In honour of the 90th Anniversary of the Birth of Prof.Li Si-guang(J.S.Lee),One of the Outstanding Scientists in China……Edited by the Editorial Board of the Institute of Geomechanics,China Problems about the Structural Control of Rocks and Ores and the Structural Petrogenesis and Metallogenesis Yang Kai-qing A Possible Mechanism of En Echelon Arranged Equidistant Fractures Wang Lian-jie An Experimental Study of the Relation between the Present State of Stress and the Tangshan Earthquake,July 28,1976 Huang Qing-hua,Wang Yan-qing A Preliminary Discussion on the Characteristic Stress Field and Its Trend of Migration in the District of Beijing,Tianjin and Tangshan…Shen Shu-min Brief Notes on the Structural Control of Mineral Deposits Liu Xun,Sun Bao-shan Tectonic Environment for the Formation of Diamond Ore——An Example in China Li Shang-huai The Characteristic Distribution of Some Chemical Components in Qi-jia Shan,Anhui and Its Bearing upon Ore Exploration Yin Hua-ren et al. Structural Systems in Northern Guangdong and Their Bearing upon the Preservation of Late Palaeozoic Coal Series Ning Chong-zhi et al. Determination of Petrofabrics with X-ray Technique Jiang Guang-xi et al. A Study on Xi-type Structural System Zhang Guo-duo Reports and Discussions On the Possibility about the Variation of Earth's Rotation to Produce Tectonic Movements Wang Ren,Ding Zhong-yi Characteristic Features of the Tancheng-Lujiang Fracture Zone Deng Nai-gong Some Problems Concerning the Cathaysian Structural System (On Behalf of the Map Compilation Group,lst Division,Institute of Geomechanics)Li Shu-jing