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A Study of Mesoproterozoic Iron Cosmic Micro-spherules from 1.8 Ga and 1.6 Ga Old Strata in the Ming Tombs District,Beijing

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Acta geologica Sinica(English Edition) 2007年第4期81卷 649-657页

作者： SONG Tianrui HE Zhengjun WAN Yusheng and LIU Yanxue institute of geology,Chinese Academy of geological Sciences,Beijing 100037 Chinese Acad geol Sci Inst Geol Beijing 100037 Peoples R China

Numerous iron cosmic micro-spherules have been discovered from Mesoproterozoic strata including the Changzhougou Formation （1.8 Ga） and the Dahongyu Formation （1.6 Ga） of the Ming Tombs district, Beijing. There are 1 to 30 grains of cosmic spherules per 2 kg of a sandstone sample taken from the bottom of a coarse sandstone bed of the Changzhougou Formation and 56 grains per 3.69 kg of a rock sample from silicified carbonate rocks of the Dahongyu Formation. The surface textures of cosmic spherules analyzed by means of the secondary electron imagery are identical with those reported from references either domestic or abroad. So far the geo-ages of 1.8 Ga and 1.6 Ga of cosmic spherules from the Changzhougou and Dahongyu formations might be older than those reported in the world. Table 1 gives the electron probe analysis data of cosmic spherules for 30 spherule grains and 44 testing points as follows （%）： FeO, 80-95; Cr2O3; 0-9.56; NiO, 0-0.78; CoO, 0-0.46; indicating that the Cr2O3 content is higher and FeO content lower in the Changzhougou Formation than in the Dahongyu Formation. The helium isotopic data of cosmic spherules as well as their host rocks vary greatly between the Changzhougou and the Dahongyu formations as shown in Table 2. The data of cosmic spherules of the Changzhougou Formation vs the Dahongyu Formation are 57.5/1.23 in ^3He/^4He （10^-8）; and 55.54/809.60 in ^4He （10^-6cm^3STP/g）; those of coarse sandstone of the Changzhougou Formation vs silicified carbonate of the Dahongyu Formation are 3.39/2.59 in ^3He/^4He （10^-8） and 4.56/2.34 in ^3He （10^-6cm^3STP/g）. The ratio of analytic data of helium isotopes are different for cosmic spherules and their host rocks; for example, the ^3He/^4He （10^-8） values are 16.96 and 0.48, and the ^4He （10^-6 cm^3STP/g） are 12.18 and 345.98 for the Changzhougou and Dahongyu formations respectively. It was reported that the world＇s oldest micrometeorites had been found in the Meso-Proterozoic Satakunta Formation, Finland

关键词： Proterozoic cosmic spherule helium isotopes extraterrestrial material carbonaceous chondrite

^(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 institute 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 218.0±2.9 Ma and isochron age of 219.8Ma, indicating that the earlier event of the ampibolite-facies deformation probably took place about 220 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 213.1±0.3 Ma and isochron age of 213.4±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 203.4±0.3 Ma, 203.6±0.4 Ma and 204.8±2.2 Ma, and isochron ages of 204.0±2.0 Ma, 200.6±3.1 Ma and 204.0±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 204 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 240 Ma) to the lower crust (at the depth of about 20-30km at 220 Ma), and at the rate of 1-2 km/Ma to the middle crust (at the depth of about 15 km at 213 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

Thrust Propagation in the Aqqikkol Lake Area, the East Kunlun Mountains, Northwestern China

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Acta geologica Sinica(English Edition) 2003年第4期77卷 468-478页

作者： CUI Junwen, CHEN Wen, LI Pengwu, ZHANG Xiaowei and LI Li institute of geology, Chinese Academy of geological Sciences, Beijing 100037 Chinese Acad geol Sci Inst Geol Beijing 100037 Peoples R China

The western segment of the East Kunlun Mountains is one of the poorly studied regions in northwestern China. Through a structural analysis of the typical sections, we have the following views: (1) There is a very well developed fault system in the western segment of the East Kunlun Mountains and thrust propagation, normal slip and decoupling are the chief deformation events in this area. (2) Although the thrusting started in the Late Carboniferous and Late Triassic-Early Jurassic, strong activity took place in the Miocene-Quaternary when the Kumkol basin was strongly downwarped. (3) The tectonic pattern of coexistence of N-directed thrust propagation and S-directed normal slip in this area is consistent with the general tectonic pattern of the northern Qinghai-Tibet plateau and also very similar to that of the Himalayan region on the southern margin of the Qinghai-Tibet plateau, but their directions between the thrust propagation are opposite and all the strong thrust propagations occurred from the Miocene-Pliocene to Quaternary, a period featuring strong collision between the Indian plate and the Eurasian plate and abrupt uplift of the Qinghai-Tibet plateau. This oppositely directed thrust propagation and normal slip reveal such kinematic characteristics as symmetric propagations of deep-seated materials towards the north and south beneath the Qinghai-Tibet plateau and gravitational sliding of superficial materials towards the interior of the plateau. Therefore, the establishment of the fault system in the study area may provide an approach to the study of deep processes of the northern Qinghai-Tibet plateau and the construction of a unified geodynamic model for the uplift of the Qinghai-Tibet plateau.

关键词： western segment of the East Kunlun Mountains thrust propagation normal slip plate collision dynamic model

Early-Middle Permian Reef Frameworks and Reef-building Models in the Eastern Kunlun Mountains

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Acta geologica Sinica(English Edition) 2001年第2期75卷 115-125页

作者： TIAN Shugang institute of geology, Chinese Academy of geological Sciences, Beijing 100037and FAN Jiasong institute of geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 Chinese Acad geol Sci Inst Geol Beijing 100037 Peoples R China Chinese Acad Sci Inst Geol & Geophys Beijing 100029 Peoples R China

Reef frameworks and building models of the Early-Middle Permian in the eastern Kunlun Mountains have been verified through studies of reef-building communities, palaeoecology and carbonate facies. The eastern Kunlun reefs are built mainly by 6 reef-building communities, which include 11 major categories of frame-building organisms and 6 categories of reef-associated organisms. Eight types of reef-frames have been distinguished and eleven kinds of rocks identified to belong to 6 reef facies. Three sorts of reefs classified by previous researchers, namely mudmounds, knoll reefs and walled reefs, are well developed in the study area. Such reef-facies association and reef distribution show that there are 4 models of reef growth and development, i.e. the tidal-bank knoll-reef model, the plateau-margin wall-reef model, the composite wall-reef model and the deep-water mudmound model. The reefs are mainly constructed by calcareous sponge and calcareous algae, which are similar to all Permian reefs in other area

关键词： reef model Early-Middle Permian eastern Kunlun reefs

Carbon isotopic study of individual n-alkanes in certain modern organisms

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Chinese Science Bulletin 1999年第12期44卷 1139-1142页

作者： Linye Zhang Tieguan Wang Difan Huang Juyuan Li Xiangchen Li Mei Shan Xinzhou Wang Shengli Petr Adm Geol Res Inst Dongying 257015 Peoples R China Univ Petr Dept Geosci Beijing 102200 Peoples R China res inst geol Dept Petr Explorat & Dev Beijing 100083 Peoples R China

Simulation experiment was carried out on all kinds of modern organisms significant to oil-gas generation and the C-isotopic values of n-alkanes in different organisms. The distribution characteristics of individual n-alkane isotopes are studied. The experimental results supply important clues in biological provenance of n-alkanes in sedimentary organisms.

关键词： n-alkanes. carbon isotope modern organisms thermal simulation provenance.

A model for carbon isotope distribution of methane duringdiagenesis

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Chinese Science Bulletin 1998年第7期43卷 576-578页

作者： Ping Guan Yongchang Xu Wenhui Liu Darui Wang Peking Univ Dept Geol Beijing 100871 Peoples R China Chinese Acad Sci Lanzhou Inst Geol Lanzhou 730000 Peoples R China res inst Petr Explorat & Dev Beijing 100083 Peoples R China

The evolution of methane carbon isotope with depth has been discussed based on diagenetic reaction kinetics and isotopic Rayleigh fractionational theory. A mathematical model to describe data of methane carbon isotope... 详细信息

关键词： methane carbon isotope maturity Rayleigh fractionation.

Age distribution of the fauna 5.3 Ma B. P. and climatic deterioration events in North China

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Chinese Science Bulletin 1997年第21期42卷 1826-1829页

作者： Zhang, YX Chen, DL Xue, XX NW Univ Xian Dept Geol Inst Cenozoic Geol & Environm Xian 710069 Peoples R China

THE climatic deterioration is an important event in the geological history and generally recog-nized by composition of strata and variation in some elements. However, the study on the cli-matic deterioration events in terms of age distribution of animals has been rarely *** note reports the study on a climatic deterioration event and its affected area during theMiocene Epoch based on thousands of fossils of Hipparion fauna from Longjiagou in Wudu,

关键词： Hipparion fauna taphonomy climatic event.

Megaclasts from the Carboniferous-Permian Rocks in the Langkawi Islands, Malaysia, and Their Implications

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Acta geologica Sinica(English Edition) 1999年第1期73卷 120-122页

作者： Chen Tingyu institute of geology 26 Baiwanzhuang Road,Chinese Academy of geological Sciences, Beijing 100037,China Chinese Acad geol Sci Inst Geol Beijing 100037 Peoples R China

The Ninth Regional Congress on geology, Mineral andEnergy resources of Southeast Asia was held in KualaLumpur of Malaysia in August of 1998. After the Con-gress, the author participated in the geological fieldexcursion and investigation in the Langkawi Islands,and noted that the Carboniferous-Permian rocks con-tain megaclasts of metamorphic and pegmatitic rocks,which indicate the existence of pre-Carboniferousmetamorphism and magmatism. The observation resultsare as follows:

关键词： Malaysia and Their Implications Megaclasts from the Carboniferous-Permian Rocks in the Langkawi Islands

Earthquake events in Neoproterozoic and Early Paleozoic and its relationship with supercontinental Rodinia in North China

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Chinese Science Bulletin 2000年第10期45卷 931-935页

作者： Xiufu Qiao Linzhi Gao Chinese Acad geol Sci Inst Geol Beijing 100037 Peoples R China

Carbonate liquefied veins in limestone and liquefied mud veins in mudstone are the result by earthquake, which is liquefied in sediments and a strong earthquake event remains clearly records in strata. 24 strata units with earthquake events (molar tooth), which are subdivided into 11 seismic periods, have been distinguished from Mid-Proterozoic to Early Paleozoic strata in the Sino-Korean platform. The distributions of them represent paleo-seismic tectonic zones in different periods, which is tallied with convergent continental block before Proterozoic supercontinental Rodinia and the evidence of the breakup or splitting developed in the inner Sino-Korean Platform in 700 Ma.

关键词： seismites carbonate liquefied veins paleo-Tanlu zone rodinia.