摘要:

AbstractThe Qinghai‐ Xizang (Tibet) Plateau and the “Sanjiang” area2, where are extensively developed the Tethys‐type marine Triassic sequences with Indosinian tectonic disturbance and magmatism, provide an important region for the study of the tectonic evolution and the Indosinian movement of China as well as for the study of the boundary between Gondwana and Laurasia and the characteristics of the time‐space distribution of the Tethys oceanic crust within the territory of China. Over a long period of time in the past, quite a number of scholars made substantial studies and discussions from various viewpoints on the geotectonic and regional geological evolution of this region. Based on some new data obtained recently and the field observations by the author, and by using the plate tectonic theory, the author considers that there developed a Pacific‐type (active type) ancient continental margin bordering the Palaeo‐Tethys ocean (or North Tethys ocean) in the south in Late Permian to Triassic times in the region of south‐central Qinghai, northeastern Xizang (Tibet), western and southwestern Sichuan, and western Yunnan. Its characteristics basically represent the Indosinian tectonic evolution

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001001.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractIn Guangxi, the Lower‐ Middle Devonian boundary beds yield abundant corals, brachiopods, stromatoporoids and conodonts. The former three were common in tropical and subtropical zones, while the last occurred only round the equator. This reveals that the South China Plate in the Early‐Middle Devonian was at or near the equator, which was also supported by palaeomagnetic study giving the palaeolatitude of the Guangxi Region at the time to be 0 ° 3

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001002.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractA new exsolved copper‐iron‐sulfur phase in sphalerite has been found in the Dajing cassiterite‐sulfide copper‐silver‐tin deposit, Inner Mongolia, China. After investigating the optical properties, chemical composition, crystal structure and exsolved characters of the exsolved phase, the authors present important evidence for its being a new exsolved copper‐iron‐sulfur phase mineral. Its formation mechenism is discussed in considering heating experiments, phase equilibrium data and the geology o

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001003.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractOn the basis of previous studies and by means of field geological, remote sensing, petrographical, mineralogical, petrochemical and geochemical investigations, the authors studied the temporal‐spatial distribution of the regional structures, volcanic structures and products of volcanic activity in the coastal area of southeastern Zhejiang. On the basis and through a systematic comparison of the products of magmatism in the area, it is considered that there exists a compsite volcanic structural belt composed of linear and circular structures and it has been demonstrated that there exist volcanic intrusive complexes‐“trinity” composed of volcanic, subvolcanic and plutonic rocks. It is suggested that the volcanic intrusive complexes in the area belong to, the typical syntexis series and that its materials were derived from a mixed source of crust and

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001004.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractCopper and tin in cassiterite‐sulfide deposits of the Gejiu metallogenic province are intimately associated and show peculiar primary metal zoning. The authors made use of computer techniques to simulate numerically the zoning of these ore deposits. The study shows that the regular spatial zoning probably resulted from the succession of multiple, intermittent and pulsatory mineralizations. The successive transports with diverse velocities along channelways of the ore‐forming solutions, taking place under conditions of definite difference between metal concentrations, in solutions and wallrocks, followed by differential deposition, constitute possible dynamic mechanisms for the primary metal zon

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001005.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractThe bauxite in northern Guizhou is shown by its unique palaeokarst forms and weathering textures and structures to be of palaeokarst‐weathering origin. On the basis of detailed studies of the sections of the bauxite deposits, the genetic types of minerals, the hydrogen and oxygen stable isotopic composition of diaspore and compositions of parent materials, the writer has revealed that Early Carboniferous laterization was the main mineralizing stage of the bauxite, and the various mineralizing processes dominated by desilication and iron‐separation created an excellent time‐space environment for the formation of the ba

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001006.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractIn this paper, the evolutional characteristics of palaeoclimate and oxidation‐reduction conditions as well as acidity‐alkalinity environment are discussed by means of the step‐regression, cluster, optimal partitioning and correlation analyses of CaCO3, C / P2O5, Fe2+/ Fe3+, pH and Eh values, taking the Xiaodukou section in the Nihewan basin as an example. The CaCO3, C / P2O5and pH were calculated respectively using the optimal partitioning method. Thus five cold zones and six warm zones as well as five reduction and six oxidation zones were distinguished. Then the inductive method was used to produce four numerical groups: 8.10, 8.3–8.4, 8.6–8.7 and 8.9–8.97. The above‐mentioned results are respectively based on CaCO3content, C/ P2O5and pH values. From Fig. 3, Tables 1 and 2 it can be seen that the Nihewan Beds were formed mainly under a reduction and slightly alkaline environment of cold climate, with pH values of 8.3–8.4. Fig. 3 shows that bed 35 is approximately near the boundary between the Brunhes and Matuyama polarity epochs, 0.73 Ma in age; bed 26 is roughly near the Jaramillo event (base), 0.97 Ma in age; bed 18 coincides roughly with the magnetostratigraphic boundary of 2.00 Ma (?). Bed 13 may be the Pleistocene‐Pliocene boundary, 2.48 Ma in age. Thus geochemical zones I, ?, IH and IV include respectively cold zones 1;

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001007.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo terranes formed since the Late Palaeozoic can be distinguished in southwestern China. One is characterized by the Permo‐Carboniferous ice‐rafted marine gravel‐bearing clastic formation and the cold‐water fauna of the Gondwana facies, including the Gangmar Co, Lhasa, Sa ' gya, Tengchong and Baoshan terranes and the other is marked by the Upper Palaeozoic of the Yangtze type with the Cathaysian flora and the Pacific‐type fusulinids, comprising the Changning‐Menglian, Shuangjiang‐Lancang, Qamdo and Bayan Har terranes. The Longmu Co‐Shuanghu‐Dêngqên‐North Lancang River‐Kejie‐Mengding suture zone between the two groups of terranes is the boundary between Gondwana and Pacifica in southwestern China. On the grounds of the sedimentary formation and successive southwestward migration of the Asian nonmarine Jurassic‐Cretaceous endemic bivalves, the ages of the suture and some terranes to the southwest of the suture zone are discussed. The Baoshan terrane and the Nyainrong‐Sog terrane in the Lhasa composite terrane were firstly pieced together with the Asian continent in the early Early Jurassic. The northern Tibet‐western Yunnan microplate, including the Gangmar Co, Lhasa and Tengchong terranes, collided with the Asian continent at the end of

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001008.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Meishucun secton has been recommended as an international candidate stratotype secton of the Precambrian‐Cambrian boundary. The paper deals with the palaeomagnetic study on the section. A total of 159 palaeomagnetic samples were successively collected from the platform‐facies sequence of carbonates and phosphates at the section. Thermal demagnetization results indicate a great majority of the rocks at the section have been strongly overprinted by recent magnetic field, but 57 samples have preserved remanent magnetization with antipodal directions (mean D /1 = 4.2 ° / 7.1 °, K= 9, α95= 6.6 ° ). Baaed on calculation, the location of the palaeomagnetic pole was at 68.8 ° N and 270.7 ° E, which is different from any palaeopoles obtained from younger Phanerozoic rocks in South China. The results reveal a polarity zonation which includes at least 9 reversal events. A comparison of China' s magnetostratigraphic records with those from Siberia, Australia and the western U.S.A. shows that all the sections are characterized by frequent polarity r

ISSN:1000-9515    

DOI:10.1111/j.1755-6724.1991.mp4001009.x

出版商:Geological Publishing House    

年代:1991

数据来源: WILEY