TECTONIC FRAMEWORK OF THE CONTINENTAL BASEMENT OF SOUTHEAST CHINA

The chronology and tectonic evolution model of the continental basement in southeast China margin is an important debatable geological subject. The Cathaysia is shown in this paper to be in accordance with many geological facts and also with the age data obtained by multi-dating method. Its age has been determined to range from 900 to 2000 Ma. The age of the unconformity plane in the Cathaysia is 1400 Ma. The collision and suture between the Jiangnan oldland and the Cathaysia took place during the early Jinning Period. Toward Jiangxi, Hunan, Guangdong and Guangxi, these two continents gradually opened to form a residual oceanic basin. The sedimentation centre of the basin continuously migrated southwestward from the Jinning through the Caledonian Period, and finally closed in the Guangxi Movement and Dongwu Movement. The drift-rotation of the Cathaysia after the Jinning Period has been inferred.     

构造作用与瓦斯突出和超量煤层气

统计表明,煤矿瓦斯突出几乎都发生于剪切带(构造煤)中,与构造变形关系非常密切。构造煤中可能蕴藏着远超出最大吸附量的超量煤层气,正确认识其赋存状态,将是瓦斯突出机理和煤层气赋存理论的重要突破。作者及所在课题组近年来对两淮、沁水等地的构造煤进行了一系列的实验对比和研究。初步研究结果显示,韧性变形作用可以导致结构单元缺陷增加,不到10%的应变就足以使煤结构中的含氧基团或醚键发生降解并生成气态小分子。因此,含有大量低键能烷烃侧链的低煤阶煤,在构造变形作用下更容易发生降解,产生大量气体,当气体聚集到一定程度时就会发生瓦斯突出。另外,强变形煤纳米级孔隙的比表面积和孔容远大于原生结构煤,也可为超量煤层气提供可能的赋存空间。     

WAVE CHARACTERISTICS OF CRUSTAL TECTONICS IN CONTINENTAL MARGINS

Continental margins are the transitional zone between continents and oceans. The tectonic deformation of crust in continental margins is very complex. This paper deals with the complex crust tectonics of continental margins in terms of the basic principle that elastic waves travel through semi-infinlte medium and the wave theory of crust. The continental margin off the North American coasts of the Atlantic used to be the active Pacifictype margin. At present, the crust movement in this margin tends to be stable; therefore it becomes the Atlantic type.     

HEAT FLOW ON THE QINGHAI-XIZANG(TIBETAN) PLATEAU AND THE MODELING OF THE TECTONO-THERMAL EVOLUTION

Thirteen observed heat flow values in combination with relevant geological and geophysical information are employed in the current paper to conduct a model study by means of direct inversion. The modeling demonstrates the tectono-thermal evolution of the Tibetan Plateau during the last 40 Ma since the continent-continent collision. The authors stress the fact that the tectonic deformations of terranes are usually the inducing factors for the deep-seated thermal activities in the crust and upper mantle. On this basis a series of kinematic equations of 3-D deformations of terranes in forms of shortening-thickening-uplifting-erosion-mass sliding were deduced using the principle of plate kinematics. These equations are further used as systematically defined initial and boundary conditions for simulating the integrated processes of tectono-thermal evolution, The results of the model study suggest that there exist sharp differences in the tectono-thermal evolution between the old northern terranes and the new     

Tidal stress triggering effects of earthquakes based on various tectonic regions in China and related astronomical characteristics

Dividing the mainland China into different tectonic stress regions, we calculate tidal stress components along the seismic compressive and extensional principal stress axes at every earthquake’s focus in different tectonic stress regions. Tidal stress triggering effect on every earthquake fault is analyzed. Based on this, the lunar-solar location parameters on the occurring times of earthquakes which suffered tidal triggering effects are calculated, and the distribution patterns of the lunar-solar location parameters in different tectonic stress regions are obtained. The results indicate that earthquake tidal triggering effects and related astronomical characteristics are dependent on the properties of regional tectonic stress and the geographic locations of earthquake faults. Supported by the National Natural Science Foundation of China (Grant No. 40764001)