| 胶东金翅岭金矿床黄铁矿原位微量元素和硫同位素特征及对矿床成因的指示 |
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| 引用本文： | 朱照先,赵新福,林祖苇,赵少瑞.胶东金翅岭金矿床黄铁矿原位微量元素和硫同位素特征及对矿床成因的指示[J].地球科学,2020,45(3):945-959. |
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| 作者姓名： | 朱照先 赵新福 林祖苇 赵少瑞 |
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| 作者单位： | 中国地质大学资源学院, 湖北武汉 430074 |
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| 基金项目： | 科技部重点研发计划2016YFC0600104国家自然科学基金项目41822203国家自然科学基金项目91514303中央高校基本科研业务费专项资金CUG140618 |
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| 摘 要： | 位于招远-莱州金成矿带中西部的金翅岭金矿床是胶东地区典型的石英脉型高品位金矿，但其成矿流体来源和矿床成因一直存在争议.在详细的矿相学和黄铁矿显微结构研究基础上，利用LA-ICP-MS技术原位分析与成矿有关黄铁矿的微量元素特征，结合原位硫同位素分析成矿流体来源，为进一步认识矿床成因提供制约.成矿阶段的黄铁矿划分为2种类型（PyI和PyII），PyI产在石英-黄铁矿阶段，PyII产在石英-多金属硫化物阶段，伴随大量可见金的出现.根据背散射的核-边结构，PyII可细分为含有较多硫化物的核部PyIIa和表面较为干净的边部PyIIb，但二者有明显溶蚀结构.LA-ICP-MS分析结果显示PyI含有一定量的Au（< 0.015×10-6~2.18×10-6，均值0.62×10-6）和As（78.98×10-6~857×10-6，均值542×10-6），但Pb、Zn等其他元素含量较低.核部PyIIa和PyI微量元素分布特征较为相似，但Au（< 0.015×10-6~0.59×10-6，均值0.11×10-6）和As（0.62×10-6~198×10-6，均值35.81×10-6）的含量相对下降.边部PyIIb较核部PyIIa明显富集Au（< 0.015×10-6~19.71×10-6，均值5.91×10-6）和As（399×10-6~18 153×10-6，均值6 412×10-6），且Au与As表现出良好的正相关性.PyI和核部PyIIa原位δ34S的分布范围较为一致，集中在3.0‰~4.9‰；而边部PyIIb的原位δ34S值较高（5.2‰~6.6‰）.根据黄铁矿结构、微量元素和硫同位素特征，推断在主成矿期富34S和富Au-As的热液流体加入形成了边部PyIIb且与核部的PyIIa发生了交代作用，同时大量可见金直接从热液中沉淀形成.该研究表明多期次富Au-As成矿流体的注入可能是高品位石英脉矿床形成的主要机制.
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| 关 键 词： | 含As黄铁矿 黄铁矿结构 微量元素 激光原位硫同位素 金翅岭金矿床 地球化学 矿床学 |
| 收稿时间： | 2019-02-11 |
In Situ Trace Elements and Sulfur Isotope Analysis of Pyrite from Jinchiling Gold Deposit in the Jiaodong Region: Implications for Ore Genesis |
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| Abstract: | The Jinchiling gold deposit,located in the central and western part of Zhaoyuan-Laizhou gold metallogenic belt,is a typical lode gold deposit hosted in Late Jurassic Linglong granitoids in the Jiaodong region. The source of its ore-forming fluids and ore genesis,however,are still in debate. Based on the detailed study of mineralogy and microstructure of pyrite,trace elements and sulfur isotopes of gold bearing pyrite are analyzed by LA-(MC)-ICP-MS to constrain the source of ore-forming fluids and ore genesis. Two types (PyI and PyII) of gold-bearing pyrite can be identified. PyI is hosted in the quartz-pyrite stage,and PyII occurs in the quartz-polymetallic sulfide stage,which is associated with abundant visible gold. BSE images show that PyII commonly has core-rim texture. The PyIIa core contains many sulfide inclusions,whereas PyIIb rim is relatively clean. LA-ICP-MS analyses show that PyI contains medium contents of Au (< 0.015×10-6-2.18×10-6,mean 0.62×10-6) and As (78.98×10-6-857×10-6,mean 542×10-6),but very low contents of other metal elements (Pb and Zn). PyIIa has trace elements similar to those of PyI,but lower Au (< 0.015×10-6-0.59×10-6,mean 0.11×10-6) and As (0.62×10-6-198×10-6,mean 35.81×10-6). However,PyIIb has significantly high Au (< 0.015×10-6-19.71×10-6,mean 5.91×10-6) and As (399×10-6-18 153×10-6,mean 6 412×10-6),which shows a positive correlation. In addition,PyI and PyIIa have consistent in situ δ34S values,ranging from 3.0‰ to 4.9‰,whereas PyIIb is higher (5.2‰-6.6‰). Our data thus suggest that a new pulse of Au-As enriched ore-formed fluids were input into the mineralizing vein system during quartz-polymetallic sulfide stage,inducing the metasomatism of PyIIa and deposition of abundant visible gold. Our study hence implies that multiple phases of ore-forming fluids may be involved in the formation of high-grade lode gold deposits in Jiaodong. |
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