2003 Vol. 9, No. 3

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2003, 9(3): 193-200.
Abstract (94) PDF (184KB)(6)
Abstract:
MESO-CENOZOIC INTRACONTINENTAL OROGENIC PROCESS IN THE BEIJING AREA——A Case Study Based on Geological Observations from the Ming Tombs to Badaling Mountain
CUI Sheng-qin, WU Zhen-han, MA Yin-sheng, LI Jin-rong, YI Ming-chu, ZHAO Yue, WU Gan-guo, ZHU Da-gang, FENG Xiang-yang
2003, 9(3): 201-219.
Abstract (155) PDF (869KB)(12)
Abstract:
The magnificent Yanshan Mountains, famous for their unique structural features, lie north of the North China Plain. They are the place o f the world-renowned Meso-Neoproterozoic stratotype(formerly called the "Sini an System of Northern China" or the "Sinian Suberathem"), the area of the old est continental crust exposed in China, and the place from which the well-known Yanshanian Movement was named. The field trip route of the Ming Tombs-Longqing Gorge-Badaling extends in a NW direction across the NE-trending Archean metam orphic complex, famous Meso-Neoproterozoic stratotype, Mesozoic tectono-magmatic belt and Cenozoic basin-range system. Through observations of the tectonic features and stratigraphic system along the traverse, one can gain a general know ledge of the Meso-Cenozoic intracontinental orogenic process of the Beijing are a in the western segment of the Yanshanian intracontinental (intraplate) orogenic belt.
TETHYAN TECTONIC BELT AND GLOBAL LATITUDINAL TECTONIC SYSTEM
QIU Yuan-xi
2003, 9(3): 220-231.
Abstract (132) PDF (438KB)(7)
Abstract:
The eastern segment of Eastern Tethys is located in the present South China Sea and its surrounding areas. As the petrological record of the occeanic crust,the ophiolite belt is distributed like the letter "U". It was formed by contortion of the Tethyan tectonic belt during the collision of the Indian plate and the Eurasian plate,spreading of the South China Sea and west-directed compression of the Phillipine-Pacific plate.Its position and shape in the terminal Cretaceous-initial paleogene reconstruct ed based on the paleo-magnetic and petrological records indicate that it was nearly E-W trending compressive tectonic belt which extended from the south end of the present Indian subcontinent eastward through the northern margin of Kalimantan to the southeastern Phillipine Archipelago by the end of the Late Cretacous.Towards the west it linked with the Qinghai-Tibet area and then the central Asian Zagros Mountains and the European Alps Mountains to form a global Tethyan tec tonic belt.It is controlled by the global latitudinal tectonic system.Study indicates that Gondwana dispersion,Asian accretion and geological evolution of the Tethyan tectonic belt were controlled by the global latitudinal tectonic system.The global latitudinal tectonic system is one of the important forces controlling the plate boundary and movement.
ANALYSIS OF ORE-CONTROLLING STRUCTURE OF THE XORKOL BEISHAN Cu-Ag DEPOSIT IN THE NORTHERN ALTUN MARGINAL AREA,NORTHWESTERN CHINA
CHEN Bai-lin, WANG Xiao-feng, YANG Feng, LI Xue-zhi, CHEN Zheng-le, CHEN Xuan-hua
2003, 9(3): 232-240.
Abstract (180) PDF (327KB)(15)
Abstract:
The Xorkol Beishan Cu-Ag deposit,located at the northern side of the Xorkol Corridor at the northern margin of the Altun(Altyn Tagh) Mou ntains,is a hydrothermal deposit controlled by second-order faults in the thrust block of nappe structure.There outcrop the thich-bedded lime stone member and medium-bedded limestone member of the Jinyanshan Formation of the Jixianian System and the thin-bedded schist member of the Xiaoquandaban Formation of the Qingbaikouan System in the ore district.The closed folds and foliation substitution in the autochthonous block of nappe structure formed by the th in-bedded schist member,the intermediate,open folds in the allochthonous block formed by the thick-bedded limestone member and medium-bedded limestone member,nappe structure and late-stage steep-angle strike-slip fault make up the basic structural framework of the ore district.The nappe is overthrust from south to north and cut by the late-stage Altum strike-slip fault.The secondary faults developed in the thrust block at the inflection point of the nappe structural plane are the principal ore-hosting structure.The shape,attitude,distribution and size of the mineralization zone and orebodies are strictly controlled by ore-hosting structure.
POTENTIAL OF URANIUM MINERALIZATION IN MESO-CENOZOIC STRATA IN THE NORTHWESTERN JUNGGAR BASIN
LIU Jian, CHEN Zheng-le, ZHANG Hong-xi, HU Jian-min
2003, 9(3): 241-245.
Abstract (199) PDF (151KB)(9)
Abstract:
Parameters of organic matter(Cy),pyrite(FeS2),magnesia (MgO),phosphate(P2O5),iron oxide(Fe2O3,FeO) and Fe3+/Fe2+ play an important role in the formation of in-situ leachable sandstone-type uranium deposits.Comparative study of parameters of sandstone of the primary zone in the ore target in the no rthwestern part of the Junggar basin and those of sandstone of the primary zone in the 512 uranium deposit on the southern margin of the Ilibasin indicates that a pronounced inherent shortage exists for the potential of uranium mineralization in the sandstone of the primary zone in the northwestern part of the Junggar basin.Changesin sedimentary facies and sedimentary environment are the cause re sponsible for the great difference in the aforesaid parameters.Additonally,the authors point to the direction in future mineral exploration in the area.
TECTONIC CHARACTERISTICS OF THE BAIYANGPING-HUACHANGSHAN ORE BELT,YUNNAN PROVINCE AND ITS ORE-CONTROLLING EFFECT
SHAO Zhao-gang, MENG Xian-gang, FENG Xiang-yang, ZHU Da-gang
2003, 9(3): 246-253.
Abstract (138) PDF (272KB)(6)
Abstract:
The Baiyangping ore belt is located in the northern segment of the Lanping-Simao Indosinian-Yanshanian-Himalayan metallogenic belt.The mi neralization occurred on the basis of the Mesozoic marine to continental carbonate formation and clastic formation intercalated with the volcanic formation,and the Himalayan tectonic overthrusting and hydrothermal modification played a dominant role.Study of the ore-field geology and ore-controlling structure in the ore belt indicates that the stratabound plus hydrothermally modified deposits in the area is closely related to ore-controlling structure.
GEOLOGICAL CHARACTERISTICS OF THE DAYINGEZHUANG GOLD DEPOSIT IN THE JIAODONG AREA AND ITS RESOURCE PROSPECTS AT DEPTH
LI Wei-ge, LI Long-yi, ZHANG Rui-zhong, QIAN Jin, GUO Jun-li
2003, 9(3): 254-260.
Abstract (126) PDF (260KB)(12)
Abstract:
The Dayingezhuang gold deposit in the Jiaodong area,Shan dong Province,is a hidden(to a burial depth of more than 250 m from the surface),mesothermal,alteration-type gold deposit in a fractured zone.It has been mined for more than ten years.Check drilling has revealed that the orebody has a tend ency of the second enrichment at depth.The orebody has a controlled maximum dip width of 890 m or more and still extends downward without pinching out,indicating that the deposit has very vast ore prospects at depth.
Re-Os AGES OF THE ZHONGJIA TIN POLYMETALLIC DEPOSIT,SOUTHWESTERN FUJIAN, AND THEIR GEOLOGICAL SIGNIFICANCE
ZHANG Da, WU Gan-guo, WU Jian-she, CHEN Xiang-yun
2003, 9(3): 261-267.
Abstract (129) PDF (250KB)(7)
Abstract:
The mineralization age of ore deposits is one of the important subjects in the study of the genesis of ore deposits and it has long been obtained by means of indirect methods.The Re-Os dating technique is an effective means for the direct accurate determination of the model ages of molybdenite and related mineralization.The alkali fusion combined with ICPMS was used in this study to determine the Re-Os ages of molybdenite in the Zhongjia tin poly metallic deposit.The results indicate that the model age of mineralization of the Zhongjiatin polymetallic deposit is 193-196 Ma,assigned to the early stage of the early Yanshanian period.The biotite granite related to mineralization was emplaced during the late Indosinian-early Yanshanian The transformation from the Tethys tectonic domain to the circum-Pacific tectonic domain in the continent of southeastern China began in the late Indosinian.The tin polymetallic mineralization resulted from the transformation of the two tectonic domains.The determination of the early Yanshanian mineralization provides direct chronological evidence for looking for new regional ore prospect areas.
TRIASSIC PALEOGEOGRAPHY AND SEDIMENTARY FACIES OF THE KUQA DEPRESSION,TARIM BASIN
JI Yun-long, DING Xiao-zhong, LI Xi-chen, YU Kai-ning
2003, 9(3): 268-274.
Abstract (129) PDF (275KB)(8)
Abstract:
After the deposition of Late Permian thick-bedded molasses,the Kuqa depression began to enter a stage of development of a closed compressional flexural basin in the Triassic,thus ushering in the stage of development of a Mesozoic foreland basin,when the tectonic framework and style were very different from those in the Paleozoic.The Triassic climate in the basin was wet and hot and the sedimentary facies were very diverse.There are deposits of alluvial fans,fan deltas and braided deltas near the piedmont belt in the northern part.Towards the center of the depression,there are deposits of braided deltas and meandering rivers and lakes.Several coal beds are developed in backswamp deposits.Lakeshore and swampy carbonaceous mudstone and coal measures are major hydrocarbon source rocks of the Kuqa depression.In different phases of the entire Triassic evolution,thrust compressional stresses increased gradually and weakened gradually. The paleogeographic features in various phases were different.From the Early Triassic to Late Tiassic,the depocenter and subsidence center moved southward progressively,while the frontal uplift retreated toward the foreland continually.The Triassic frontal uplift and northern thrust belt were connected to the east of Luntai.This connected old land moved westward steadily from the Early to Late Triassic but the magnitude of migration was not large.In the Late Triassic it became a subordinate material source.
SOME PROBLEMS OF IN-SITU CRUSTAL STRESS MEASUREMENTS
TAN Cheng-xuan, SUN Ye, WANG Lian-jie
2003, 9(3): 275-280,260.
Abstract (224) PDF (219KB)(14)
Abstract:
Measuring data at home and abroad confirm that tectonic stress near the surface is interfered with by several influence factors and is usually overlapped by non-tectonic stress,e.g.stress caused by topography.This paper discusses the problems that need consideration before and after crustal str ess measurements.Before the measurements,we should give full consideration to the determination of measuring sites and the influences of landforms,rock types,fractures and so on.After the measurements,an analysis on the various influence factors and reliability of measuring values and correction and comparative analysis of the mechanical properties of rocks,as well as a representative analysis of the measuring values are necessary.
NUMERICAL MODEL OF THE INSTABILITY-FAILURE PROCESS OF THE COAL-BED FLOOR DUE TO CONFINED WATER INRUSH
YANG Tian-hong, TANG Chun-an, LIU Hong-yuan, ZHU Wan-cheng, FENG Qi-yan
2003, 9(3): 281-288.
Abstract (184) PDF (326KB)(6)
Abstract:
In this paper the instability-failure process of floor due to confined water inrush is numerically simulated by using the Coupling System of Flow & Solid in Rock Failure Process Analysis(F-FRPA2D) that has be en recently developed by CRISR,Northeastern University.In this numerical model the fluid pressure transmission during the rupture-failure process of material is achieved by the coupling and iteration of flow-damage of an element.According to the results of the simulation the instability-failure mechanism of floor associated with the confined aquifer is analyzed and the position where water inrush is liable to happen is predicted.The results are in the main consistent with t he phenomena at the site,which indicates that the F-RFPA2D,as a newly developed numerical simulation code,can be used to study water inrush from the confin ed aquifer through the floor.

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