投稿时间：2020-08-27
修订日期：2020-12-22
网络发布日期：2021-03-06
中文摘要:姚安金矿床位于金沙江-哀牢山富碱斑岩带中段，大地构造位置处于扬子板块西缘与三江特提斯造山带结合部位，其成矿与新生代富碱岩浆-岩浆热液密切相关。野外调查发现矿化仅存在于黑云母正长斑岩体内，而与黑云母正长斑岩空间关系密切的石英正长斑岩却未发现矿化。为探讨黑云母正长斑岩与石英正长斑岩岩体含矿性差异，运用电子探针、LA-ICP-MS分析方法，以富矿黑云母正长斑岩和贫矿石英正长斑岩岩体内的磷灰石作为研究对象，对比磷灰石之间的差异，探讨磷灰石记录的岩浆演化以及反映岩浆氧化还原条件和流体活动性相关信息。测试结果表明，姚安矿区富矿岩体与贫矿岩体磷灰石均为岩浆磷灰石且富F、低Cl；富矿岩体磷灰石相比于贫矿岩体磷灰石具有较大的δEu变化范围与较低的δCe，指示富矿岩体具有较高的氧逸度，高的氧逸度会抑制金以硫化物形式沉淀，从而增强了岩体的成矿潜力。富矿岩体磷灰石具有较高的Ce/Pb比值与低的Th/U比值，表明岩浆形成过程中成矿岩体流体活动性较强，岩浆分异较强。富矿岩体角闪石和黑云母的发育表明岩浆具有较高的水含量，高水含量可以增加金属元素在熔体中的溶解度，并且高水含量的岩浆在演化过程中水也较易达到饱和，发生对成矿有重要意义的流体出溶。总之，在姚安地区，高氧逸度，高水含量以及强流体活动性是成矿的关键。
Abstract:The Yaoan gold deposit is located in the middle domain of the Jinshajiang-Ailaoshan alkali-rich porphyry belt as well as at the junction of the western margin of the Yangtze Plate and the Sanjiang Tethys orogenic belt. Its mineralization is closely related to Cenozoic alkali-rich magmatic-magmatic hydrothermal fluid. It is found that mineralization only exists in biotite syenite porphyry, but quartz syenite porphyry which is closely related to biotite syenite porphyry has not been mineralized. To explore the difference in mineralization between biotite syenite porphyry and quartz syenite porphyry, the authors used electron microprobe analysis and LA-ICP-MS method, chose apatite in fertile biotite syenite porphyry and barren quartz syenite porphyry as the research object, compared the differences of magmatic evolution recorded by apatite and related information reflecting magmatic redox conditions and fluid activity. The experimental data show that the apatite of fertile porphyry and barren porphyry are both magmatic apatite and rich in F and lack of Cl; the apatites from ore-rich porphyry have relative large variation in δEu and low δCe, indicating that ore-rich porphyry has higher oxygen fugacity than barren porphyry. The high oxygen fugacity inhibits the precipitation of gold in the form of sulfide, thus enhancing the ore-forming potential of the rock. The high Ce/Pb and low Th/U ratios of apatite in the mineralized porphyry indicate that the ore-forming porphyry has strong fluid activity and magmatic differentiation during the formation of magma. The development of hornblende and biotite in ore-rich porphyry indicates that magma has high water content. The high water content could increase the solubility of metal elements in the melt. The high water content magma could easily reach water saturation in the process of evolution, and fluid exsolution is important for mineralization. In a word, high oxygen fugacity, high water content and strong fluid activity constitute the key factors for mineralization in Yaoan area.
keywords:geochemistry apatite electron microprobe LA-ICP-MS oxygen fugacity trace elements Yaoan gold deposit
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基金项目:本文得到深地资源项目（编号：2016YFC0600305）、国家自然科学基金（编号：41602103）和中国地质调查局项目（编号：DD20190182）联合资助
引用文本：
郑瑜林,张长青,刘欢,孙嘉,张盼盼.2021.滇西姚安金矿床磷灰石化学特征及指示意义[J].矿床地质,40(1):156~168ZHENG YuLin,ZHANG ChangQing,LIU Huan,SUN Jia,ZHANG PanPan.2021.Apatite chemical feature of Yaoan gold deposit in western Yunnan and its geological significance[J].Mineral Deposits40(1):156~168
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