胶东蓬莱黑岚沟金矿床黄铁矿微区地球化学特征及对成矿流体的启示

胶东地区是中国最大的金矿集区, 金矿成因类型一直存在较大争议。黑岚沟金矿床是胶东蓬莱地区最大的金矿床, 曾以产出"明金"而闻名胶东。采用LA-ICP-MS方法分析黑岚沟金矿各成矿阶段黄铁矿中微量元素的组成、变化趋势及相关性, 探讨了Au的富集沉淀过程。通过野外地质调查, 结合矿相学和背散射图像观察, 将主成矿阶段(S1~S3)的黄铁矿(Py1~Py3)进一步划分为6个亚类; 通过微量元素分析发现, 研究区黄铁矿As含量高, 为富砷黄铁矿, 从早到晚, 黄铁矿中Cu、As、Ag、Au、Zn、Co、Ni、Pb、Sb、Bi等微量元素变化趋势不一致, As与Au在各阶段均呈现极强的正相关性, Cu-Zn、Ag-Sb等多对元素具有高的正相关性, Pb与Bi在Py1-1、Py2-1和Py2-2三个黄铁矿亚类中也具有较高的正相关性, 大部分黄铁矿亚类中Co与Ni存在正相关关系, Co/Ni元素含量比值为1.1~3.3, 说明黄铁矿主要为岩浆热液成因。黑岚沟金矿成矿流体是富Au-As流体, S1阶段与S3阶段微量元素相对富集, 说明成矿流体活动持续时间较长, 具有脉动式活动的特点, 金由多次活动的富Au-As流体多次沉淀成矿。

Micro-geochemical characteristic of pyrites in the Heilangou gold deposit of penglai area and its implications for ore-forming fluid,Jiaodong gold province

In China, the largest gold concentration area is Jiaodong, in which the genetic type of gold deposits has always been controversial.Heilangou gold deposit is the largest one in Penglai area of Jiaodong and was well-known for producing gold nugget.In this paper, LA-ICP-MS was used to analyze the composition, variation trend and correlation of trace elements in pyrite of Heilangou gold deposit, and to discuss the formation of Au.Through field investigation, combined with mineralogy and backscatter electron image(BSE), the pyrite(Py1~Py3)in the main metallogenic stage(S1~S3)is divided into six subtypes.Through trace element analysis, it is found that the change trends of Cu, As, Ag, Au, Zn, Co, Ni, Pb, Sb and Bi are inconsistent from early to later stage.As and Au show strong positive correlation in every pyrite subtype, Cu-Zn, Ag-Sb and several other element pairs have high correlation, Pb-Bi has an upper correlation especially in three subtypes of Py1-1, Py2-1 and Py2-2, and also Co-Ni in most pyrite subtypes.The Co/Ni ratio is mainly in the range of 1.1 ~ 3.3, which indicates that the pyrite is mainly of magmatic hydrothermal origin.The ore-forming fluid of Heilangou gold deposit is rich in Au-As, and the trace elements are relatively enriched in S1 and S3 stages, which indicates that the ore-forming fluid activity lasts for a relatively long time and has the pulsating characteristics.Gold is precipitated by the fluid rich in Au-As for multiple activities and several times.