Resende Rosana Silveira, Sáenz Carlos Alberto Tello, Curvo Eduardo Augusto Campos, Constantino Carlos José Leopoldo, Aroca Ricardo F, Nakasuga Wagner Massayuki
Universidade Estadual Paulista (UNESP), Departamento de Física, Química e Biologia, Rua Roberto Simonsen, 305, 19060-900 Presidente Prudente, SP, Brazil.
Appl Spectrosc. 2014;68(5):549-56. doi: 10.1366/13-07302.
Spectroscopic and morphological studies, designed to improve our understanding of the physicochemical phenomena that occur during zircon crystallization, are presented. The zircon fission track method (ZFTM) is used routinely in various laboratories around the world; however, there are some methodological difficulties needing attention. Depending on the surface fission track density observed under an optical microscope, the zircon grain surfaces are classified as homogeneous, heterogeneous, hybrid, or anomalous. In this study, zircon grain surfaces are characterized using complementary techniques such as optical microscopy (OM), micro-Raman spectroscopy, and scanning electron microscopy (SEM), both before and after chemical etching. Our results suggest that anomalous grains have subfamilies and that etching anisotropy related to heterogeneous grains is due to different crystallographic faces within the same polished surface that cannot be observed under an optical microscope. The improved methodology was used to determine the zircon fission track ages of samples collected from the Bauru Group located in the north of Paraná Basin, Brazil. A total of 514 zircon grains were analyzed, consisting of 10% homogeneous, about 10% heterogeneous, about 20% hybrid, and 60% anomalous grains. These results show that the age distributions obtained for homogeneous, heterogeneous, and hybrid grains are both statistically and geologically compatible.
本文介绍了旨在增进我们对锆石结晶过程中发生的物理化学现象理解的光谱学和形态学研究。锆石裂变径迹法（ZFTM）在世界各地的各种实验室中被常规使用；然而，存在一些需要注意的方法学难题。根据在光学显微镜下观察到的表面裂变径迹密度，锆石颗粒表面被分类为均匀、不均匀、混合或异常。在本研究中，在化学蚀刻前后，使用光学显微镜（OM）、显微拉曼光谱和扫描电子显微镜（SEM）等互补技术对锆石颗粒表面进行表征。我们的结果表明，异常颗粒有亚类，并且与不均匀颗粒相关的蚀刻各向异性是由于在同一抛光表面内不同的晶面，而这些晶面在光学显微镜下无法观察到。改进后的方法用于确定从巴西巴拉那盆地北部的包鲁群采集的样品的锆石裂变径迹年龄。总共分析了514颗锆石颗粒，其中10%为均匀颗粒，约10%为不均匀颗粒，约20%为混合颗粒，60%为异常颗粒。这些结果表明，均匀、不均匀和混合颗粒获得的年龄分布在统计和地质上都是兼容的。
