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Cenozoic low temperature cooling history of the eastern lhasa terrane:Implications for high-relief topography of external drainage area in the southern Tibetan Plateau

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Geoscience Frontiers 2023年第5期14卷 126-140页

作者： Wenbo Su Zhiyuan He Linglin Zhong Stijn Glorie Kanghui Zhong Johan De Grave Laboratory for Mineralogy and Petrology Department of GeologyGhent UniversityKrijgslaan 281 S89000 GhentBelgium College of Earth Sciences Chengdu University of TechnologyChengdu 610059China Department of Earth Sciences School of Physical SciencesThe University of AdelaideSA-5005Australia

The Tibetan Plateau geographically contains internal and external drainage areas based on the distributions of river flows and catchments.The internal and external drainage areas display similar highelevations,while their topographic reliefs are not comparable;the former shows a large low-relief surface,whereas the latter is characterized by relatively high relief.The eastern lhasa terrane is a key tectonic component of the Tibetan Plateau.It is characterized by high topography and relief,but the thermal history of its basement remains relatively poorly constrained.In this study we report new apatite fission track data from the eastern part of the central lhasa terrane to constrain the thermo-tectonic evolution of the external drainage area in the southern Tibetan Plateau.Twenty-one new AFT ages and associated thermal history models reveal that the basement underlying the external drainage area in southern Tibet experienced three main phases of rapid cooling in the Cenozoic.The Paleocene-early Eocene(-60–48 Ma)cooling was likely induced by crustal shortening and associated rock exhumation,due to accelerated northward subduction of the NeoTethys oceanic lithosphere.A subsequent cooling pulse lasted from the late Eocene to early Oligocene(-40–28 Ma),possibly due to the thickening and consequential erosion of the lhasa lithosphere resulted from the continuous northward indentation of the India plate into Eurasia.The most recent rapid cooling event occurred in the middle Miocene-early Pliocene(-16–4 Ma),likely induced by accelerated incision of the lhasa River and local thrust faulting.Our AFT ages and published low-temperature thermochronological data reveal that the external drainage area experienced younger cooling events compared with the internal drainage area,and that the associated differentiated topographic evolution initiated at ca.30 Ma.The contributing factors for the formation of the high-relief topography mainly contain active surface uplift,fault activity,and the enhanced incision of the Yarlung River.

关键词： Cenozoic Apatite fission track thermochronology Exhumation lhasa terrane External drainage area Tibetan Plateau

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A Compilation of New and Existing Thermochronology Data Concerning the lhasa terrane Combined with a Geological Synthesis of the Area

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Acta Geologica Sinica(English Edition) 2022年第5期96卷 1534-1544页

作者： ZHAO Zhongbao LI Chao MA Xuxuan LI Haibing Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China

The history and geodynamic mechanisms of Cenozoic exhumation and denudation of the lhasa terrane(LT),southern Tibetan Plateau, remain poorly constrained. Most previous studies investigating the exhumation of the LT have relied on extrapolating interpretations based on a few well-studied but small areas, which inevitably introduce bias. Here,our compilation of new and published thermochronologic ages are plotted against latitude, longitude, and elevation, to illustrate the distribution of cooling ages across broad regions of the LT. Primary results reveal that(1) the north LT experienced significant exhumation during 80–40 Ma;(2) compared with north LT, exhumation and erosion in the south LT continued after ~40 Ma;and(3) N–S striking rifting, E–W striking river incision, and thrusts led to continued local denudation of the south LT between 20–5 Ma.

关键词： thermochronology exhumation and denudation Gangdese lhasa terrane Tibetan Plateau

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Records of Indosinian Orogenesis in lhasa terrane, Tibet

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Journal of China University of Geosciences 2009年第2期20卷 348-363页

作者：李化启许志琴杨经绥蔡志慧陈松永唐泽民 Key Laboratory for Continental Dynamics of the Ministry of Land and Resources Institute of GeologyChinese Academy of Geological Sciences

Based on the deformation characteristics of the ductile shear zones in Sumdo （松多） Group, the quartz fabric by EBSD （electron backscatter diffraction）, the data of muscovite 40Ar-39Ar geochronology （220-230 Ma） from ductile shear zones and the zircon SHRIMP U-Pb chronology （190 Ma） of granites in Sumdo region, lhasa （拉萨） terrane is thought to have experienced an important Indosinian orogenic event at 220-230 Ma, which caused the closure of the paleo-Tethys Ocean along the tectonic zone of eclogite and the collision between northern part and southern part of the lhasa terrane. The zircon SHRIMP U-Pb chronology of 190 Ma for biotite adamellite, with the distributing characteristics of the granite massif intruding in Sumdo Group, indicates that the biotite adamellite should be the late orogenic or post-orogenic granite resulting from the Indosinian orogenesis. The discovery of Indosinian orogenic belt in lhasa terrane expansed the southern boundary of Indosinian orogenic belt in Qinghai （青海）-Tibet plateau to lhasa terrane from Qiangtang （羌塘） terrane, which changed the understanding about the distribution of Indosinian orogenic belt in Qinghai-Tibet plateau and extended the ＂T＂ type Indosinian orogenic belt in China. The study is very important for the formation and distribution of paleo-Tethys Ocean in Tibet. The ancient terrane framework and evolution of Qinghai-Tibet plateau need further research.

关键词： lhasa terrane eclogite ductile shear belt 40Ar-39Ar geochronology Indosinian orogenesis.

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Indosinian Orogenesis in the lhasa terrane, Tibet: New Muscovite ^(40)Ar-^(39)Ar Geochronology and Evolutionary Process

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Acta Geologica Sinica(English Edition) 2012年第5期86卷 1116-1127页

作者： LI Huaqi XU Zhiqin YANG Jingsui TANG Zhemin Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China

Muscovite 40 Ar-39 Ar dating of muscovite-quartz schist, eclogite and retrograde eclogite indicates an Indosinian orogenesis occurred at 220-240 Ma in the lhasa terrane, which is caused by the closure of Paleo-Tethyan ocean basin and the following collision of the northern lhasa terrane and southern Gondwana land. This Indosinian orogenesis is further confirmed by the regional sedimentary characteristics, magmatic activity and ophiolite mélange. This evidence suggests that the Indosinian orogenic belt in the lhasa terrane is widely distributed from the Coqen county in the west, and then extends eastward through the Ningzhong and Sumdo area, finally turning around the eastern Himalayan syntaxis into the Bomi county. Based on the evolutionary process, the geological development of lhasa terrane from early Paleozoic to early Mesozoic can be divided into seven stages. All of the seven stages make up a whole Wilson circle and reveal a perfect evolutionary process of the Paleo-Tethys ocean between the northern lhasa terrane and southern Gondwana land. The Indosinian orogenisis is a significant event for the evolution of the lhasa terrane as well as the Tibetan Plateau.

关键词： 40 Ar-39 Ar geochronology lhasa terrane Indosinian orogenesis Tibet

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In Situ Stress Measurements in the lhasa terrane,Tibetan Plateau,China

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Acta Geologica Sinica(English Edition) 2016年第6期90卷 2022-2035页

作者： MENG Wen GUO Changbao ZHANG Yongshuang DU Yuben ZHANG Min BAO Linhai ZHANG Peng Institute of Geomechanics Chinese Academy of Geological SciencesBeo'ing 100081China Key Laboratory of Neotectonic Movement and Geohazard Ministry of Land and ResoursesBeijing 100081China China Railway Eryuan Engineering Group CO.L TD Siehuan 610031China The Institute of Crustal Dynamics China Earthquake AdministrationBeijing 100085China

the India and Eurasia plates. Knowledge of the stress state is critical to evaluate the crustal stability and the design of underground excavations. Because of the limitations imposed by natural conditions, little research has been performed on the present crustal in situ stress in the Tibetan Plateau, and further study is imperative. In this study, hydraulic fracturing measurements were conducted in Nyching County （LZX） and Lang County （LX）, lhasa terrane to characterize the shallow crustal stress state. The results indicate that the stress state in the LZX borehole is markedly different from that in the LX borehole, in both magnitude and orientation. At the same measurement depths, the magnitudes of horizontal principal stresses in the LX borehole are 1.5–3.0 times larger than those in the LZX borehole. The stress regime in the LX borehole favors reverse faulting characterized by SH〉Sh〉Sv, where SH, Sh, and Sv are maximum horizontal, minimum horizontal, and vertical principal stresses, respectively. The SH and Sh values are approximately three and two times greater than Sv. Fracture impression results reveal that SH in the LX borehole are predominantly N–S, while in the LZX borehole the maximum horizontal principal stress is mainly in the NNE-direction. The heterogeneity of the regional stress state might be a result of the population and distribution of local structures and seismic activities. The stress state in the LX borehole has exceeded the critical state of failure equilibrium, and there is an optimally orientated pre-existing fault near the borehole. It can be concluded that the optimally orientated fault is likely to be active when the stress has built up sufficiently to destroy the frictional equilibrium; it is suggested that research focus should be placed on this in future. The stress states in boreholes LZX and LX indicate uniformity of the regional stress field and diversity of the local stress fields resulting from the interactions among regional dynamic forces, tectonic stress field, and geologi

关键词： in situ stress hydraulic fracturing lhasa terrane

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Characteristics of the crustal and mantle structures across lhasa terrane

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Earthquake Science 2009年第4期22卷 431-434页

作者： Hongwei Zheng Rizheng He Xuan Guo Department of Geophysics Peking University Beijing 100871 China Institute of Geology Chinese Academy of Geological Sciences Beijing lO0037 China Research Institute of Petroleum Exploration and Development-Northwest (NWGI) PetroChina Lanzhou 730020 China

The Himalayan-Tibetan orogen is the youngest and arguably most spectacular of all the continent-continent collisional belts on the Earth. There are not only north-south extrusions but also east-west extensions in the Tibetan Plateau. All these phenomena are the results of the Indian plate subducting into the Eurasia plate about 70 Ma ago （Yin and Harrison, 2000）, but the deep dynamics mechanism is still an enigma. Exploring the crust and upper mantle structure of Tibetan plateau and revealing the process and the effect of collision are crucial for solving the puzzle of the Tibet uplift and the continent-continent collision. This research is based on the data from the 360km-long Dagze-Deqen-Domar profile, which can be divided into two sections. The Dagze-Deqen section traverses the Nyainqntanglha Mountains and the Yadong-Gulu rift, the biggest rift in the Tibet. The Deqen-Domar section crosses lhasa terrane and Qiangtang terrane. We study the transverse density structure of the crust and mantle beneath the Dagze-Deqen-Domar profile using a joint gravity-seismic inversion technique in order to obtain the Moho and the asthenospheric configuration beneath the profile and understand the deep dynamics mechanism of the Yadong-Gulu rift.

关键词： the Dagzeo Deqen-Duoma Profile crest and mantle structure lhasa terrane

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Geochronology,Geochemistry and Geological Significance of Volcanic Rocks of the Bangba District,Western Segment of the Central lhasa Subterrane

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Journal of Earth Science 2022年第3期33卷 681-695页

作者： Yan Cao Zhiqiang Kang Feng Yang Tong Zhou Dongmei Liu Rui Wang State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences(Beijing)Beijing 100083China College of Earth Sciences Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources in GuangxiGuilin University of TechnologyGuilin 541004China

The lhasa terrane records voluminous magmatism related to the subduction of the Neo-Tethyan oceanic lithosphere,the study of which constrains the tectonomagmatic evolution of the region.We report zircon U-Pb ages,whole-rock compositions and Sr-Nd isotopic data from volcanic rocks in the Bangba district within the central lhasa subterrane to constrain their magmatic source and petrogenesis.Zircon U-Pb dating of two volcanic rock samples yields End Cretaceous ages of 70.0±0.8 and 74.3±1.2 Ma.The rocks have high SiO_(2)(65.41 wt.%-68.45 wt.%),Al_(2)O_(3)(16.16 wt.%-16.59 wt.%)and K_(2)O(5.00 wt.%-6.73 wt.%)contents,and low TFe2O3(2.33 wt.%-2.79 wt.%),MgO(0.64 wt.%-1.44 wt.%)and TiO_(2)(0.61 wt.%-0.65 wt.%)contents,with aluminium saturation indices(A/CNK)of 0.99-1.06.The major-and trace-element compositions of the rocks show they are metaluminous to slightly peraluminous high-K calc-alkaline trachydacite.The relatively high SiO2 and Sr-Nd isotopic compositions((^(87)Sr/^(86)Sr)_(i)=0.722654,0.722038 and 0.725787 andε_(Nd)(t)=-12.27,-12.36 and-6.09,respectively)indicate that the trachydacites formed by partial melting of crustal material.The trachydacites are relatively enriched in light rare earth elements,depleted in heavy rare earth elements,have high(La/Yb)_(N) and(Gd/Yb)_(N) ratios(>61 and>6,respectively),and low Y(lhasa crust was likely triggered by underplating mafic magmas during rollback of the Neo-Tethyan slab.

关键词： trachydacite zircon U-Pb age geochemistry End Cretaceous lhasa terrane

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Paleomagnetism of late Cretaceous dykes in the Gangdese belt: New constraints on the position and structure of the southern margin of Asia prior to the India-Asia collision

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China Geology 2023年第2期6卷 269-284,I0001-I0003页

作者： Zhi-yu Yi Si-lin Yang Joseph G.Meert Xu-xuan Ma Planetary Environmental and Astrobiological Research Laboratory(PEARL) School of Atmospheric SciencesSun Yat-sen UniversityZhuhai 519000China Key Laboratory of Tropical Atmosphere-Ocean System Ministry of EducationZhuhai 519082China Department of Earth&Planetary Sciences 112 Williamson HallUniversity of FloridaGainesvilleFL 32611USA Key Laboratory for Continental Tectonics and Dynamics Institute of GeologyChinese Academy of Geological SciencesBeijing 100037China

This paper report paleomagnetic data from late Cretaceous diorite dykes that sub-vertically intrude granodiorites in the eastern Gangdese belt near the city of lhasa.Our research goals are to provide further constraints on pre-collisional structure of the southern margin of Asia and the onset of the India-Asia collision.Magnetite is identified as the main magnetic carrier in our study.The magnetite shows no evidence of metamorphism or alteration as determined from optical and scanning electron microscope observations.A strong mineral orientation is revealed by anisotropy of magnetic susceptibility analysis both for the intruded dykes and the country rocks.The authors interpret this AMS fabric to have formed during intrusion rather than deformation.Fifteen of 23 sites yield acceptable site mean characteristic remanences with dual polarities.A scatter analysis of the virtual geomagnetic poles suggests that the mean result adequately averaged paleosecular variation.The paleomagnetic pole from the Gangdese dykes yields a paleolatitude of 14.3°N±5.8°N for the southern margin of Asia near lhasa.The paleolatitude corresponds to an in-between position of the lhasa terrane during about 130‒60 Ma.Furthermore,the mean declination of the characteristic remanent magnetization reveals a significant counterclockwise rotation of 18°±9°for the sampling location since about 83 Ma.In the light of tectonic setting of the dykes,the strike of the southern margin of Asia near lhasa is restored to trend approximately about 310°,which is compatible with the hypothesis that the southern margin of Eurasia had a quasi-linear structure prior to its collision with India.

关键词： Paleomagnetism Diorite dyke Granodiorite India-Asia collision Southern Tibet Geological survey engineering lhasa terrane

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Petrogenesis of Miocene ultrapotassic rocks in the western lhasa terrane, Tibetan Plateau: evidence from in situ zircon U–Pb dating, Hf–O isotopes, and whole-rock geochemistry

Petrogenesis of Miocene ultrapotassic rocks in the western L...

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2014年中国地球科学联合学术年会——专题34：特提斯...

作者： Shihong Tian Zengqian Hou Xuanxue Mo Zhusen Yang Yue Zhao Wenjie Hu MLR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral Resources Chinese Academy of Geological Sciences School of Earth Science and Mineral Resources China University of Geosciences Institute of Geology Chinese Academy of Geological Sciences Jiangxi Provincial Institute of Geological Survey

Major and trace elements, whole rock Sr–Nd–Pb isotopic data, zircon U–Pb geochronology, and in situ zircon Hf–O isotopic compositions have been determined for the ultrapotassic lavas from Chajiasi, Dangreyong lake, Xuru lake, and Chazi in the western lhasa terrane of the Tibetan Plateau. The results provide new insights into the nature of the source region of the lavas and their petrogenesis, and also into the mechanism of crust–mantle interaction related to the India–Eurasia continental collision. The lavas are mainly trachyte and trachyandesite. Secondary ion mass spectrometer（SIMS） U–Pb analyses of zircons from the lavas yield Miocene ages of 24–11 Ma, consistent with a range of previously published ages from other parts of the Tibetan Plateau. The lavas are characterized by high SiO2, K2 O, and MgO contents, and they are enriched in light rare earth elements and large ion lithophile elements, and depleted in high field strength elements. They have highly radiogenic Sr（87Sr/86Sr（i）=0.715922–0.732492） and Pb（206Pb/204Pb=18.4547–18.8885, 207Pb/204Pb=15.7394–15.7848, 208Pb/204Pb=39.3997–39.6433）, together with negative values of εNd（t）（–12.8 to –11.3）. Altogether, these data indicate the lavas were derived from an enriched mantle with some crustal contamination. Magmatic zircons from the Chajiasi and Dangreyong lake areas display δ18O values of 6.7‰ to 11.3‰ and εHf（t） values of –17.0 to –7.9 with relatively old Hf crustal model ages of 1.61 to 2.19 Ga, indicating little or no involvement of juvenile crust and/or new mantle-derived materials. However, magmatic zircons from the Xuru lake and Chazi areas exhibit δ18O values in the range 6.8‰ to 8.5‰ and εHf（t） values from –13.1 to –6.3, with relatively old Hf crustal model ages varying from 1.50 to 1.93 Ga. The negative correlation between δ18O and εHf（t） values indicates a two-component mixing of mantle and crust-derived melts. All the εHf（t） and 176Hf/177 Hf values fall around the line of the lower crust, indicating a lower crustal source. Taking into account var

关键词： U–Pb zircon ages geochemistry in situ zircon Hf–O isotopes ultrapotassic lavas magma source petrogenesis lhasa terrane

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How does the elevation changing response to crustal thickening process in the central Tibetan Plateau since 120 Ma?

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China Geology 2021年第1期4卷 32-43页

作者： Zhong-bao Zhao Chao Li Xu-xuan Ma Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China

When and how the Tibetan Plateau formed and maintained its thick crust and high elevation on Earth is continuing debated.Specifically,the coupling relationship between crustal thickening and corresponding paleoelevation changing has not been well studied.The dominant factors in crustal thickness changing are crustal shortening,magmatic input and surface erosion rates.Crustal thickness change and corresponding paleoelevation variation with time were further linked by an isostatic equation in this study.Since 120 Ma crustal shortening,magmatic input and surface erosion rates data from the central Tibetan Plateau are took as input parameters.By using a one-dimensional isostasy model,the authors captured the first-order relationship between crustal thickening and historical elevation responses over the central Tibetan Plateau,including the Qiangtang and lhasa terranes.Based on the modeling results,the authors primarily concluded that the Qiangtang terrane crust gradually thickened to ca.63 km at ca.40 Ma,mainly due to tectonic shortening and minor magmatic input combined with a slow erosion rate.However,the lhasa terrane crust thickened by a combination of tectonic shortening,extensive magmatic input and probably Indian plate underthrusting,which thickened the lhasa crust over 75 km since 25 Ma.Moreover,a longstanding elevation>4000 m was strongly coupled with a thickened crust since about 35 Ma in the central Tibetan Plateau.

关键词： Crustal thickness Paleoelevation Isostatic modeling Qiangtang terrane lhasa terrane Tibetan Plateau China

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