Clumped fluoride-hydroxyl defects in forsterite: Implications for the upper-mantle
Clumped fluoride-hydroxyl defects in forsterite: Implications for the upper-mantle
复制标题
DOI：
10.1016/j.epsl.2014.01.020
复制
发表时间：
2014-03-15
影响因子：
5.3
通讯作者：
Balan, Etienne
中科院分区：
文献类型：
--
作者：
Crepisson, Celine;Blanchard, Marc;Balan, Etienne
通过实验和理论相结合的方法，研究了含氢镁橄榄石中氟的掺入机理和掺入量。镁橄榄石样品合成在活塞缸压机在2和4 GPa，在含水条件下，有或没有氟。高氟溶解度1715和1308 ppm的F测量颗粒诱导γ射线发射（PIGE）在镁橄榄石样品合成在2和4 GPa，分别。此外，基于密度泛函理论的第一性原理计算，以探讨氟和水在镁橄榄石中的耦合掺入机制。我们的研究结果表明，氟，羟基和硅空位的密切关联。实验和理论红外吸收光谱的比较，使分配的9个OH伸缩带（3500-3700 cm（-1））富F合成镁橄榄石中观察到的镁橄榄石晶体结构中的氟-羟基缺陷成团。值得注意的是，类似的带先前记录在一些天然橄榄石与Mg/（Mg+Fe）摩尔比低至0.86。因此，氟和水循环通过名义上的无水矿物强烈耦合，地幔氟收支可以完全由这些矿物相容纳。(c)2014爱思唯尔有限公司版权所有。
The mechanism and magnitude of fluorine incorporation in H-bearing forsterite were investigated through a combined experimental and theoretical approach. Forsterite samples were synthesized in a piston cylinder press at 2 and 4 GPa, in hydrous conditions, with or without fluorine. High fluorine solubilities of 1715 and 1308 ppm F were measured by particle induced gamma-ray emission (PIGE) in forsterite samples synthesized at 2 and 4 GPa, respectively. In addition, first-principles calculations based on density functional theory were performed in order to investigate the coupled incorporation mechanisms of fluorine and water in forsterite. Our results demonstrate the close association of fluoride, hydroxyl groups and Si vacancies. Comparison of experimental and theoretical infrared absorption spectra enables assignment of the nine OH stretching bands (3500-3700 cm(-1)) observed in F-rich synthetic forsterite to clumped fluoride-hydroxyl defects in the forsterite crystal structure. Noteworthily, similar bands were previously recorded on some natural olivine with Mg/(Mg+Fe) molar ratio down to 0.86. Fluorine and water cycles are therefore strongly coupled through the nominally anhydrous minerals and the mantle fluorine budget can be entirely accommodated by these mineral phases. (c) 2014 Elsevier B.V. All rights reserved.