铅硫同位素在地球化学勘查中的应用

The application of lead and sulfur isotopes to geochemical exploration

铅硫同位素用于地球化学勘查是一项探索性的工作。为进一步证实其在多金属矿床勘查中的作用,选择热液铅锌矿床开展铅同位素追踪深部矿体试验,选择斑岩型铜矿床开展硫同位素识别矿化蚀变分带试验及δ34S垂向变化规律探讨。试验结果表明,铅同位素组成和三维拓扑V值可预测深部矿体,由上而下,数值增高预示着深部还有矿体;水平方向上,δ34S均值由高温蚀变区到低温蚀变区呈现出增高的趋势,此特点可用于鉴别矿化蚀变分带;垂直方向上,矿体δ34S均值总体随深度增加逐渐增大,若不同层位(标高)的岩石性质及其硫同位素背景存在差异,当其与成矿溶液叠加后,可导致δ34S均值呈跳跃式变化。

The application of lead and sulfur isotopes to geochemical exploration is still at the stage of exploratory work. In order to further confirm its effect on the exploration of polymetallic deposits,the authors selected a hydrothermal lead and zinc deposit to trace deep orebody by means of Pb isotope and a porphyry copper deposit to detect alteration zoning by means of S isotope and,on such a basis,discussed the δ34S vertical regularity. The test results demonstrate that Pb isotopic composition and V value of three-dimensional topology can predict deep orebodies,the V value increases from the top to the bottom,suggesting the existence of orebodies in the depth. Theδ34S mean value in the horizontal direction shows increasing tendency from the high-temperature alteration area to the low-temperature alteration area,and these characteristics can be used to distinguish mineralization and alteration zone. General speaking,the δ34S mean value gradually increases with depth in the vertical direction,there are differences in rock properties and the background values of S isotope in different horizons,and the stacking of the rocks and ore-forming solution may lead to the saltatorial change of the δ34S mean value.