西藏多龙矿集区水系沉积物地球化学数据定量分析与解释OACSCDCSTPCD

Geochemical data are typical compositional data and their closure effect exists in the rock major elements as well as in all trace elements and their arbitrary subsets. However, the closure effect is often ignored in many cases. Ten porphyry and epithermal Cu-Au deposits were recently found in Duolong mineral district, northwest Tibet, China. There are still great prospecting potential of copper resources in Duolong. The geochemical data of the stream sediment in Duolong were analyzed using Minimum Message Length-Expectation Maximization Algorithm ( MML-EM) and Isometric Logratio Transformation ( ILR) based on principal component analysis. It is found that all the fifteen elements data contain two log-normal populations. The high-average population of most elements reflects the multiple magmatic activities or hydrothermal processes in Duolong. The closure effect was overcome after ILR transformation and the element associations in the first principal component were interpreted to be indicators for the Cu-Au mineralization potential in Duolong. The areas with high scores of the first component are consistent with most of the found Cu-Au deposits and the alteration zones exposed at surface. Four zones with high scores are suggested for further investigation on their mineral potential.