浅覆盖区隐伏萤石矿找矿预测:以内蒙古赤峰俄力木台为例

内蒙古赤峰地区发育一系列受断裂控制的热液脉型萤石矿床,区内成矿地质条件优越,找矿潜力较大。本文利用地质特征-地球物理-地球化学-遥感解译(地-物-化-遥)综合找矿方法进行浅覆盖区萤石矿体的定位预测研究,对寻找隐伏矿床和探寻萤石接替资源具有重要意义。俄力木台地区是林西水头萤石成矿带的南段延伸,第四系覆盖严重,是开展浅覆盖区隐伏矿体找矿预测方法实践的理想地区。研究区域的萤石矿体在垂向上呈现分带特征,自上而下分为硅质顶盖、头部矿体、中部矿体和尾部矿体4部分。俄力木台地区的硅质顶盖露头以发育强硅化角砾岩、次生石英岩和石英网脉带为特征,头部矿体露头见萤石粗脉体产出,二者矿化露头的高差30~50 m。WorldView-2遥感影像揭示俄力木台地区含矿断裂带的空间展布与线性变化特征,矿化带中-北段呈近SN向,南段主要呈NNE-NE向。地-物-化综合剖面中矿化露头、甚低频低阻异常带、便携式X射线荧光分析土壤Ca元素高值异常带和土壤偏提取地球化学测量F元素高值异常带分布一致,该异常组合可作为本区含矿断裂带和隐伏萤石矿体的重要预测标志。结合甚低频电磁测量扫面,俄力木台断续出露的矿化蚀变带与SN向甚低频低阻异常带相吻合,预示该区可能发育隐伏-半隐伏萤石矿体。在俄力木台东段重点预测地带布置的钻孔见矿效果良好,目前揭露的部位为硅质顶盖、头部矿体或构造狭缩带,较高品位的萤石主矿体尚未揭露,其深部具有良好的资源潜力和找矿前景。

Exploration of concealed fluorite deposit in shallow overburden areas: A case study in Elimutai,Inner Mongolia,China

The Chifeng area in Inner Mongolia, China possesses a series of fracture-hosted hydrothermal vein-type fluorite deposits and is considered having a superior economic mineralization potential. In this study, we present an integrated prospecting approach integrating geological, geophysical, geochemical, and remote sensing techniques for exploration of concealed fluorite deposit in shallow overburden areas. The study area in Elimutai in the southern extension of the Shuitou fluorite belt, covered widely by Quarternary sediments, is ideal for such exploration. The fluorite orebodies in the study area show vertical zonation with, from top to bottom, distributions of silicified cap and head, main, and tail orebodies. The silicified cap in Elimutai is characterized by highly silicified breccia, secondary quartzite and quartz stockwork, whereas the head orebody contains fluorite vein. The outcrop of silicified cap is 30-50 m higher in latitude than the head orebody. The WorldView-2 remote sensing image reveals a linear distribution of ore-controlling fractures in the SN-striking northern/central segment and NNE-NE-striking southern segment. The results show the overlapping of mineralized outcrop, low-resistivity anomaly zone (by very low frequency electromagnetic (VLF-EM) analysis), positive Ca anomaly zone (by portable X-ray fluorescence (PXF) analysis), and positive F anomaly zone (by partial extraction geochemistry (PEG) analysis). The multi-anomalies can be used as indicator for the exploration and prediction of ore-controlling fractures and concealed fluorite orebody. In combination with VLF-EM mapping, the mineralized and altered outcrop zone overlaps with the SN-trending VLF low-resistivity anomaly zone, indicating the mineralization potential of the Elimutai area for concealed and semi-concealed fluorite. At the key prediction zone in Elimutai, the drill cores reveals the concealed fluorite ore well, exposing silicified cap, head orebody or narrow fractures. The overall evidence suggests that the deeper level of Elimutai is highly likely to contain the economically significant main fluorite orebody.