岩石学 & 矿物学

岩石学和矿物学主要研究固体岩石和矿物。大多岩石和矿物种类丰富，结构精细。在这两个学科中，识别单个矿物至关重要。扫描电子显微镜和显微分析为此提供了解决方法。它们提供了岩石矿物的形貌信息和各颗粒的化学成分信息。

在地学领域，利用扫描电子显微镜研究矿物和岩石样品是常规手段。扫描电子显微镜与光学显微镜相似，但具有更高的分辨率，电子显微镜揭示了矿物颗粒间的构造关系。由于电子束和固体物质之间的相互作用，产生了多种有效信息，因此它具有很大的分析潜力。这些信息包括背散射电子(BSE),二次电子(SE), 特征X 射线 (X-rays) 和可见光子。

背散射电子（ Backscattered Electrons）的强度与所观测样品的平均原子序数成正比。通过背散射电子成像，可鉴别矿物颗粒和识别离散相区。原子序数分辨率可以区分低至 0.1 的原子序数差异。背散射电子信号可以让用户追踪矿物相的带状分布，找到最佳的分析点。同样，它可以观察并且定位包含重元素的特定相，这对寻找稀有贵金属尤为重要，这些金属相通常颗粒较小，如：金、铂族元素等。利用 BSE 强度的差异也可以识别单个晶体的晶体取向。
二次电子（ Secondary Electrons ）可以观察三维样品的形貌。与 BSE 相比，二次电子的形成更接近样品表面，具有高空间分辨率、大景深的特点，对于样品的原子序数的差异不那么敏感。

特征 X 射线（ X-rays ）是电子束和固体物质间相互作用产生的，可以根据化学成分来识别相，是很重要的表征信息。利用特征 X 射线可以进行定性分析和更重要的定量分析。TESCAN 电子显微镜系统完全兼容第三方探测器，实现定性定量分析。
可见光子（ Light Photons ）是电子束和样品间相互作用产生的另一有用信息。这种发光被称为阴极荧光（ CL ）不同矿物之间产生的发光现象也不同，许多矿物种类发射的光子颜色有差异。岩石是由不同矿物形成的，彩色阴极荧光可以分辨这些矿物，如长石或碳酸盐。CL 对一些矿物的微量元素组成和排列结构的差异比较敏感，这些都可以利用全色（黑白）或彩色 CL 探测器探测到。TESCAN 研发生产的全色探测器，以及全色和彩色相结合的四通道 Rainbow CL 探测器，可以同步收集 BSE 和 CL 图像信息。

天然银的枝状晶体

Cathodoluminescence analysis of zircons

Zircons (ZrSiO₄) are ubiquitous in the crust of Earth and are a common accessory to trace mineral constituent of most granite and felsic igneous rocks. Zircons have low solubility in most melt and fluid compositions and can survive geological processes such as erosion, transport, or high-grade metamorphism. This makes zircon one of the most important minerals for geochronology. Different types of zircon domains are identified by CL imaging and U-Pb dating is then used to determine ages of different zones within the crystal. This helps to recognize various geological processes recorded during the history of the grain.

pdf – 1.8 MB

Cathodoluminescence imaging of mineralogical samples

Cathodoluminescence (CL) - light emission produced by electron beam - reveals information about material composition and structure that often cannot be obtained by other methods. In geosciences, optical cathodoluminescence became a standard technique. With the development of scanning electron microscopes, SEM-CL is gaining in popularity. In comparison with optical CL microscopes, where the sample is irradiated with stationary unfocussed electron beam, SEM-based CL imaging achieves much better resolution and it can be combined in situ with other analytical methods.

pdf – 3.9 MB

Characterization of Platinum Group Minerals

The platinum-group metals (PGM) consists of six elements – platinum, palladium, rhodium, iridium, ruthenium and osmium. Chemical inertness, oxidation-resistance, biocompatibility, high melting temperature, good conductivity and electronic and catalytic properties are unique properties that make PGM irreplaceable starting material in many specific applications. The deposits in the Norilsk-Talnakh region of Northern Russia are the largest nickel-copper-palladium deposits in the world and, the intensive mining activity in this region, positions Russia as the world’s second global PGM supplier. In addition to PGM output, a by-product of this mining is nickel and copper extraction. In this application example the effectiveness of the separation process (gravity separation and hydro-separation) by comparison of PGM mineral content, both in concentrate and in tailings, is studied.

pdf – 2 MB

Exoscopy of quartz grains in SEM

Exoscopy (surface micromorphology) of quartz grains is one of the geomorphological methods used to determine the predominant type of sediment transport. Sediments can contain several genetically diverse types of quartz grains, for example with glacial, fluvial or aeolian features of transport. Grains of glacial origin usually show sharp edges. There are no signs of roundness or smoothing. Their surface can be either matt or glossy. Fluvial transport makes surface of the grain round. Typical is the presence of V-shaped pits. Grains of aeolian origin are more rounded to oval and usually have a matt surface. The genesis of sediments can be influenced by more than one factor; therefore grains can carry on theirsurface complex structural features. The most frequently, exoscopic research it is performed by means of scanning electron microscopy methods, because they allow users to identify any surface irregularities of clasts.

pdf – 1.6 MB