Petrochronology of Zircon and Baddeleyite in Igneous Rocks: Reconstructing Magmatic Processes at High Temporal Resolution

1区地球科学 Q1 Earth and Planetary Sciences

Reviews in Mineralogy & Geochemistry Pub Date : 2017-02-01 DOI:10.2138/RMG.2017.83.10

U. Schaltegger, J. Davies

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引用次数: 77

Abstract

Zircon (ZrSiO4) and baddeleyite (ZrO2) are common accessory minerals in igneous rocks of felsic to mafic composition. Both minerals host trace elements substituting for Zr, among them Hf, Th, U, Y, REEs and many more. The excellent chemical and physical resistivity of zircon makes this mineral a perfect archive of chemical and temporal information to trace geological processes in the past, utilizing the outstanding power and temporal resolution of the U–Pb decay schemes. Baddeleyite is a chemically and physically much more fragile mineral. It preserves similar information only where it is shielded from dissolution and physical fragmentation as an inclusion in other minerals or in a fine-grained or non-reactive rock matrix. It offers the potential for dating the solidification of mafic rocks with high-precision through its crystallization in small pockets of Zr-enriched melt, after extensive olivine and pyroxene fractionation. Zircon and baddelelyite U–Pb dates are, for an overwhelming majority of cases and where we can assume a closed system, considered to reflect the time of crystallization. The development of the U–Pb dating tool CA-ID-TIMS (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) since 2005 has led to unprecedented precision of better than 0.1% in 206Pb/238U dates (Bowring et al. 2005). Increased sensitivity of mass spectrometers and low laboratory blanks due to reduction of acid volumes allow routine U–Pb age determinations of micrograms of material at sufficiently high radiogenic/common lead ratios (see Schoene and Baxter 2017, this volume). In situ U–Pb age analysis using laser ablation or primary ion beam sputtering allows analysis of sub-microgram quantities of zircon material from polished internal sections or zircon surfaces with spot diameters ranging from ~30 μm for laser-ablation, inductively coupled plasma mass spectrometry (LA-ICP-MS) to 10 μm for secondary ion mass spectrometry (SIMS), lateral resolutions of 2–5 μm for NanoSIMS …

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火成岩中锆石和坏长岩的岩石年代学:在高时间分辨率下重建岩浆过程

锆石(ZrSiO4)和坏辉石(ZrO2)是长英质-基性火成岩中常见的副矿物。这两种矿物都含有取代Zr的微量元素，其中包括Hf、Th、U、Y、ree等。锆石优异的化学和物理电阻率使这种矿物成为一个完美的化学和时间信息档案，可以利用U-Pb衰变方案的出色功率和时间分辨率来追踪过去的地质过程。坏辉石是一种化学上和物理上都脆弱得多的矿物。只有当它与其他矿物或细粒或非反应性岩石基质中的包裹体一样不受溶解和物理破碎的影响时，它才保留类似的信息。它提供了在广泛的橄榄石和辉石分馏后，通过富锆熔体小袋中的结晶，以高精度确定基性岩石凝固年代的潜力。在绝大多数情况下，锆石和坏橄榄石的U-Pb年龄反映了结晶的时间，我们可以假设这是一个封闭的系统。自2005年以来，U-Pb测年工具CA-ID-TIMS(化学磨损-同位素稀释-热电离质谱)的发展使206Pb/238U测年的精度达到了前所未有的0.1%以上(Bowring et al. 2005)。由于酸体积减少，质谱仪的灵敏度提高，实验室空白减少，因此可以在足够高的放射性/普通铅比下对微克级物质进行常规U-Pb年龄测定(见Schoene和Baxter 2017，本卷)。使用激光烧蚀或一次离子束溅射进行原位U-Pb年龄分析，可以从抛光的内部切片或锆石表面分析亚微克数量的锆石材料，光斑直径范围从激光烧蚀的~30 μm，电感耦合等离子体质谱(LA-ICP-MS)到二次离子体质谱(SIMS)的10 μm，纳米SIMS的横向分辨率为2-5 μm…

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来源期刊

Reviews in Mineralogy & Geochemistry 地学-地球化学与地球物理

CiteScore

8.30

自引率

0.00%

发文量

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.