1983 Vol. 5, No. 3

Display Method:
PROBLEMS ON THE TECTONICS OF CHINA
Huang Jiqing
1983, 5(3): 165-169. doi: 10.11781/sysydz198303165
Abstract:
This article puts forward several arguments as follows, 1. The three development stages of Pangea suggested by Prof. Zhu Xia in his latest works are feasible for the tectonics of China. Their corresponding structural frame works show themselves on Chinese mainland. 2. Characteristics of plate tectonics of Chinese mainland are discussed with stress on the multicyclic and accordion-like movements. By making comparison of the folded belts of China's Qilian and Mongolia with the Variscian folded belts of western Europe and northern America, it is suggested that the Variscian folded belts can not fully fit with the four main signs of plate activity. Prof. Zhu Xia proposes that the regime of plate tectonics took shape posterior to Pangea A, and the regime of trough-platform dominated during Paleozoic time. To this statement,I can not take a clearcut stand because I have not made a thorough study on it. 3. The structural frame works of the Qinghai-Tibet, western Sichuan nd western Yunnan are briefly described here. It is most likely that the bordering between Gondwana and paleo-Eurasian is the ophiolitic belt stretching from Longmucuo-Yushu to Changnin-Shuangjiang. 4. The oil and gas prospecting in China should be focused on the Mesozoic of the eastern China.
COGNITION ON THE SEDIMENTARY ENVIRONMENT OF DA’ANZHAI MEMBER, NORTH SICHUAN, AND ITS SIGNIFICANCE IN OIL EXPLORATION
Wang Dangqi
1983, 5(3): 170-176. doi: 10.11781/sysydz198303170
Abstract:
The lacustrine Da'anzhai member of Northern Sichuan can be subdivided into two different sedimentary facies areas, To the north of Yonghe (Jiulong shan)-Fuyangba, there is the Baitianba facies area; and to the south of it, there is the Ziliujing facies area. The later, from the bottom tothe top, can be divided into three different sedimentary layers. The lower layer is of transgression sediments. It is mainly a suite of interbedding shell limestones and shales with equal thickness. The middle layer was deposited when the lake area reached its climax. It is mainly a suite of black shales intercalated with more or less argillaceous shell limestones. The upper layer is of regression sediments. It is mainly a suite of shell limestones intercalated with argillacous shales. The lacustrine Da'anzhai member of northern Sichuan consists of from north to south a series of beach, shallow water lacustrine, moderately-deep water lacustrine, deep water lacustrine sediments. The first surrounds the second, the second surrounds the third and etc., forming half ring-shaped belts or ring-shaped belts. The inner zone of the shallow water zone, which was adjacent to the moderately-deep water-deep water zones, always emerged above the wave base and received a shell deposit of high energy beach. The shell beach is a good reservoir for oil and gas, and lithological and/or structural-stratigraphic oil and gas pools were formed there. Therefore the objective for oil search in Da'anzhai member of northern Sichuan, should be a good geologic body with proper porosity and permeability in the inner shallow water zone around the moderately-deep water and deep water zones (oil-generating depression). This means the shallow water shell beach deserves to lay emphasis.
EXPERIMENTAL EVIDENCE OF THE GENERATION OF OIL-GAS IN PERMOCARBONIFEROUS COAL-BEARING STRATA OF NORTHERN ORDOS BASIN
He Zhongheng
1983, 5(3): 177-188. doi: 10.11781/sysydz198303177
Abstract:
In this paper, the problems of the generation of oil-gas in the Carboniferous-Permian coal-bearing strata of northern Ordos Basin are studied through the geochemical parameters of coal, mudstone, crude oil and natural gas, as well as the pyrolysis simulation test of coal. It is concluded that, (1) Terrestrial plant debris predominate in the abundant organic matter of the Carboniferous-Permian coal-bearing strata. The organic matter belongs to humuic type, containing much aromatic hydrocarbons and high pristane/phytane ratio offering low transformation efficiency and low potential for oil generation; (2) The natural gas and crude oil of Shihezi Formation are the products of the Carboniferous-Permian coal-bearing strata· In view of the carbon isotope fractionation occurred during the formation of gaseous molecules, the correlation between the isotopic and chemical compositions of reservoired gas and those of absorbed gas of coal bed is an effective method for identifying the source of thermogenic gas; (3) The formation of different combustible mineral products such as coal, petroleum and natural gas is in close connection with the composition of original organism possessing specialized chemical components. In coal series, the original organic matter is rich in lignin and cellulose, and the major pyrolytic products are gaseous hydrocarbons, while the potential of generating liguid hydrocarbons is limited. Therefore, the prospecting effort conducting in the Carboniferous-Permian coal-bearing strata of northern Ordos. Basin should be focussed on thermogenic gas.
COLOUR ALTERATION OF FOSSIL SPORO-POLLEN AND THE EVOLUTION OF ORGANIC MATTER
Zhu Shenzhao, Li Yongxing, Chang Yongying
1983, 5(3): 189-199. doi: 10.11781/sysydz198303189
Abstract:
The colour of fossil sporo-pollen is increasingly altered from light to dark with burial depth, pressure and temperature, when the temperature reaches a critical point, original organic matter is transfered into petro leum. Therefore, by means of the colourity of fossil sporo-pollen, the organic alteration stage can be inferred. In Dongpu Depression, on the basis of our research, a conclusion has been reached as follows, For yellow section, underground temperature is 65-93℃, the colour alteration indicates an immature stage. For brown section, 93-125℃, the colour alteration indicates a mature stage. For dark brown section, 125-151℃, the colour alteration indicates a highly-mature stage. For brown-black section, the underground temperature exceeds 151℃, the colour alteration indicates a supermature stage. The study of the colour alteration of fossil sporo-pollen is an important tool for inferring. The evolution of organic matter provides basic information for oil and gas exploration. For this reason, the colour alteration of fossil sporo-pollen can be taken as an indicator of petroleum generation.
REMOTE SENSING INTERPRETATION OF THE STRUCTURAL FRAMEWORK OF TARIM PLATFORM
Cheng Riyin
1983, 5(3): 200-207. doi: 10.11781/sysydz198303200
Abstract:
This article provides an interpret at ion of the mosaic photos of the Tarim platform taken from setellite. The Tarim platform is a rhombic block defined by the previously existing boundary rift system. The arcuate rift system can be divided into two groups, one trending NWW-SEE and the other NEE-SWW. Most of the rifts have been mapped by previous geological research. There develop an "X" shaped and a "Y" shaped rift systems within the platform. A Ruoqiang shear structure system appears in the southeastern part of the platform and an arcuate interlayer slipping system resulted from lateral compression develops in the peripheral areas. The tectonic history includes three stages, the first is the stage of formation and stabilization; the second is the stage of activation and disintegration and the third is the stage of superimposition and transformation. The present day structural framework is resulted from the tectonic movement of the latest stage, as it is more intensely transformed in the southern part as compared with the northern part, in the western part as compared with the eastern part and in the marginal areas as compared with the central part.
X-Ray Radiography Analysis of Massive Sandstone and a Discussion on Their Genetic Mechanism
Yu Jie
1983, 5(3): 208-213. doi: 10.11781/sysydz198303208
Abstract:
The term "massive sandstone" in this paper is designated to deseribe those sandstones which show no visible internal structures. X-ray radiography has provided to be a new method for the study of massive sandstones. Some of the massive sandstones show different kinds of stratification on X-ray exposures, but some of them remain structureless and homogeneous even under the radiation of X-ray. The former can be produced by vertical or lateral accretion and may be called "pseudomas-sive"; the latter are mainly formed by gravity flow and may be called "true massive". In the present paper, the principle and process of this method have been briefly introduced, and the genetic mechanisms of the two types of massive sandstones have been discussed in rather detail, exemplified by the Dainan Formation of northern Jiangsu, China. Finally, according to the associated sequences of sedimentary structures, several kinds of depositional environments which account for the formation of massive sandstones are recognized. The result of the study indicates that this method is of practical significance for identifying the sedimentary environments of reservoir rocks and for guiding hydrocarbon exploration.
1983, 5(3): 214-216. doi: 10.11781/sysydz198303214
Abstract: