Technical note: Rapid phase identification of apatite and zircon grains for geochronology using X-ray micro-computed tomography

Technical note: Rapid phase identification of apatite and zircon grains for geochronology using X-ray micro-computed tomography
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技术说明：使用 X 射线微计算机断层扫描快速鉴定磷灰石和锆石颗粒的物相，用于地质年代学

DOI：
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发表时间：
2022
期刊：
Geochronology
影响因子：
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通讯作者：
A. Celestian
A. Celestian
中科院分区：
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文献类型：
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作者：
E. Cooperdock;F. Hofmann;Ryley M. C. Tibbetts;Anahi Carrera;Aya Takase;A. Celestian

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抽象。磷灰石和锆石是研究最多、应用最广的副矿物 地质年代学和热年代学的矿物。考虑到磷灰石和 锆石通常存在于相同的岩性中， 粉碎矿物分离物中的相是地质年代学的常见任务， 热年代学和岩石年代学研究。在这里，我们提出了一种方法， 有效和准确的磷灰石和锆石矿物相鉴定， 使用X射线微计算机断层扫描（microCT）对药柱支架进行验证 提供额外的三维晶粒尺寸、形状和夹杂物， 套房信息。在这项研究中，我们分析了磷灰石和锆石颗粒， 鱼峡谷凝灰岩样品，通过碘甲烷（MEI）和锂 杂多钨酸盐（LST）重液密度分离。我们验证了 使用已知标准品的microCT结果和使用拉曼的相位识别 光谱，表明磷灰石和锆石是可区分的， 彼此和其他公共相位，例如，钛铁矿，基于microCT X射线 密度的我们提出了推荐的microCT扫描协议后， 系统地测试不同扫描参数的影响， 样本位置。此方法有助于减少执行 使用高毒性化学品进行密度分离，并进行目视检查 颗粒在光学显微镜下，和改进的矿物鉴定， 特征化可以使地质年代学数据更加可靠。
Abstract. Apatite and zircon are among the best-studied and most widely used accessory minerals for geochronology and thermochronology. Given that apatite and zircon are often present in the same lithologies, distinguishing the two phases in crushed mineral separates is a common task for geochronology, thermochronology, and petrochronology studies. Here we present a method for efficient and accurate apatite and zircon mineral phase identification and verification using X-ray micro-computed tomography (microCT) of grain mounts that provides additional three-dimensional grain size, shape, and inclusion suite information. In this study, we analyze apatite and zircon grains from Fish Canyon Tuff samples that went through methylene iodide (MEI) and lithium heteropolytungstate (LST) heavy liquid density separations. We validate the microCT results using known standards and phase identification with Raman spectroscopy, demonstrating that apatite and zircon are distinguishable from each other and other common phases, e.g., titanite, based on microCT X-ray density. We present recommended microCT scanning protocols after systematically testing the effects of different scanning parameters and sample positions. This methodology can help to reduce time spent performing density separations with highly toxic chemicals and visually inspecting grains under a light microscope, and the improved mineral identification and characterization can make geochronologic data more robust.