Synthetic ANaB(NaxLi1 − xMg1)CMg5Si8O22(OH)2 (with x = 0.6, 0.2 and 0) P21/m amphiboles at high pressure: a synchrotron infrared study
Synthetic ANaB(NaxLi1 − xMg1)CMg5Si8O22(OH)2 (with x = 0.6, 0.2 and 0) P21/m amphiboles at high pressure: a synchrotron infrared study
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高压下合成 ANaB(NaxLi1 − xMg1)CMg5Si8O22(OH)2（x = 0.6、0.2 和 0）P21/m 角闪石：同步加速器红外研究
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发表时间：
2009
期刊：
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通讯作者：
G. Della Ventura
中科院分区：
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作者：
G. Iezzi;Zhenxian Liu;G. Della Ventura
通过原位同步加速器红外吸收光谱研究了在室温条件下Li2O-Na2O-MgO-SiO2-H2O体系中三种空间群P21/m结晶的合成角闪石的高压行为。角闪石的组成为 ANa B(NaxLi1 − xMg1) CMg5 Si8 O22(OH)2，其中 x 分别为 0.6、0.2 和 0.0。在布鲁克海文国家实验室（美国纽约）的 U2A 光束线上，使用金刚石砧室在非静水或准静水条件下进行了高达 32 GPa 的高压实验。 OH拉伸红外光谱中两个最强的吸收带可以分配给P21/m结构中的两个非等价的O-H偶极子，它们键合到相同的局部环境M1M3Mg3-OH-ANa，并指向两个不同扭结的四面体环。在所有样品中，随着压力的增加，这些带逐渐合并，产生独特的对称吸收，表明对称性从 P21/m 到 C2/m 的变化。发生转变的压力似乎与总 B 位尺寸线性相关。在 50 至 1,400 cm−1 频率范围内收集的角闪石 B(Na0.2Li0.8Mg1) 的红外光谱也显示出随着压力增加而发生的一系列变化。这里报告的数据支持 Iezzi 等人的推论。 (Am Miner 91:479–482, 2006a) 关于一种新的高压角闪石多晶型物。
The high-pressure behavior of three synthetic amphiboles crystallized with space group P21/m at room conditions in the system Li2O–Na2O–MgO–SiO2–H2O has been studied by in situ synchrotron infrared absorption spectroscopy. The amphiboles have compositions ANa B(NaxLi1 − xMg1) CMg5 Si8 O22(OH)2 with x = 0.6, 0.2 and 0.0, respectively. The high-P experiments up to 32 GPa were carried out on the U2A beamline at Brookhaven National Laboratory (NY, USA) using a diamond anvil cell under non-hydrostatic or quasi-hydrostatic conditions. The two most intense absorption bands in the OH-stretching infrared spectra can be assigned to two non-equivalent O–H dipoles in the P21/m structure, bonded to the same local environment M1M3Mg3–OH–ANa, and pointing toward two differently kinked tetrahedral rings. In all samples these bands progressively merge to give a unique symmetrical absorption with increasing pressure, suggesting a change in symmetry from P21/m to C2/m. The pressure at which the transition occurs appears to be linearly correlated to the aggregate B-site dimension. The infrared spectra collected for amphibole B(Na0.2Li0.8Mg1) in the frequency range 50 to 1,400 cm−1 also show a series of changes with increasing pressure. The data reported here support the inference of Iezzi et al. (Am Miner 91:479–482, 2006a) regarding a new high-pressure amphibole polymorph.