硫、铅同位素对地表土壤微细粒金属全量测量异常的示踪——以水银洞卡林型隐伏金矿体为例

Sulfur-lead isotopes based tracing of the metal element anomalies identified in the total metal measurement of surface fine-grained soils: A case study of the Shuiyindong Carlin-type concealed gold deposit

在覆盖区寻找隐伏矿床是解决目前资源困境的重要途径之一。国内外所发展的深穿透地球化学方法对已知隐伏矿床开展了大量试验研究,取得了较好的效果。由于无法确定地表金属元素异常是否直接来自深部矿体,使上述方法未在未知覆盖区开展广泛的找矿工作,因此急需发展地表异常示踪技术。贵州水银洞金矿是我国超大型全隐伏的卡林型金矿床,成矿流体富含S、Au、As、Sb、Hg等元素。本文以该矿床为研究对象,采集地表微细粒土壤样品,分析5种微量元素(Au、As、Cu、Sb、Hg)的含量,以验证微细粒土壤全量测量技术在该矿床的找矿效果,并用S、Pb同位素识别地表土壤异常来源。研究发现:(1)微细粒土壤测量技术在该矿区的指示效果好,Au-As-Sb-Hg高异常区与隐伏矿体和断层的分布较为吻合,其中Hg对隐伏矿体的指示效果最好;(2)隐伏矿体及断层上方土壤中δ^(34)S值、放射成因的w(^(207)Pb)/w(^(204)Pb)和w(^(206)Pb)/w(^(204)Pb)显著高于围岩区土壤,可有效示踪地表微细粒土壤中的异常来自于深部的隐伏矿体。该研究为在同类型覆盖区用微细粒土壤全量测量技术寻找隐伏卡林型金矿提供了理论依据。

Exploring concealed deposits in covered areas is an important way to solve the current resource dilemma.Extensive experi-mental studies using the deep-penetration geochemical methods developed at home and abroad have been conducted targeting some known concealed deposits,yielding satisfactory results.However,these methods have yet to be widely employed for prospecting in un-known covered areas due to the failure in determining whether surface metal element anomalies are directly from deep ore bodies.Ac-cordingly,it is urgent to develop a tracing technique for surface anomalies.The Shuiyindong gold deposit in Guizhou Province is a su-per-large fully-concealed Carlin-type gold deposit in China,and its ore-forming fluids are rich in elements such as S,Au,As,Sb,and Hg.This study sampled surface fine-grained soils in the Shuiyindong gold deposit for the concentration analysis of five trace elements(Au,As,Cu,Sb,and Hg),verifying the prospecting effect of the total metal measurement technique of fine-grained soils in this de-posit.Moreover,the source of surface soil anomalies was identified using sulfur(S)and lead(Pb)isotopes.This study found that:①The total metal measurement technique of fine-grained soils showed encouraging indicative effects,with the high Au-As-Sb-Hg a-nomalies obtained roughly consistent with the distribution of concealed ore bodies and faults,and Hg exhibited the best indication effect on concealed ore bodies.②Theδ^(34)S values and the ratios of radiogenic w(^(207)Pb)/w(^(204)Pb)and w(^(206)Pb)/w(^(204)Pb)in the soil a-bove concealed ore bodies and faults were significantly higher than those in the soil of the surrounding rock area,effectively indicating that the anomalies in the surface fine-grained soils were from deep concealed ore bodies.This study provides a theoretical basis for ex-ploring concealed Carlin-type gold deposits in the same type of covered areas using the total metal measurement technique of fine-grained soils.