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Exhumation P-T path of UHP eclogites in the hong'an area,western Dabie Mountains,china

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Exhumation P-T path of UHP eclogites in the Hong'an area,wes...

中国科学院地质与地球物理研究所2006学术年会

作者： Jingbo Liu~a,Kai Ye~a,Min Sun~b a State Key Laboratory of Lithosphere Tectonic Evolution,Institute of Geology and Geophysics, Chinese Academy of sciences,Beijing,100029,china b department of earth sciences,The University of hong kong,Pokfulam Rd.,hong kong

Four generations of mineral assemblages have been identified in ultrahigh-pressure (UHP) eclogites from the hong’an area,recording four metamorphic stages of the exhumation trajectory,i.e.,garnet+omphacite+kyanite+ zoisite/epidote+rutile+coesite formed at the UHP stage,garnet+omphacite+paragonite+phengite+amphibole+epidote+quartz at the high-pressure (HP) eclogitic stage,amphibole+epidote+albite-oligoclase+paragonite+quartz at the epidote-amphibolite facies(EA) stage,and actinolite+ albite and pumpellyite+albite+K-feldspar+muscovite+chlorite+margarite+epidote+quartz at the greenschist facies(GS) *** formed at the UHP stage was overgrown by atoll garnet at the HP stage. X-ray images,mineral compositions and compositional profiles indicate that the UHP garnet experienced a variable Fe-Mg modification in response to Fe-Mg exchange between garnet and omphacite prior to the overgrowth of atoll HP garnet.A volume diffusion zone was also observed between the UHP and HP *** following P-T conditions were estimated for these mineral assemblages:4.0 to 560℃and 2.5 to 2.9 GPa with median values of 520℃and 2.8 GPa at UHP stage,575 to 685℃and 1.6 to 1.9 GPa with the average results of 634.37℃and 1.8±0.06 GPa at the HP stage,500 to 64.℃and 0.4.to 1 GPa at the EA stage,and 160 to 320℃and 0.2 to 0.8 GPa at the GS *** hong’an UHP eclogites experienced a temperature increase of over 100℃from the UHP to HP stages and continued to exhume from the HP to EA stages through a process of approximately isothermal depression,which was followed by a significantly cooling from the EA to GS *** the process of exhumation,UHP eclogites witnessed a series of events involving fluid influx,resulting in the formation of hydrous minerals at different stages. The nature of fluids changed from K-rich at the HP stage to K-poor at the EA stage and then K-rich again at the GS stage.

关键词： UHP metamorphism Eclogite Coesite P-T path Exhumation The Dabie Mountains

Secular evolution of the lithosphere beneath the eastern North china Craton:Evidence from Mesozoic basalts and high-Mg andesites

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Secular evolution of the lithosphere beneath the eastern Nor...

中国科学院地质与地球物理研究所2003学术年会

作者： hong-FU ZHANG,~(1,*) MIN SUN,~2 XIN-HUA ZHOU,~1 MEI-FU ZHOU,~2 WEI-MING FAN,~1 and JIAN-PING ZHENG~3 1 Laboratory of Lithosphere Tectonic Evolution,Institute of Geology and Geophysics,Chinese Academy of sciences, P.O.Box 9825,Beijing 100029,P.R.china 2 department of {4. sciences,The University of hong kong,Pokrulam Road,hong kong,P.R.china 3 Faculty of {4. sciences,china University of Geosciences,Wuhan 4.0074.P.R.china

Geochemical and isotopic data from Mesozoic lavas from the Jianguo,Niutoushan,Wulahada,and Guancaishan volcanic fields on the northern margin of the North china Craton provide evidence for secular lithospheric evolution of the *** lavas are alkaline basalts with LILE- and LREE-enrichment ((La/Yb)=12.2-13.2) and MORB-like Sr-Nd-Pb isotopic ratios((Sr/Sr)4.ε=3.9-4.8;(Pb/ Pb)≈18).Niutoushan basalts are similar but show evidence of olivine *** lavas are high-Mg andesites(Mg#～67) with EM1 Sr-Nd-Pb isotopic *** data suggest that the basalts originated from MORB-type asthenosphere whereas the high-Mg andesites were derived an EM1 mantle source,i.e.,a refractory lithospheric mantle modified by a previously subducted *** result, combined with the available data of the Mesozoic basalts from the southern portion of the NCC(Zhang et al., 2002),manifests a vast secular evolution of the lithospheric mantle beneath the eastern NCC from the Paleozoic refractory continental lithosphere to this Mesozoic modified *** with the cratonic margin,the lithospheric mantle beneath the center of the craton was less extensively modified, implying the secular evolution was related to the subduction processes surrounding the ***,we suggest that the interaction of the slab-derived silicic melt with the old refractory lithospheric mantle converted the Paleozoic cratonic lithospheric mantle into the late Mesozoic fertile mantle,which was also different from the Cenozoic counterpart.A geodynamic model is proposed to illustrate such a secular lithosphere evolution.

关键词：

ACCRETION OF AN EARLY CRETACEOUS INTRA- OCEANIC ISLAND ARC TO INDIA: EVIDENCE FROM THE YARLUNG ZANGBO SUTURE ZONE

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地学前缘 2000年第S1期7卷 94-96页

作者： J.C.Aitchison 1, Badengzhu 2, A.M.Davis 1, Liu J. 1, Luo, H. 1, J.Malpas 1, I.McDermid 1, Zhou M.F. 1, Wu H. 2, S.Zyabrev 1[WT5,5”BX](1 Tibet Research Group, Dept of earth sciences, University of hong kong, Pokfulam Rd,{4., Chi

A discontinuous line of ophiolitic bodies occurs along the Yarlung Zangbo Suture Zone (YTSZ), which stretches across southern Tibet and beyond. This zone marks the locus of collision between Eurasia and India in the Early Cenozoic. Should we assume that the entire Tethyan Ocean basin that lay between these two continental blocks was oceanic or might it have been more complex? Fragments of any terranes that developed within this once extensive ocean potentially lie within the YTSZ. Detailed investigations over the past three field seasons reveal the presence of several terranes distributed along this zone. Work is currently underway to analyze the nature of individual terranes and the timing of any inter\|relationships.

关键词： Yarlung Zangbo Suture Zone Cretaceous island arc ophiolite subduction complex

Geochemistry of Mesozoic Basalts and Mafic Dikes,Southeastern North china Craton,and Tectonic Implications

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Geochemistry of Mesozoic Basalts and Mafic Dikes,Southeaster...

中国科学院地质与地球物理研究所2002学术年会

作者： ZHANG hong-FU~a and SUN MIN~b a.Laboratory of Lithosphere Tectonic Evolution,Institute of Geology and Geophysics,Chinese Academy of sciences,P.O.Box 9825,Beijing 100029,P.R.china b.department of {4. sciences,The University of hong kong,Pokfulam Road,hong kong

Mesozoic basaltic magmatism in the North china craton(NCC) is a key for probing the nature of the Mesozoic lithospheric mantle,including the process of lithosphere thinning over Phanerozoic *** Cretaceous calc-alkaline basalts and mafic dikes are widespread in the Fangcheng,Mengyin,Jimo,and Jiaodong regions of the southeastern *** rock types have similar geochemical signatures;are high in SiO content;moderately high in MgO,CaO,and AlO;highly enriched in LREE((Ce/Yb)>10) and LILE(Rb,Ba,U,Th);and depleted in HFSE(Ti and Nb).These rocks are highly enriched in Sr-Nd isotopes(Sr/Sr>0.7072,Nd(t))=-11.5～-17.5) and depleted in Pb isotopes(Pb/Pb38.1). Theirgeochemistry demonstrates that these basalts and mafic dikes were derived from enriched lithospheric mantle,which differs considerably from the Paleozoic and Cenozoic lithosphere of the *** indicate that the Mesozoic lithosphere was extensively modified by silicic melt, derived from the partial fusion of subducted silicic *** underplating of the Yangtze continental crust beneath the base of the NCC lithosphere is well *** melting of the enriched lithosphere and tectonic collapse of the continental root provide a possible mechanism for lithosphere thinning linked to the Dabie collision.

关键词：

Does the Archean Dongwanzi ophiolite complex exist?

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Does the Archean Dongwanzi ophiolite complex exist?

中国科学院地质与地球物理研究所2002学术年会

作者： Mingguo ZHAI~a Guochun ZHAO~b Qi ZHANG~a a.Institute of Geology and Geophysics,Chinese Academy of sciences,Beijing,Chaoyang District,100029,china, b.department of earth Science,University of {4. kong,James Lee Science Building,Pokfulam Road, {4. kong,china

Kusky et al(Science,2001,11 May,292) reported an ophioiite complex of late Archean age in the Dongwanzi area,North china *** found that some of their descriptions and interpretations on the Dongwanzi ophiolites are,although convincing,not consistent with the practical geological occurrences,and we think that the so-called"Archean Dongwanzi ophiolites"are questionable for the following reasons: 1) In Kusky’s report,the Dongwanzi ophioiite complex was considered to be composed of three NE-SW-trending parts,along which large amounts of pillow lavas and sheeted dykes were described to be *** fact,however,these three parts of the complex are a composite body of lithologies ranging in age from late Archean to Proterozoic or Mesozoic(Fig.1).They are separated by the Mesoproterozoic, unmetamorphosed,cover or juxtaposed by *** addition,we did not find any convincing pillows and sheeted dykes as described in the ***,we only found numerous highly sheared amphibolites and metagabbros in the south part and banded felsic gneisses in the north part. 2) In the report,the mafic-ultramafic accumulates in the Dongwanzi ophiolite complex are described as harzburgites,wehrlites,lherzolites,webbsterites and other peridotites interlayered with olivine-proxene ***,our field observation and thin-secction examination do not verify the existence of these rocks;they are only pyroxenes,hornblendites and *** rocks are characterized by high Fe and high REE and contain apatite-bearing V-Ti magnetites,which are now being mined by local ***,V-Ti magnetites are not associated with oceanic mantle rocks,which are normally characterized by high Mg and contain chromites. 3) At Dongwanzi village(Fig.3),they show gabbros intruded by six sheeted diabase dykes that are chilled predominantly on their northeast ***,our field observations combined with thin-section examinations show that the host rock in this locat

关键词： Where Archaean Dongwanzi Ophiolite

Cosmogenic^(10)Be dating of the oldest moraine in the Hengduan Mountains

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Science china earth sciences 2023年第10期66卷 2211-2223页

作者： Zhigang ZHANG Jiahong ZHENG Haitao CUI Zhijun ZHAO Xinggong kong Chaogang ZHENG hong ZHANG Fei GUO Zhiyang CHANG Xue YUAN Mingyang YAN Jie ZHANG Jian WANG School of Geography Nanjing Normal UniversityNanjing210023China Key Laboratory of Virtual Geographic Environment(Nanjing Normal University) Ministry of EducationNanjing210023China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing210023China Tourism and Social Administration College NanJing XiaoZhuang UniversityNangjing211171China

The Hengduan Mountains is in the transitional zone between the Qinghai-Tibet Plateau(QTP)and the YunnanGuizhou Plateau in china,and a key area for elucidating the Quaternary environmental changes in *** paleo-Daocheng ice cap was located on the Shaluli Hilly Plateau in the northeastern Hengduan Mountains,the oldest moraines in the Hengduan Mountains region were found in the ice cap *** glacial landforms provide key evidence to study the timing when this area entered the cryosphere with the uplift of the ***,it is difficult to collect suitable glacial boulders from these moraines for traditional terrestrial in-situ cosmogenic nuclide(TCN)exposure dating because of long-term severe moraine ***,we collected clast samples from the moraine surface and depth profile to constrain the age of the oldest moraine in Kuzhaori(moraine E)using TCN^(10)Be dating *** minimum^(10)Be ages of five clast samples from the moraine surface range from 187.4.1.5 to 576.8±4.3 ka,implying that the moraine has been seriously degraded since *** on the TCN^(10)Be concentrations of the samples from a depth profile and simulations,the exposure-erosion-inheritance history of the profile was *** fitting to the profile^(10)Be concentrations using the chi-square test,the simulations yielded a reliable age of 626.0±52.5 ka for the ***,the oldest moraine(moraine E)in Kuzhaori was most likely formed at about 0.63Ma ago,corresponding to the marine isotope stage(MIS)*** glaciation represents the maximum Quaternary glaciation after the QTP was elevated into the cryosphere by the Kunlun-Yellow River Tectonic Movement.

关键词： Hengduan Mountains Paleo-Daocheng ice cap Terrestrial in-situ cosmogenic nuclide^(10)Be Depth profile Exposure dating

The diurnal and seasonal characteristics of urban heat island variation in Beijing city and surrounding areas and impact factors based on remote sensing satellite data

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Science china earth sciences 2005年第Z2期48卷 220-229页

作者： ZHANG Jiahua, HOU Yingyu, LI Guicai, YAN Hao YANG Limin & YAO Fengmei The Chinese Academy of Meteorological sciences, Beijing 100081, china The National Meteorological Center, Beijing 100081, china The National Satellite Meteorological Center, Beijing 100081, china Joint Laboratory for Geoinformation Science, The Chinese University of {4. kong, {4. kong, china department of Geosciences, Graduate School of Chinese Academy of sciences, Beijing 100039, china The Chinese Academy of Meteorological sciences Beijing 100081 China The National Meteorological Center Beijing 100081 China The National Satellite Meteorological Center Beijing 100081 China Joint Laboratory for Geoinformation Science The Chinese University of Hong Kong Hong Kong China

Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4.6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously *** scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.64.1).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and la

关键词： urban heat island, vegetation cover, LST, MODIS, Beijing city and surrounding areas.

In-situ U-Pb,Hf and Re-Os isotopic analyses of the Xiangshan Ni-Cu-Co deposit in Eastern Tianshan(Xinjiang),Central Asia Orogenic Belt:Constraints on the timing and genesis of the mineralization

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In-situ U-Pb,Hf and Re-Os isotopic analyses of the Xiangshan...

中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： Chunming Han~(a,*),Wenjiao Xiao~a,Guochun Zhao~b,Songjian Ao~a,Jien Zhang~a,Wenjun Qu~c,Andao Du~c a Institute of Geology and Geophysics,Chinese Academy of sciences,Beijing 100029,china b department of earth sciences,The University of hong kong,Pokfulam Road,hong kong,china c National Research Center of Geoanalysis,Beijing,100037,china

The timing and genesis of the major Ni-Cu-Co sulfide deposit in the Xiangshan intrusion have been studied based on newly obtained in-situ U-Pb,Hf and Re-Os isotopic *** SIMS U-Pb zircon ages of the gabbro hosting the Ni-Cu-Co sulfide deposit indicate that the Xiangshan intrusion was emplaced at 279.6±1.1 Ma(95%confidence level,MSWD=1.30,n=15).On the basis of combined geological and geochronological evidence,we suggest that the Xiangshan and other adjacent Ni-Cu deposits were formed in the same *** have low common Os concentrations and high Re/Os ratios,similar to sulphide ores from the Duluth,Sally Malay and Voisey Bay *** Re-Os isotopic data from the disseminated and massive ores from the Xiangshan intrusion do not form a single isochron,as they have different initial Os *** Hf and Os isotopic data suggest that the Xiangshan intrusion and associated Ni-Cu-Co mineralization were derived from crustally contaminated mantle *** geochemical data show a tholeiitic affinity and a strong suprasubduction zone signature with negative Nb,Sr,and Ti anomalies similar to N-MORB and *** suggest that the mafic-ultramafic rocks and associated Ni-Cu mineralization of the Eastern Tianshan orogen formed in an Alaska-type subduction zone-arc *** diagnostic features of ridge-trench interaction are present in the Chinese East Tianshan orogen(***,adakites,high-Mg andesites,near-trench magmatism,Alaskan-type mafic-ultramafic complexes,high-temperature metamorphic belts that prograde rapidly from low-grade belts,and orogenic gold deposits).The above distinctive rock groups are probably related to the same thermal event,ridge subduction,as in the Cenozoic orogen of Alaska. We suggest that ridge subduction is the most plausible mechanism to provide the necessary *** subduction provides an important promising model for understanding many aspects of the evolution of the Chinese Eastern Tianshan orogen,and by inference,t

关键词： Xiangshan intrusion U-Pb geochronology Zircon Re-Os isotopic data

Re-Os dating of the Kalatongke Cu-Ni deposit,Altay Shan,NW china,and resulting geodynamic implications

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Re-Os dating of the Kalatongke Cu-Ni deposit,Altay Shan,NW C...

中国科学院地质与地球物理研究所2007学术年会

作者： Chunming Han~(a,*),Wenjiao Xiao~a,Guochun Zhao~b,Wenjun Qu~c,Andao Du~c * State Key laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of sciences,Beijing,100029,china b department of earth sciences,The Uttiversity of hong kong,Pokfulam Road,hong kong,china c National Research Center of Geoanalysis,Beijing,100037,china

Kalatongke is a large Cu-Ni deposit in the southern part of the Altay orogenic belt,northwestern *** and osmium isotopic analyses of Ni- and Cu-bearing sulfide minerals from the deposit have been used to determine the timing of mineralization, the source of osmium,and,by inference,the source of ore *** ore samples have Os and Re concentrations varying in the ranges 0.29 to 3.07 ppb and 6.605 to 61.10 ppb,*** of these data yield a six-point isochron with an age of 305±15 *** initial

关键词： Re-Os isotopic dating Cu-Ni deposit Geodynamics Kalatongke Altay china