Full analysis of feldspar texture and crystal structure by combining X-ray and electron techniques
Full analysis of feldspar texture and crystal structure by combining X-ray and electron techniques
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DOI：
10.2138/am.2013.4124
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发表时间：
2013
影响因子：
3.1
通讯作者：
T. Balić-Žunić;S. Piazolo;A. Katerinopoulou;J. Schmith
中科院分区：
文献类型：
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作者：
T. Balić-Žunić;S. Piazolo;A. Katerinopoulou;J. Schmith
摘要 长石晶体通常表现出一系列的外溶和多合成孪晶结构，这可能会给其全面表征带来问题，但同时也提供了有关其成因的重要信息。我们提出了一种集成程序，用于长石共生中所有成分的微观结构分析、孪晶定律识别以及晶体结构细化。该程序适用于挪威奥斯陆地区南部拉尔维克深成杂岩中两种不同伟晶岩长石中的长石共生体。研究表明，两种起始高温（HT）长石具有相似的整体化学成分，但经历了显着不同的冷却历史，冷却时间可能相差一个数量级以上。采用 Rietveld 精修的粉末 X 射线衍射用于矿物成分的初步鉴定并得出定量相分析。使用电子微探针分析来对成分的化学成分进行分组。电子背散射衍射用于揭示样品的织构、孪生定律以及晶域的空间分布和晶体取向。应用区域探测器记录的单晶 X 射线衍射，对具有不同方向和严重衍射重叠的所有晶域的反射强度进行同步积分。使用 JANA2006 程序对晶体结构进行了细化，该程序允许同时计算结构不同的组件。各种方法的组合结果有助于提高准确性并解决因应用单一技术而产生的歧义。该方法广泛适用于矿物共生体的研究，并弥补了岩石成分结构特征常规数据中现有的空白。
Abstract Feldspar crystals typically show a range of exsolution and polysynthetic twinning textures that can present problems for their full characterization, but at the same time give important information about their genesis. We present an integrated procedure for the micro-texture analysis, twin law identification plus crystal structure refinement of all components in a feldspar intergrowth. This procedure was applied to perthitic intergrowths in feldspars from two different pegmatites in the Larvik plutonic complex in the southern part of the Oslo region, Norway. It revealed that the two starting high-temperature (HT) feldspars had similar global chemical compositions but underwent significantly different cooling histories, with cooling times probably differing by over an order of magnitude. Powder X-ray diffraction with Rietveld refinement was used for a preliminary identification of the mineral components and concluding quantitative phase analysis. Electron microprobe analysis was used to bracket the chemical compositions of the constituents. Electron backscatter diffraction was used to reveal the texture of the samples, twin laws and spatial distribution and crystallographic orientation of the crystal domains. Single-grain X-ray diffraction recorded by an area detector was applied for a simultaneous integration of reflection intensities for all crystallographic domains with different orientations and severe diffraction overlaps. The crystal structures were refined using the program JANA2006 that allows a simultaneous calculation for structurally different components. Combined results of various methods helped improve accuracy and resolve ambiguities that arise from the application of a single technique. The approach is widely applicable to the study of mineral intergrowths and bridges an existing gap in the routinely accessible data on the structural characteristics of rock constituents.