope facies and basin facies. Influenced by the northern Lazhuglung-Jinshajiang suture zone, central uplift region and southern Bangongco-Nujiang suture zone, these facies belts extended east-west. The sedimentary model was established based on observed depositional features. From their biological features and sedimentary characteristics, it is suggested that the paleoclimate was warm and humid at that time. The Buqu Formation is a promising target for oil and gas exploration in Shuanghu-Duoyong area in future.

The Characteristics of Yongzhu–Guomang Lake Ophiolitic Melange in Bangong-Nujiang Suture, Xizang(Tibet),China

Yongzhu–Guomang Lake ophiolitic melange exposed about 100 km with large scale and complete ophiolitic uint in Xainza County,Xizang(Tibet).It is connected with Nam Lake,Kaimeng ophiolitic mélange to the east,and

Tectonic Evolution of the Dongbo Ophiolite in Western Yarlung Zangbo Suture Zone, Xizang(Tibet)

The Dongbo ophiolite in the western part of the Yarlung-Zangbo suture zone in southern Tibet rests tectonically on the middle-late Triassic and Cretaceous flysch units,and consist mainly of peridotites,mafic dikes,

The Metamorphic Processes and Its Geological Implications of Gneisses from the Duoba Terrane of Xizang(Tibet) Plateau, China

A suit of metamorphic rocks experienced amphibolite and partly granulite facies metamorphism exposed on the Lhasa block,which are recognized as the basement of the Lhasa block named as Nyainqentanglha Group in the

藏西北多龙矿集区拿若斑岩铜(金)矿床磷灰石矿物学特征及地质意义

拿若矿床目前是藏西北改则县多龙矿集区第三大斑岩型铜(金)矿床,前人开展了系统的成岩成矿年代学、成矿地质背景等研究,但空间蚀变分带和岩浆演化过程等方面研究较为薄弱。笔者等以拿若矿床磷灰石作为研究对象,在大量钻孔科研编录的基础上,开展了磷灰石矿物学和矿物化学研究,探讨拿若矿床磷灰石矿物彩色阴极发光特征与蚀变分带的耦合关系,揭示含矿岩浆演化期次及氧化还原状态。磷灰石彩色阴极发光特征显示,拿若矿床磷灰石彩色阴极发光(CL)特征主要表现为黄褐色、绿色—亮黄色和灰黑色,分别对应未蚀变、钾化蚀变和绢英岩化蚀变环境,磷灰石彩色CL特征与其所处蚀变环境的关系验证了笔者等重新厘定的拿若矿床斑岩系统“双钾化带”空间蚀变分带结构。磷灰石电子探针(EPMA)主量元素测试结果显示,磷灰石的CaO=53.5%~56.5%,P_(2)O_(5)=39.5%~42%,F=1.26%~3.24%,Cl=0.01%~1.99%,SO_(3)=0~1.28%,由此计算的X_(F)=0.68~1.76,XCl=0.001~0.58,X_(OH)=0.21~1.05。不同类型、阶段的磷灰石挥发分(F、Cl、OH)、SO_(3)等成分含量变化趋势反映了拿若矿床岩浆—热液演化过程发生了气体饱和→流体出溶→金属沉淀的过程,并揭示了成矿岩浆高氧逸度的性质。此外,环带状岩浆磷灰石反映了隐爆角砾岩系统发育了三期次岩浆作用,并指示了第I、III期岩浆活动具有更高氧逸度特征,与成矿关系更加密切。因此,笔者等认为在多期次岩浆热液叠加型斑岩铜矿床中,磷灰石在辅助厘定蚀变类型和反演岩浆—热液演化过程中具有重要的价值。

Early Triassic Volcanic Rocks in the Western Yarlung Zangbo Suture Zone:Implications for the Opening of the Neo-Tethys Ocean

In this study,zircon U-Pb dating of volcanic rocks from the Zhongba ophiolite of the Yarlung Zangbo Suture Zone(YZSZ)in southern Xizang(Tibet)yielded an age of 247±3 Ma.According to whole rock geochemical and Sr-NdPb isotopic data,the Early Triassic samples could be divided into two groups:Group 1 with P-MORB affinity,showing initial^(87)Sr/^(86)Sr ratios of 0.70253–0.70602,ε_(Nd)(t)values of 4.2–5.3,(^(206)Pb/^(204)Pb)_(t)ratios of 16.353–18.222,(^(207)Pb/^(204)Pb)_(t)ratios of 15.454–15.564,and(^(208)Pb/^(204)Pb)_(t)ratios of 35.665–38.136;Group 2 with OIB affinity,showing initial^(87)Sr/^(86)Sr ratios of 0.70249–0.70513,ε_(Nd)(t)values of 4.4–4.9,(^(206)Pb/^(204)Pb)_(t)ratios of 17.140–18.328,(^(207)Pb/^(204)Pb)_(t)ratios of 15.491–15.575,and(^(208)Pb/^(204)Pb)_(t)ratios of 36.051–38.247.Group 2 rocks formed by partial melting of the mantle source enriched by a former plume,and assimilated continental crustal material during melt ascension.The formation of Group 1 rocks corresponds to the mixing of OIB melts,with the same components as Group 2 and N-MORBs.The Zhongba Early Triassic rocks belong to the continental margin type ophiolite and formed in the continental–oceanic transition zone during the initial opening of the Neo-Tethys in southern Xizang(Tibet).

青藏高原东构造结林芝地热田浅部典型电性结构及热储关系

约40 Ma以来,受控于印度板块的俯冲及后期演化,青藏高原喜马拉雅山系东构造结成为了板块活动最强烈的地区之一;由于深部动力学过程中的浅表响应,该地区地热资源极为丰富。笔者等通过对两条音频大地电磁(AMT)测线进行数据处理与分析,查明了测点覆盖区域范围内二维电性结构及主要存在的深大断裂。依据电性结构推测研究区地下1 km深度范围内可分为4层,浅部低阻层为松散砂泥卵石层,下伏的中阻为砾卵石层,其下的低阻为砂岩、板岩、页岩强风化层,最底部的中高阻层推测为古元古界林芝岩群真巴岩组以片岩、花岗岩为主的地层。结合以往大地电磁测深及地震研究发现的地下10~20 km存在大规模近东西向展布且向上延伸熔融流变导致的低速高导体,推测可能是该地区深部热源所在。进一步通过对深部及浅部电阻率模型的综合对比研究,基于地热地质背景、电性结构特征,探讨了该地区的深部热源及热储关系。

青藏高原盐湖铷铯资源现状、富集规律与提取技术

铷、铯是重要矿产资源,在航天、通讯、能源、医药、化学和电子设备等领域有着广泛用途。青藏高原盐湖铷铯资源主要分布于柴达木盆地和羌塘地块、拉萨地块的盆地,盐湖的铷铯资源主要来自于泉水和河水的补给。羌塘地块、拉萨地块的铷铯主要来自印度板块。笔者等收集了85个青藏高原盐湖铷铯含量和资源量数据,铷含量较高的盐湖有扎布耶和麻米错等,铯含量较高的盐湖有聂尔错和扎西错等。青藏高原盐湖氧化铷资源量共47.50 kt,为大型铷矿床规模的23.73倍;达到详查程度的资源量共37.40 kt。盐湖氧化铯资源量共28.53 kt,为大型铯矿床规模的14.265倍;达到详查程度的资源量共27.10 kt。85个盐湖中氧化铷的资源量达到大型矿床要求的盐湖有5个,达到中型矿床要求的盐湖有4个。氧化铯资源量达到大型矿床要求的盐湖有2个,达到中型矿床要求的盐湖有2个。盐湖铷铯在蒸发过程中基本处于浓缩阶段,残卤中铷铯浓度很高,扎布耶盐湖湖水蒸发残卤中铷、铯质量分数最高为0.496‰和0.372‰,拉果错残卤中铷、铯最高为0.84‰和1.76‰,麻米错残卤中铷、铯最高为0.224‰和0.297‰,这有利于铷铯的开发利用。目前,从盐湖卤水中提取铷、铯的方法以溶剂萃取法方法最具有应用前景。

西藏南部绒布地区上白垩统宗卓组沉积相与沉积环境演化

宗卓组地层作为中生代海相沉积的重要组成部分,记载了西藏南部地区白垩纪古海洋、古气候等重要地质历史信息。通过对砂岩进行镜下观察、物源分析、粒度分析等方面的研究,笔者等对绒布地区上白垩统宗卓组的沉积相类型和沉积环境演化有了新的认识。粒度分析指示沉积时期水体搬运动力较弱、存在浊流沉积;宗卓组内3种不同类型的砂岩镜下特征、地球化学特征和锆石U-Pb年龄,指示3类砂岩的物源不同。笔者等在宗卓组共识别出陆棚相、大陆斜坡相和深海盆地3类沉积相,并对其进行了更为详细的划分。晚白垩世新特提斯洋壳向北俯冲,俯冲结束后印度—亚洲大陆发生初始碰撞。结合研究区构造背景分析,笔者等推测这是导致研究区沉积环境由半深海环境变为深海环境的原因。对研究区宗卓组地层和砂岩来源进行分析后得出:在洋壳俯冲阶段,宗卓组为被动大陆边缘沉积;在之后印度—亚洲陆陆碰撞的初始碰撞阶段,特提斯喜马拉雅被动陆缘已不复存在,并完全过渡为前陆盆地。

Geothermal-type Lithium Resources in Southern Xizang,China

High-temperature geothermal water has abundant lithium(Li)resources,and research on the development and utilization of geothermal-type lithium resources around the world are increasing.The Qinghai–Tibetan Plateau contains huge geothermal resources;especially,Li-rich geothermal resources in southern Xizang,southwestern China,are widely developed.The Li-rich geothermal spots in Xizang are mainly distributed on both sides and to the south of the Yarlung Zangbo suture zone.Such resources are often found in the intensely active high-temperature Li-rich geothermal fields and,compared with other Li-rich geothermal fields around the world,the Li-rich geothermal fluid in the Xizang Plateau,southern Xizang is characterized by good quality:the highest reported Li concentration is up to 239 mg/L;the Mg/Li ratio is extremely low and ranges from 0.03 to 1.48 for most of the Li-rich geothermal fluid;the Li/TDS value is relatively high and ranges from 0.25–1.14%compared to Zhabuye Li-rich salt lake(0.19%)and Salar de Uyuni(Bolivia)(0.08–0.31%).Continuous discharge has been stable for at least several decades,and some of them reach industrial grades of salt lake brine(32.74 mg/L).In addition,elements such as boron(B),caesium(Cs),and rubidium(Rb)are rich and can be comprehensively utilized.Based on still-incomplete statistics,there are at least 16 large-scale Li-rich hot springs with lithium concentration of 20 mg/L or more.The total discharge of lithium metal is about 4300 tons per year,equivalent to 25,686 tons of lithium carbonate.Drilling data has shown that the depth is promising and there is a lack of volcanism(non-volcanic geothermal system).With a background of the partial-melting lower crust caused by the collision of the Indo-Asia continent and based on a comprehensive analysis of the tectonic background of southern Xizang and previous geological,geophysical,and geothermal research,deep molten magma seems to provide a stable heat source for the high-temperature Li-rich geothermal field.The Li-rich parent geothermal fluid rushes to the surface to form hot springs along the extensively developed tectonic fault zones in southern Xizang;some of the Li-rich fluid flows in to form Li-rich salt lakes.However,most of the Li-rich geothermal fluid is remitted to seasonal rivers and has not been effectively exploited,resulting in great waste.With the continuous advance of lithium extraction technologies in Li-rich geothermal fluid,the lithium resource in geothermal water is promising as a new geothermal type of mineral deposit,which can be effectively exploited.This is the first study to undertake a longitudinal analysis on the characteristics,distribution and scale,origin and utilization prospects of Li-rich geothermal resources in southern Xizang,research that will contribute to a deeper understanding of Li-rich geothermal resources in the area and attract attention to these resources in China.

Petrogenesis of an Early Cretaceous Xiabie Co I-type Granite in Southern Qiangtang,Tibet:Evidence from Geochemistry,Geochronology,Rb-Sr,Sm-Nd,Lu-Hf and Pb isotopes

Cretaceous magmatism is widely distributed on both sides of the Bangong-Nujiang suture zone(BNSZ).These rocks record the subduction to closure history of the Bangong-Nujiang Tethys Ocean(BNO)and the collisional history between the Lhasa(LS)and Qiangtang(QT)terranes.The Xiabie Co granite in Nyima County,which located on the southern margin of the QT terrane,Tibet.In this study,whole-rock geochemistry;Rb-Sr,Sm-Nd,and Pb isotopes;and laser ablation inductively coupled mass spectrometry(LA-ICP-MS)zircon U-Pb ages and Lu-Hf isotopes of the Xiabie Co granite in the Nyima area have been studied to constrain its petrogenesis and tectonic setting.Our study can help explain the tectonic evolution of the BNSZ and crust-mantle interaction.Zircon U-Pb dating indicates that the granite was emplaced at ca.120 Ma.The granite contains a small amount of hornblende and has high silicon(SiO2=73.97-78.03 wt%),potassium(K_(2)O=4.75-6.53 wt%),and total alkali(K_(2)O+Na_(2)O=7.98-8.98 wt%)contents;low calcium content(CaO=2.33-4.11 wt%);and variable A/CNK(1.00-1.18)and A/NK(1.09-1.22)values.The P_(2)O_(5) content of the granite negatively correlated with the SiO_(2)content.Thus,the Xiabie Co granite is a weakly peraluminous I-type granite belonging to the high-K calcalkaline to Shoshone series.It is enriched in light rare earth elements(LREEs)and relatively depleted in heavy rare earth elements(HREEs),with LREE/HREE ratios of 8.03-16.40 and La_(N)/Yb_(N) ratios of 10.2-27.1.Samples show right-leaning chondrite-normalized rare earth element patterns with pronounced negative Eu anomalies(Eu/Eu*=0.67-0.76).The primitive-mantle-normalized trace element spider diagrams of the samples are right-leaning zigzag curves,showing relative enrichment in large-ion lithophile elements(LILEs,e.g.,Rb,Th,U,and K)and depletion in high-field-strength elements(HFSEs,e.g.,Nb,P,Ti,and Yb)and displaying striking Sr and Ba negative anomalies.The graniteεHf(t)values were positive(2.9-9.9),whereas the whole-rockεNd(t)values were negative(−2.841 to−2.33).The calculated(^(87)Sr/^(86)Sr)t,(^(206)Pb/^(204)Pb)t,(^(207)Pb/^(204)Pb)t,and(^(208)Pb/^(204)Pb)t values are 0.7014-0.7057(0.7044 on average),18.422-18.851(18.670 on average),15.625-15.642(15.633 on average),and 38.332-38.681(39.571 on average),respectively.On the basis of the aforementioned data,we propose that the Xiabie Co granite was derived from a primitive magma that originated from partial melting of juvenile lower crust with the addition of mantle materials.In addition,strong fractional crystallization occurred during the rock-forming process.Given the geodynamic setting,our new data,together with previously reported achievements,imply that the Xiabie Co granite was formed during the LS-QT collision.

三维成像揭示的青藏高原地壳流体层分布

应用三维地球物理成像技术可以揭示陆域地壳的流体分布。在青藏高原,高分辨率的地震波速度三维图像是揭示高原地壳流体层分布的主要方法。从取得的三维波速、密度和电阻率图象可见,低波速、低密度和低电阻率异常指示了地壳流体层的位置和范围。同时,高波速高密度异常也揭示上方发育的屏蔽盖层。据此,划分出高原地壳的多个流体发育层的分布范围。根据地壳高分辨率地震层析成像的结果还发现,青藏高原地壳流体发育层分布,与其下面的软流圈上涌有密切关联。