2007 Vol. 13, No. 2

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2007, 13(2): 97-98.
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2007, 13(2): 98-98.
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BAIDUNZI-XIAOXUGONG DUCTILE SHEAR ZONE AND ITS ORE-CONTROLLING EFFECT IN THE SOUTHERN BEISHAN AREA, GANSU
CHEN Bai-lin, WU Gan-guo, YANG Nong, YE De-jin, SHU Bin, LIU Xiao-chun
2007, 13(2): 99-109.
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The Baidunzi-Xiaoxigong ductile shear zone, as the southernmost one of the eight ductile shear zones in the Beishan area, Gansu, is situated at the southern border of the southern Beishan area and near the northern border of the Dunhuang massif.It extents in a nearly E-W direction with a length of 160 km and a width of 5-8 km.This shear zone is characterized by subhorizontal dextral shear and formed under the conditions of low-middle to middle-slightly high temperatures and relatively low differential structural stresses (53-106 MPa).The principal strain (Rxz)is 4-20, the shear strain (γ)is 1.41-2.42 and the shear displacement is up to 10-25 km.The ductile shear zone has a marked controlling effect on gold deposits:it controls the distribution of gold deposits (occurrences)on a regional scale and the shape, attitude and size of gold mineralization zones and orebodies on a deposit scale.The features of transpressional ductile deformation determine that gold mineralization is mainly of altered mylonite type and that alteration is featured by metasomatism.Gold mineralization occurred a little later than ductile shear deformation.
ORE-CONTROLLING EFFECT OF NAPPE STRUCTURE IN THE EAST ORE ZONE OF THE BAIYANGPING AREA, LANPING BASIN, YUNNAN
HE Long-qing, JI Wei, CHEN Kai-xu, YU Feng-ming, WEI Jun-qi, YANG Ai-ping, YANG Wei-guang
2007, 13(2): 110-118.
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The nappe structure in the east ore zone of the Baiyangping area, Yunnan, is a front of the thrust nappe system of a foreland basin related to the Jinshajiang-Ailaoshan orogenic belt, belonging to the emergent imbricate fan-type front.In the mining area the Huachangshan fault and Shuimofang fault form the pop-up structure of the nappe front.The two faults are not only the main ore-conducting structure but also the main ore-hosting structure.The hot brine that circulated at depths rose along the faults and then filled in their secondary faults or interstratal fractured zones inside the thrust faults and in their hanging walls.In the Huachangshan fault zone, the change of ore-forming element contents has certain relation to different types of structural rock.
SYSTEM ANALYSIS OF ORE-CONTROLLING STRUCTURE IN THE NORTHWESTERN JIAODONG GOLD METALLOGENIC BELT
GUO Tao, LÜ Gu-xian
2007, 13(2): 119-130.
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Take for example the northwestern Jiaodong metallogenic belt, this paper attempts to use the system analysis to study the characteristics of regional mineralization and regional ore controls.The authors think that deep structure controlled the spatial distribution of the northwestern Jiaodong metallogenic belt.Faults not only controlled the mode of occurrence of deposits, characteristics of orebodies and deposit types, but also controlled the clustering and quasi-equidistance of deposits and pitching and horizontal zoning of orebodies.The tectono-metallogenic system shows the multi-level, stacking and interdependent feature in space and the cogenetic evolution feature in time.The tectonic evolution and brittle-ductile superposition of faults brought about the diversity and complexity of mineralization.
SULFUR ISOTOPE FEATURES OF CU-AU POLYMETALLIC DEPOSITS IN THE HONGLIUGOU-LAPEIQUAN AREA ON THE NORTHERN MARGIN OF THE ALTYN TAGH MOUNTAINS AND THEIR RELATION TO THE TECTONIC EVOLUTION
LI Yue-chen, CHEN Bai-lin, CHEN Zheng-le
2007, 13(2): 131-140.
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The northern margin of the Altyn Tagh Mountains is one of the important metallogenic provinces recently found in northwestern China.Based on the sulfur isotope study of Cu-Au polymetallic deposits in the area, combined with the geological characteristics of the mineral deposits, the authors consider that there are mainly three genetic types of Cu-Au polymetallic deposit in the area:stratified submarine volcanic-sedimentary type Cu-polymetallic deposits, ductile shear zone type gold (Cu) deposits and lode magmatic hydrothermal type Cu-Au polymetallic deposits controlled by structural fractures.According to the characteristics of the tectonic evolution, the authors discuss the relation between the deposit genetic types and stages of tectonic evolution.Three mineralization stages may be distinguished.The first stage was a period of sea-floor spreading in the early-mid Early Paleozoic, forming submarine volcanic-sedimentary type Cu-polymetallic deposits represented by the Kaladawan copper deposit.The second stage was a period of plate convergence and collision in the mid-late Early Paleozoic, forming ductile shear zone type (dynamometamorphic hydrothermal type)(copper-) gold deposits represented by the Dapinggou and Hongliugou gold deposits.The third stage was a period of magmatic activity and brittle faulting after plate collision at the end of the Early Paleozoic, forming lode magmatic hydrothermal type copper-polymetallic deposits controlled by fractures, as exemplified by the Xorkol Beishan and Lapeiquan deposits.Based on an analysis of the sulfur isotope features and the genetic types of the copper-gold deposits and their relation to the tectonic evolution, the authors suggest that this area has favorable prospects for copper-gold polymetallic deposits.
RELATIONSHIPS BETWEEN COPPER MINERALIZATION AND THE DUCTILE SHEAR ZONE IN THE KALAXIANGEER HALASU COPPER DEPOSIT IN THE ALTAY AREA, XINJIANG
LI Hao-bin, WEN Chang-shun, WANG Zhi-ping
2007, 13(2): 141-149.
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The Kalaxianggeer Halasu copper deposit is situated in the eastern segment of the southern margin of the Altay metallogenic belt.Analysis of the structural deformation in the copper deposit shows that the brittle-ductile shear zone in the copper area has a certain controlling effect on mineralization and country rock alteration and their distribution.In the future copper exploration in the area, attention should be paid not only to the controls of the lithology on mineralization but also to the constraints of the ductile shear zone on the mineralization.In particular, importance should be attached to the contact zone between porphyries and country rocks in the shear zone, where well developed microfractures favored the concentration of orebodies.
BASIC CHARACTERISTICS OF THE YANSHAN MOVEMENT IN NORTHEASTERN SHANXI -A SUMMARY OF REGIONAL SURVEY OF THE 1: 250000 YINGXIAN COUNTY SHEET
ZHAO Zhen-xiang, DU Jin-feng
2007, 13(2): 150-162.
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The Yanshanian crustal activity in northeastern Shanxi was intense and frequent and underwent a process of extension→transpression→uplift and magmatism.The early stage of the Yanshan movement generated an Early Jurassic downfaulted basin and a Middle Jurassic compressional-downwarped coal-accumulating basin.In the middle stage, the Mid-Late Jurassic witnessed the formation of a volcanic downfaulted basin bounded by NW and NE deep faults, intermediate-basic and acid volcanic eruption and hypabyssal and near-surface intermediate-acid magmatic intrusion, and the terminal Late Jurassic witnessed the formation of a number of NNE-trending folds and overthrust zones.In the late stage, in the Early Cretaceous a downfaulted basin and open gentle folds once again formed and the Yixian Formation unconformably rested on volcanic rocks; the Late Cretaceous was a stage of mountain uplift after compressional orogeny, when the Yixian Formation was unconformably overlain by the Zuoyun Formation, accompanied by intrusion of crust-derived granite, and NE-and NE-trending faults were revived, forming a graben-and horst-type fault combination and resulting in mountain uplift.
FAULT DISTRIBUTION PATTERNS OF THE LUXI BLOCK, SHANDONG, AND MESOZOIC SEDIMENTARY-MAGMATICSTRUCTURAL EVOLUTION SEQUENCE
ZHANG Xi-ming, ZHANG Yue-qiao, JI Wei
2007, 13(2): 163-172.
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Faults in the Luxi block have two different distribution patterns:one is the radiate distribution pattern, and the other is the concentric circular distribution pattern, with faults encircling the core of the block basement.The former is composed of NW-striking, steep-dipping, basement dextral ductile shear zones and faults of complex mechanical nature in the cover sediments, and the latter consists of three major cover extensional detachment zones, with the main detachment surfaces lying at the unconformities between the Paleozoic cover and Precambrian basement, disconformities between the Carboniferous and Ordovician and faults between the Meso-Cenozoic downfaulting-sedimentary series and Cenozoic volcanicsedimentary rocks.Mesozoic structural styles include three levels:Indosinian overthrusts and folds, middle Yanshanian NNE-oriented box folds and late Yanshanian conjugate (NW and NNE), normal to strike-slip faults.Accordingly, the Luxi block experienced three stages of basin formation, i.e.:the Early to Middle Jurassic, Early Cretaceous and Late Cretaceous.The superimposition of these Mesozoic basins in space gave rise to a complex basin-mountain coupling relation inside the block.There were two periods of magmatic activity, i.e.the Early Jurassic (190-180Ma)and Early Cretaceous (132-110Ma).By integrating the sedimentary records, magmatism and structural deformation, the Mesozoic structural history of the Luxi block may be divided into six stages:Late Triassic compression, Early to Middle Jurassic weak extension, Middle to Late Jurassic compression and crustal thickening, Early Cretaceous continental rifting and crustal extension, terminal Early Cretaceous compression and basin inversion event, and Late Cretaceous uplift.These structural evolution stages and events have great significance for the study and understanding of the Mesozoic structural regime transition and dynamic transformation in the deep interior of the lithosphere in eastern China.
MICRO-EARTHQUAKES IN THE SHIZIGOU OILFIELD, QINGHAI, AND THEIR GEOLOGICAL SIGNIFICANCE
FENG Mei, AN Mei-jian, WANG Xiao-feng, MA Yin-sheng, JIANG Rong-bao, LI Li
2007, 13(2): 173-178, 172.
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A large number of high-quality seismic data are recorded in the Shizigou oilfield of the western Qaidam basin by monitoring micro-earthquakes for more than one year.After processing and analyzing these data, the authors find that micro-earthquakes occur relatively frequently in the study area and are mainly concentrated at ~2 km depth on the NE side of the NW-trending Huatugou fault in the basinmountain transition zone of the area.Analyses of the relation between earthquakes and oil well distribution and the slope b in the linear relation between log frequency and magnitude show that microearthquakes in the study area are mainly related to the Huatugou fault and its secondary structures though fluid injection through the wells has a certain microearthquake-inducing effect in the area.
DEEP-SEA HYDROTHERMAL ACTIVITY: A HOT RESEARCH TOPIC
XIA Jian-xin, LI Chang, MA Yan-fang
2007, 13(2): 179-191, 118.
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Deep seafloor hydrothermal activity is a hot frontier research topic of modern marine geoscience.In China research on this aspect just begins and it is very necessary to summarize the available research results.This paper reviews the history and current state of the study of seafloor hydrothermal activities, with the focus on the analysis of the results of theoretical research on the dynamic process of hydrothermal venting.The authors found various factors that affect the shapes and distribution of hydrothermal plumes from various field measurements of events and analyzed various hot topics of oceanographic research such as hydrothermal black smokers and extreme ophiles, which provides a basis for the investigation and theoretical study of deep-sea hydrothermal activity.
2007, 13(2): 192-192.
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