地表土壤微细粒测量中微量元素和同位素对福建罗卜岭隐伏铜钼矿床的示踪与判别

Tracing and identification of concealed Luoboling copper-molybdenum deposit in Fujian Province using trace elements and isotopes in fine-grained surface soils

在已知隐伏矿——罗卜岭斑岩型铜钼矿床上方采集了表层土壤以及典型钻孔中的矿石和围岩样品,分析了6个微量元素(Cu、Mo、Ba、Pb、Zn、V)的含量变化以及硫、铅同位素的组成特征,来验证土壤金属活动态测量技术、微细粒级土壤全量测量技术在隐伏矿区的找矿效果,并根据铅、硫同位素的组成特征来识别地表地球化学异常的来源。研究表明:微细粒级土壤全量测量技术对该矿区深部矿体的指示效果最好,其中Cu、Ba、Mo的含量高值区与深部隐伏矿体的展布相关性较强。土壤金属活动态、微细粒级土壤全量均显示出14、15号采样点下方极有可能存在着隐伏矿体,同时两种测量方法均可以根据V、Pb、Zn的含量变化较为准确地圈定出接近地表矿化岩体的范围。由于异常区土壤全量的硫同位素组成大多数信息继承自非赋矿围岩,掩盖了来自深部矿体的贡献,故在本矿区用硫同位素指示地表土壤中的异常来源效果较差,建议测量土壤金属活动态中的硫同位素组成应更为合理。异常区土壤全量的铅同位素继承了来自深部矿体铅同位素的特征,直接为微细粒级土壤全量测量技术在覆盖区的矿产勘查提供了证据,同时^(206)Pb/^(204)Pb在地表微细粒级土壤全量中的变化与下伏隐伏矿体的展布相关性较强,可以有效指示深部隐伏矿体。

This paper collected surface soil above the known concealed deposit the Luoboling porphyry-type copper-molybdenum deposit and acquired samples of ore and surrounding rocks from typical boreholes of the deposit.Then,it analyzed the changes in the contents of six trace elements(Cu,Mo,Ba,Pb,Zn,and V)and the isotopic composition of S and Pb,aiming to verify the ore prospecting effects of the measurement technology of mobile forms of metals in soil and full analysis of fine-grained soil in concealed deposits and to identify the sources of surface geochemical anomalies according to the isotopic composition of Pb and S.The study results are as follows.The total analysis of fine-grained soil showed the best effects in indicating deep ore bodies in the Luoboling deposit,and the areas with high contents of Cu,Ba,and Mo correlated strongly with the distribution of deeply concealed ore bodies.Both the mobile forms of metals in the soil and the total analysis of fine-grained soil showed that it is quite possible that concealed ore bodies occur below sampling points No.14 and 15.Meanwhile,the changes in the contents of V,Pb,and Zn obtained using both methods can accurately delineate the scopes of mineralized rock masses close to the ground surface.However,most of the total sulfur isotopic composition in the soil of anomaly zones inherits from the non-ore-hosting surrounding rocks and masked the contribution from the deep ore bodies.Consequently,sulfur isotopes showed poor effects in indicating the sources of anomalies in the surface soil in the Luoboling deposit.Therefore,it is more reasonable to measure the sulfur isotopic composition according to the mobile forms of metals in the soil.In contrast,the total Pb isotopes in the soil of the anomaly zones inherit the characteristics of the Pb isotopes of deep ore bodies.This serves as direct evidence of full analysis of fine-grained soil in the mineral exploration of coverage areas.Moreover,the changes in the ^(206)Pb/^(204)Pb ratio in the full analysis of surface fine-grained soil correlated strongly with the distribution of underlying concealed ore bodies and thereby can effectively indicate the deep concealed ore bodies.