A 3D reconstruction of plagioclase crystals in a synthetic basalt
A 3D reconstruction of plagioclase crystals in a synthetic basalt
复制标题
合成玄武岩中斜长石晶体的 3D 重建
DOI：
10.2138/am.2008.2679
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发表时间：
2008
影响因子：
3.1
通讯作者：
M. Toplis
中科院分区：
文献类型：
--
作者：
S. Duchêne;E. Pupier;C. L. C. de Veslud;M. Toplis
摘要 重建了实验冷却的玄武岩液体中斜长石晶体的三维形状，目的是（1）更好地了解晶体生长过程和冷却过程中产生的晶体形状的多样性，以及（2）评估从二维截面得出的晶体尺寸分布（CSD）的有效性。实验装料以 0.2 °C/h 的速率从高于液相线 (~1175 °C) 冷却。在 ~1120 °C 的淬火温度下，它含有 ~40% 的晶体。为了对晶体进行 3D 量化，使用反射光在光学显微镜下拍摄了一系列 2D 抛光切片的照片。使用 gOcad 地理建模软件对 261 个单个晶体进行插值和 3D 重建，并测量了它们的短 (S)、中 (I) 和长 (L) 尺寸。斜长石晶体通常呈板状，具有几乎恒定的 I/L 比。另一方面，S/I 和 S/L 形状因子变化更大，尽管两者都与 S 轴的长度相关。这些观察结果被认为是由晶体聚集和附着（优先沿（010）面）产生的，或者是由冷却过程中变化的热力学或动力学条件产生的。沿 S、I 和 L 轴的生长速率是根据最大晶体的尺寸计算的，变化范围分别为 1.5 × 10-10 至 5.1 × 10-10 和 7.2 × 10-10 m/s。给出了 3D 晶体最大长度和短轴的 CSD，并将其与从 2D 截面获得的 CSD 进行了比较。人们发现已发布的切割效果修正通常非常令人满意。
Abstract The three-dimensional shapes of plagioclase crystals in an experimentally cooled basaltic liquid have been reconstructed, with the aim of (1) better understanding crystal growth processes and the diversity of crystal shapes produced during cooling, and (2) to assess the validity of crystal-size distributions (CSDs) derived from 2D sections. The experimental charge was cooled from above the liquidus (~1175 °C) at a rate of 0.2 °C/h. It contained ~40% crystals at the quenching temperature of ~1120 °C. To quantify the crystals in 3D, photographs of a series of 2D-polished sections were taken under an optical microscope using reflected light. Interpolation and 3D reconstruction of 261 individual crystals was performed using the gOcad geomodeling software, and their short (S), intermediate (I), and long (L) dimensions were measured. Plagioclase crystals are generally tabular, with a nearly constant I/L ratio. On the other hand, S/I and S/L shape factors are more variable, although both are found to be correlated with length of the S axis. These observations are believed to result either from crystal agglomeration and attachment, preferentially along (010) faces, or from varying thermodynamic or kinetic conditions during cooling. Growth rates along the S, I, and L axes have been calculated from the size of the largest crystals and vary from 1.5 × 10-10 to 5.1 × 10-10 and 7.2 × 10-10 m/s, respectively. The CSDs for the maximal length and short axes of 3D crystals are presented and compared with CSDs obtained from 2D sections. Published corrections for cutting effects are found to be generally very satisfactory.