投稿时间：2021-02-18
修订日期：2021-04-21
网络发布日期：2021-07-12
中文摘要:胶东是中国最大的金矿集区，其金矿成因目前还存在较大争议。作为最重要的载金矿物，黄铁矿显微结构及元素-同位素组成能够很好地示踪成矿物质来源和成矿过程。利用SEM、EPMA和LA-ICP-MS微区原位分析方法对胶东代表性蚀变岩型金矿—三山岛金矿的黄铁矿开展详细的BSE显微结构以及As含量和S同位素耦合关系研究，发现矿区至少存在3种不同结构和As含量的黄铁矿：①含金石英-黄铁矿细脉中具交代残余结构的低As黄铁矿（Py-1），在BSE图像中显示暗色的核部（Py-1a）和亮色的边部（Py-1b），Py-1a和Py-1b的w（As）分别为48×10-6~524×10-6和183×10-6~1134×10-6，δ34S值分别为10.4‰~10.8‰和11.6‰~11.9‰；②含金石英-黄铁矿细脉中具韵律环带结构的高As黄铁矿（Py-2），在BSE图像中显示富含矿物包裹体并多孔的核部（Py-2a）以及很少含矿物包裹体的“干净”边部（Py-2b），Py-2a和Py-2b的w（As）分别为0.14%~0.31%和0.47%~0.97%；③含金石英-多金属硫化物细脉中具核边结构且As含量变化大的黄铁矿（Py-3），其核部Py-3a富含黄铜矿、闪锌矿等矿物包裹体并贫As，w（As）仅为1×10-6~10×10-6，δ34S值为4.2%~5.8‰，边部Py-3b几乎不含矿物包裹体但富As，w（As）为8877×10-6~17 839×10-6，δ34S值为7.7%~10.1‰。上述黄铁矿中，从Py-1a到Py-1b，w（As）和δ34S值缓慢升高，可能主要受水岩相互作用的控制；Py-2具韵律环带且核部多孔、多矿物包裹体，指示了较为剧烈的流体沸腾作用；Py-3a和Py-3b具有截然不同的w（As）和δ34S值，指示了外来富As流体的加入。这些过程有利于As和Au的进一步富集，多种形式的富As和Au机制表明胶东金矿存在复杂的矿化过程和物质来源，特别是流体在迁移过程中萃取围岩中的成矿物质不可忽视。
Abstract:Jiaodong Peninsula is the largest gold Province in China. How the huge amounts of gold were accumulated in such an area is still controversial. Pyrite is the most important Au-carrier mineral, the elemental and isotopic compositions of which, coupled with its microtexture, can well record the specific ore-forming processes and the origin of Au. In this study, SEM, EPMA and LA-(MC)-ICP-MS analyses were conducted on microtextures as well as As contents and S isotopic compositions of pyrite from the giant Sanshandong gold deposit. The results show that at least three types of pyrite occur: ① Low-As pyrite (Py-1) in the Au-bearing quartz-pyrite vein, which shows metasomatic relict texture. Under the BSE imaging, a dark relict core (Py-1a) is surrounded by a grey rim (Py-1b). The Py-1a has As contents of 48×10-6~524×10-6 and δ34S values of 10.4‰~10.8‰ while the Py-1b has As contents of 183×10-6~1134×10-6 and δ34S values of 11.6‰~11.9‰; ② High-As pyrite (Py-2) in the Au-bearing quartz-pyrite vein, which shows rhythmic zoning texture. Under the BSE imaging, the pyrite has a dark porous core containing abundant mineral inclusions (Py-2a) and a bright clean rim (Py-2b). The Py-2a and Py-2b have As contents of 0.14%~0.31% and 0.47%~0.97%, respectively; ③ Pyrite in the Au-bearing quartz-polymetallic sulfide vein (Py-3). This pyrite is characterized by core-rim texture, showing a dark As-poor core (Py-3a) and a grey As-rich rim (Py-3b). The Py-3a and Py-3b have As contents of 1×10-6~10×10-6 and 8877×10-6~17839×10-6, δ34S values of 4.2‰~5.8‰ and 7.7‰~10.1‰, respectively. The slight increase of As and δ34S from Py-1a and Py-1b was most likely induced by fluid-rock interaction. The rhythmic zoning texture of Py-2, coupled with its mine-ral inclusion-bearing and porous core, likely suggests a fluid boiling. The contrasted As and δ34S values between the Py-3a and Py-3b indicate the injection of another As-rich fluid. The above processes facilitate the As and Au to be further enriched, implying that complex ore-forming processes and multiple origins of ore-forming metals contributed to the giant gold mineralization. Especially, the fluids extracting ore-forming metals from wall rocks cannot be ignored.
keywords:geochemistry In situ analysis of pyrite microtexture enrichment mechanisms of As sulfur isotope Sanshandao gold deposit Jiaodong Peninsula
文章编号：
中图分类号：
文献标志码：
基金项目:本文得到国家自然科学基金（编号：41873048）和国家重点研发计划（编号：2016YFC0600105）联合资助
引用文本：
许杨,蓝廷广,舒磊,胡换龙,陈应华,王洪.2021.胶东三山岛金矿床黄铁矿As富集机制及其对金成矿作用的指示[J].矿床地质,40(3):419~431XU Yang,LAN TingGuang,SHU Lei,HU HuanLong,CHEN YingHua,and WANG Hong.2021.Enrichment mechanisms of arsenic in pyrite from Sanshandao gold deposit (Jiaodong Peninsula, China) and implications for gold metallogenesis[J].Mineral Deposits40(3):419~431
图/表
