| 变质岩中的球状结构及其对变质作用的指示 |
| |
| 引用本文： | 陈安平,石永红,曾晓燕.变质岩中的球状结构及其对变质作用的指示[J].岩石学报,2019,35(10):3262-3270. |
| |
| 作者姓名： | 陈安平 石永红 曾晓燕 |
| |
| 作者单位： | 中国科学院地质与地球物理研究所, 岩石圈演化国家重点实验室, 北京 100029;中国科学院大学, 北京 100049,合肥工业大学资源与环境工程学院, 合肥 230009,中国科学院地质与地球物理研究所, 岩石圈演化国家重点实验室, 北京 100029;中国科学院大学, 北京 100049 |
| |
| 基金项目： | 本文受国家自然科学基金项目（41573029、41641016、41873040）资助. |
| |
| 摘 要： | 球状结构是指由纤维状晶体组成的放射状集合体,其为一种高度不平衡的结构。它们常见于火山岩、假玄武玻璃、沉积岩以及热液沉积物中,在不同变质级别的变质岩中也有广泛报道。变质岩中的球状结构记录了丰富的变质作用信息,然而其在变质岩中的成因机制和对变质作用的指示意义尚缺少详细的研究。球状结构的生长需要温度、压力或成分的改变使得结晶体系远离平衡,它的结晶动力学过程受物质的扩散控制,要求晶体生长速率远大于物质扩散速率。详细解析球状结构和分析导致不平衡的因素有助于限定变质作用的条件和过程。本文拟从变质岩中报道的代表性球状结构出发,基于球状结构结晶所需的热力学和动力学条件,总结变质岩中球状结构的四种可能成因机制:流体结晶、变质熔体结晶、冲击变质作用和高度不平衡的变质反应。组成球状结构的纤维状晶体具有大的表面能,在持续保持温压和流体条件不变的情况下会快速重结晶使得球状结构消失,球状结构得以保留意味着其所处的环境要迅速转变为它不再结晶的条件。因此,变质岩中的球状结构指示寄主岩石经历了持续时间很短的非平衡变质作用过程。借鉴其它学科研究球状结构的定量方法和在变质作用条件下开展球状结构的实验研究是变质岩中球状结构研究的潜在方向。
|
| 关 键 词： | 球状结构 不平衡结晶 变质岩结构 变质条件 变质作用时间尺度 |
| 收稿时间： | 2019/1/1 0:00:00 |
| 修稿时间： | 2019/4/16 0:00:00 |
Spherulite in metamorphic rocks and its implication for metamorphism |
| |
| CHEN AnPing,SHI YongHong and ZENG XiaoYan.Spherulite in metamorphic rocks and its implication for metamorphism[J].Acta Petrologica Sinica,2019,35(10):3262-3270. |
| |
| Authors: | CHEN AnPing SHI YongHong and ZENG XiaoYan |
| |
| Institution: | State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;University of Chinese Academy of Sciences, Beijing 100049, China,School of Resources and Environment Engineering, Hefei University of Technology, Hefei 230009, China and State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;University of Chinese Academy of Sciences, Beijing 100049, China |
| |
| Abstract: | Spherulite or spherulitic texture is a highly non-equilibrium texture consisting of radially arranged fibrous crystals. Spherulites are not only commonly observed in volcanic rocks, pseudotachylyte, sedimentary rocks and hydrothermal sediments, but also widely reported in metamorphic rocks of variable metamorphic grades. Abundant petrogenetic information is recorded in metamorphic spherulites, however, their crystallization mechanism and implication for metamorphism are rarely discussed. From the view of thermodynamics, far from equilibrium conditions induced by temperature, pressure or composition change are required for the crystallization of spherulite. Considering kinetics, spherulite growth is diffusion-controlled and requires very small ratio of diffusion rate to growth rate. Detailed deciphering the controlling factors responsible for formation of spherulites provides valuable constrains on metamorphic conditions and process. Here in this paper, four mechanisms, including crystallization from solute-rich fluid, metamorphic melt, shock metamorphism and highly non-equilibrium metamorphic reaction, are suggested for the growth of spherulites in metamorphic rocks, based on representative spherulites reported in metamorphic rocks and the conditions required by the growth of spherulites. If the crystallization conditions are kept for a fairly long period of time, fibrous crystals in the spherulites with large interface energies are susceptible to recrystallization, which would inevitably obliterate the spherulitic texture. The preservation of spherulites is possible only if they rapidly stay away from crystallization conditions subsequent to their formation. Therefore, the occurrence of spherulites in metamorphic rocks indicates that the host rocks have suffered a highly non-equilibrium and short-lived metamorphic process. Applying quantitative methods used in other subjects and conducting experimental studies at metamorphic conditions are potential ways for further study of spherulites in metamorphic rocks. |
| |
| Keywords: | Spherulite Non-equilibrium crystallization Metamorphic texture Metamorphic conditions Timescale of metamorphism |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《岩石学报》浏览原始摘要信息 |
| 点击此处可从《岩石学报》下载免费的PDF全文 |
|
