【摘要】 为了解蛇纹石矿物在全球碳循环中的作用,我们以二氧化碳（CO₂）为压力介质,对蛇纹石[Mg₃-Si₂O₅（OH）₄]进行了高压X射线衍射（XRD）实验研究。同步辐射XRD图谱表明,在170℃和2.5（1） GPa条件下,样品加热1 h后形成了菱镁矿和纤蛇纹石高压相。Rietveld精修结果表明,在菱镁矿形成时,初始的纤蛇纹石晶胞组成变为Mg_2.4（1）Si₂O₅（OH）_2.4（1）,这似乎是由于最内层羟基（OH3）的脱氢和M1位置上镁元素的重新排布,从而导致亚稳态单层脱羟基纤蛇纹石的形成。亚稳态纤蛇纹石压力和温度测量至5.0（1） GPa和500℃,这与苏门答腊南部和琉球俯冲带所在的莫霍板块地热温压条件相对应。在恢复到常温常压条件后,最初的纤维状纤蛇纹石已转变为土状。这些结果可以帮助我们了解沿俯冲带分布的深部碳循环作用过程,并可能促使设计利用压力和温度对石棉解毒的一种新方法。更多还原

【Abstract】 In order to understand the role of serpentine minerals in the global carbon cycle, high-pressure X-ray diffraction（XRD） experiments were performed on chrysotile（Mg₃Si₂O₅（OH）₄） using carbon dioxide（CO₂） as a pressure medium. Synchrotron XRD patterns revealed the formation of magnesite and high-pressure chrysotile after heating at 170 °C for 1 h at 2.5（1） GPa. The Rietveld refinement suggests that the unit cell composition of the original chrysotile changes to Mg_2.4（1）Si₂O₅（OH）_2.4（1）upon the formation of magnesite, which appears to be driven by the dehydrogenation of the innermost hydroxyl group, OH3, and the rearrangement of magnesium（Mg） at the M1 site, leading to the formation of metastable monodehydroxylated chrysotile. Metastable chrysotile is observed up to 5.0（1） GPa and 500 ℃, which corresponds to the slab Moho geotherms for the South Sumatra and Ryukyu subduction zone. After recovery to ambient conditions, the characteristic fibrous morphology of the original chrysotile was found to have changed to an earthy form. These results can help us to understand deep carbon cycling along the subduction zones, and may prompt the design of a novel method of asbestos detoxification using pressure and temperature.更多还原