地幔柱的概念、分类、演化与大规模成矿——对中国西南部的探讨

自核幔边界上升的物质 ,当其汇聚成圆柱状的结合体 ,并因其相对于周围地幔环境来说具有温度更高、活动性更强、粘度更低等特点而能够上升到壳幔边界时 ,一般可以演化成为具有宽厚的冠状构造和细长的尾部构造的地幔柱。地幔柱进一步与地壳发生作用 ,可以在地表记录下一系列的热点或形成巨大的火成岩省。根据地幔柱最后出露的位置 ,可以将其分为洋壳和陆壳环境下产出的两种基本类型 ,也可以根据其演化历史分出不同的阶段 ,如初始阶段、上升阶段、成熟阶段和衰退阶段。中国西南部地区可能经历了两次以上的地幔柱冲击 ,二叠纪的峨眉山玄武岩是一个古生代晚期演化比较彻底的地幔柱留下的记录 ,而新生代以来的地幔柱活动可能正在发育 ,深部物质的大规模上隆可能是青藏高原隆升的一个原因 ,大量的散布的幔源岩浆活动和流体作用可能是中国西南部大规模成矿作用的重要原因。

BASIC CONCEPT, CLASSIFICATION, EVOLUTION OF MANTLE PLUME AND LARGE SCALE MINERALIZATION--PROBE INTO SOUTHWESTERN CHINA

Mantle plume is usually referred to a large amount of materials originated from the mantle/core boundary, with characteristics of higher temperature, lower viscosity and more active than its surrounding mantle, which has a general shape of plume within the mantle and evolves into a mushroom shape with a large head and a small tail beneath the crust. After the interaction between mantle plume and crust, a trail of hotspots and a large igneous province will be formed by mantle plume on the surface of the Earth. Two basic types of mantle plumes can be identified according to their final environment (continental or oceanic), and a typical mantle plume will evolve from initial stage, to ascending stage, to mature stage and to waning stage. Southwestern China might have been affected by two mantle plumes, i.e. the Permian Emei mantle plume and the Cenozoic mantle plume. The former fossil plume has waned and produced the Emei large igneous province, while the later adolescence plume is swelling up and has produced a lot of mantle-originated magmatism, regional fluid movement, and large scale mineralization in southwestern China.