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 Jianping Guangzhou Institute of Geochemistry , Chinese Academy of Sciences , Guangzhou , Chinaand Kornprobst JACQUES Departement des Sciences de la Terre , Universite Blaise Pascal , Clermont-Ferrand , France
1999, 73(4).
Abstract:Experiments on partial melting of mantle lherzolite have been realized at 0.6 and 1.0 GPa and the chemical compositional variations of melts during different melting stages have been first discussed. The results show that the trends of variations in SiO2, CaO, Al2O3, Na2O and TiO2 are different at different melting stages. The melts produced at lower pressure are richer in SiO2 than those at higher pressure. The mantle-derived silica-rich fluids (silicate melts) are polygenetic, but the basic and intermediate-acid silicate melts in mantle peridotite xenoliths from the same host rocks, which have equivalent contents of volatile and alkali components and different contents of other components, should result from in-situ (low-degree) partial melting of mantle peridotite under different conditions (e.g. at different depths, with introduction of C-O-H fluids or in the presence of metasomatic minerals). The intermediate-acid melts may be the result of partial melting (at lower pressure) Opx + Sp + K-Na-rich f
YANG Zhuliang , SHEN Weizhou , SHEN Jialin , TAO Kuiyuan , XIE Fanggui Nanjing Institute of Geology , Mineral Resources , Nanjing Department of Earth Sciences , Nanjing University , Nanjing
1999, 73(4).
Abstract:To the north of the Qinling-Dabie orogen there exists a Mesozoic (K1) granite-syenite belt called the Beihuaiyang granite-syenite belt, in which the Xianghongdian alkaline complex outcrops in the Devonian Foziling schist and also intruded into the slightly earlier volcanic rocks. This alkaline complex is composed of syenite, alkaline syenite and nepheline syenite, but the nepheline syenite occurs inside the alkaline syenite in the pod-like, irregular, lenticular or layered shape. Researches on the petrogenesis of the alkaline complex and the relationship between the alkaline syenite and the nepheline syenite must rely on precise isotopic ages. Previous researches have reported iso-topic dating results merely by the 40Ar/39Ar method on hornblende and biotite separated from the alkaline syenite and nepheline syenite. In view of this, the authors have made fairly detailed isotopic geochronological studies of the alkaline syenite and nepheline syenite by using Rb-Sr isochron for the whole rock and minerals, U-Pb for single zircon separate and the 40Ar/39Ar method for hornblende and potash feldspar. The results of this research are completely different from those of previous researches and show that the nepheline syenite was formed far earlier than the alkaline syenite.
LUO Xingzhang , MIN Maozhong , ZHANG Guanghui , State Key Laboratory of Mineral Deposit Research , Nanjing University , Nanjing LI Xianguo , YANG Zhe , ZHAI Liying No. Geological Party , Central-South China Bureau of Nuclear Geology , Guangxi and Zhu Deling The Open Laboratory of Nuclear Energy Resource Research , Beijing
1999, 73(4).
Abstract:Elements and natural radionuclides in the contact zone of two granites with different ages would migrate from one to the other because of the difference in their chemical contents and later water-rock interactions. This migration could serve as an analogue for the near-field process of radwastes in a high-level radwaste deep geological disposal repository.In the contact between the Indosinian granite (whole-rock Rb-Sr isochron age at 214@3 Ma) and Hercynian granite (zircon U-Pb isochron age at 296@31 Ma) located in Ziyuan County, Guangxi, the O and Pb isotope characteristics and the activity ratios of 234U/238U, 230Th/238U, 230Th/234U and 226Ra/230Th show that, based on the whole-rock chemical contents, both of the two granites have maintained a relatively open chemical system in their evolution processes. However, as there is no obvious open fault, the migration of major elements, trace elements and natural U-series nu-clides takes place within only 1-2 m in the contact zone, and water-rock interaction
CHEN Bailin , LIU Jianmin , ZHANG DaInstitute of Geomechanics , CAGS , Beijing , and WU Jianshe West Fujian Geological Party of FBEDGMR , Sanming ,
1999, 73(4).
Abstract:Low-angle faults include those occurring in thrust-nappe structures in a compressive setting and the detachment of metamorphic core complexes in an extensional setting. All low-angle faults have their own particularities. The low-angle fault plays an important role in controlling over some endogenetic metallic ore deposits. Based on studies of the Xiaoban gold deposit, Xinzhou gold deposit, and Longfengchang polymetallic ore deposit, and comparisons with other mines, the authors conclude the ore-controlling implications of low-angle faults as follows. (1) Because of high temperature and high pressure, as well as strong ductile deformation, the internal energy of the elements rises in the large-scale deep ductile low-angle faults, which causes the elements to activate and differentiate from the source rocks, forming ore-bearing hydrothermal solution, and bring mineralization to happen. (2) When rising from depths and flowing along the low-angle faults, the ore-bearing hydrothermal solution will alter and replace the tectonites in the fault zone. The rocks of the hanging side and the heading side differ in lithology, texture and structure, which results in changes or dissimilarities of the physical-chemical conditions. This destroys the balance of the hydrothermal solution system and causes the dissolved ore-forming elements to precipitate; as a result, a deposit is formed. Therefore, the meso-shallow ductile-brittle low-angle faults play the role of a geochemical interface in the process of mineralization. (3) Low-angle faults are often one of the important host structures.
LIU Hailing , SUN Yan , GUO Lingzhi , SHU Liangshu YANG Shukang , ZHOU Di , ZHANG YixiangEarth Science Department , Nanjing University , Nanjing Open Lab of Geology , Palaeoenvironment of Marginal Seas , South China Sea Institute of Oceanology , Academia Sinica , Guangzhou
1999, 73(4).
Abstract:The Nansha ultra-crust layer-block is confined by ultra-crustal boundary faults of distinctive features, bordering the Kangtai-Shuangzi-Xiongnan extensional faulted zone on the north, the Baxian-Baram-Yoca-Cuyo nappe faulted zone on the south, the Wan'an-Natuna strike-slip tensional faulted zone on the west and the Mondoro-Panay strike-slip compressive faulted zone on the east. These faults take the top of the Nansha asthenosphere as their common detachmental surface. The Cenozoic dynamic process of the ultra-crust layer-block can be divided into four stages: K2-E21, during which the northern boundary faults extended, this ultra-crust layer-block was separated from the South China-Indosinian continental margin, the Palaeo-South China Sea subducted southwards and the Sibu accretion wedge was formed; E22-E31, during which the Southwest sub-sea basin extended and orogeny was active due to the collision of the Sibu accretion wedge; E32-N11, during which the central sub-sea basin extended, the Miri accretion wedge was formed and "A-type" subduction of the southern margin of the north Balawan occurred; N12-the present, during which large-scale thrusting and napping of the boundary faults in the south and mountain-building have taken place and the South China Sea stopped its extension.
XU Jiandong , QU Guosheng Institute of Geology , China Seismological Bureau , Beijing , PRCand Robert D. JACOBI Department of Geology , State University of New York at Buffalo , USA
1999, 73(4).
Abstract:The Cantor's dust theory is applied to investigate the scaling properties of the spatial distribution of natural fractures obtained from detailed scanline surveys of 27 field sites in the Appalachian Plateau of western New York, USA. The results obtained in this study indicate: 1) fracture spacing is characterized by fractal and multifractal properties. On small scales analyses yield an average fractal dimension of 0.15, which suggests a very high degree of clustering. In contrast, on large scales, fractures tend to be more regular and evenly distributed with an average fracture dimension of 0.52; 2) fractal dimension varies with different sets in different orientations, which can be attributed to interactions between pre-existing fractures and younger ones, as well as variations of the intensity of the stresses under which the fractures were formed; 3) a time sequence of fracture set formation can be proposed based on fractal and multifractal analyses, which consists of (from old to young): N-S, NW, ENE, and NE-striking sets. This time sequence is confirmed by the study of the abutting relationships of different fracture sets observed in the field.
1999, 73(4).
Abstract:1. Papers should be devoted mainly to various aspects of research concerning geosciences and related disciplines in China, such as stratigraphy, palaeontology, origin and history of the Earth, structural geology, tectonics, mineralogy, petrology, geochemistry, geophysics, geology of mineral deposits, hydrogeology, engineering geology, environmental geology, regional geology and new theories and technologies of geological exploration. Those of scientific interest to the geological community in China or of international interest are also welcome.
1999, 73(4).
Abstract:The Reservior Characteristics of Lower Ordovician Dolomites Below Pre-Mesozoic Unconformity in Yukela Faultconvex, Tarim Basin AI Huaguo, LAN Lingying, WANG Yun and LI Demao(Exploration Research Intitute, CNSPC, Jingzhou, Hubei, 434100) The study shows that the reserviors of dolomites in the lower Ordovician below the Pre-mesozoic unconformity of this re-
WANG TongheInstitute of Geology , Bureau of Oil Geophysical Prospecting , P.O. Box - , Zhuozhou , Hebei
1999, 73(4):371.
Abstract:The front of a thrust-detachment fault may have various styles such as decoupling, fold, forethrust and backthrust ones because of differences in magnitude, direction and time of the forces exerted on the fault and the inhomogeneity of rock mechanical properties. They have different characteristics and are usually associated with gravity structure, inverse structure and diapir structure. These structures exist together in the same thrust-detachment fault and can influence, compensate for and convert into each other. They provide important grounds not only for the study of the dynamic state, propagation mode, evolutionary process and formation mechanism but also for the analysis of the petroleum generation, migration, accumulation and preservation and arrangement of drill holes in foreland basins.
Gong Yiming Faculty of Earth Science , China University of Geosciences , Wuhan , Hubei Province
1999, 73(4):384.
Abstract:Twenty-three ichnotaxa have been found in the Silurian and Carboniferous turbidites of the Tianshan orogenic belt and the Triassic turbidites of the East Kunlun-West Qinling orogenic belt of northwestern China. They are Acanthorhaphe isp., ?Arthrophycus isp., Aulichnites parkerensis, Chondrites isp., C. intricatus, C. targionii, Cochlichnus anguineus, coprolite, Dendrotichnium haentzscheli, Helminthopsis isp., Helminthopsis abeli, H. hieroglyphica, H. cf. irregularis, Imbrichnus isp., Kunlunichnus qinghaiensis, Laevicyclus rotaeformis, Lophoctenium tianshanensis, Megagrapton isp., Micatuba verso?, Muensteria isp., Neonereites, Palaeophycus, and Zoophycos caudagalli, two of which, namely, Kunlunichnus qinghaiensis and Lophoctenium tianshanensis, are new ichnospecies. The described trace fossils can be grouped into five ichno-assemblages the Aulichnites-Imbrichnus ichno-assemblage representing turbidity current deposits of a restricted anoxic deep-sea basin, the Lophoctenium ichno-assemblage showing the deep-sea or ocean environments relevant to a plate subduction, the Zoophycos-Helminthopsis ichno-assemblage representing the upper-middle turbidity fan deposits of a pelagic and hemipelagic environment, the Megagrapton-Chondrites ichno-assemblage representing the middle-lower turbidity fan deposits of an oceanic archipelago and the Kunlunichnus ichno-assemblage indicating bathyal turbidity current deposits.
JIAO Shuqiang , JIN Zhenmin , JIN Shuyan , TAN Zishan Department of Environmental , Resource Engineering , Fuzhou University , Fujian Faculty of Earth Sciences , China University of Geosciences , Wuhan
1999, 73(4):411.
Abstract:The rheological characters of omphacites in Dabie ultra-high-pressure eclogite have been studied interms of fabric, dislocation and micro-structures. 1. The eclogite has undergone high-temperature deformation, thus forming omphacite lattice preferred orientation. In addition to creep dislocation, the omphacite ductile deformation may have other mechanisms, such as diffusion creep and grain boundary migration. 2. The main-phase deformation of eclogite is coaxial, but asymmetry strain also exists due to strain partitioning in the Dabie erogenic belt. 3.The twin measured by the universal stage is (100), indicating that omphacite high-T deformation was superimposed by low-T deformation. 4. Subgrain structure is common in omphacite, but the deformation features of the omphacites in the Shuanghe area and Bixiling area are different, the latter being dominated by dynamic recrystallization. 5. The Flinn plots show that the strain of omphacite belongs to the constriction ellipsoid and stretching strain, which is similar to the result of the omphacite fabric analysis.
1999, 73(4):429.
Abstract:The Xiaotongjiapuzi gold deposit occurs in a Palaeoproterozoic rift accretionary terrane in eastern Liaoning and is hosted by a carbonate formation of the Dashiqiao Formation, Liaohe Group. The metamorphic grade of the host rock is low amphibolite-high greenschist facies. Gold, which is mainly invisible, is distributed in pyrite and arsenopyrite. The grains of Au-bearing sulphide minerals are fine, ranging from 0.0 n to 1 mm. The wall-rock alterations are characterized by low-temperature silification, hydro-sericitization, sericitization and carbonatization. The homogenization temperatures of the fluid inclusions in quartz closely associated with gold mineralization range from 140 to 240° C. The metallogenic age represented by the Ar-Ar isotopic age of sericite is 167 Ma. Comparisons and studies show that the Xiaotongjiapuzi gold deposit can be classified as the submicron-sized disseminated deposit (analogous to the Carlin-type) hosted in metamorphic rocks.
WU Yucheng Institute of Atmospheric Physics , Chinese Academy of Sciences , Beijing ZHONG Zuoxin Department of Environmental Sciences , China University of Geosciences , Beijing
1999, 73(4):447.
Abstract:The biodcgradation of benzene and toluene was studied by aquifer material microcosm experiment in laboratory under enhanced denitrifying conditions. Based on analyses and contrast of the experiment results, the following important conclusions were obtained. Microorganisms can utilize nitrate as the electron acceptor to degrade benzene and toluene under enhanced denitrifying conditions. The denitrifiers come from the aquifer material. The macro-nutrient that microorganisms need is provided by benzene, toluene and nitrate, and the trace elements come from the aquifer material. Environmental conditions have great effects on the biodegradation of benzene and toluene, and the pH values strongly inhibit the biodegradation when they are too high or too low.
WU Nengyou , ZENG Weijun , LI Zhenwu , CHEN Yizhong , WEN Xiwen , DU Deli , LI Guosheng Guangzhou Marine Geological Survey , MGMR , PO Box , Guangzhou
1999, 73(4):464.
Abstract:According to computed results of the mantle traction field beneath the lithosphere based on satellite-modelled gravity anomalies of different degrees, it has been revealed that the three types of mantle convection on different scales existing in the South China Sea region is the key factor controlling the geodynamics. The mantle convection models on large and middle scales have been proved by natural seismic S-wave tomographic data and interpreted by using the present mantle plume concept In consideration of other relevant geological and geophysical data, the authors put emphasis on discussing the expression form, origin and age of the Indochina mantle plume and its important effect on the conversion of organic matter and hydrocarbon accumulation in Cenozoic basins.
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