Zircon with polycrystalline or polygranular appearance is either produced in the magmatic environment through crystallization, or due to deformation in metamorphic settings (including regional metamorphism and ductile shear zones), or as a result of shock-induced recrystallization. All three types can be easily confused and potentially lead to incorrect interpretations, especially if the crystallographic orientation analyses of zircon are not conducted. It is particularly important to establish the difference between tectonically-deformed polygranular zircon and shock-induced polygranular zircon because the latter serves as an indicator of shock event and is often used for dating asteroid impacts. In this paper, a series of polycrystalline zircon grains from ductile shear zones and metamorphic rocks are analyzed using a combination of techniques (BSE, CL, orientation contrast, EBSD, and microprobe mapping), and their properties are compared to reported polycrystalline zircons from magmatic and impact settings. This work shows how appearance, crystallographic orientation, and CL signature of “granules” differ between the different types of deformed zircon.

中文翻译：

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多晶岩浆，构造变形和与冲击有关的锆石聚集体的组织鉴定

具有多晶或多颗粒外观的锆石，是在岩浆环境中通过结晶产生的，或者是由于变质环境中的变形（包括区域变质和韧性剪切带）产生的，或者是由于激振引起的再结晶而产生的。这三种类型很容易混淆，并可能导致错误的解释，特别是如果未进行锆石的晶体学取向分析的话。建立构造变形的多晶锆石与激波诱发的多晶锆石之间的差异尤为重要，因为后者可作为冲击事件的指标，并且常用于确定小行星撞击的时间。在本文中，结合多种技术（BSE，CL，取向对比，EBSD和微探针测绘）分析了韧性剪切带和变质岩中的一系列多晶锆石晶粒，并将其性质与岩浆和撞击环境中报道的多晶锆石进行了比较。这项工作显示了不同类型的变形锆石之间的外观，结晶取向和“颗粒”的CL特征如何不同。