2001 Vol. 7, No. 3

Display Method:
TECTONIC ENVIROMENTS OF MAGMATISM IN EARLY PALEOZOIC IN THE NORTH ALTYN TAGH, CHINA
CHEN Xuan-hua, WANG Xiao-feng, YANG Feng, CHEN Zheng-le, CHEN Bai-lin, WANG Ke-zhuo
2001, 7(3): 193-200.
Abstract (120) PDF (351KB)(6)
Abstract:
The North Altyn Tagh is located at the northewst area to Altyn Fault between Tarim and Qaidam Basins. Granitoids from this area formed mainly in Ordovician,and are classified as calc alkaline based on alkaline-lime index,and metaluminous and peraluminous on Shand's index. I and A-types are the principal granitoids,no S-type granitoids found here. Volcanic rocks occurring together with ophiolite suite in this area,mainly of Early Paleozoic,consist of pillow basalts and rhyolites,and smaller amounts of trachybasalts,basaltic trachyandesites and dacites,belonging to subalkali and showing bimodal distribution in SiO2-Na2O+K2O plot. Major-and trace-element trectonic discrimination of the granitoids shows the evolution of tectonic environments from destructive active plate margin/volcanic arc in Early Paleozoic,the continental apeirorogenic uplift in Mesozoic and post orogenic in Cenozoic of North Altyn Tagh. Tholeiitic basalts had formed in several environments from MORB to island arc and within-plate. Acid volcanic rocks here of calc alkali series may belong to within plate environment only. The existing of "Altyn Ocean" in early Paleozoic is then deduced from the analyses above.
Cu-Au ENRICHMENT AND MINERALIZATION IN ALTYN TAGH
WANG Xiao-feng, CHEN Xuan-hua, CHEN Zheng-le, CHEN Bai-lin, YANG Feng, WANG Ke-zhuo, ZHANG Li-rong, YUAN Jia-yin
2001, 7(3): 201-207.
Abstract (200) PDF (311KB)(7)
Abstract:
The Cu-Au enrichment and mineralization is studied here. It is concluded that the different order structures in Altyn Tagh fault system controlled the spatial distribution of metallogenic belts,ore fields and ore deposits. Regionally,it is divided into north Altyn Tagh gold-copper-iron multi-metal metallogenic zone and Altyn Tagh iron-copper-gold multi-metal metallogenic zone. Two main mineralization periods occurring at 502.3Ma±10.1Ma and 207.6Ma±4.2Ma respectively have been recognized through the analysis of gold and copper abundances and 40Ar/39Ar geothermochronology. The evolution of tectonic stress field,related to the enrichment and mineralization of Cu and Au,is divided into three stages:pre-Mesozoic compression,Mesozoic extension and Cenozoic strike-slip stages. Areas with relatively low stress are prospected to be benefited for the enrichment and mineralization of Cu and Au.
THE CHARACTERISTICS OF ROCK MAGNETIC FABRIC AND ITS RELATIONSHIP TO GOLD MINERALIZATION IN SAWAYAERDUN GOLD DEPOSIT, XINJIANG
CHEN Xuan-hua, MA Tian-lin, SUN Li-qian, ZHOU Jian-hai, ZHANG Xin-li
2001, 7(3): 208-216.
Abstract (173) PDF (347KB)(9)
Abstract:
The magnetic fabric characteristics and its relationship to the gold mineralization in Sawayaerdun gold deposit,Xinjiang,China,are reported here. The data given here show compression in NW-SE direction and sinistral shearing vertical to this direction. There are contraction-type and flaser-type strains occurring alternatively in NW-SE,where flaser-type strains are much more developed. Gold-bearing veins occur in en echelon,which are products of sinistral shearing. The ore vein Ⅳ,the most important gold-bearing vein,occurs in the weakly strained area close to the most strongly strained belt. Gold mineralization exists in weakly deformed rocks closely related to quartz vein,showing post-tectonic filling and crystalling of the gold -bearing fluid. Combined with the microtexture analysis of rocks in this area,Sawayaerdun gold deposit is proposed to be a shearing zone-type gold deposit,where gold bearing fluid coming from rocks in this area through pressure solution during ductile deformation,filled fractures due to tectonic compresso-shearing.
GENETIC TYPE CHARACTERISTICS AND EXPLORATION OF GOLD DEPOSIT IN BEISHAN AREA, GANSU PROVINCE
CHEN Bai-lin, WU Gan-guo, YE De-jin, LIU Xiao-chun, SHU Bin, YANG Nong
2001, 7(3): 217-223.
Abstract (259) PDF (250KB)(42)
Abstract:
There occurs a lot of gold deposits which belong to three genetic types:ductile shear zone-type,magmatic-hydrothermal type and marine-volcanic type.Source materials of gold deposits in the area are derived mainly from the metamorphic rocks,Variscan intermediate-acid intrusive rock,and marine volcanic rocks and sub-volcanic rocks of Carboniferous system.Except the metamorphic rocks and volcanic rocks of Carboniferous system,there is little selectivity of stratigraphic time for gold deposit to occur.Ore fluid of magmatic-hydrothermal type and marine-volcanic type gold deposits is drawn mainly from magmatic water,but one of ductile shear zone-type from magmatic water and dynamic metamorphic hydrothermal solution.The study of structure controls of gold deposits shows that tectonics and regional structure control the distribution of ore bearing rock series,secondary structure controls the distribution of ore forming rock mass and mineralization belts.The ore-hosting structures are ductile shear zone,low angle faults,and fractures in the magmatitic mass.And most of gold deposit in the area fromed mainly in late Paleozoic era.The prospective places for gold deposit are Xiaoxigong and its peripheral area,Baidunzi Shibandun area,Jinwozi Zhaobishan area,Shijinpo -Nanjintan area,Mazhuangshan -Nanjinshan area and Gubaiquan Laojinchang area.
THE CHARACTERISTICS OF NEOGENE SERTENGSHAN XIETIESHAN OBLIQUE THRUST FAULT IN THE NORTHERN MARGIN OF QAIDAM BASIN
WANG Gen-hou, RAN Shu-ming, LI Ming
2001, 7(3): 224-230.
Abstract (198) PDF (258KB)(9)
Abstract:
A Neogene left-lateral oblique turst fault-Sertengshan-Xitieshan oblique trust zone is recognized in the northern margin of Qaidam basin based on the analysis of structures of the area.This oblique trust fault zone with northwestern -southeastern trending consists of fault gouge,fault breccia and fault cleavage.Fault hanging wall is Sertengshan -Xitieshn napple,which is distribution in dextral en echelon.Fault footwall consists of Youcangshan Formation in Neogene.It is discussed that geological setting of the oblique thrust faults zone,is considered in connection with the long distance effection of Himalayan orogenic belt intracontinent subducting.
GEOLOGICAL CHARACTERISTICS OF THE METAMORPHIC CONGLOMERATE IN SINIAN STRATIGRAPHY IN THE LUODING AREA, THE WESTERN GUANGDONG
KUANG Yong-guang, HUANG Ji-chun, XIAO Si-ming, ZHUO Wei-hua
2001, 7(3): 231-237.
Abstract (194) PDF (320KB)(9)
Abstract:
Based on the study of petrology,mineralogy,microelements,palaeontology and geological occurrence characteristics,the authors hold that the thick-beded metamorphic conglomerate in Sinian strata in Laoshouxia,Luoding area of westren Guangdong province,is a sedmental basal conglomerate with simple component suffered structural deformation.Its bottom surface is corresponding to one of Nantou Formation in South China,and is the structural surface of Chengjiand movement between early to late Sinian period in Guangdong region.
THE THERMAL STRUCTURE OF MAIN SEDIMENTARY BASINS IN THE NORTHERN MARGIN OF THE SOUTH CHINA SEA
ZHANG JIAN, SONG Hai-bin
2001, 7(3): 238-244.
Abstract (151) PDF (279KB)(11)
Abstract:
Geothermal study,for main sedimentary basins of the northern margin of the South China Sea,reveals that the distribution of temperature at depth is different.Especially,the constitutions of heat flow among these basins are not uniform with respect to each other.Calculation shows that in Preal River Mouth basin the contribution of crustal heat flow is lower than 25% and decreased by degrees from margin to sea.In Yinggehai basin,the contribution of crustal heat flow is lower than 30% and increased by degrees along the northeast direction.In Beibuwan basin,the contribution of crustal heat flow varies between 38% and 42%.The results suggest that the instability of thermal structure in this region can be attributed to the thinning of marginal crust and the up flowing of hot material of asthenosphere.
THE METALLOGENETIC STRESS FIELD AND RECONSTRUCTION OF DYNAMIC MECHANISM IN FUSHAN GOLD FIELD, SHANDONG
LIU Du Juan, GUO Tao, LU Gu-xian
2001, 7(3): 245-253.
Abstract (159) PDF (383KB)(9)
Abstract:
The space distributions of differential stress and principal stress in Fushan gold field are got from measuring tectonic differential stress value.Results show that the gold orebodies are always located in the areas where the tectonic stress value varies highly,not the minimum or maximum.Based on strain measurement and analysis of susceptibility anisotropy,the tectonic strain fields of the diagenetic and mineralization periods in Fushan gold field are given respectively.There was a transition of stress field from NW trending compression to NE trending compression during mineralization,and the tectonic environment of minerallization was changed from shear compress to shear -extension.
RESEARCH AND PRACTICE ON TECTONIC STRESS FIELD
SUN Ye, TAN Cheng-xuan
2001, 7(3): 254-258.
Abstract (196) PDF (156KB)(29)
Abstract:
The study of tectonic stress field,which was founded by J.S.Lee,can be divided into the following two periods:①initial research period(1926-1966),which focuses on the tectonic stress fields of some typical structural patterns by the analysis of stress states of structural features.②in situ measurement period(1966-),which focuses on the plane tectonic stress field research in the former part of this period and later on the 3-D tectonic stress field study and on the deep tectonic stress field research in the future mainly by the insitu measurements of crustal deformation,crustal stress,fault displacement,rock fabrics,stress minerals,as well as modeling experiments.The research on tectonic stress field has not only the significance in exploring mineral resources,protecting geological environments,controlling geological hazards and in application in engineering construction,but also the important role in discussing crustal movement.
STRESS MEASUREMENT OF ANQING COPER MINING
DONG Cheng, WANG Lian-jie, YANG Xiao-cong, WANG Hong-cai, WANG Wei
2001, 7(3): 259-264.
Abstract (157) PDF (188KB)(8)
Abstract:
In this paper, the results of rock stress mesurement of -580m level by hollow inclusion gauge at Anqing coper mine are introduced, the characteristics of stress distribution are discussed. The mesurement results show that the magnitude of the maximal principle stress is 24MPa, its orientation is NE to EW. The horizontal stress is in the dominating position and it is bigger than verticle stress. The measurement results can apply to mine design.
THEORETICAL ANALYSIS OF RELATIONSHIP BETWEEN STRESS AND STRAIN IN CONSIDERATION OF CONFINING PRESSURE AND PORE PRESSURE OF ROCK SAMPLE
WANG Xue-bin, PAN Yi-shan
2001, 7(3): 265-270.
Abstract (192) PDF (229KB)(6)
Abstract:
Based upon shear strain gradient plastic theory of rock deformation localization, it is assumed that the failure pattern of rock in the shear band is shear failure. The confining pressure and the pore pressure are involved in the model and a theoretical stress strain relationship is obtained. The result of the theoretical analysis coincides with many experimental results. The localization is the cause of the confining pressure and pore pressure. The theoretical analysis has theoretical and practical significance for prevention from some natural hazards.
THE STUDY OF FINITE ELEMENT SIMULATING OF SEEPAGE IN THE UNDERGROUND ENGINEERING
LI Jie, LI Qiang
2001, 7(3): 271-277.
Abstract (248) PDF (244KB)(7)
Abstract:
In the underground engineerings of waterpower, petroleum and traffic, the problem of seepage often happens. If it is not deal with correctly, worse stress will be induced, which willinfluence the stability of structure. Based on the model of unsaturated seepage, the analysis of unsteady seepage is accomplished.
In this paper, according to the construction by stages, under the continuity premise of seepages variance, the guasi-steady seepage for every stages is analyzed and accordingly a numerical model of three-dimensional unsaturated seepage is constituted. Based on the principle of water quantity balance the excavation is simulated with the model of substructure; the waterproof curtain with the model of interlayer; the drainge with the model of shank element.
According the above models a finite element program of unsaturated and unsteady seepage analysis is compiled using finite differnce method and the dynamical simulating of seepage field in complex region is done. The crnalysis and calculation of engineering case show that the results obtained by calculation of above models are reasonable.