闽西南坳陷带中生代地质历史演化与钼矿床成矿时代

Molybdenum deposit metallogenic epoch and Mesozoic geological history evolution in the depression basin of southwestern Fujian

闽西南坳陷带是特提斯构造域向环太平洋大陆边缘构造域转换的典型地区,又是华南地区主要的钨、铜、钼、金、银、铁和稀土成矿带.初步总结了闽西南坳陷带中生代钼矿床的类型、空间分布特征和成矿时限,阐述了区域地质构造与演化、岩浆作用的期次及岩石系列组合,探讨了钼成矿系列问题以及区域构造—岩浆—成矿之间的关系.研究表明,闽西南坳陷带钼成矿作用主要发生在165～145 Ma、135～115Ma和115～105 Ma三个时间段,分别对应的构造环境为挤压、伸展扩张及扩张增强和裂解阶段.这三个阶段的成矿作用分别形成于华南和华北地块后碰撞及太平洋板块向欧亚板块东南缘俯冲引起弧后多阶段岩石圈伸展构造环境.

The depression basin of southwestern Fujian is not only a typical transitional area from Tethyan tec- tonic regime to Pacific epicontinental tectonic regime, but also is one of the most important metallogenic belts in South China, which comprises plenty of W, Cu, Mo, Au, Ag, Fe and REE ore deposits. In this paper, the type, spatial distribution character and the time of molybdenum mineralization are preliminarily concluded. The regional geological structure and its evolution, the phase of magmatism and its rock series assemblage are described, and the molybdenum metallogenic series and the relationship among metallogeny, tectonic setting and magmatism are also discussed. According tO the available high precisely geochronological data, it is proposed that there are three pulses of molybdenum mineralization in the depression basin of southwestern Fujian, i.e. 165-145 Ma, 135-115 Ma and 115- 105 Ma, which is corresponded to the compression, the extension expanding and the break-up tectonic settings respectively. The three mineralization pulses are related to the tectonics of post-collision between Yangtze craton and North China craton, and the multistage lithospheric extension of the back arc caused by the Pacific plate subducting to the southeastern margin of the Eurasian continent.