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Discovery of double-peaking potassic volcanic rocks in Langshan Group of the Tanyaokou hydrothermal- sedimentary deposit, Inner Mongolia, and its indicating significance

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Science China Earth Sciences 2005年第6期48卷 822-833页

作者： PENG Runmin1, ZHAI Yusheng1, WANG Zhigang2.& HAN Xuefeng2.1. Key laboratory of Lithospheric Tectonics and Lithoprobing Technology, Ministry of Education, China university of {2., beijing 100083. China 2. Inner Mongolia geological Prospecting Institute, Ministry of Chemical Industry, Hohhot 010074, China Correspondences should be addressed to Peng Runmin 1. Key laboratory of Lithospheric Tectonics and Lithoprobing Technology Ministry of Education China University of Geosciences 100083 Beijing China 2. Inner Mongolia geological Prospecting Institute Ministry of Chemical Industry 010074 Hohhot China

It is revealed that the protolith of gray-light brown potash-feldspar-leucogranulites and granulites in the 2.d formation of the LG in Tanyaokou deposit are quartz kerotophyre of synsedimentary eruption based on the following facts and features: (1) The rocks look compact and homogeneous without obvious crystals with naked eyes; (2. they contain blastoporphyritic or glomeroporphyritic and blasto-crystalloclastic crystals consisting of quartz with wavy extinction and albite with obvious alteration and deformation; (3) they also contain radiated and fibrous blasto-microspherulitic texture and swallow-tailed bifurcate and blasto-hollow-skeleton crystal texture, representing the rapid cooling characteristic of the magma during submarine volcanic eruption; (4) the major chemical compositions of the rocks are: SiO2.= 70.80%―76.00%, K2. (4.83%―6.2.%)>Na2.(2.78%―3.80%), and K2.+Na2. = 8.63%―9.00%; and (5) their petro-chemical diagrams indicate that they are volcanic rocks. Together with the characteristic that they occur in the same sequence with potassic spilite (SiO2.= 46.12.―50.68%, K2. = 4.2.%―5.93%>Na2. = 2.15%―3.14%, K2.+Na2. = 6.51%―8.08%), it can be confirmed that the vol-canics occurring in the 2.d Formation of the LG in Tanyaokou district are double-peaking potas-sic volcanic rocks. The discovery, together with the tuffs with ore minerals and the distribution of lead isotopic as well as the value of Co/Ni of pyrites >1 showing the obvious endogenic metali-zation, can prove that the Tanyaokou deposit is an untypical SEDEX-type deposit formed in the extension fault basin in the Mesoproterozonic aulacogen of the northern margin of the North China Platform, and its metallogenesis is related to the synsedimentary volcanic activities and the hydrothermal exhalation, and both the ore-forming material source and volcanics came from mantle or lower crust. These facts mentioned above, together with the meta-volcanic rocks (double-peaking) found in the Dongshengmiao and Huog

关键词： extensional rift basin, double-peaking potassic volcanic rocks, Mesoproterozoic, the 2.d formation of LG, Tanyaokou deposit, Inner Mongolia.

Effect and mechanism of stresses on rock permeability at different scales

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Science China Earth Sciences 2006年第7期49卷 714-723页

作者： YIN Shangxian1 & WANG Shangxu2.1. Safety Engineering College, North China Institute of Science and Technology, Yanjiao, beijing 101601, China 2. Key laboratory of Geophysics Exploration, China {2. of Petroleum, beijing 100083. China 1. Safety Engineering College North China Institute of Science and Technology Yanjiao Beijing 101601 China 2. Key laboratory of Geophysics Exploration China University of Petroleum Beijing 100083 China

The effect of geo-stress fields on macroscopic hydro-geological conditions or micro-cosmic permeability of water-bearing media should follow some laws or principles. Cases study and tests show that: (1) At macro-geologic large scale, deformed and crashed rocks which were induced by geo-stress fields changing provided space for groundwater storage and flow. Groundwater adjusts water-bearing space and dilatants fractures by flowing and press transferring. Coupling of liquid and solid can be implemented for rocks and groundwater. Although tectonic fields witness several times of change and build-up in geological time, stress fields forming regional tectonic framework are coherent with seepage fields, orientation of the maximum horizontal stress demonstrates main seepage direc-tions. (2. At macro-geologic middle scale, zones of stresses changing sharply, quite low stresses, stress or shear concentration can be used to show locations and types of main fractures, zones of geo-stresses changing equably can be acted as normal base media zones of tri-porosity media. (3) At micro-geologic small scale, tri-porosity media include fractured rocks, porous rocks and capillary rocks. Investigations indicate that porosity or permeability is functions of effective stresses, and po-rosity or permeability changing rules of porous rocks with variation of effective stresses can be de-scribed as the index model, the model of power exponent functions is suitable for those of fractured rocks, the model of the second power parabola for capillary rocks. The porosity and permeability loss in fractured rocks, which are greater than that in porous rocks, are shown by calculation of effective compressive coefficient and closing pressure in cracks. The calculations can also explain the mecha-nism why porosity changes are always larger than permeability changes. It is proved by the thick wall cylinder theory that the second power parabola relation between porosity or permeability loss and effective

关键词： geo-stress fields, seepage fields, tri-porosity media, effective stresses, permeability, porosity,scale.

Dehydration melting of solid amphibolite at 2.0 GPa: Effects of time and temperature

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Science China Earth Sciences 2005年第8期48卷 1120-1133页

作者： ZHOU Wenge1, XIE Hongsen1, LIU Yonggang1, ZHENG Xiaogang1, ZHAO Zhidan2.& ZHOU Hui3 1. laboratory of Material in the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002. China 2. Department of Geology, China university of {2., beijing 100083. China 3. Department of Geology, Peking university, beijing 100871, China 1. laboratory of Material in the Earth’s Interior Institute of Geochemistry Chinese Academy of Sciences 550002 Guiyang China 2. Department of Geology China University of Geosciences 100083 Beijing China 3. Department of Geology Peking University 100871 Beijing China

Two sets of dehydration-melting with a natural solid amphibolite, collected from North Himalayan structure zone, Tibet, have been carried out in multi-anvil apparatus at 2.0 GPa and 800―1000℃, for 12.2.0 h. One is keeping the pressure at 2.0 GPa and the annealing time of 12.h, changing the temperature (800―1000℃). The other is keeping the pressure at 2.0 GPa and temperature at 850℃, varying the annealing time (12.2.0 h). The products are inspected with microscope and electron probe. The results indicate that at 2.0 GPa, annealing time of 12.h, garnets, melts and clinopyroxenes occur in amphibolite gradually with increasing temperature and the chemical compositions of melt vary from tonalite to granodiorite, and then to tonalite. However, at 2.0 GPa and 850℃, with the annealing time increasing, the garnets, melts and cli-nopyroxenes also occur in amphibolite gradually and the chemical compositions of melt vary from tonalite to granodiorite. In both cases, melts interconnect with each other when the contents of melt are over the 5 vol.%. the viscosities of the melt produced in amphibolite at temperature higher than 850℃ are on a level with 104 Pa·s. The interconnected melt with such a viscosity may segregate from the source rock and form the magma over reasonable geological time. Therefore, it is believed that at the lower part of the overthickened crust, the tonlitic and grano-dioritic magma may be generated through the dehydration melting of amphibolite.

关键词： solid amphibolite, high pressure, high temperature, time, partial melting.

Differential retardation of organic matter maturation by overpressure

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Science China Earth Sciences 2004年第9期47卷 783-793页

作者： HAO Fang1,2. JIANG Jianqun1, ZOU Huayao1, FANG Yong1 & ZENG Zhiping2.1. Key lab for Hydrocarbon Accumulation Mechanism in the Ministry of Education, Petroleum university, {2. 102.49, China 2. Department of Petroleum Geology, China university of geosciences, Wuhan 430074, China Key lab for Hydrocarbon Accumulation Mechanism in the Ministry of Education Petroleum University Beijing 102249 China Department of Petroleum Geology China University of Geosciences Wuhan 430074 China

The thermal evolution of organic matter (OM) is composed of a series of reactions that are paralell and successive with each other. Different reactions have different activation energy, different rates of product concentration variation, and different volume expansion effects, and therefore have different responses to overpressure, which determines the differential retardation of different OM maturation reactions and maturity parameters. Based upon comprehensive studies on the OM maturation in different pressure systems in the Yinggehai, Qiongdongnan and Bohai Bay basins, 4 hierarchies of overpressure retardation have been recognized. (1) OM maturation in all aspects has been retarded by overpressure. (2. The thermal evolution of hydrocarbons and thermal degradation of hydrogen-rich kerogens has been retarded, but the thermal evolution of hydrogen-poor kerogen components has not been affected by overpressure. As a result, vitrinite reflectance has not been retarded. (3) The thermal cracking of hydrocarbons has been retarded, yet overpressure has had little or no effect on thermal degradation of kerogens. (4) Overpressure has no detectable effect on all aspects of OM maturation. The hierarchy that overpressure has retarded all aspects of OM maturation is the combined result of early overpressure (overpressure began to develop when the source rock was still immature) and the protracted maintenances of closed fluid system. Any case that overpressure had developed too late, or overpressure was too small to reach the threshold values, or overpressured fluid had been frequently released, could give rise to the occurrence of state 4 that overpressure had no detectable effect on all aspects of OM maturation. It seems that in many basins, overpressure retardation of hierarchies 2.and 3 developed where the most commonly used maturity parameter, vitrinite reflectance, had not been affected. In theses cases, multiple parameters must be used to distinguish overpressure retardati

关键词： overpressure, organic matter maturation, hydrocarbon generation, differential retardation.

Discovery of Cu-Zn,Cu-Sn intermetallic minerals and its significance for genesis of the Mianning-Dechang REE Metallogenic Belt,Sichuan Province,China

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Science China Earth Sciences 2006年第6期49卷 597-603页

作者： XIE Yuling1, HOU Zengqian2. XU Jiuhua1, YUAN Zhongxin2. BAI Ge2.& LI Xiaoyu3 1. Civil and Environmental Engineering School, university of Science and Technology beijing, beijing 100083. China 2. Institute of Geology, Chinese Academy of geological Sciences, beijing 100037, China 3. The 109th geological Team, Sichuan Bureau of Mineral Exploration, Chengdu 610100, China 1. Civil and Environmental Engineering School University of Science and Technology Beijing Beijing 100083 China 2. Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China 3. The 109th geological Team Sichuan Bureau of Mineral Exploration Chengdu 610100 China

Mianning-Dechang Himalayan REE Metallogenetic Belt in Sichuan Province lies along the western margin of the Yangtze Craton. We have conducted detailed mineralogical studies on ore minerals collected from Maoniuping and Dalucao, the two largest deposits in the belt. With optical microscope, SEM/EDS, and EPMA, three rare intermetallic minerals, i.e., zinccopperite (Cu2.n), Sn- bearing native copper, and Cu-bearing jupiter were found to occur in the main ore along with barite, fluorite, apatite, sulfide and bastnaesite. Since the conditions under which zinccopperite and Sn- bearing native copper formed are quite unique, finding of these minerals, for the first time in domestic REE deposits, has significant implications for the genesis of the ore deposits in which they occur. In comparison with Cu-Zn intermetallic minerals in other occurrences, we propose that the formation of this REE metallogenetic belt is associated with fast upwelling of the Himalayan magma from deep source.

关键词： Mianning-Dechang REE metallogenetic belt, Cu-bearing intermetallic minerals, EPMA, genesis significance, deep source magmatic activity.

The attenuation anisotropy of mudstones and shales in subsurface formations

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Science China Earth Sciences 2005年第11期48卷 1882-1890页

作者： SHI Ge1 & DENG Jixin1,2.1. The Key labratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking university, {2. 100871, China 2. Geophysical Prospecting Key lab (CNPC), university of Petroleum, {2. 102.49, China 1. The Key labratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University 100871 Beijing China 2. Geophysical Prospecting Key lab (CNPC) University of Petroleum 102249 Beijing China

We have measured the relationships in the laboratorial condition between the at-tenuation in three samples of mudstones and shales as well as two samples of layered sand-stones and the alteration in direction, confining pressure and pore fluid. The relative contributions of different attenuation mechanisms are also discussed. Studies show that the attenuation in dry and saturated samples is strongly related to pressure and direction. The attenuation coefficient of P-wave propagating parallel to bedding (PH ) is less than that of P-wave propagating vertical to bedding (PV ), while the attenuation coefficient of S-wave both propagating and vibrating parallel to bedding (SH ) and that of S-wave propagating vertical to bedding while vibrating parallel to bedding (SV1) are less than that of S-wave propagating parallel to bedding while vibrating verti-cal to bedding (SV ). Under oil saturated conditions, the Biot flow attenuation acts as the domi-nant mechanism for waves propagating parallel to bedding, while the frame anelastic attenuation and squirt flow attenuation seem to play important roles in condition of propagation vertical to bedding.

关键词： mudstone, shale, attenuation, anisotropy, attenuation mechanism

Transport network and flow mechanism of shallow ore-bearing magma in Tongling ore cluster area

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Science China Earth Sciences 2006年第4期49卷 397-407页

作者： DENG Jun1,2. WANG Qingfei1,2., HUANG Dinghua3 , WAN Li4, YANG Liqiang1,2.& GAO Bangfei1,2.1. State Key laboratory of geological Processes and Mineral Resources, China {2. of geosciences, beijing 100083. China 2. Key laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education, China {2. of Geo- sciences, beijing 100083. China 3. Faculty of Earth Sciences, China {2. of geosciences, Wuhan 430074, China 4. School of Mathematics and Information Science, Guangzhou {2., Guangzhou 510405, China 1. State Key laboratory of geological Processes and Mineral Resources China University of Geosciences Beijing 100083 China 2. Key laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education China University of Geosciences Beijing 100083 China 3. Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China 4. School of Mathematics and Information Science Guangzhou University Guangzhou 510405 China

Abundant studies revealed that shallow intrusions of the Yanshanian epoch resulted in the mass mineralization of the Tongling region. Various evidences showed there existed a concealed magma chamber at ?10 km depth in the middle part of this region during Yanshanian epoch, from which the ore-forming magma was generated and then transported to the superficial layer. Yet the transport network and flow mechanism of the shallow ore-bearing magma, the key problem associ- ated with ore-forming process, was relatively little focused on. Integrate analysis of structural me- chanics, statistical fractal and geological facts suggested that NE trending high-angle fold-related thrust faults and the tessellated basement ones served as the main pathways for the shallow magma’s transporting, moreover, the saddle void spaces among adjacent strata in the folds upon this fault system provided the place for magma’s emplacement. So the folds in the upper part and faults in the lower part of the upper crust constituted the fluid’s transport and emplacement network. During the deformation of geologic body with multi-layer structure, the layers in the upper part tended to fold when received the jacking stress from the lower part, while the lower one inclined to fault undergoing loads of the upper part. And the producing probability of this structure assemblage was highly in- creased in the condition, such as in the Tongling area, that the mechanic rigidity of the lower layers was stronger than that of the upper ones. For the pre-existence of fluid-conducting network, the top magma with high volatile in the magma chamber transported rapidly to the superficial layer in dyking pattern, located in the void spaces of folds, filled and reconstructed them. The sudden drop of pres- sure caused the fluid unmixing from the magma and mass ore-forming elements concentration. Pulse activity of the dyking may be the principal reason why magmatic bodies in the Tongling area were spatially-temporally con

关键词： Tongling, structural network, magma intrusion, fractal, dyke.

The^(40)Ar/^(39)Ar age record of formation and uplift of the blueschists and eclogites in the western Tianshan Mountains

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Chinese Science Bulletin 2000年第11期45卷 1047-1052页

作者： GAO Jun, ZHANG Lifei & LIU Shengwei1. Institute of Geology, Chinese Academy of geological Sciences, beijing 100037, China 2. Department of Geology, Peking {2., beijing 100871, Chin Institute of Geology Chinese Academy of Geological Sciences Beijing China Department of Geology Peking University Beijing China

The 40Ar/39Ar ages indicate that the eclogite facies rocks of the Hasiate slice in the western Tianshan Mountains were formed at the early stage of Devonian （401 Ma） and had been uplifted to the greenschist facies tectonic level in the middle stage of Devonian （381 Ma）. The formation and uplift of the blueschists of the Akesayi slice are constrained to the late stage of Devonian （370-364 Ma）. The different tectonic slices in the high-pressure metamorphic belt have experienced the different uplift history.

关键词： western Tianshan Mountains eclogite blueschist 40Ar/39Ar age.

Multifractal modelling and spectrum analysis: Methods and applications to gamma ray spectrometer data from southwestern Nova Scotia, Canada

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Science China Earth Sciences 2006年第3期49卷 283-294页

作者： CHENG Qiuming1,2.1. State Key lab of geological Processes and Mineral Resources, China {2. of geosciences, Wuhan 430074, China 2. Department of Earth and Space Science and Engineering, Department of Geography, York {2., 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada 1. State Key lab of geological Processes and Mineral Resources China University of Geosciences Wuhan 430074 China 2. Department of Earth and Space Science and Engineering Department of Geography York University 4700 Keele Street Toronto Ontario M3J 1P3 Canada

Multifractal spectrum, autocorrelation/semivariogram and power spectrum are three dif- ferent functions characterizing a field or measure from different aspects. These functions are interre- lated in such that the autocorrelation/semivariogram and power spectrum are related to the low order statistical moments (0 to 2.nd) which may determine the local multifractality (τ ″(1)) of a multifractal measure. A better understanding of the interrelationships among these three functions is important because, on one hand, the multifractal modelling characterizes a multifractal measure in a more de- tailed manner since it involves moments of all orders. On the other hand, the commonly used semivariogram and power spectrum functions can be used as alternatives to study the dominant mul- tifractal properties around the mean measure. Moreover, semivariogram and power-spectrum func- tions provide spatial and spectral information, which is highly valued in geological applications. A new fractal relation found between area and power-spectrum will be useful for investigation of new meth- ods of spatial-spectral analysis for pattern recognition, anomaly separation, classification, etc. These results have been demonstrated with the case study of modelling gamma ray spectrometer data from the mineral district, southwestern Nova Scotia, Canada. The results have shown that the values of uranium (U), thorium (Th) and potassium (K) may possess monofractal properties whereas the ratios of these values show high multifractality. The values of the ratios U/K and U/Th show relatively large variances and may provide more information for distinguishing the distinct phases of the granites, country rocks as well as possible gold mineralization-associated regional hydrothermal alteration zones. In addition, the power spectra for U, Th, K, U/Th and U/K consistently show two distinct power-law relationships for two ranges of wave number 12.ω ≤160 km and 0≤ω ≤12.km. These properties might provide usefu

关键词： gamma ray spectrometer data, gold mineralization, alteration zones, multifractal modelling, spectral analysis, GIS.