Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P
- Most Read
- Most Cited
- Most Downloaded
WU Shuren Institute of Geomechanics , CAGS , Beijing and WU Ganguo China University of Geosciences , Beijing Liu Xinzhu
1999, 73(2).
Abstract:Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannushan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of σI is N-S in direction with differential stresses of 150-250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.
PEI Rongfu , WANG Ping''''an , and PENG Cong Institute of Mineral Deposits , CAGS , Baiwanzhuang Rd. , Beijing Institute of Geomechanics , CAGS , Beijing
1999, 73(2).
Abstract:The Nanling region is an important nonferrous and rare metal metallogenic province in South China, in which most of the deposits are related to granitoids in genesis. It covers southern Hunan, southern Jiangxi, Guangxi, Guangdong and Fujian provinces, with a total area of about 550,000 km2. This metallogenic province is well known in the world for its rich tungsten and tin resources. In the past 40-odd years, a vast amount of mineral exploration activities and studies of the geology of mineral deposits have been carried out and great achievements obtained in the province. This paper is focused on a discussion about the deep tectonic processes in the orogenic belt during the Mesozoic and their contribution to the superaccumulation of metals. Tectonically, this metallogenic province is composed of three units: (1) the marginal continental orogenic belt in the Southeastern Coast fold system in the Yanshanian; (2) the intercontinental orogenic belt in the collision suture belt between the Yangtze and Cathay
LI Jinyi , WANG Zongqi , ZHAO Min Institute of Geology , Chinese Academy of Geological Sciences , Beijing
1999, 73(2).
Abstract:Silurian, Devonian and Carboniferous geological bodies in the Mianxian-Lueyang (Mian-Lue) collisional belt (MLB) and its neighbouring areas, southern Qinling Mountains, China, show similar characteristics of having undergone deformation of two stages. The earlier one, which is inferred to be related to collisional orogeny between the Yangtze and Sino-Korean palaeocontinents based on previous geological data, is responsible for large-scale, north-verging recumbent folds and overthrusts, and associated with low greenschist fades metamorphism. 40Ar/39Ar dating of three muscovite samples taken from different localities yields plateau ages of 226.9±0.9 and 219.5±1.4 Ma and an apparent age of 194.5±3.0 Ma. Thus, the late Triassic collision between the Yangtze and Sino-Korean palaeocontinents has been constrained.
1999, 73(2):2.
Abstract:Abstracts of Acta Geologica Sinica (Chinese Edition) Vol.73, No. 2, 1999
JIN Yugan , SHANG Qinghau , WANG Xiangdong , WANG Yue , SHENG Jinzhang Nanjing Institute of Geology & Palaeontology , Chinese Academy of Sciences , Nanjing
1999, 73(2):127.
Abstract:Since the principle of multiple stratigraphic classification has been widely accepted by Chinese stratigraphers, various new Permian chronostratigraphic units have been proposed in China, and they need to be redefined. The establishment of a new global chronostratigraphic scheme of the Permian, compilation of Permian lithostratigraphic units and updating of Permian biostratigraphic sequences of China makes it possible to present a revised regional chronostratigraphic succession for the Permian System in China. This succession consists of three series and eight stages. The Chuanshanian Series includes two stages, the Zisongian and the Longlinian; the Yanghsinian (Yangxinian) Series is subdivided into the Chihsian (Qixiaan) and the Maokouan Subseries, of which the former comprises the Luodianian and the Xiangboan Stage, and the latter the Kufengian (Gufengian) and the Lengwuan Stage; the Lopingian (Lepingian) Series includes the Wuchiapingian (Wujiapingian) and the Changhsingian (Changxingian) Stage.
1999, 73(2):139.
Abstract:There are two extensional systems in the Xiaoqinling metamorphic core complex (XMCC). One is the detachment fault system developed along the peripheries of the XMCC, which extended in an ESE-WNW direction and whose upper plate moved towards the WNW. The other extensional system includes the retrograde shear zones and normal faults developed within the XMCC, which represent the collapse of the XMCC. Ar-Ar and K-Ar dating shows that the extension of the detachment fault system continued from 135 to 123 Ma, i.e. in the late stage of its evolution at about 127 Ma. The collapse represented by the extensional system within the XMCC was operative during 120(106 Ma, and its main activity occurred about 116 Ma ago. These suggest that the XMCC experienced two extensional stages in its evolution, i.e., the syn-orogenic regional extension and post-orogenic collapse extension.
SHU Liangshu , CHARVET Jacques , GUO Lingzhi , LU Huafuand LAURENT-CHARVET Sebastien Department of Earth Sciences , State Key Lab of Metallization , Nanjing University , Nanjing , P.R. of China Departement des Sciences de la Terre , URM , Universite d''''Orleans , Orleans , France
1999, 73(2):148.
Abstract:The nearly E-W-trending Aqqikkudug-Weiya zone, more than 1000 km long and about 30 km wide, is an important segment in the Central Asian tectonic framework. It is distributed along the northern margin of the Central Tianshan belt in Xinjiang, NW China and is composed of mylonitized Early Palaeozoic greywacke, volcanic rocks, ophiolitic blocks as a mélange complex, HP/LT-type bleuschist blocks and mylonitized Neoproterozoic schist, gneiss and orthogneiss. Nearly vertical mylonitic foliation and sub-horizontal stretching lineation define its strike-slip feature; various kinematic indicators, such as asymmetric folds, non-coaxial asymmetric macro- to micro-structures and C-axis fabrics of quartz grains of mylonites, suggest that it is a dextral strike-slip ductile shear zone oriented in a nearly E-W direction characterized by "flower" strusture with thrusting or extruding across the zone toward the two sides and upright folds with gently plunging hinges. The Aqqikkudug-Weiya zone experienced at least two stages of ductile shear tectonic evolution Early Palaeozoic north vergent thrusting ductile shear and Late Carboniferous-Early Permian strike-slip deformation. The strike-slip ductile shear likely took place during Late Palaeozoic time, dated at 269(5 Ma by the40Ar/39Ar analysis on neo-muscovites. The strike-slip deformation was followed by the Hercynian violent S-type granitic magmatism. Geodynamical analysis suggests that the large-scale dextral strike-slip ductile shearing is likely the result of intracontinental adjustment deformation after the collision of the Siberian continental plate towards the northern margin of the Tarim continental plate during the Late Carboniferous. The Himalayan tectonism locally deformed the zone, marked by final uplift, brittle layer-slip and step-type thrust faults, transcurrent faults and E-W-elongated Mesozoic-Cenozoic basins.
1999, 73(2):163.
Abstract:Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannüshan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of (1 is N-S in direction with differential stresses of 150(250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.
LI Tingdong , GAO Rui , WU Gongjian Chinese Academy of Geological Sciences , Baiwanzhuang Rd. Beijing Fei Zhenbi
1999, 73(2):173.
Abstract:The Tibet Geoscience Transect (Yadong-Golmud-Ejin) has revealed the basic structures, tectonic evolution and geodynamic process of the lithosphere of the Qinghai-Tibet plateau. The evidence of northward thrusting of the Indian plate beneath the Himalayans on the southern margin and to southward compression of the Alxa block on the northern margin has been found. They were the driving forces causing the plateau uplift. The plateau is a continent resulting from amalgamation of eight terranes. These tenanes are separated by sutures or large-scale faults, and different terranes have different lateral inhomogeneities and multi-layered lithospheric structures. At depths of about 20-30 km of the crust in the ulterior of the plateau there commonly exists a low-velocity layer. It is an uncoupled layer of the tectonic stress; above the layer, the upper crustal slices were thrust and overlapped each other and the rocks underwent brittle deformation, thus leading to shortening and thickening of the upper crust Below the layer, the lateral change of the structure of the lower crust varies most greatly and ductile deformation occurs. The lower crust velocity of southern Tibet shows the reversed feature; whereas the lower crust velocity of northern Tibet increases and displays strong gradient variation and the character of the double Moho. On the whole, the Moho of the plateau is greatly undulatory. Although the crust of the Qinghai-Tibet Plateau has a great thickness, the lithosphere does not thicken markedly. The plateau is in a state of bi-directional compression. The unstable change of the Moho, the interaction between the crust and mantle and between the lithosphere and astheno-sphere caused by the sinking of the lithospheric mantle and the strike slip and extension of the crust are the major dynamic factors for maintaining the present height and scope of the Qinghai-Tibet Plateau.
PENG Cong , PEI Rongfu Institute of Mineral deposits , CAGS , Beijing and GAO Rui Institute of Geology , CAGS , Beijing Liu Xinzhu
1999, 73(2):193.
Abstract:Based on the study of tens of geophysical profiles (seismic, geothermal flow and magnetotelluric sounding profiles) and 3-D shear wave velocity structures of the Chinese continent and its neighbouring regions, this paper describes the 3-D crustal and upper mantle structures and discusses briefly the deep geophysical background of superlarge ore deposits in the Chinese continent. Superlarge deposits are usually very few in number, but they are distributed still in certain forms such as "point", "zone" and "area". Most of the large-, medium- and small-sized deposits occur near the margins of different tectonic units; while the superlarge endogenic polymetallic deposits occur mostly in thinned mantle lithosphere, uplifts of the asthenosphere (vertical low-velocity zones) and the transformation zones of lateral inhomogeneity (weak zones) in the upper mantle. The superlarge endogenic polymetallic deposits are almost unevenly distributed in three major ore zones in China, corresponding to the boundaries of inhomoge-neous regions in the asthenosphere.The authors argue that the lithospheric structure is to some extent in agreement with the geotectonic units, suggesting that the crust structure is influenced and restricted by the lithosphere, and that the crust and upper mantle both exhibit low-velocity nature. Therefore, vertical low-velocity zones of seismic waves are considered to be a favourable environment for endogenic polymetallic ore belts.
WEI Junhao LI Jianwei , YUAN Yanbin Faculty of Earth Resources , China University of Geosciences , Wuhan , Hubei
1999, 73(2):201.
Abstract:The Shibangou gold deposit in western Henan is associated with irregular quartz veinlets occurring in altered shear zones dissecting a dioritic intrusion. The altered shear zones are characterized by silicification, pyriti-zation, sericitization, chloritization and K-feldspar alteration. Zoning of altered rocks adjacent to the Au-bearing quartz veins is obviously exhibited. Fine-grained sulphides and quartz veinlets of different ages and small-scale fissures are widely distributed in the central part of the altered zones. Major mineralization types in this gold deposit are Au-bearing quartz vehlets and altered rocks in the shear zones. Samples were collected from drilling cores according to the alteration zoning and mineralization type and all samples were analyzed for major and trace elements. Mass balance, volume change (fv=97.3-71.9%) and major element variation sequences are studied in terms of major elements. The changes of mobile components (SiO2, K.2O, Fe2O3 and CaO) and immobile component (Al2O3) in the wall-rock alteration are discussed. The gold mineralization is associated with the enrichment of As, Ag, Hg and Pb and depletion of Cu and Zn. The study of compositional variation of altered rocks proves to be a very efficient method for defining the extent of wall-rock alteration, fluid activity and mineralization and enrichment.
LI Jinyi , WANG Zongqi , ZHAO Min
1999, 73(2):208.
Abstract:Silurian, Devonian and Carboniferous geological bodies in the Mianxian-Lüeyang (Mian-Lüe) collisional belt (MLB) and its neighbouring areas, southern Qinling Mountains, China, show similar characteristics of having undergone deformation of two stages. The earlier one, which is inferred to be related to collisional orogeny between the Yangtze and Sino-Korean palaeocontinents based on previous geological data, is responsible for large-scale, north-verging recumbent folds and overthrusts, and associated with low greenschist facies metamorphism. 40Ar/39Ar dating of three muscovite samples taken from different localities yields plateau ages of 226.9(0.9 and 219.5(1.4 Ma and an apparent age of 194.5(3.0 Ma. Thus, the late Triassic collision between the Yangtze and Sino-Korean palaeocontinents has been constrained.
CHEN Junren , WAN Ling Guangzhou Marine Geological Survey , MGMR , P. O. Box , Guangzhou
1999, 73(2):216.
Abstract:Experimental examinations and analyses have been made of the sediments from drill holes in the Zhuhai area, Guangdong Province. The studies show that there occurred four transgressions in this area over the historical times. The first transgression occurred at 7500 a B.P., with the maxium sea level up to about 1 m above the present level. The second transgression occurred at 5750 a B.P., with the sea level possibly 4 m higher than the present. The third and fourth transgressions took place at 4650 a B.P. and 2600 a B.P. respectively, which lasted for a long time with multiple fluctuations. The fifth transgression is in process. It could be predicted that the sea level at Zhuhai would rise by 15-20 cm in the coming 50 years.
REN Jinzhang , SUN Rubo , DUANMU Heshun
1999, 73(2):225.
Abstract:The origins of gases in springs, pools and wells from the Wudalianchi (WDLC) volcanic area are discussed based upon molecular and isotope compositions of the gases. Nine gas and water samples were collected from bubbles and water of the springs and pools in the WDLC volcanic area, Northeastern China, in August 1997. The molecular components were measured with a MAT-271 mass spectrometer (MS), helium isotope ratios with a VG-5400 MS, and (13C with a MAT-251 MS in the Lanzhou Institute of Geology. The gases are enriched in CO2 , and most of the CO2 concentrations are over 80% (V). The helium and methane concentrations have relatively wide ranges of 0.7 to 380×10-6 and 4 to 180×10-6, respectively. The 3He/4He ratios are between 1.05 Ra and 3.1 Ra (Ra = 1.4×10-6); the 4He/20Ne values are between 0.45 and 1011, larger than the atmospheric value (0.32). The (13C (PDB) values of carbon dioxide range from (9.6 to (4.2‰. These geochemical data demonstrate that the spring water is from aquifers at different depths, and that helium and carbon dioxide are derived from the mantle, and are contaminated by crust gases during deep fluid migration. Also, there are larger fluxes of deep-earth matter and energy in the WDLC volcanic area.
MAO Jingwen , ZHANG Xiaoyu Institute of Mineral Deposits , Chinese Academy of Geological Sciences , Beijing ZHANG Zhaochong Institute of Geology , Chinese Academy of Geological Sciences , Beijing )REN Fengshou , ZUO Guochao Gansu Bureau of Geology , Mineral Resources , Lanzhou , Gansu ZHANG Zuoheng , YANG Jianmin , WANG Zhiliang Institute of Mineral Deposits , Chinese Academy of Geological Sciences , Beijing and YE Dejin Gansu Bureau of Geology , Mineral Resources , Lanzhou , Gansu
1999, 73(2):230.
Abstract:The west sector of the northern Qilian Mountains is well-known for the Jingtieshan-type iron deposits. A new breakthrough has been made in prospecting for gold and copper in recent years. In this paper, the distribution characteristics of ore deposits in the study area are discussed from the viewpoint of tectonic evolution. It is suggested that there are 9 stages of mineralization from the Palaeoproterozoic to Indosinian. Four minerogenetic series and two minerogenetic subseries of ore deposits are recognized. Iron mineralization occurred in several stages, while most of the metals were accumulated in large amounts in the Caledonian. The enrichment and mineralization of gold is related to large-scale shear-strike-slip faults and the ascent and unloading of deep-seated fluids.
HUANG Yongyang , CHEN Fang Guangzhou Marine Geological Survey , MGMR , Guangzhou
1999, 73(2):242.
Abstract:Based upon the features of nannofossil composition, distribution, abundance and diversity, the fossil-bearing sediments exposed by five drill holes in the offshore area of southern Hongkong can be divided into the upper Middle Pleistocene, the Upper Pleistocene and Holocene. There were two palaeoclimatic stages in the Holocene in this area according to fossil palaeoecologic and sedimentation analyses: the temperature-rising stage and the warm stage. The latter involves two temperature-falling periods, which could be the major factor causing sea-level fall during that time.
Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P