High Pressure Response of Rutile Polymorphs and Its Significance for Indicating the Subduction Depth of Continental Crust |
| |
| Authors: | MENG Dawei WU Xiuling FAN Xiaoyu ZHANG Zhengjie CHEN Hong MENG Xin ZHENG Jianping |
| |
| Institution: | [1]Faculty of Materials Science and Chemical Engineering, China University of Geosciences, Wuhan 430074, China [2]Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China [3]Imperial College London, London SW 72AZ, United Kingdom |
| |
| Abstract: | Abstract: α‐PbO2‐type TiO2 (TiO2‐II) is an important index mineral for ultrahigh‐pressure metamorphism. After the discovery of a natural high‐pressure phase of titanium oxide with α‐PbO2‐structure in omphacite from coesite‐bearing eclogite at Shima in the Dabie Mountains, China, a nano‐scale (<2 nm) α‐PbO2‐type TiO2 has been identified through electron diffraction and high‐resolution transmission electron microscopy in coesite‐bearing jadeite quartzite at Shuanghe in the Dabie Mountains. The crystal structure is orthorhombic with lattice parameters a = 4.58times10?1 nm, b = 5.42times10?1 nm, c = 4.96times10?1 nm and space group Pbcn. The analysis results reveal that rutile {011}R twin interface is a basic structural unit of α‐PbO2‐type TiO2. Nucleation of α‐PbO2‐type TiO2 lamellae is caused by the displacement of one half of the titanium cations within the {011}R twin slab. This displacement reduces the Ti‐O‐Ti distance and is favored by high pressure. The identification of α‐PbO2‐type TiO2 in coesite‐bearing jadeite quartzite from Shuanghe, Dabie Mountains, provides a new and powerful evidence of ultrahigh‐pressure metamorphism at 4–7 GPa, 850°C‐900°C, and implies a burial of continental crustal rocks to 130–200 kilometers depth or deeper. The α‐PbO2‐type TiO2 may be a useful indicator of the pressure and temperature in the diamond stability field. |
| |
| Keywords: | Rutile twin TiO_2 UHP polymorphs Phase transformation HRTEM Dabie Mountains |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
| 点击此处可从《Acta Geologica Sinica》浏览原始摘要信息 |
| 点击此处可从《Acta Geologica Sinica》下载免费的PDF全文 |
|
