| 传统温压计在低温榴辉岩应用中的局限:以西南天山超高压变质带为例 |
| |
| 引用本文： | 张丽娟,张立飞,初旭.传统温压计在低温榴辉岩应用中的局限:以西南天山超高压变质带为例[J].地球科学,2018,43(1):164-175. |
| |
| 作者姓名： | 张丽娟 张立飞 初旭 |
| |
| 作者单位： | 北京大学地球与空间科学学院, 造山带与地壳演化教育部重点实验室, 北京 100871 |
| |
| 基金项目： | 国家自然科学基金项目41330210国家自然科学基金项目41520104004中国博士后基金项目8201400768 |
| |
| 摘 要： | 榴辉岩相变质岩石的温压研究对理解高压-超高压变质带的形成和演化具有重要意义，但西南天山低温榴辉岩运用石榴石-绿辉石（-多硅白云母）温压计计算的压力普遍低于相平衡模拟的结果.为此，在Zhang et al.（2017）对含霓辉石榴辉岩研究结果的基础上，对该区域内榴辉岩及其脉体中的绿辉石进行了岩相学和矿物化学的研究，结果表明绿辉石普遍发育环带结构:从核部到边部，Fe3+含量降低，Al含量增加，Fe3+/Al比值的降低对应于霓石含量的降低和硬玉含量的升高.相平衡模拟中硬玉分子等值线的计算结果表明具有最高硬玉含量的边部绿辉石在降压阶段生长.因此，具有最高含量的硬玉组分的绿辉石并不一定代表峰期压力，在应用石榴石-单斜辉石（-多硅白云母）传统温压计时需谨慎，尤其是应用于低温的、具有复杂环带模式的矿物组合时要尤为慎重.
|
| 关 键 词： | 传统温压计 视剖面图 绿辉石 低温榴辉岩 西南天山 岩石学 |
| 收稿时间： | 2017-10-12 |
Limitations of Traditional Thermobarometer in Applications to Low-Temperature Eclogites: A Case Study of UHP Metamorphic Belt in Southwest Tianshan |
| |
| Abstract: | The temperature and pressure of eclogite facies metamorphic rocks are very important to understand the formation and evolution of HP-UHP metamorphic belt. However, the pressures calculated by the traditional thermobarometer that involves omphacite are generally lower than those of the phase equilibrium modeling, for eclogites from the UHP metamorphic belt of the Southwest Tianshan. Petrographic and mineral chemical analyses on omphacite in eclogites and HP veins are conducted, inspired by the study of Zhang et al.(2017). The results show that the omphacite is typically zoned. From core to rim, Fe3+ content continuously decreases, and Al content increases in response; the decrease in Fe3+/Al ratio corresponds to a general decline in the aegirine content and increase in the jadeite content. Phase equilibrium modeling shows that the omphacite rim with the highest jadeite content grew during decompression after the pressure peak. Thus, the maximum in jadeite component does not necessarily represents peak pressure, and the conventional thermobarometers should be used with caution, especially for the low-temperature assemblages with complicated zonation patterns. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
| 点击此处可从《地球科学》下载免费的PDF全文 |
