Table of Content

20 March 2009, Volume 15 Issue 1

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Article

Major Transformation of Subcontinental Lithosphere beneath North China in Cenozoic-Mesozoic: Revisited

ZHOU Xin-hua

2009, 15(1):  1-18. 

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The dramatic change of subcontinental lithosphere mantle (SCLM) beneath North China in Cenozoic-Mesozoic has been a hotly debatable issue in Earth science community. This paper presents an overview on topics related to this field, such as temporal and spatial characteristics of lithospheric transformation, progresses in geophysical and geological studies, latest applications of new analytical technology, mechanism and deep processes involved, as well as the dynamic regime in tectonics.The author emphasizes to adopt the term of transformation, instead of the term of thinning as used so far, to describe this large scale geodynamic event in East Asia. It is also noted that "the destruction of craton" is not a proper phrase for delineating such an event in North China. Meanwhile, a global link between Mesozoic mantle overturn and transformation of SCLM in eastern China has been proposed and stressed, which opens a variety of research approaches to further studies.

Progress in Research on geochemistry of Tungsten

MA Dong-sheng

2009, 15(1):  19-34. 

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China's tungsten reserves, production, consumption and volume of export all rank first in the world. China has been producing more than 80% of the total production in the world since 2000, and has preponderant influence in the nonferrous metal market of the world. Tungsten as an important strategic resource has found a wide utilization in modern life, industry, oil exploration, military equipments etc. The present paper reviews the progress in research on geochemistry of tungsten in last 20 years, including tungsten distributions in the solar system, in the earth and in the principal units and products from both endogenesis and supergenesis. The geochemical behavior of tungsten in magmas, hydrothermal fluids, supergenesis, and related effects on bionts, environment and health are also discussed. It is pointed out that the geochemistry of tungsten in its effects on environment and health is still a research gap in our country now. Special attention should be paid to this aspect of research.

Rare Earth Elements of Ores in Gold Deposits and Copper Deposits of Shizishan Ore-Field, Tongling Region, Anhui province

XU Xiao-chun , ZHAO Li-li , XIE Qiao-qin , ZHU Ping-li , FANG Hai-bo , WANG Wen-jun

2009, 15(1):  35-47. 

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The REE data of ores, altered rocks and related rocks, and minerals in gold and copper deposits in Shizishan ore-field of Tongling region are collected to compare and discuss the differences of REE geochemical characteristics between gold deposits and copper deposits. The magmatic rocks, ores and related altered rocks in gold and copper deposits have similar chondritenormalized REE patterns, LREE/HREE and (La/Yb)N values, which displays that the ore-forming elements mainly come from the magmatic rocks, and are rich in crust materials. The deep ore-forming hydrothermal fluids may gain REE and ore-forming elements by leaching the crystallized magmatic rocks, and then superimpose and reform the sedimentary rocks. The mineralization is closely associated with magmatism. The REE geochemical characteristics in different stages and in different kinds of ores and altered rocks imply that the origin and evolution of REEs is closely related with that of ore-forming elements. On the other hand,REE geochemical characteristics of ores in gold and copper deposits also have significant differences. The REE contents in ores are lower in skarn stage than in quartz-sulfide stage. The REE distribution patterns of some skarns and skarn ores are LREE enriched, but with La and Ce depletion, which indicates a magmatic origin of these skarns and skarn ores in copper deposits;while the skarns in gold deposits and the other skarns in copper deposits were formed by metasomatism. The δEu values of the ores indicate that the ore-forming hydrothermal fluids had different pressures and different evolutionary features in different mineralization stages.

Paleoproterozoic High Temperature Paired Metamorphic Belt in Central Part of Sounthern Inner Mongolia and Its Tectonic Implication

LIU Shou-jie，LI Jiang-hai

2009, 15(1):  48-56. 

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An ultra-high temperature (UHT) metamorphic rock belt occurs in Jining-Fengzhen-Tuguiwula, central part of southern Inner Mongolia. Detailed study on the mineral assemblages shows UHT indicators such as Spl+Qtz, Spr+Qtz and Opx+Sil+Qtz.UHT rocks underwent initial isobaric cooling followed by isothermal decompression in the field of UHT metamorphism. Available age data suggest peak metamorphism at 1 920 Ma followed by retrogressive metamorphism at 1 850 Ma of the UHT rocks. To the southeast, including Huai'an-Xuanhua area, outcropped a high pressure granulite, which has a isothermal decompression retrograde metamorphic history along a clockwise P-T path. Most of the ages show a peak metamorphism at ~1 900 Ma followed by a ca. 1 850 Ma retrograde metamorphism. Both the UHT rocks and high pressure granulite have a foliation striking NEE and dipping to NNW at ca. 70°. UHT rock belt and high pressure granulite formed a paired metamorphic belt due to the coincidence of distribution, attitude and metamorphic age. Since the metamorphic temperature is relatively higher than the traditional paired metamorphic belt, it could be defined as high temperature paired metamorphic belt, which is one of the oldest paired metamorphic belts. This high temperature paired metamorphic belt indicates that the crustal material at different levels in mid-southern Inner Mongolia underwent metamorphisms with entirely different P-T paths during a collision event at ca. 1 900 Ma, then the UHT rocks and high pressure granulite were uplifted as a whole block. Further research on the high temperature paired metamorphic belt provides a chance to study the early structural framework and crustal thermal evolution of North China Craton, especially the plate tectonics and structural process at different crustal levels.

The Discovery of Seismites in the Lower Cretaceous of Baiyinchagan Depression, Erlian basin and Its Geological Implications

YUE Xin-dong, LIN Chun-ming, LI Yan-li, XU Shen-mou, ZHANG Zhi-ping, QI Bin-wen,WANG Xiu-lin, ZHANG Fang-dong

2009, 15(1):  57-62. 

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In the lower Cretaceous drilling cores of Baiyinchagan Depression, Erlian Basin, two types of special geological phenomena are discovered, of which the syn-depositional plastic deformations and saucer-shaped structures belong to deformation,and the micro-faults, net-shaped fractures, sand dykes and syn-depositional breccia belong to cracking. The special geological phenomena were initiated by the outside viberation and are characterized by seismites. The deformation phenomena were mostly formed during the non-solidification-semisolidification phase, and the cracking often came into being after the diagenesis. The micro-faults, net-shaped fractures and sand dykes were attributed to the extensional stresses. The special geological phenomena were abundantly distributed in the Tenggeer Formation and Du 1 Member of Duhongmu Formation, and they gradually evolved from cracking into deformation upwards along the vertical direction. The research also showed that they were related to the tectonic background of regional extension and the activities of palaeo-faults and palaeo-earthquakes, of which the intensely active faults and strong earthquakes often caused cracking and the gently active faults and weak earthquakes mostly caused deformation.

Numerical Simulation of Coupled Binary Gas-Solid Interaction During Carbon Dioxide Sequestration in a Coal Bed

FENG Qi-yan, ZHOU Lai, CHEN Zhong-wei, LIU Ji-shan

2009, 15(1):  63-68. 

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The prospect of geological sequestration and storage of CO2 as a means of reducing global emission of this greenhouse gas and enhancing coalbed methane recovery (ECBM) has recently attracted worldwide interest due to the global warming and the resource shortage. Complicated coupled binary gas-solid interaction arises during carbon dioxide sequestration in a coal seam,which combines effects of CO2-CH4 counter adsorption, CO2-CH4 counter diffusion, binary gas flow and coal bed deformation.Through solving a set of coupled field governing equations, a novel full coupled Finite Element (FE) model was established by COMSOL Multiphysics. The new FE model was applied to the quantification of coal porous pressure, coal permeability, gas composition fraction and coal displacement when CO2 was injected in a CH4 saturated coal bed. Numerical results demonstrate that CH4 is swept by the injected CO2 accompanied by coal volumetric deformation. Compared to the single CH4 in situ, CH4-CO2 counter-diffusion induced coal swelling can make more compensation for coal shrinkage due to effective stress. Competing influences between the effective stress and the CH4-CO2 counter-diffusion induced volume change governs the evolution of porous pressure and permeability, which is controlled by the porous pressure correspondingly. Initially, the coal permeability keeps descending due to the coal swelling. Afterwards, it behaves rising when the porous pressure dominates the coal deformation. In this simulation, coal permeability rebounded at the 4.66×107s. This achievement extends our ability to understand the coupledmulti-physics of the CO2 geological sequestration and CO2 enhanced coal bed methane recovery under field conditions.

The Sequence Architecture and Sandbody Predicition of the Second Member of Shanxi Formation in Changbei Gas Field, Ordos Basin

ZHENG Rong-cai，ZHOU Qi，WANG Hua，LI Feng-jie

2009, 15(1):  69-79. 

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On the basis of integrated study of core description，well logging and sample analysis，the sedimentary facies and sequences of the Member 2 of the Shanxi Formation are analyzed thoroughly with the application of high-resolution sequence stratigraphy．The Member 2 of the Shanxi Formation is composed of a sedimentary system of marine braided river delta and can be divided into one long term，two middle terms, four short terms, nine super-short terms base-level cycle sequences, and two categories and five kinds of texture of base-level cycles. The stacking patterns and distribution and evolution of sandbodies at different orders of base-level cycles are studied in detail. The chronological stratigraphic units established on the basis of ascending and descending hemicycles of the medium term are used to trace and correlate the sandbodies in the Member 2 of the Shanxi Formation. It is indicated that the continuous stacking thick sandbodies in the delta channel developed at the ascending hemicycle and the fine-grained sediments deposited at the descending hemicycle which was the main development stage of regional restraining barrier and caprock. Based on above analysis and application of high-resolution sequence stratigraphy the isopach map of sandstone and ratio of sandstone to mudstone, the sedimentary microfacies map and 3-D simulation of sequence indicator of sandbodies distribution were plotted in a chronological stratigraphic framework which provides reliable evidence for the prediction and evaluation of favorable sandbodies of the Member 2 of the Shanxi Formation in the Changbei Gas Field.

Sequence Stratigraphy and Sedimentary System Distribution in QUM Basin, Kashan Region, Iran

JIANG Hui-chao，REN Feng-lou，ZHANG Yong，SONG Lai-liang，XIAO Yong-jun

2009, 15(1):  80-92. 

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The central Iran basin is a back-arc marginal sea basin formed in Late Oligocene to Early Miocene with mixed carbonate, evaprites and clastics succession. Based on the integrated study on the sufficient outcrops, wells, loggings and seismic profiles, the sequence stratigraphy framework of Qum Formation was set up. Two second-order sequences (SS1 and SS2) and five third-order sequences (S1-S5) were identified in Qum Formation. This paper analysized sedimentary system evolution and distribution of each sequence period. The results indicted that three times transgression dominated three periods of sedimentary system evolution. They are: sequence S1, the first transgression period (A, B members, C1 sub-member), sequence S2, the subsidence filling period (C2, C3, C4 sub-members), sequences S3-S5, the transgression period again (D-E members). Finally, the authors discussed its signiffcance for oil-gas exploration.

Characteristics of Petroleum System and Oil-Source in Dongying Depression

LIU Hua，JIANG You-lu，REN Jing-lun

2009, 15(1):  93-99. 

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Oil-source correlation is the basis of the petroleum system research. The relationship of source rocks and petroleum in Dongying depression is discussed by analyzing the geochemical characteristics of source rocks, and three petroleum systems (Es3z-Es3z (!), Es3x-Es2/Es3 (!) and Es4s-Es2/Es4 (!)) are classified for the Tertiary of Dongying depression according to oilsource correlation. Study shows that the oil and gas patterns of these three petroleum systems are circular and their formation is controlled by migration pathways, distribution of source faults, scale of sand bodies in source rocks, and spatial association of faults and sand bodies etc. Among them, the occurrence and distribution of oil and gas reservoirs are mainly controlled by spatial association of faults and sand bodies.

Hydrocarbon Accumulation Pattern of Carbonate Buried Hills in the Yingmaili-Yaha Area

CUI Hai-feng, TENG Tuan-yu, ZHENG Duo-ming, DONG Xue-hua

2009, 15(1):  100-107. 

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Yingmaili-Yaha buried hills are of abundant petroleum resources and good petroleum geologic conditions. The hydrocarbon was dirived from the Manjiaer sag marine facies in the south of the buried hill and the Kuqa depression terrestrial facies in the north. Two regional caprocks, the Middle- to Upper-Ordovician mudstone and the Cretaceous Kapushaliang Group mudstone play the most important roles in formation of hydrocarbon reservoir. The oil-gas distribution in the buried hill is chiefly controlled by reservoir space which is mainly featured by cavities and cracks. The hydrocarbon accumulation pattern is controlled by the lateral distribution characteristics of these cavities and cracks. The hydrocarbon accumulation pattern in the Yingmaili-Yaha buried hills is more complex because the reservoir has more lateral heterogeneity and less pore space and continuity, as compared with the Lunnan buried hill. Generally speaking， these buried hill pools are characterized by massive oil accumulation and bottom water. The oil-gas-water interfaces have different depths due to the connected tube effect in different parts of fracture and cave reservoirs and the displacement process of oil and gas controlled by the reservoir space size.

Use Seismic Moment Tensor and GPS Data to Analyse the Recent Crustal Movement Energy Distribution Characteristics of

JING Yan, LI Hong,XIONG Yu-zhen, FAN Liang-long, ZHANG Shi-zhong, SUN Qi-wei, DONG Jian-ye, LIU Feng-qiu, WANG Hai-zhong

2009, 15(1):  108-114. 

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For a relatively unified and integrated system, the acumulated energy and released energy are basically equal in a cycle of earthquake activity. The crustal deformation fields inferred from earthquake data represent the results of strain energy that had been released. On the other hand, the deformation fields inferred from GPS data represent the strain energy summation of accumulated energy and released energy. According to the geotectonic and active blocks distribution characteristics in China continent and its neighborhood, 32 subregions are subdivided. On this basis, two groups of unit volume energy accumulated rate are calculated and compared with each other in this paper. It can be concluded that crustal strain energy of most areas in our research are released ultimately. Only in the North Tibet, Sichan-Yunnan, Kunlun and Altyn areas, the probability of strong earthquakes is greater. More attention should be paid to these areas.

Paleozoic Salt Structure Styles of Yingmai 2 Work District in Yingmaili Area, Western Tabei Uplift

ZHAO Xing, LI Jiang-hai, CHENG Hai-yan

2009, 15(1):  115-125. 

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Research on salt tectonics is a crucial element of petroleum exploration and scientific problems. Tabei Uplift, one of the most important exploration areas in Tarim basin, has the most proved reserves and oil production in all the first level structure units of this region. Based on seismic and well data, the salt structure styles, formation mechanism and influence on regional tectonics of Tabei Uplift is investigated in this paper in Yingmai 2 work district, Yingmaili area, western Tabei Uplift. Middle Cambrian salt structures are extensively developed in western Tabei Uplift. Salt structure styles, such as salt domes, suprasalt reverse faults and suprasalt normal faults are recognized. Using event similarity prediction technique, the regular variation of salt domes from bottom to top can be clearly revealed in coherent horizontal slices, which shows that a intensely deformed bottom part usually has a slightly deformed top, and vice versa. In the coherent horizontal slices, this differential deformation forms a series of ellipses, which rotate 30° counter clockwise from bottom to top. It is implied that western Tabei Uplift underwent strike slip movement in Late Paleozoic when salt deformation took place. Salt structures were deformed in compressional tectonic setting in Late Paleozoic and, according to the analysis of the structural evolution section, the main fault was remobilized as a synsedimentary fault in Triassic with a limited scale. After Triassic these structures were relatively stable. Salt layers significantly influenced the tectonic deformation. In structural layers below and above them, inharmonious structure styles were formed. In addition, the Palaeozoic fractures, which were formed during salt movement, controlled the space distribution of latter developed magmatism.

Substitute Indices of Summer Monsoon in Eolian Sediment and Its Paleoclimatic Significance

SUN Yu-bing， CHEN Tian-hu， XIE Qiao-qin

2009, 15(1):  126-134. 

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This paper systemically measured the proxy indices of the summer monsoon from the loess-paleosol sequences in the red clay sequences of the Xifeng profile, Gansu Province, including the values of magnetic susceptibility (MS) and frequency dependent magnetic susceptibility, and the contents of carbonate, organic matter and free iron oxides. We reconstructed the change characteristics of the paleoclimate by the carbonate contents and the values of magnetic susceptibility. The results showed that the frequency dependent magnetic susceptibility and the contents of organic matter and free iron oxides are positively correlated with the magnetic susceptibility, while the carbonate contents are negatively correlated with it. All these features can be regarded as the proxy indices of the summer monsoon. The paleoclimatic change of the whole Quaternary by the mathematic model could be divided into three periods: 0~1.1 Ma BP, 1.1~1.9 Ma BP and 1.9~2.6 Ma BP. The annual mean precipitation and annual mean temperature decreased obviously since 0.1Ma BP, which indicates that the climate will be more and more dry and cold in the future.

Palaeoclimate Changes Recorded by Loess Deposit around Qinghai Lake (Northeastern Qinghai-Tibetan Plateau) since Last Deglaciation

ZHAO Cun-fa, LU Hua-yu, ZHOU Ya-li, YI Shuang-wen, MASON Joseph

2009, 15(1):  135-140. 

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Loess and aeolian deposits were found in the area around Qinghai Lake. It is well known that loess is regarded as one of the best terrestrial archives of palaeoclimatic and palaeoenvironmental change. However, investigation on the loess and the aeolian deposits, compared with the lacustrine sediments, is limited and weak in this region. In this paper we dated the loess section by the optically stimulated luminescence (OSL) method, and measured the magnetic susceptibility, Fe/Mg value, grain size distribution and organic matter contents of the Heimahe loess profile. Based on the absolute ages and variations of these climatic proxy indicators, our results show that there are clearly warm/cold and humid/arid alternation in Qinghai Lake area since the late deglaciation. During around 14-9 ka, the palaeolclimate was cold and dry, while the climate was better at about 11 ka. A distinct climate ameliorating occurred from 9 ka to 2.5 ka. Strong disturbance by human activity appeared in loess deposit since 2.5 ka, so it is difficult to analyze the climatic change during the latest Holocene. The environmental changes inferred from the loess deposit are in well comparison with the lacustrine records.