Laser Raman microspectrometry of metamorphic quartz: A simple method for comparison of metamorphic pressures
Laser Raman microspectrometry of metamorphic quartz: A simple method for comparison of metamorphic pressures
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DOI：
10.2138/am.2007.2438
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发表时间：
2007-08-01
影响因子：
3.1
通讯作者：
Mouri, Takashi
中科院分区：
文献类型：
--
作者：
Enami, Masaki;Nishtyama, Tadao;Mouri, Takashi
采用激光拉曼显微光谱分析方法，对石英榴辉岩、绿帘角闪岩和角闪岩相岩石中的变质石英进行了拉曼频移与变质压力之间的定量相关分析。封闭在石榴石和其他相中的石英晶体的频率漂移比晶格中的石英晶体高。此外，榴辉岩中的石英包裹体表现出特定于单个寄主晶体的频移(石榴石近似蓝晶石和GT；绿辉石近似绿帘石)。这些观察结果表明，石英包裹体保留的残余压力取决于宿主晶体的弹性参数，正如之前的研究人员所讨论的那样。从角闪岩相(0.30~0.55 Gpa/470~570℃)到绿帘石-角闪岩相(0.8~1.1 Gpa/470~635℃)到石英-榴辉岩相(2.1~2.5 Gpa/660~710℃)，石榴石中石英包裹体的拉曼频移随峰期变质压力的增加而系统地增大。基于实验工作的标定表明，测量的拉曼频移表明，这三组变质岩的剩余压力分别为0.1-0.2、0.4-0.6和0.8-1.0 Gpa。用弹性模型数值模拟了石榴石中石英包裹体的法向应力(内压)，推断出峰期变质阶段的压力-温度条件与由频移估计的残余压力是一致的。激光拉曼显微光谱分析是一种简单而有效的方法，可用于(1)比较在不同压力-温度条件下形成的变质岩中的压力条件，以及(2)探测在随后的折返和水化阶段广泛重结晶的变质岩中的高压特征。
A Laser Raman microspectrometry method was applied to metamorphic quartz in quartz-eclogite-, epidote-amphibolite-, and amphibolite-facies rocks to assess the quantitative correlation between the Raman frequency shift and metamorphic pressure. Quartz crystals sealed in garnet and other phases have a higher frequency shift than those in the rnatrix. Furthermore, the quartz inclusions show a frequency shift specific to the individual host crystals in eclogites (garnet approximate to kyanite > omphacite approximate to epidote). These observations imply that the residual pressures retained by quartz inclusions depend on elastic parameters of the host crystals, as discussed by previous researchers. The Raman frequency shift of quartz inclusions in garnet systematically increases with increasing peak metamorphic pressures from the amphibolite facies (0.30-0.55 GPa/470-570 degrees C), through the epidote-amphibolite facies (0.8-1.1 GPa/470-635 degrees C) to the quartz-eclogite facies (2.1-2.5 GPa/660-710 degrees C). Calibrations based on experimental work suggest that the measured Raman frequency shifts signify residual pressures of 0.1-0.2, 0.4-0.6, and 0.8-1.0 GPa for these three groups of metamorphic rocks, respectively. Normal stresses (internal pressures) of quartz inclusions in garnet, numerically simulated with an elastic model, and inferred pressure-temperature conditions at peak rnetamorphic stage are compatible with the residual pressures estimated from the frequency shifts. Laser Raman microspectroscopic analysis of quartz is a simple and effective method for (1) comparison of pressure conditions in metamorphic rocks formed under various pressure-temperature conditions, and (2) detection of a higher-pressure signature in metamorphic rocks extensively recrystallized during the subsequent exhumation and hydration stage.