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Isotopic compositions of small shelly fossil Anabarites from Lower Cambrian in yangtze Platform of South china: Implications for palaeocean temperature

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Progress in Natural Science:Materials International 2007年第10期17卷 1185-1191页

作者： chen Yongquan1,2. Jiang Shaoyong1, Ling Hongfei1, yang Jinghong1 and Wan Defan3(1. State Key Laboatory for Mineral Deposits Research and Center for Marine Geochemistry Research, Department of Earth {2., Nanjing University, Nanjing 2.0093, china 2. Tarim Oilfield Company Exploration & Development Research institute, Ku’erle 841000, china 3. institute of Mineral Resources, chinese academy of geological sciences, Beijing 100037, china) State Key Laboratory for Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing 210093 China Exploration and Development Research institute Tarim Oilfield Company Ku'erle 841000 China institute of Mineral Resources Chinese Academy of Geological Sciences Beijing 100037 China

Anabarites belong to small shelly fossils (SSF), which occur widely in the Lower Cambrian strata of yangtze Platform in South china. They are phosphate shell in composition and represent the earliest stage of the Cambrian bioradiation of Bilateria, the so-called "Cambrian Explosion". In this study, we attempted to separate Anabarites fossils from Lower Cambrian dolostones, and we obtained samples of both the fossils (SSF) and the granular phosphates (GP). Isotopic analyses were performed on samples of SSF, GP, and matrix dolostone (DH-2.). The results showed that the δ30Si values of the quartz filling in fossils celoms, and the siliceous materials in granular phosphates are -0.6‰ and -0.7‰, which is different from normal sedimentary siliceous rocks from the Lower Cambrian strata (0—0.7‰) as reported by Li et al., but is consistent with the data for siliceous rocks and cherts of submarine hydrothermal origin. It is likely that a later hydrothermal replacement could have taken place in the SSF-bearing sedimentary rocks. The oxygen isotope values of the phosphate of SSF and GP are 16.8‰ and 17.0‰, respectively. These are significantly higher than the Neoproterozoic phosphate ores (10.9‰—13.9‰) as reported by Ling et al., hence, late diagenesis and hydrothermal replacement may not have caused a significant change in the oxygen isotope compositions of the small shelly fossils, and the calculated temperatures (2..4—2..3℃) for palaeo-seawater using a SSF phosphate oxygen isotope thermometer are therefore considered here as the upper limit of seawater temperature in the Early Cambrian ocean of the yangtze Platform.

关键词： Anabarites oxygen isotope silicon isotope paleo-temperature.

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^(40)Ar/^(39)Ar Dating of Deformation Events and Reconstruction of Exhumation of Ultrahigh-Pressure Metamorphic Rocks in Donghai, East china

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Acta Geologica Sinica(English Edition) 2003年第2期77卷 155-168页

作者： LI Jinyi, yang Tiannan, chen Wen and ZHANG Sihong {2. of geology, chinese academy of geological sciences, Beijing 100037E-mail: jyli@*** chinese Acad Geol Sci Inst Geol Beijing 100037 Peoples R China

Recent investigations reveal that the ultrahigh-pressure metamorphic (UHPM) rocks in the Donghai region of East china underwent ductile and transitional ductile-brittle structural events during their exhumation. The earlier ductile deformation took place under the condition of amphibolite facies and the later transitional ductile-brittle deformation under the condition of greenschist facies. The hanging walls moved southeastward during both of these two events. The 40Ar/39Ar dating of muscovites from muscovite-plagioclase schists in the Haizhou phosphorous mine, which are structurally overlain by UHPM rocks, yields a plateau age of 2.8.0±2.9 Ma and isochron age of 2.9.8Ma, indicating that the earlier event of the ampibolite-facies deformation probably took place about 2.0 Ma ago. The 40Ar/39Ar dating of oriented amphiboles parallel to the movement direction of the hanging wall on a decollement plane yields a plateau age of 2.3.1±0.3 Ma and isochron age of 2.3.4±4.1 Ma, probably representing the age of the later event. The dating of pegmatitic biotites and K-feldspars near the decollement plane from the eastern Fangshan area yield plateau ages of 2.3.4±0.3 Ma, 2.3.6±0.4 Ma and 2.4.8±2.2.Ma, and isochron ages of 2.4.0±2.0 Ma, 2.0.6±3.1 Ma and 2.4.0±5.0 Ma, respectively, implying that the rocks in the studied area had not been cooled down to closing temperature of the dated biotites and K-feldspars until the beginning of the Jurassic (about 2.4 Ma). The integration of these data with previous chronological ages on the ultrahigh-pressure metamorphism lead to a new inference on the exhumation of the UHPM rocks. The UHPM rocks in the area were exhumed at the rate of 3-4 km/Ma from the mantle (about 80-100 km below the earth's surface at about 2.0 Ma) to the lower crust (at the depth of about 2.-30km at 2.0 Ma), and at the rate of 1-2.km/Ma to the middle crust (at the depth of about 15 km at 2.3 Ma), and then at the rate of less than 1 km/Ma to the upper crust about 10 km

关键词： ultrahigh-pressure metamorphic rocks structural deformation 40Ar/39Ar dating exhumation Donghai East china

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Discovery of Fossil Charophytes from the Late Triassic Xujiahe Formation and Early Jurassic Lower Yimen Formation, Sichuan Province, and Its Significance

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Acta Geologica Sinica(English Edition) 1992年第3期66卷 301-309,327页

作者： Liu Junying chen Zhongliang institute of {2., chinese academy of geological sciences, Beijing Panxi geological Party, Sichuan Bureau of {2. and Mineral Resources, Xichang Liu Linqun institute of geology Chinese Academy of Geological Sciences Beijing China

This paper describes the fossil charophytes collected from the Late Triassic Xujiahe Formation in Dazuand Early Jurassic Lower Yimen Formation in Xichang, Sichuan Province, and their significance. Up to now,papers dealing with fossil charophytes of the Late Triassic, especially of the Early Jurassic, have been rarelypublished. The description of the two new species of Porochara, P. dazuensis and P. xichangensis, and theirfossil assemblage not only provides an important basis for classification and correlation of red beds insouthwestern china but reveals for the first time the features of the charophyte flora of the Late Triassic-EarlyJurassic in the area, thus offering valuable data for the establishment of Triassic and Jurassic charophyte fossilzones in china.

关键词： Sichuan Late Triassic Early Jurassic charophyte fossil

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Geochronology of Yanshanian Magmatism and Metamorphism in the Hinterland of the Dabie Mountains and Their Geologic Implications

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Acta Geologica Sinica(English Edition) 1992年第2期66卷 155-163,222页

作者： chen Tingyu Niu Baogui Liu Zhigang Fu Yunlian Ren Jishun institute of {2., chinese academy of geological sciences, Beijing institute of geology Chinese Academy of Geological Sciences Beijing

A strong tectono-magmatic thermal event has been revealed by field observations of granitic, migmatiticand metamorphic rocks in the hinterland of the Dabie Mountains. K-Ar, Ar-Ar and Rb-Sr determinationsshow that the event took place 133-117 Ma ago (Yanshanian). Contemporaneously, a southwestwardthrust-type ductile shearing at multiple levels occurred in the lower crust or at even deeper levels, suggestingthat the Dabie Mountains region was still under the influence ot strong continent-continent overlappingtectonism of the yangtze block under the Sino-Korean block at depth. Metamorphic rocks of amphibolitefacies, migmatites and deep structural deformations resulting from this tectonothermal event are now exposedto the surface. The present features of the Dabie Mountains thus have appeared only since ca. 100 Ma B.P. Theblock composed of the Dabie Group is not an uplift or shield which would have undergone a long-continuederosion.

关键词： Geochronology of Yanshanian Magmatism and Metamorphism in the Hinterland of the Dabie Mountains and Their Geologic Implications

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Hydrogen and Oxygen Isotope Fractionation Mechanism in the Hydrothermal System and Its Geologic Significance

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Acta Geologica Sinica(English Edition) 1992年第4期66卷 397-409页

作者： chen Zhensheng Zhang Ligang Yichang institute of {2. and Mineral Resources, chinese academy of geological sciences, Yichang, Hubei Jiang Minxi Yichang institute of geology and Mineral Resources Chinese Academy of Geological Sciences Yichang Hubei

The geochemical behaviors of hydrogen and oxygen isotopes in the hydrothermal system and their inher-ent relationship with the water / rock exchange are discussed in this paper In addition to the temperature con-ditions, the effective W / R ratio is another factor controlling the changes in H and O isotope compositions ofthe altered rock and hydrothermal water. Besides, the application and geological significance of the water-rockexchange theory are also discussed in the light of the H and O isotope compositions and their variation charac-teristics of the mineralizing hydrothermal water and altered rocks from several mineral deposits. Finally, abrief evolutional model of H and O istotope compositions of meteoric and magmatic hydrothermal waters in ahydrothermal system is given.

关键词： hydrothermal system isotope fractionation mechanism water/rock exchnage effective W/R ratio evolutional model

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Petrogenesis and significance of early Yanshanian syenite-granite complex in eastern Nanling Range

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Science china Earth sciences 2005年第7期48卷 912-924页

作者： chen Peirong1, ZHOU Xinmin1, ZHANG Wenlan1, LI Huimin2. FAN Chunfang1, SUN Tao1, chen Weifeng1 & ZHANG Min1 1. State Key Laboratory of Mineral Deposits Research, Department of Earth {2., Nanjing University, Nanjing 2.0093, china 2. Tianjin institute of geology and Mineral Resources, china geological Survey, Tianjin 300170, china State Key Laboratory of Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing 210093 China Tianjin institute of geology and Mineral Resources China Geological Survey Tianjin 300170 China

In the eastern Nanling Range there exists the early Yanshanian syenite-granite assemblage. A representative example is the Pitou-Tabei complex composed of the Tabei syenite pluton and the Pitou syenogranite pluton in southern Jiangxi Province. U-Pb zircon dating yields ages of 188.6±2.2.Ma for the Tabei pluton and 186.3±1.1 Ma for the Pitou pluton. The Tabei syenite is characterized by relatively low SiO2.content (62.40% - 68.75%), high alkalis (K2.+Na2. = 10.56%-11.96%), low percent K2./Na2. ratios (0.56-0.93), metaluminous fea- ture (A/CNK = 0.80-1.00), enrichment in LILE (Rb, Ba, K) and HFSE (Th, U, Nb, Ta, Zr, and so on), weakly negative to positive Eu anomalies (δ Eu = 0.63-1.82., relatively low (87Sr/86Sr)i (0.70412.0.70543), and relatively high ε Nd(t) (3.14-3.52.. The Pitou syenogranite is charac- terized by high silicon content (SiO2.= 71.06%-76.2.%), relatively low alkalis (K2.+Na2. = 8.10%-9.80%), high percent K2./Na2. ratios (1.2.0}.94), metaluminous feature (A/CNK = 0.94-1.07), enrichment in Rb, Th (U), K, depletion in Ba, Nb, Ta, Sr, P , Zr, Ti, high ΣREE (av- eraging 451.03 μg/g), strong negative Eu anomalies (δ Eu = 0.2.-0.33), relatively high (87Sr/86Sr)i (0.70805-0.70912., and relatively low ε Nd( t ) (?5.35-?6.2.). The Tabei syenite and Pitou syenogranite both have the characteristics of A-type granites. The former is considered to be from the asthenosphere mantle, and the latter was the product of the crust-mantle mixture. They both were probably formed in a rifting setting.

关键词： syenite-granite assemblage single zircon U-Pb age rifting environment Nanling Range.

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Discovery of the Changtu Fauna in the Xia' ertai and Hulan Groups in Liaoning and Jilin and Its Significance

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Acta Geologica Sinica(English Edition) 1992年第4期66卷 427-438,445-447页

作者： Liu Xiaoliang chen Congyun yang Xuezeng yang Sen Zhang Jiongfei Gao Yuhua Shenyang institute of geology and Mineral Resources, chinese academy of geological sciences, Shenyang, Liaoning Sun Sheping Shenyang institute of {2. and Mineral Resources Chinese Academy of Geological Sciences Shenyang Liaoning

The Ordovician Changtu Fauna is recently discovered in the Xia' ertai and Hulan Groups in northernLiaoning-central Jilin. The fauna, containing 10 genera and 14 species (including 3 new genera, 9 new speciesand an unidentified species), is closely related in evolution with the Early Cambrian Qinghezhen Fauna. Thediscovery of this fauna is significant to the study on the age of the strata, Ordovician biostratigraphy and geo-logical evolution of the tectonostratigraphical terrane on the northern margin of the Sino-Korean plate.

关键词： Northern Liaoning-central Jilin Ordovician Changtu Fauna

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Mars exploration——In situ K-Ar dating of jarosite

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Science china Earth sciences 2024年第3期67卷 641-656页

作者： Jing yang Dewen ZHENG Ying WU Hong chen Li yang Bin ZHANG Key Laboratory of Active Tectonics and geological Safety Ministry of Natural ResourcesInstitute of GeomechanicsChinese Academy of Geological SciencesBeijing 100081China State Key Laboratory of Earthquake Dynamics Institute of GeologyChina Earthquake AdministrationBeijing 100029China institute of Earth sciences China University of GeosciencesBeijing 100083China Key Laboratory of Cenozoic geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029Chin

To accurately determine the chronological framework of climatic variations recorded by various Martian terrains, the absolute ages of Martian events and cratering rate need to be constrained by either in situ dating or returned samples. In situ K-Ar dating is currently a more plausible dating technique as compared with sample return. Jarosite(KFe_(3)[SO_(4)]_(2.[OH]_(6)) is the only confirmed K sulfate mineral that is widely present on Mars, as indicated by in situ detection, orbital remote sensing, and meteorite studies. Jarosite can be used for precise K-Ar and (40)Ar/(39)Ar dating. The preservation of jarosite on Mars provides information about the nature and duration of aqueous processes on the Martian surface. Different ages of Martian jarosite represent the key to constraining the transition from Martian surface water activity to arid climatic conditions. This paper summarizes recent advances in our knowledge of the spatial distribution of Martian jarosite, its mineralogical properties and stability on Mars, the Ar diffusion kinetics of jarosite, and the current status of in situ K-Ar dating. Moreover, we examine the key scientific issues to be addressed for in situ K-Ar dating of jarosite and Martian sample return missions, and discuss future research directions.

关键词： Mars Jarosite In situ K-Ar dating Ar diffusion Stability

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Geochemical characteristics of the independent cadmium deposit, Niujiaotang, Duyun, Guizhou

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chinese Science Bulletin 1999年第S2期44卷 61-63页

作者： LIU Tiegeng~1, YE Lin~1 and chen Guoyong~2.1. {2. of Geochemistry, chinese academy of sciences, Guiyang 550002. china 2. Team No. 104, Bureau of geology and Mineral Resources, Duyun, Guizhou 558000, china institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China Team No. 104 Bureau of Geology and Mineral Resources Duyun Guizhou 558000 China

A large independent cadmium deposit has been found at Niujiaotang, Duyun, in recent years. To the bestof our knowledge this represents the first case of its kind in the world. With a reserve of over 5 000 tonsof cadmium, the deposit is unique in its high concentrations of cadmium which are tens of to over onehundred times higher than in ordinary cadmium mineralizations associated with Pb-Zn deposits. 1 geological characteristics The Niujiaotang deposit is located at the southwest margin of the yangtze Plate. The region consistsof a thick sedimentary cover ranging from Sinian to Triassic in age overlying unconformably the basementof Mid-Proterozoic metamorphosed volcanic-sedimentary rocks. Lower Cambrian carbonate strata arcoutcropped in the mining district. Cadmium mineralizations, with seven layers recognizable, are devel-

关键词： independent cadmium deposit mode of occurrence of cadmium inclusion fluid feature stable isotope geochemistry.

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DEEP SEISMIC SOUNDING EVIDENCE FOR TECTONIC INTERACTION BETWEEN TARIM AND WEST KUNLUN MT

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地学前缘 2000年第S1期7卷 221-222页

作者： Li Qiusheng 1,Lu Deyuan 1,Gao Rui 1,Li Jingwei 2.Fan Jingyi 2.Zhang Zhiying 2.Liu wen 2.(1 Lithosphere Research Center, chinese academy of geological sciences, Beijing 100037,{2. 2.562.institute, chinese academy of geological sciences, Hebei

The Tarim basin, located in the northern margin of Tibet, plays a key role in comprehending Tibetan plateau rapid uplift process. Focuses have been on the contribution of basin block to create high mountain (e.g.,chen and Molnar,1977, Molnar et al.,1993, Ph. Matte, Tapponnier et al.,1996) since 1970. The models, which mainly depend on result of geological survey and other geophysical observation in the region excepted Deep Seismic Sounding, remained unsure because of blank(or absence ) of DSS data until our experiment was performed. How Tarim and west Kunlun to contact in depth ? What different is in crust structure between Tarim and west Kunlun Mt.? This is what we will reply to in our *** finished the program in 1997. A total of 12. set seismograms (with 3\|component sensors) and 18000kg (AT and TNT) dynamos were used for the DSS field project. 6 shot in Tarim basin and 1 shot in west Kunlun Mt. (Quanshuigou) had been shoot successfully. One shot (Pishan shot) is used as fan\|shape observation (offset is from 150km to 2.0km) in 6 shots located in Tarim basin. The survey line is along Hotan river across the Tarim basin from the north to the south. In particular, we carried 2. set seismic recorders to Kunlun Mt. to make a short line about 60 km as the southern tendency of our line. The seismic recorders were placed in an interval of 3km from one stations to the next and covered a distance of more than 300km. The stations have to be moved their location per 2.|shotting to form a meeting system or a tracing system (layout). Fig.1 showed our survey line and location of shot as well as recorder stations. Finally we gained 62. cassettes with original seismic record (include cassettes of shooting time recorder et al.). After data process total 1147 quite high\|quality three\|component digital records have been used to analyze. Here, only results of analyzing P wave data is given.

关键词： seismic evidence tectonic interaction Tarim West Kunlun Mt.

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