金属元素形成原生晕能力定量评价--以青海省扎家同哪金矿为例

Quantitative evaluation of the ability of elements in forming primary halos:A case study of the Zhajiatongna gold deposit,Qinghai Province

在进行原生晕元素分带研究时,所选元素多未进行筛选,不利于正确认识分带规律及指导矿产预测。本文基于扎家同哪金矿2779个钻孔样品数据,拟通过定量评价不同金属元素在围岩、矿化围岩、矿石等中的富集程度,研究不同元素在矿化过程中形成原生晕的能力差异。研究发现,扎家同哪金矿Au、As、Sb、Hg、W、Ag在围岩、矿化围岩和矿石中富集程度递增,易形成原生晕,Zn仅在矿石中富集,成晕规模有限,Mo、Cu、Pb、Sn富集微弱或表现为亏损,较难形成原生晕;扎家同哪金矿不同位置与成矿有关的富集元素为Au、As、Sb(围岩)—Au、As、Sb、W、Hg(Ag)(矿化围岩)—Au、As、Ag、Sb、W、Hg、Zn(矿石),成矿过程中元素在矿化围岩中富集的权重由大至小为As、Hg、Au、Sb、W、Mo、Sn、Pb、Zn、Cu、Ag,进入围岩能力总体表现为低—高—中温元素递减的趋势。对于扎家同哪金矿,在研究原生晕分带特征、指导进一步找矿时,宜优先选用As、Hg、Au、Sb和W等元素。

A procedure to screen the elements used in the research on the elemental zonation in a primary halo is rarely conducted,which is not conducive to the acquisition of an accurate understanding of the rules of elemental zonation.In this paper,the authors chose the Zhajiatongna gold deposit in Qinghai Province as a study case and aimed to study the difference between ore-forming metallic elements in the ability of forming a primary halo through comparing the elemental enrichment degrees in the wall rocks,mineralized wall rocks,and orebodies and on the basis of 2779 samples from the drill cores of the deposit.It is found that the concentrations of Au,As,Sb,Hg,W,and Ag progressively increase from the wall rocks through mineralized wall rocks to orebodies,indicating a greater possibility of forming a primary halo for these elements.Zinc is enriched only in the orebodies,with less possibility of forming a large-scale primary halo.Elements of Mo,Cu,Pb,and Sn show insignificant enrichment or even show depletion,indicating a less possibility of forming a primary halo.A trend of enrichment zonation of ore-forming elements was recognized:Au,As,Sb in the wall rocks,Au,As,Sb,W,Hg(Ag)in the mineralized wall rocks,and Au,As,Ag,Sb,W,Hg and Zn in the orebodies.Elements show a decreasing weight of enrichment in the mineralized wall rocks in order of As,Hg,Au,Sb,W,Mo,Sn,Pb,Zn,Cu,and Ag,suggesting the progressively decreasing ability of entering into the wall rocks from the orebodies in order of low-temperature metallogenic elements through medium-temperature metallogenic elements to high-temperature metallogenic elements.Therefore,in the Zhajiatongna gold deposit,elements such as As,Hg,Au,Sb and W are optimal for researches on elemental zonation and mineral prediction.