拉曼Mapping研究霓石型稀土独居石矿物分布特征和取向相位

The Crystal Orientation Maps and Distribution of Mnoazite Minerals in Aegirine-Type Ores in Bayan Obo:Constraints From Raman Mapping

在地球科学等研究领域自动化分析,逐步取代了传统的光学观察法。然而,这些方法获得结果,过于依赖元素组成到矿物组成的转换。同时,也会破坏掉完整描述矿物材料来源和蚀变历史所需的重要信息。因此,利用合适的检测手段,对分析矿物成矿规律及成因具有重要现实性意义。研究利用拉曼Mapping、光学显微镜、自动矿物分析仪(TIMA)三种技术做对比。对具有代表性霓石型稀土矿物分布特征、化学成分、矿物结构及晶体取向等方面进行研究。通过TIMA与光学显微镜研究结果分析可知,独居石矿物多呈自形-半自形不等粒结构,粒度大小不均约为100~500μm之间,部分颗粒有被磷酸盐溶液交代痕迹,可初步判断独居石矿物经多期成矿;氟碳铈矿物呈细粒状分布较散以不规则颗粒包裹在其他矿物中,具有明显的早期成矿特征;易解石矿物以不规则团块状或放射状集合体,具有明显方向性与方解石形成时间一致。利用拉曼光谱技术在微区进行Mapping扫描,通过数据分析得到独居石矿物[PO4]3-的P—O对称伸缩模式(ν1)与P—O对称弯曲振动模式(ν2)所在峰位面积比值,得到独居石矿物不同生长取向相图。经与独居石矿物光镜特征相结合,进一步证明了浸染状霓石型铁稀土矿石中独居石矿物是多期成矿的事实,成矿期数最少为三期。该发现也为白云鄂博矿床多阶段成矿提供有力证据支撑。此外,该技术也可作为一种快速判断磷酸盐矿物不同生长取向的图像方法。该技术对于碳酸矿物、硫酸盐矿物也同样适用。由此可扩展到多种矿物类型,成为判断矿物多期成矿事实提供了重要依据。也为拉曼Mapping技术应用于复杂矿物的矿物学研究矿物的赋存特征奠定基础。

The automated analysis technique has gradually replaced the traditional optical observation method in the geoscience fields.However,mineral phase maps obtained from these newer approaches are overly dependent on transforming from elemental to mineralogical compositions.And then,the important pieces of information are destroyed with a complete description of the origin and history of mineral materials.Therefore,using appropriate detection means to analyze the mineralization and genesis which have important implications for mineral mineralization.Here,through comparison with the Raman Mapping,optical microscope,and TMSCAN integrated mineral analyzer for SEM(TIMA),the distribution characteristics,chemical composition,mineral structure,and crystal orientation are studied of typical aegirine rare earth minerals.The results show monazite grains are mostly euhedral-semieuhedral unequal grain structures and fine particle sizes of 100~500μm.Some particles were metasomatized by phosphorus solution indicating that the deep monazite minerals formed multi-stage mineralization.Bastnaesite minerals are fine-grained and particles are distributed and wrapped irregularly.Aeschynite minerals aggregate clumps or radial forms in irregular.It has obvious directivity that the formation time is consistent with calcite.The ratio of peak area of P—O symmetric stretching mode(ν1)and P—O symmetric bending vibration mode(ν2)is obtained by Raman Mapping data analysis,in which the different growth orientations phase diagrams were obtained of[PO4]3-monazite minerals in micro areas.Combined with the light microscopic characteristics of monazite.It is proved that monazite mineral has at least three stages of mineralization.The discovery also provides strong evidence for the multi-stage mineralization of the Bayan Obo deposit.In addition,as a fast image method to judge different growth orientations of phosphate,carbonate,and sulfate minerals.It can provide important evidence for judging the fact of multi-stage mineralization for various mineral types.The application of Raman Mapping technology in mineralogy lays the foundation for mineral occurrence characteristics.