华南地区中生代以来岩石圈伸展及其与铀成矿关系研究的若干问题

Some problems concerning relationship between Mesozoic-Cenozoic lithospheric extension and uranium metallogenesis in South China

华南地区中生代以来存在大规模的岩石圈伸展作用,与伸展作用相对应,形成了大量花岗岩型、火山岩型和碳硅泥岩型铀矿床。文章详细总结了华南中生代以来岩石圈伸展作用和铀成矿作用的研究进展。通过系统分析,认为要深刻揭示岩石圈伸展与区域铀成矿的关系,至少尚有两大重要科学问题未解决:其一是华南白垩纪—第三纪岩石圈伸展和铀成矿的准确期次及其空间迁移规律;其二为岩石圈伸展期铀成矿的必然性或铀为什么会集中在岩石圈伸展期成矿。要解决第一个问题,需要对铀矿床和岩石圈伸展期形成的基性脉岩开展系统的高精度定年工作;要解决第二个问题,则需要系统研究成矿流体中CO2等气体组分在铀成矿中的作用及其成因。

Previous studies have shown that there existed large-scale lithospheric extension events during the Cretaceous-Tertiary period in South China, and that large-scale uranium mineralization occurred at the same time in this area, which resulted in the formation of many important uranium deposits such as granite-hosted, volcanicshosted and Carbonaceous-siliceous-pelitic sedimentary rock-hosted ones. This paper reviews previous researches on lithospheric extension and uranium metallogenesis in South China since Mesozoic, and preliminarily discusses their temporal and spatial associations. In order to precisely reveal the relationship between lithospheric extension and uranium metallogenesis, it is suggested that at least two fundamental problems should be solved. The first is the accurate episodes of extension and uranium mineralization, and the second is the mechanism governing the control of the tectonic regime over the formation of the uranium deposits. To probe into these problems, it is necessary to accurately date the uranium deposits and the mafic dikes intruded during the Mesozoic extension and to determine the role and origin of gaseous components such as CO2 in ore-forming fluids.