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Acta Geologica Sinica(English Edition) 2019年第1期93卷 1-11页

作者： XU Zhiqin JI Shaocheng ZHOU Xin School of Earth Sciences and Engineering Nanjing University Département des Génies Civil Géologique et des Mines école Polytechnique de Montréal Institute of Geology Chinese Academy of Geological Sciences

Although the Indus-Tsangpo Suture(ITS) is the most spectacular thrust system of continent-continent collision in the world, fundamental questions about its strength evolution and deformation behavior transition remain unanswered. Here we reported, for the first time, frictional melting-induced pseudotachylytes in the intensively deformed felsic rocks along the ITS zone in southern Tibet. This study reveals that pseudotachylytes induced profound weakness of the boundary fault between Indian and Asian plates. The intrinsically low strength of the foliated microlites crystallized from frictional melt or glass(i.e., pseudotachylyte) at seismogenic depths compared with the surrounding coarse-grained quartzofeldspathic rocks in the brittle and semi-brittle regime is sufficient to explain the localization of shear strain, the development of ductile shear zones embedded in strong wall rocks, and the transition from the strong to weak fault behaviors without invoking the presence of high fluid pressure or low friction coefficient metasomatic materials(e.g., smectite or lizardite) within the faults.

关键词： pseudotachylyte mylonite fault strength strain localization Indus-Tsangpo suture Tibet

Research on China's Regional Economic Linkages: Based on the Analyses of Carbon Emission Transfers and Labor Mobility

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Chinese Journal of Urban and Environmental Studies 2019年第2期7卷 38-57页

作者： QI Yawei XU Zhiqin School of Information Technology Jiangxi University of Finance and Economics School of Statistics Jiangxi University of Finance and Economics

In the face of the dual challenges of coordinated development of regional economy and sustainable development, strengthening the regional economic linkages is critical to realizing the coordinated development of the regional economy based on the reasonable transfer of carbon emissions. Under the background of industrial transfer, the authors used the inter-regional input–output model to measure the carbon emissions and labor transfers among 30 provinces in 2002,2007 and 2010, analyzed the relationship between labor mobility and the spatial transfer of carbon emissions and introduced their scales and directions into a gravity model to measure the economic relations among regions. The results show that the embodied carbon emission tends to transfer from western and northeastern China to central and eastern China, which is consistent with the direction of labor mobility, and both of them show the feature of spatial clustering. Under the effects of carbon emission transfers and labor mobility, the radiation effects of the central node provinces in China such as Guangdong, Zhejiang, Hebei, Beijing, Henan and Gansu have given rise to the integrated regional spatial organizations of Beijing–Tianjin–Hebei, Yangtze River Delta Pan-Pearl River Delta and northwestern China, among which Yangtze River Delta and Pan-Pearl River Delta enjoy a relatively stable structure.

关键词： Regional economic linkages carbon emission transfers labor mobility input–output model

Late Triassic Granites From the Quxu Batholith Shedding a New Light on the Evolution of the Gangdese Belt in Southern Tibet

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Acta Geologica Sinica(English Edition) 2018年第2期92卷 462-481页

作者： MENG Yuanku XU Zhiqin xu Yang MA Shiwei College of Earth Science and Engineering Shandong University of Science and Technology Qingdao 266590 Shandong China Key Laboratory of Depositional Mineralization and Sedimentary Mineral of Shandong province Qingdao 266599 Shandong China Qingdao Institute of Marine Geology China Geological Survey Qingdao 266061 China Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China School of Earth Sciences andEngineering Nanjing University Nanjing 210023 China

The Gangdese magmatic belt formed during Late Triassic to Neogene in the southernmost Lhasa terrane of the Tibetan plateau. It is interpreted as a major component of a continental margin related to the northward subduction of the Neo-Tethys oceanic slab beneath Eurasia and it is the key in understanding the tectonic framework of southern Tibet prior to the India-Eurasia collision. It is widely accepted that northward subduction of the Neo-Tethys oceanic crust formed the Gangdese magmatic belt, but the occurrence of Late Triassic magmatism and the detailed tectonic evolution of southern Tibet are still debated. This work presents new zircon U-Pb-Hf isotope data and whole-rock geochemical compositions of a mylonitic granite pluton in the central Gangdese belt, southern Tibet. Zircon U-Pb dating from two representative samples yields consistent ages of 225.3~=1.8 Ma and 229.9~1.5 Ma, respectively, indicating that the granite pluton was formed during the early phase of Late Triassic instead of Early Eocene （47-52 Ma） as previously suggested. Geochemically, the mylonitic granite pluton has a sub-alkaline composition and low-medium K calc-alkaline affinities and it can be defined as an I-type granite with metaluminous features （A/CNK〈I.1）. The analyzed samples are characterized by strong enrichments of LREE and pronounced depletions of Nb, Ta and Ti, suggesting that the granite was generated in an island-arc setting. However, the use of tectonic discrimination diagrams indicates a continental arc setting. Zircon Lu-Hf isotopes indicate that the granite has highly positive till（t） values ranging from ＋13.91 to ＋15.54 （mean value ＋14.79）, reflecting the input of depleted mantle material during its magmatic evolution, consistent with Mg# numbers. Additionally, the studied samples also reveal relatively young Hf two-stage model ages ranging from 238 Ma to 342 Ma （mean value 292 Ma）, suggesting that the pluton was derived from partial melting of juvenile crust. Geochemical discrimination diagrams also suggest that the grani

关键词： Late Triassic Neo-Tethys Ocean active continental margin Gangdese batholith southern Tibet

In-situ Moissanite in Dunite: Deep Mantle Origin of Mantle Peridotite in Luobusa Ophiolite, Tibet

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Acta Geologica Sinica(English Edition) 2014年第2期88卷 517-529页

作者： LIANG Fenghua XU Zhiqin ZHAO Jianan State Key Laboratory of Continental Tectonics and Dynamics Institute of GeologyChinese Academy of Geological Sciences School of Earth Sciences and Resources China University of Geosciences

We report the discovery of an in-situ natural moissanite as an inclusion in the Cr-spinel from the dunite envelope of a chromitite deposit in Luobusa ophiolite,Tibet.The moissanite occurs as a twin crystal interpenetrated by two quadrilateral signal crystals with sizes of 17 pm × 10 μm and 20 μm × 7 μm,respectively.The moissanite is green with parallel extinction.The absorption peaks in its Raman spectra are at 967-971 cm-1,787-788 cm-1,and 766 cm-1.The absorption peaks in the infrared spectra are at 696 cm-1,767 cm-1,1450 cm-1,and 1551 cm-1,which are distinctly different from the peaks for synthetic silicon carbide.Moissanites have been documented to form in ultra-high pressure,high temperature,and extremely low fO2 environments and their 13C-depleted compositions indicate a lower mantle origin.Combined with previous studies about other ultra-high pressure and highly reduced minerals in Luobusa ophiolite,the in-situ natural moissanite we found indicates a deep mantle origin of some materials in the mantle sequence of Luobusa ophiolite.Further,we proposed a transformation model to explain the transfer process of UHP materials from the deep mantle to ophiolite sequence and then to the supra-subduction zone environment.Interactions between the crown of the mantle plume and mid-ocean ridge are suggested to be the dominant mechanism.

关键词： moissanite deep mantle origin mantle peridotite Luobusa ophiolite Tibet

Rock Damage Structure of the South Longmen-Shan Fault in the 2008 M8 Wenchuan Earthquake Viewed with Fault-Zone Trapped Waves and Scientific Drilling

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Acta Geologica Sinica(English Edition) 2014年第2期88卷 444-467页

作者： LI Yonggang XU Zhiqin LI Haibing State Key Laboratory of Continental Tectonic and Dynamics Institute of GeologyChinese Academy of Geological Science Department of Earth Sciences University of Southern California

This article is to review results from scientific drilling and fault-zone trapped waves （FZTWs） at the south Longman-Shan fault （LSF） zone that ruptured in the 2008 May 12 M8 Wenchuan earthquake in Sichuan,China.Immediately after the mainshock,two Wenchuan Fault Scientific Drilling （WFSD） boreholes were drilled at WFSD-1 and WFSD-2 sites approximately 400 m and 1 km west of the surface rupture along the Yinxiu-Beichuan fault （YBF）,the middle fault strand of the south LSF zone.Two boreholes met the principal slip of Wenchuan earthquake along the YBF at depths of 589-m and 1230-m,respectively.The slip is accompanied with a 100-200-m-wide zone consisting of fault gouge,breccia,cataclasite and fractures.Close to WFSD-1 site,the nearly-vertical slip of ～4.3-m with a 190-m wide zone of highly fractured rocks restricted to the hanging wall of the YBF was found at the ground surface after the Wenchuan earthquake.A dense linear seismic array was deployed across the surface rupture at this venue to record FZTWs generated by aftershocks.Observations and 3-D finite-difference simulations of FZTWs recorded at this cross-fault array and network stations close to the YBF show a distinct low-velocity zone composed by severely damaged rocks along the south LSF at seismogenic depths.The zone is several hundred meters wide along the principal slip,within which seismic velocities are reduced by ～30-55％ from wall-rock velocities and with the maximum velocity reduction in the ～200-m-wide rupture core zone at shallow depth.The FZTW-inferred geometry and physical properties of the south LSF rupture zone at shallow depth are in general consistent with the results from petrological and structural analyses of cores and well log at WFSD boreholes.We interpret this remarkable low-velocity zone as being a break-down zone during dynamic rupture in the 2008 M8 earthquake.We examined the FZTWS generated by similar earthquakes before and after the 2008 mainshock and observed that seismic velocities within fault core zone was reduced by ～10％ due t

关键词： Rupture zone rock damage structure scientific drilling fault-zone trapped waves Wenchuan Earthquake Longmen-Shan Fault

Neoproterozoic–Early Paleozoic Tectonic Evolution of the South China Craton： New Insights from the Polyphase Deformation in the Southwestern Jiangnan Orogen

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Acta Geologica Sinica(English Edition) 2018年第5期92卷 1700-1727页

作者： ZHAO Zhongbao XU Zhiqin MA xuxuan LIANG Fenghua GUO Peng Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources China Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China State Key Laboratory for Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing 210046 China School of Earth Science and Resources China University of Geosciences Beijing 100083 China

A 〉1500–km–long northeast–southwest trending Neoproterozoic metamorphic belt in the South China Craton（SCC） consists of subduction mélange and extensional basin deposits. This belt is present under an unconformity of Devonian–Carboniferous sediments. Tectonic evolution of the Neoproterozoic rocks is crucial to determining the geology of the SCC and further influences the reconstruction of the Rodinia supercontinent. A subduction mélange unit enclosed ca.1000–850–Ma mafic blocks, which defined a Neoproterozoic ocean that existed within the SCC, is exposed at the bottom of the Jiangnan Orogen（JO） and experienced at least two phases deformation. Combined with new（detrital） zircon U–Pb ages from metasandstones, as well as igneous rocks within the metamorphic belt, we restrict the strongly deformed subduction mélange as younger than the minimum detrital age ca. 835 Ma and older than the ca. 815 Ma intruded granite. Unconformably overlying the subduction mélange and the intruded granite, an intra–continental rift basin developed 〈800 Ma that involved abundant mantle inputs, such as mafic dikes. This stratum only experienced one main phase deformation. According to our white mica ^40Ar/^（30）Ar data and previously documented thermochronology, both the Neoproterozoic mélange and younger strata were exhumed by a 490–400–Ma crustal–scale positive flower structure. This orogenic event probably induced the thick–skinned structures and was accompanied by crustal thickening, metamorphism and magmatism and led to the closure of the pre–existing rift basin. Integrating previously published data and our new results, we agree that the SCC was located on the periphery of the Rodinia supercontinent from the Neoproterozic until the Ordovician. Furthermore, we prefer that the convergence and dispersal of the SCC were primarily controlled by oceanic subduction forces that occurred within or periphery of the SCC.

关键词： Rodinia supercontinent South China Craton Jiangnan Orogen intra–continental rifting intra–continental orogen

Pressure-temperature Evolution of the Metapelites in the Motuo Area, the Eastern Himalayan Syntaxis

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Acta Geologica Sinica(English Edition) 2014年第2期88卷 544-557页

作者： DONG Hanwen XU Zhiqin LI Yuan LIU Zhao State Key Laboratory of Continental Tectonics and Dynamics Institute of GeologyChinese Academy of Geological Sciences China University of Geosciences

The Motuo area is located in the east of the Eastern Himalayan Syntaxis.There outcrops a sequence of high-grade metamorphic rocks,such as metapelites.Petrology and mineralogy data suggest that these rocks have experienced three stages of metamorphism.The prograde metamorphic mineral assemblages （M1） are mineral inclusions （biotite ＋ plagioclase ＋ quartz ± sillimanite ± Fe-Ti oxides） preserved in garnet porphyroblasts,and the peak metamorphic assemblages （M2） are represented by garnet with the lowest Xsps values and the lowest XFe# ratios and the matrix minerals （plagioclase ＋ quartz ± K-feldspar ＋ biotite ＋ muscovite ＋ kyanite ± siilimanite）,whereas the retrograde assemblages （M3） are composed of biotite ＋ plagioclase ＋ quartz symplectites rimming the garnet porphyroblasts.Thermobarometric computation shows that the metamorphic conditions are 562-714℃ at 7.3-7.4 kbar for the M1 stage,661-800℃ at 9.4-11.6 kbar for the M2 stage,and 579-713℃ at 5.5-6.6 kbar for the M3 stage.These rocks are deciphered to have undergone metamorphism characterized by clockwise P-T paths involving nearly isothermal decompression （ITD） segments,which is inferred to be related to the collision of the India and Eurasia plates.

关键词： metamorphic rocks P-T path Motuo area the Eastern Himalayan Syntaxis

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

V_p/V_s Anisotropy and Implications for Crustal Composition Identification and Earthquake Prediction

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Acta Geologica Sinica(English Edition) 2009年第4期83卷 801-815页

作者： WANG Qian JI Shaocheng XU Zhiqin Departement des Genies Civil Geologique et des Mines Ecole Polytechnique de Montreal Montreal H3C 3A7 Canada Key Laboratory of Continental Dynamics Ministry of Land and Resources Chinese Academy of Geological Sciences 10037 Beijing China

The ratio of P- to S-wave velocities （Vp/Vs） is regarded as one of the most diagnostic properties of natural rocks. It has been used as a discriminant of composition for the continental crust and provides valuable constraints on its formation and evolution processes. Furthermore, the spatial and temporal changes in Vp/Vs before and after earthquakes are probably the most promising avenue to understanding the source mechanics and possibly predicting earthquakes. Here we calibrate the variations in Vp/Vs in dry, anisotropic crustal rocks and provide a set of basic information for the interpretation of future seismic data from the Wenchuan earthquake Fault zone Scientific Drilling （WFSD） project and other surveys. Vp/Vs is a constant （Ф0） for an isotropic rock. However, most of crustal rocks are anisotropic due to lattice-preferred orientations of anisotropic minerals （e.g., mica, amphibole, plagioclase and pyroxene） and cracks as well as thin compositional layering. The Vp/Vs ratio of an anisotropic rock measured along a selected pair of propagation-vibration directions is an apparent value （Фy） that is significantly different from the value for its isotropic counterpart （Ф0）. The usefulness of apparent Vp/Vs ratios as a diagnostic of crustal composition depends largely on rock seismic anisotropy. A 5% of P- and S-wave velocity anisotropy is sufficient to make it impossible to determine the crustal composition using the conventional criteria （Vp/Vs≤1.756 for felsic rocks, 1.756〈Vp/Vs≤1.809 for intermediate rocks, 1.809〈Vp/Vs≤1.944 for mafic rocks, and Vp/V2〉1.944 fluidfilled porous/fractured or partially molten rocks） if the information about the wave propagation-polarization directions with respect to the tectonic framework is unknown. However, the variations in Vp/Vs measured from borehole seismic experiments can be readily interpreted according to the orientations of the ray path and the polarization of the shear waves with respect to the present-day principal stress directions （i.e., the orientation of cracks）

关键词： Vp/Vs ratio Seismic anisotropy Crustal composition Earthquake prediction

A New Insight into the Influence of Composition of Fault Rocks on Aseismic and Seismic Fault Slip

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Acta Geologica Sinica(English Edition) 2019年第3期93卷 760-762页

作者： HE Xiangli LI Haibing WANG Huan SI Jialiang ZHANG Lei XU Zhiqin SUN Zhiming Key L aboratory of Deep-Earth Dynamics of Ministry of Natural Resources Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China School of Earth Sciences and Resources China University of Geosciences Beijing 100083 China School of Earth Sciences and Engineering Nanjing University Nanjing 210023 Jiangsu China Key Laboratory of Paleomagnetism and Tectonic Reconstruction of Ministry of Natural Resources Institute of Geomechanics Chinese Academy of Geological Sciences Beijing 100081 China

Active faults can slip either slowly and continuously byaseismic creep, or abruptly by a seismic event. Both slipmodes of faults are closely related to the composition offault rocks. However, the actual materials resulting indifferences of slip behavior remain uncertain. TheGuanxian-Anxian fault (GAF) characterized by long-termaseismic creep and the Yingxiu-Beichuan fault (YBF)slipping by large earthquakes in the Longmen Shan faultzone (LSFZ) are ideal examples for exploring the aboveissues. Here, in the light of observation and componentanalyses, we find that the distribution of carbonateminerals in both faults is distinct.

关键词： Seismic Fault Slip A New Insight Fault Rocks