摘要
江西相山铀矿田是我国目前最大的火山岩型铀矿田 ,一直是铀矿地质学界的研究热点之一。大量的新资料支持以下的构造演化模式 :成矿前的走滑剪切 ;成矿期的伸展拉张 ;成矿后的挤压逆冲。这一构造演化体系是形成相山富大铀矿田的有利地质构造背景。
The uranium ore field in Xiangshan of Jiangxi province is the largest uranium ore field of volcanic rock type in China. In this paper, the authors will present a tectonic evolution model for the uranium ore field, which is supported by new geological data. The Dexing-Shuichuan deep fault is an important tectonic unit separating the Yangtzi plate from the South China plate. This fault zone recorded a multiphase tectonic and deformation history from the Neo Proterozoic to the Mesozoic-Cenozoic and directly controlled the formation and evolution of the large scale uranium ore field of the Mesozoic volcanic rock type in Xiangshan area. Our study was primarily focused on the constraining of tectonic evolution on the formation of rich and large uranium deposits during the Mesozoic-Cenozoic Period. The Dexing-Shuichuan deep fault zone had subjectede to a complex geodynamic process during the Mesozoic. Three stages of brittle deformation closely related to the formation and richness of Xiangshan uranium deposits have been confirmed by structural and geophysic evidences, which are (1) the strike slip shearing in pre metallogenic stage, (2) the extensional process during metallogenic stage and (3) the compression thrusting in post metallogenic stage. The brittle sinistral strike slip shearing along the NE trending fault zone occurred in the Jurassic and yielded a pull apart stress field, leading to the formation of a series of the Late Jurassic NE striking volcanic basins and granitic bodies. The transversal overturned fold and horsestone rotated structures were well developed. The brittle extensional processes of northwest to southeast started in the Late Cretaceous when the strong strike slip deformation ended. Extensional deformation, characterized by structurally siliceous zones, fault breccia, tensional quartz veins and some basic dykes, caused an elevation of uranium -bearing hydrothermal toward the surface. This tectonic stage corresponds with a major metallogenic period of uranium deposits in the Xiangshan area. During the Paleozoic, a compression stress field replaced the extension stress field. The compressional deformation was marked by cleavages, thrust faults and locally dynamical metamorphic rocks along the Dexing-Shuichuan fault zone. The Sinian deformed metamorphic rocks were thrusted from southeast to northwest over the Late Cretaceous red sandstone and shale along a SE dipping fault. Thrusting played an important role in protecting the uranium ore deposits. The geodynamic evolution is also discussed in this paper. The Mesozoic-Cenozoic tectonic evolution from the strike slip to the extension and then to the thrust is probably a result of intracontinental deformation caused by oblique subduction of the Pacific plate under the East Asian continent during the middle and Late Jurassic, the back arc extension during the Late Cretaceous and the collision between the Asian and Philippine plates during the Tertiary.
出处
《高校地质学报》
CAS
CSCD
1999年第4期418-425,共8页
Geological Journal of China Universities
基金
教育部博士点基金
国家自然科学重点基金!(编号 4 963 2 0 80 )资助项目
关键词
构造演化
中生代
新生代
铀矿床
形成制约
tectonic evolution, uranium deposits, Mesozoic—Cenozoic, Xiangshan of Jiangxi
