伟晶岩矿床示踪造山过程的研究进展

ADVANCE IN THE STUDY OF USING PEGMATITE DEPOSITS AS THE TRACER OF OROGENIC PROCESS

国内外伟晶岩及伟晶岩矿床的研究比较薄弱,对于伟晶岩矿床在造山过程中的示踪更是知之甚少。但是,与花岗岩和玄武岩可以指示构造演化一样,伟晶岩及其相关矿床同样可以作为构造演化尤其是造山过程的示踪标志。世界上伟晶岩矿床最集中的阿尔泰地区从加里东期到海西期、印支期、燕山期均有伟晶岩及伟晶岩型矿床形成,并具有从早到晚矿床规模越来越大、元素组合和矿物组合越来越多、伟晶岩分带越来越完善、矿种从加里东期比较单纯的白云母矿床向燕山期超大型综合性矿床演化的规律,主要的成矿阶段发生在各造山运动之后相对宁静的时期。国内外其它地区也有类似的情况,因此,伟晶岩矿床尤其是规模大、分带性好、矿种多元素全的矿床代表了造山后的产物。

Compared with deposits genetically related to granites or basalts, the study of pegmatite and its related deposits is very defective. The knowledge of pegmatite as a tracer of orogenic process is needed. In fact, as the granite and basalt can be used as good tracers of tectonic evolution, pegmatite and pegmatite-type deposits can also be used to trace the tectonic history especially the continental orogenic process. The Altay metallogenetic province is one of the most important pegmatite province in the world, with pegmatites formed in Caledonian, Hercynian, Indo-Sinian and Yanshanian. It shows a clear regularity that the largest pegmatite-type rare metal deposits formed at the last, i.e. Yanshanian, stage, with a most complex structure of pegmatite vein and most comprehensive mineral and element assemblages. So, even pegmatite can form at different stage of the continental evolution, the most evolved pegmatite and most important pegmatite-type rare metal deposits formed at the relative silent stage of the orogenic process, because melt-fluids can only concentrate and contribute to forming a well-zoned pegmatite vein at an even environment, instead of at a tectonically active environment during the peak stage of orogeny. Similar examples can be found at different orogenic belts around the world. Therefore, pegmatite deposits, especially the larger, well-zoned deposits with multi-elements and complex mineral assemblages usually represent the product of post-orogeny.