华南钨和锡大规模成矿作用的差异及其原因初探

A tentative discussion on differences between large-scale tungsten and tin mineralizations in South China

钨和锡都是中国的优势矿产资源,主要分布在华南尤其是南岭及其邻近地区,关系密切、相互共生,但两者之间仍然存在着很明显的差异。在空间分布上表现为东钨西锡:南岭东段,钨矿密集产出;中段,钨锡并重,但锡矿化明显增强;西段则为大规模锡成矿作用。在成矿时代上,钨和锡都以160～150Ma为成矿高峰期,但锡还有雪峰期、印支期成矿作用,以及燕山晚期的又一个成矿高峰期。锡的成矿作用及与其相关的花岗岩类显示出与地幔物质有较为密切的关系,因此,锡的大规模成矿作用或发生在有地幔物质参与的"十-杭带"附近,或发生在地壳强烈拉张的燕山晚期。钨与锡在元素地球化学性质上的差异,以及华南东、西两部分在构造背景、沉积物特征和岩浆活动等方面的差异,是造成华南钨与锡大规模成矿作用差异的根本原因。

Both tungsten and tin are the most prevailing mineral resources in China. Large-scale tungsten and tin mineralizations took place mostly in South China,especially in the Nanling Mountains and the neighboring areas. The two elements are very closely related to and accompanied with each other and always occur together in most ore deposits. However,differences do exist between tungsten and tin mineralizations in many aspects. Spatial distribution shows that the eastern sector of the Nanling Mountains is characterized by strong and dense W mineralization,while Sn mineralization becomes stronger westwards. China＇s two largest Sn ore deposits are distributed in the western margin of the South China fold system. Although both tungsten and tin mineralizations have the same highest ore-forming epoch of 160～150 Ma,the tin mineralization is spanned from the late Xuefeng Period （～800 Ma） to Late Yanshanian Movement （80 Ma）. The Late Yanshanian Movement is in fact another highlight of tin mineralization. The tin-bearing granite and tin mineralization show much closer relationship with the participation of mantle derived materials than tungsten mineralization. Therefore,the large-scale tin mineralization took place either near the so-called Shi-Hang Zone where long-term deep faulting was activated and A-type granites were emplaced or during the Late Yanshanian period when the South China continent was in a strong tensional geodynamic environment. The principal factors responsible for these differences may include the diversity of geochemical properties between the two elements and the differences in tectonic backgrounds,stratigraphic characteristics and magmatic activities between the eastern part and the western part of South China.