Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P
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LI Qiangzhi , CHEN Yanjing , ZHONG Zengqiu , LI Wenliang , LI Shaoru , GUO Xiaodong , JIN BaoyiCollege of Earth , Space Science , Peking University , Beijing Institute of Gold Geology , Armed Police Force of China , Langfang , Hebei College of Earth Sciences , China University of Geosciences , Wuhan , Hubei
2002, 76(4).
Abstract:The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lode gold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has been argued that it was formed in the Mesozoic, related isotopic age data have not been reported in previous studies. Based on detailed geological study, the authors have carried out isotopic dating on various metallogenic generations. The ore-forming process of the Dongchuang gold deposit consists of four stages: coarse-grained pyrite-bearing quartz veins (stage Ⅰ), fine-grained pyrite-quartz veinlets (stage Ⅱ), multi-sulfides (stage Ⅲ) and carbonate-quartz veinlets (stage IV). Ar-Ar dating on mineral separates of stages Ⅰ, Ⅱ and Ⅲ yields plateau ages of 142.9±2.9 Ma, 132.2±2.6 Ma and 128.3±6.2 Ma, respectively. Sericite separates from stage Ⅱ assemblage also yield an Ar-Ar isochron age of 132.6±2.7 Ma, similar to the Ar-Ar plateau age. These results suggest that the Dongchuang gold deposit was mainly formed during 143-128 M
WANG Deming , HAO Shougang , LIU Zhenfeng School of Earth , Space Sciences , Peking University , Beijing
2002, 76(4).
Abstract:Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang et Hao 2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation, the Qujing district, eastern Yunnan, China. They contribute to our knowledge of the flora in this district. Based on the occurrence of common plants (Hedeia, Huia, Guangnania and Zosterophyllum australianum) and their horizons, it is proved for the first time that the mid-lower assemblage of the Xujiachong flora is comparable with the Early Devonian ((late) Pragian) Posongchong flora of southeastern Yunnan and the upper Baragwanathia flora of Australia. In view of this fact and the stratigraphic sequence, the mid-lower part of the Xujiachong Formation is considered to be of (late) Pragian age. Through comprehensive analyses of plant, bivalve and fish assemblages and the lithology, the upper part of the Xujiachong Formation is dated to be of early Emsian age. The Xujiachong flora belonged to the northeastern Gondwana palaeophytogeographic unit during the Early Devonian. The early Emsian assemblage of this flora inherited the characters of the Posongchong flora and also exhibited the endemic elements. Belonging to different phytogeographic units, the Xujiachong and Posongchong floras differ from the coeval flora of the Laurussian palaeocontinent. The Xujiachong flora is comparatively simple in composition, while the Posongchong flora has abundant and highly diversified endemics. The disparity between them has resulted from the different environments.
LIU Bin , SHEN Kun Underground Construction & Engineering Department of Tongji University , Siping Road , Shanghai Shandong Institute , Laboratory of Geological Sciences , Lishan Road , Jinan
2002, 76(4).
Abstract:The Northern Qilian high-pressure metamorphic belt has experienced multiple deformation-metamorphism, which consists of at least four stages.In 550.8-526 Ma, eclogites were formed. High temperature and pressure caused the escape of a large quantity of gas-liquid fluids from rocks while silicate melt was generated. In the late stage, small amounts of CO2 and H2O infiltrating along fractures were introduced.In the formation of glaucophane schist (447-362 Ma), devolatilization reactions were dominated during the subduction-uplift stage of the paleoplate.In the uplift-exhumation stage (400-380 Ma) the increase of internal space of fractures in the rocks favoured fluid infiltration and concentration. These fluids participated in hydration reactions in the retro-metamorphism. The fluids participating in the mineral reactions have the compositions of CaCl2-NaCl-H2O.In subsequent thrusting (<380 Ma), the metamorphic terrain was uplifted to the shallower crust and ductile-shearing deformation took place, which caused mainly dehydration reactions of minerals. In a near-surface environment the metamorphic terrain experienced brittle deformation, forming many accompanying fractures. Immiscible CO2 and low-salinity aqueous fluids occurred in these secondary microfractures and were trapped and sealed.The thermodynamic conditions of different deformation-metamorphic stages of the metamorphic terrain were calculated and the corresponding P-T-t path was deduced, showing that the metamorphic terrain has experienced a clockwise path indicated by T- and P-rising, and T- and P-falling processes. This reveals that the subduction zone has undergone multiple tectono-dynamic processes, i.e. initial deep burial, subsequent quick uplift and near-surface tectonism.
JIN Chunshuang , WANG JiyangInstitute of Geology , Geophysics , Chinese Academy of Sciences , Beijing Strategic Research Center for Oil , Gas Resources , Ministry of Land , Resources , Beijing
2002, 76(4).
Abstract:Based on the analysis of sea-bottom temperature and geothermal gradient, and by means of the phase boundary curve of gas hydrate and the sea-bottom temperature versus water depth curve in the South China Sea, this paper studies the temperature and pressure conditions for gas hydrate to keep stable. In a marine environment, methane hydrate keeps stable at water depths greater than 550 m in the South China Sea. Further, the thickness of the gas hydrate stability zone in the South China Sea was calculated by using the phase boundary curve and temperature-depth equations. The result shows that gas hydrate have a better perspective in the southeast of the Dongsha Islands, the northeast of the Xisha Islands and the north of the Nansha Islands for thicker stability zones.
WANG Hejing , LU Anhuai , CHEN TaoThe Key Laboratory of Orogenic Belts , Crustal Evolution , Ministry of Education , China , School of Earth , Space Sciences , Peking University , Beijing , China
2002, 76(4).
Abstract:X-ray diffraction (XRD) peaks in a low-angle diffraction section of clay minerals, especially those of authigenic origin, have broadening and tailing features in shape. Using the five basic parameters, peak position, peak height, width, shape coefficient and asymmetry, to describe an XRD peak is more accurate, comprehensive and integrated than using only 3 of them, position, height and width. Following the concept of the five basic parameters of an XRD peak, the program Decoform proposed in this study provides more information in mineralogical analyses by fitting actual XRD profiles. In combination with the HW-IR plot, Decoform can be systematically and accurately used in the comprehensive analyses of crystallinity, domain size, lattice strain and quantitative phase. It is also of value for the geological investigations of diagenesis, metamorphism, basin maturity, structural stress field and so on.
DAI Shifeng , REN Deyi , TANG Yuegang , SHAO Longyi , HAO LimingChina University of Mining , Technology , Beijing Key Laboratory of Coal Resources , Ministry of Education , Beijing
2002, 76(4).
Abstract:The occurrences of associated elements and their genetic factors in the No. 30 coal seam in the Zhijin Coalfield were studied using instrumental neutron activation analysis, inductively coupled plasma-atomic emission spectroscopy, and a scanning electron microscope equipped with an energy-dispersive X-ray analyzer. And, a microscope photometer system (Leitz MPV-Ⅲ) was used to observe the characteristics of coal petrology. According to the influence degree by the siliceous low-temperature hydrothermal fluids, the organic matter is divided into four types: A, B, C, and D of the hydrothermally-altered organic matter (HAOM). The study shows that the high content of Fe (2.31%) is not from pyrite, but mostly from the siliceous low-temperature hydrothermal fluids. The occurrences of the associated elements in the four organic matter types are different. The contents of Fe, Si, and Al are decreasing, but S and Cu are increasing in the order of the HAOM-A, HAOM-B, HAOM-C, and HAOM-D. The losing rate of sulfur i
ZHANG Jinjiang , JI Jianqing Department of Geology , Peking University , Beijing ZHONG Dalai , SANG Haiqing , HE Shundong Institute of Geology , Geophysics , Chinese Academy of Sciences , Beijing
2002, 76(4).
Abstract:The eastern Himalayan syntaxis in Namjagbarwa is a high-grade metamorphic terrain formed by the India-Eurasia collision and northward indentation of the Indian continent into Asia. Right- and left-lateral slip zones were formed by the indentation on the eastern and western boundaries of the syntaxis respectively. The Dongjug-Mainling fault zone is the main shear zone on the western boundary. This fault zone is a left-lateral slip belt with a large component of thrusting. The kinematics of the fault is consistent with the shortening within the syntaxis, and the slipping history along it represents the indenting process of the syntaxis. The Ar-Ar chronological study shows that the age of the early deformation in the Dongjug-Mainling fault zone ranges from 62 to 59 Ma. This evidences that the India-Eurasia collision occurred in the early Paleocene in the eastern Himalayan syntaxis.
YAN Quanren , GAO Shanling , WANG Zongqi , LI Jiliang , XIAO Wenjiao , HOU Quanling , YAN Zhen , CHEN HaihongInstitute of Geology & Geophysics , Chinese Academy of Science , Beijing Institute of Geology , Chinese Academy of Geological Sciences , Beijing
2002, 76(4).
Abstract:The geochemistry of sediments is primarily controlled by their provenances, and different tectonic settings have distinctive provenance characteristics and sedimentary processes. So, it is possible to discriminate provenances, depositional environments and tectonic settings in the development of a sedimentary basin with the geochemistry of the clastic rocks. The analytical results of the present paper demonstrate that sediments in the Songliao prototype basin are enriched in silica (SiO2=66.48-80.51 %), and their ΣREE are 30-130 dmes of that of chondrite with remarkable Eu anomalies. In discriminating diagrams of Eu/Eu vs eeeeeREE and (La/Yb)N vs ΣREE, most samples locate above the line Eu/ Eu=l, on the right of the line Eu/Eu/ΣREE=1 and under the line La/Yb)N/eeeeeREE=1/8, which indicates that the depositional environment of sediments in the basin was oxidizing. In addition, variations of MgO, TiO2, A12O3, FeO+Fe2O3, Na2O and CaO vs SiO2 reflect a tendency of increasing mineral maturity of sediments
ZHONG Jianhua , SHEN Xiaohua , NI Jinren , WANG Guanmin , WEN Zhifeng , WANG Xibin , WANG Haiqiao , LI Li , WU Kongyou , LI Yong , HONG MeiEarth Resource , Information College , Petroleum University of China , Dongyin , Shandong Earth Science Department , Zhejiang University , Hangzhou , Zhejiang Center for Environment Science , Peking University , Beijing
2002, 76(4).
Abstract:Point bars are well developed on the Yellow River delta, among which the Shengli I point bar is the most typical. The point bar, being about 4 km in length and several tens to more than 100 meters in width, is located on the south side of the Shengli Bridge in Kenli County, Dongying, Shandong. It is a typical fine-grained point bar with silt, which is predominant, some clay and minor plant debris and clay boulders. The Shengli I point bar has complicated 3-D structures. Firstly, in a plane view, it comprises mainly eight sedimentary units, bar edge, bar ridge, bar platform, bar plain, bar channel, bar gully, bar pond and bar bay, developing side by side and superimposed one by one in a complex way. Secondly, its vertical structures are very complex due to the partial superimposition of the 8 sedimentary units. Besides hydatogenesis, very intensive wind erosion, eolian, ice and meltwater actions are also visible on the Shengli I point bar. The complex form is made even more complicated because of the above co-actions.
CHEN Fuwen , LI Huaqin , LU YuanfaOpen Laboratory for Isotopic Geochemistry , China Geological Survey , Yichang , Hubei
2002, 76(4).
Abstract:Many rare metal and REE deposits have been found in the Altay orogenic belt, on the northern margin of the Tarim massif and in the Kunlun-Altun orogenic belt, constituting three very important rare metal-REE mineralization belts in western China. These deposits belong to various genetic types with complex ore-forming mechanism, and were formed in certain mineralization epochs. On the basis of a systematic sum-up of geologic and geochemical achievements and 40Ar-39Ar ages of potassium-rich minerals as well as whole-rock Rb-Sr dating results, the authors systematically analyzed the spatial distribution and mineralization epochs of rare metal-REE deposits in Xinjiang, northwestern China, and concluded that although the Hercynian rare metal-REE mineralizations in this area are very important, pre- and post-Hercynian (especially Indosinian and early Yanshanian) rare metal-REE mineralizations also have important theoretical and economic significance.
GU Jiayu , ZHANG Xingyang , FANG HuiResearch Institute of Petroleum Exploration , Development of PetroChina , Beijing
2002, 76(4).
Abstract:The genetic analysis of the deep-buried reservoirs of the Lower Paleozoic carbonate rocks in the Tarim basin is a difficult task involving many factors. Firstly, the object of study is carbonate rocks, which have undergone a long term of modification. Secondly, the rocks are deeply buried with depths of 3800-7000 m in the Tarim basin. The primary reservoir properties formed in the deposition have been strongly modified during the deep burial process. Concurrently, the different burial depths in different areas result in diversities of burial temperature, pressure, underground water, hydrochemistry and various physicochemical changes, which further lead to differences in the diagenetic type, diagenetic property, diagenetic degree and their impacts on the reservoir properties. The Lower Paleozoic Cambrian and Ordovician carbonate reservoirs in the Tarim basin can be grouped into four types, i.e., paleo-weathered-crust reservoirs, reef reservoirs, buried karst reservoirs and dolomite reservoirs. This paper presents a detailed discussion on the vertical and horizontal distribution characteristics, morphological division, reservoir properties and the efficiency in accumulating hydrocarbons of the paleo-weathered-crust type. Furthermore, its genesis is also analyzed. We proposed that the composition of the carbonate rocks, the tectonic movement with associated fractures and fissures, the paleomorphology and paleoclimate, the sea level fluctuation, and the protection of the pores and fissures by the deep burial diagenesis and burial dissolution are the main factors controlling the formation of the paleo-weathered-crust reservoirs. We also consider that the petroleum exploration of the Lower Paleozoic carbonate rocks should be focused on the paleo-weathered-crust reservoirs.
2002, 76(4).
Abstract:On the occasion of the 80th anniversary of the Geological Society of China, a committee consisting of members of the Editorial Committee was organized to selectthe excellent papers published in the last decade and the result is as follows.* indicates that this paper is published only in the Chinese edition of the journal, and the volume, number, page and year correspond to those of the Chinese edition.
2002, 76(4).
Abstract:This paper preliminary reports the carbon isotopic characteristicsof kerogen, individual hydrocarbons and associated carbonatepreserved in Paleo- to Neoproterozoic (1.9-0.85 Ga) sedimentsfrom Jixian strata section, North China. A comparison wascarried out between these isotopic data and independent
Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P