M. L. Williams, M. Jercinovic, K. Mahan, G. Dumond
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引用次数: 54
Abstract
The term petrochronology has increasingly appeared in publications and presentations over the past decade. The term has been defined in a somewhat narrow sense as “the interpretation of isotopic dates in the light of complementary elemental or isotopic information from the same mineral(s)” (Kylander-Clark et al. 2013). Although complementary isotopic and elementary information are certainly a central and critical part of most, if not all, petrochronology studies, the range of recent studies that might use the term covers a much broader scope. The term “petrochronology” might alternatively be defined as the detailed incorporation of chronometer phases into the petrologic (and tectonic) evolution of their host rocks, in order to place direct age constraints on petrologic and structural processes. As noted by Kylander-Clark et al. (2013), the linkage between geochronology and petrology can involve a variety of data including mineral textures and fabrics, the distribution of mineral modes or volume proportions, compositional zoning, mineral inclusion relationships, and certainly major element, trace element, and isotopic composition of the chronometer and all other phases.
Electron probe micro-analysis (EPMA) has a central and critical role to play in establishing the linkage between chronometer phases and their host assemblage. The basic instrument is an electron microscope which can be used in either scanning or fixed beam modes, with integrated wavelength dispersive spectrometers (WDS), energy dispersive spectrometers (EDS), electron detectors (to image secondary and backscattered signals) a light optical system, and optionally cathodoluminescence (CL) detection. The electron microprobe is used to investigate the distribution, composition, and compositional zonation of all mineral phases, the data that underpin thermobarometric analysis and modeling of P–T histories. The microprobe, with μm-scale spatial resolution, can also characterize compositional zonation in very small accessory phases including monazite, xenotime, zircon, allanite, titanite, apatite, and others. This, as discussed below, can be a …
在过去的十年中,岩石年代学这个术语越来越多地出现在出版物和报告中。该术语在某种狭义上被定义为“根据来自同一矿物的互补元素或同位素信息来解释同位素日期”(Kylander-Clark et al. 2013)。虽然互补的同位素和基本信息无疑是大多数(如果不是全部的话)岩石年代学研究的中心和关键部分,但最近可能使用该术语的研究范围涵盖了更广泛的范围。“岩石年代学”一词也可以被定义为将计时相详细地结合到它们的宿主岩石的岩石学(和构造)演化中,以便对岩石学和构造过程施加直接的年龄限制。正如Kylander-Clark等人(2013)所指出的,地质年代学和岩石学之间的联系可能涉及各种数据,包括矿物结构和结构、矿物模式或体积比例的分布、成分分带、矿物包裹体关系,当然还有计时器和所有其他阶段的主元素、微量元素和同位素组成。电子探针显微分析(EPMA)在建立天文钟相及其宿主组合之间的联系方面发挥着核心和关键作用。基本仪器是一台电子显微镜,可用于扫描或固定光束模式,具有集成波长色散光谱仪(WDS)、能量色散光谱仪(EDS)、电子探测器(成像二次和背散射信号)、光学系统和可选的阴极发光(CL)检测。电子探针用于研究所有矿物相的分布、组成和成分分带,这些数据是热气压分析和P-T历史建模的基础。微探针在μm尺度的空间分辨率下,还可以表征单独居石、xenotime、锆石、allanite、钛矿、磷灰石等非常小的附属相的成分分带。正如下面所讨论的,这可能是一个……
期刊介绍:
RiMG is a series of multi-authored, soft-bound volumes containing concise reviews of the literature and advances in theoretical and/or applied mineralogy, crystallography, petrology, and geochemistry. The content of each volume consists of fully developed text which can be used for self-study, research, or as a text-book for graduate-level courses. RiMG volumes are typically produced in conjunction with a short course but can also be published without a short course. The series is jointly published by the Mineralogical Society of America (MSA) and the Geochemical Society.