| 卢 燕.福建政和东际金-银矿床的热液蚀变特征
及其勘探指示意义[J].地质与勘探,2017,53(6):1039-1050 |
| 福建政和东际金-银矿床的热液蚀变特征
及其勘探指示意义 |
| Hydrothermal Alteration and its Significance for Exploration at the Dongji Gold-Silver Deposit in Zhenghe, Fujian Province |
| 投稿时间：2017-06-24 修订日期：2017-11-01 |
| DOI： |
| 中文关键词: 东坑火山盆地 东际金-银矿床 热液蚀变 流体通道 红外光谱 福建 |
| 英文关键词: Dongkeng volcanic basin , Dongji gold-silver deposit, Hydrothermal alteration, Fluid pathway , Near-infrared reflectance spectroscopy, Fyjian Province |
| 基金项目:中国地质调查局地质调查项目《武夷山成矿带龙泉-上杭地区地质矿产调查》（编号：DD20160037）和国
家重大科学仪器设备开发专项《岩心光谱扫描仪研发与产业化》（编号：2012YQ050250）联合资助 |
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| 中文摘要: |
| 福建东际金-银矿床产于中生代东坑火山岩盆地西缘的流纹质凝灰岩中，矿区及周边火山-沉积岩系遭受了广泛且强度不等的热液蚀变。本文工作采用红外反射光谱技术在东际矿区三个勘探剖面上对钻孔岩心进行系统性高密度采样分析，结果显示蚀变矿物组合及分带的大框架样式主要受原岩成分控制，具体表现为绢云母化趋向于发育于流纹质火山岩中，而绿泥石化则富集在安山质和英安质火山岩中。在更小的矿区局部空间范围内或单一岩性中，热液作用的物化条件作为次级控制因素决定着特定蚀变矿物的成分变化和蚀变类型的强度差异。从层状硅酸盐组合考虑，东际矿区热液蚀变以绢云母化和绿泥石化为最主要类型而缺失发育良好的蒙脱石带，金-银矿化赋存在以伊利石为主的绢云母化带中，表明成矿环境属于低硫到中硫之间的浅成热液系统。含矿火山岩的热液蚀变组合和强度变化，以及金-银矿化的似层状特点，均指示成矿时流体是沿着南园组凝灰岩层内侧向流动，而蚀变分带细节显示在凝灰岩层中存在着二至三条流体主通道，金-银矿化则赋存在主通道中。流体主通道的热液蚀变标志是富铝绢云母，其与主通道之外的相对贫铝绢云母在红外光谱特征上反差明显。因此，采用红外光谱技术圈定整体热液蚀变系统的空间构型、解译成矿环境的物化条件及变化、并确定绢云母的铝含量变化用以判断成矿流体主通道位置，可以有效地缩小勘探目标和提高找矿工作的预测性。 |
| 英文摘要: |
| The Dongji gold-silver deposit is located in the western margin of the Mesozoic Dongkeng volcanic basin, Zhenghe, Fujian. The host volcanic sequence is extensively altered to predominantly sericite and chlorite with only a minor amount of smectite. Gold and silver mineralization, associated with disseminated and stockwork pyrite forming stratabound lenses and layers, is hosted in rhyolitic tuff of the Nanyuan Group unconformably overlying the metamorphosed Precambrian basement. In this work, infrared spectroscopy was used to measure spectral reflectance of drill-cores from drill-holes of three cross-sections in order to characterize and identify mineralization-related hydrothermal alteration. The results show that hydrothermal alteration at the deposit and district scales is controlled mainly by lithology, with sericitic and chloritic alteration developed preferentially in rhylitic and dacitic/andesitic volcanic rocks, respectively. At a finer scale (i.e. single lithology), environmental conditions played an important role in controlling hydrothermal alteration, such that a subtle compositional difference in octahedral Al content of sericite is evident between mineralised and unmineralised rhyolitic tuff, where sericite in or close to mineralization tends to have higher Al than that outside mineralization. It is inferred that ore-forming fluids flowed laterally along the Nanyuan Group rhyolitic tuff above the unconformity, resulting in mineralization locally in main fluid channels. Therefore, sericite Al content, measurable with infrared reflectance spectroscopy, is a useful parameter for tracing and mapping fluid flow and identifying sites of mineralization in the Dongji deposit. |
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