The intricate textural patterns commonly observed in metamorphosed and recrystallized zircon (ZrSiO4) underscore the crucial necessity of understanding the underlying mechanisms governing their formation to ensure accurate interpretation of the chemical and isotope data they contain. This study employed a combination of microanalytical techniques, including electron backscattered diffraction (EBSD) analysis, electron microprobe (EMP) mapping, and scanning electron microscope (SEM) imaging, to investigate the processes of formation and modification of zircon in a late Pleistocene (~ 35 ka) syenite enclosed within the Nari Tephra Formation on Ulleung Island in South Korea. Under cathodoluminescence (CL), zircons within the syenite reveal dark, featureless, or oscillatory-zoned cores containing numerous inclusions of britholite. These cores are partially or entirely replaced by inward-penetrating bright-CL domains that exhibit minimal inclusion presence. Despite these changes, the external morphologies of the zircons remain largely unchanged, and the faded oscillatory zoning is preserved in the replaced regions. EMP mapping discloses amoebiform micro-domains with high Y, U, and Th concentrations within the dark-CL cores, while the bright-CL domains are relatively deficient in these trace elements. Microstructural analysis of the zircons using EBSD mapping indicates no significant misorientation between the dark-CL cores and the bright-CL rims. Deformation-related low-angle boundaries by lattice distortion are clearly observed in certain grains, cutting across the discrete SEM and EMP domains, and often aligned along submicron pore trails. Microstructural and microchemical analyses carried out in this study establish that the zircons within the Ulleung syenite have undergone subsolidus recrystallization, a process likely influenced by the presence of fresh melts or fluids. This recrystallization process could be attributed to either coupled dissolution and reprecipitation or thermoactivated particle and defect volume diffusion due to inherent lattice strain. The subsequent deformation observed in the zircons might be a result of increased stress within the magma system after the recrystallization.

中文翻译：

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韩国郁陵岛火山正长岩碎屑中锆石的显微结构和微化学分析

在变质和重结晶锆石 (ZrSiO4) 中常见的复杂纹理图案强调了了解控制其形成的潜在机制的至关重要性，以确保准确解释它们所包含的化学和同位素数据。这项研究结合了微分析技术，包括电子背散射衍射 (EBSD) 分析、电子微探针 (EMP) 测绘和扫描电子显微镜 (SEM) 成像，研究了晚更新世 (~ 35 ka) 正长岩，位于韩国郁陵岛 Nari Tephra 组内。在阴极发光 (CL) 下，正长岩内的锆石显示出暗色、无特征或振荡分区的核心，其中含有大量的扁长石包裹体。这些核心部分或全部被向内穿透的明亮 CL 域取代，这些域表现出最小的内含物存在。尽管发生了这些变化，锆石的外部形态基本保持不变，并且在被替换的区域中保留了褪色的振荡分区。EMP 绘图揭示了暗 CL 核心内具有高 Y、U 和 Th 浓度的阿米巴形微域，而亮 CL 域相对缺乏这些微量元素。使用 EBSD 映射对锆石的微观结构分析表明，暗 CL 核心和亮 CL 边缘之间没有明显的定向错误。在某些晶粒中可以清楚地观察到由晶格畸变引起的与变形相关的低角度边界，跨越离散的 SEM 和 EMP 域，并且通常沿着亚微米孔隙轨迹排列。本研究中进行的微观结构和微量化学分析表明，郁陵正长岩内的锆石经历了固相线下重结晶，这一过程可能受到新鲜熔体或流体存在的影响。这种再结晶过程可归因于耦合溶解和再沉淀或由于固有晶格应变导致的热激活颗粒和缺陷体积扩散。随后在锆石中观察到的变形可能是再结晶后岩浆系统内应力增加的结果。