伊犁盆地南部新构造特征及其对砂岩型铀矿的控制作用

NEOTECTONICS IN SOUTHERN YILI BASIN AND ITS CONTROL OF SANDSTONE-TYPE URANIUM DEPOSITS

伊犁盆地新构造运动研究在该区铀矿研究中占有很重要的地位。本文通过新构造基本特征的描述、擦痕和节理的统计分析、构造产物的ESR(电子自旋共振)测年等手段研究了伊犁盆地新构造运动特征,并探讨了其对铀矿形成和展布的控制作用。研究表明,新构造以断裂构造为主,是区域近南北向挤压应力作用的结果;结合前人研究成果,可以将伊犁盆地新构造运动分为五期始新世晚期-渐新世、中新世、上新世末期-早更新世、早更新世-中更新世、中更新世至今。新构造活动与铀成矿作用有时间上的一致性,并控制了伊犁盆地南部砂岩型铀矿的形成和展布,尤以东西向断裂对铀矿的控制作用最为明显;与新构造作用东强西弱相对应,西部的成矿条件比东部好。

Research of the neotectonic activities forms an important part of the research of the uranium mineralization in the Yili basin. In this paper the characteristics of the neotectonic activities and the neotectonic control of the uranium mineralization in the Yili basin are studied, the basic characters of the neotectonic activities are described, the neotectonic scratches and joints are statistically analyzed and the neotectonic activities are dated by using the ESR technique. The analytical results show that the neotectonic activities resulted from the nearly north-south-trending compressional stress in the region. Based on previous research results, the neotectonic activities in this area can be divided into five evolution stages： late Eocene to Oligocene, Miocene, late Pliocene to early Pleistocene, early Pleistocene to Mid-Pleistocene, and Mid-Pleistocene to now. Our research demonstrates that the sandstonetype uranium mineralization is closely related to the neotectonic activities, and that the neotectonic activities control the distribution of the sandstone type uranium deposits, and especially the east-west-trending faults. Based on the characteristics of the neotectonic activities, it can be concluded that the ore-forming conditions and hence the prospecting perspective in the west part are better than those in the east part.