摘要
为探讨线理对长英质糜棱岩强度的影响,本次研究通过对面理面(xy面)内沿与线理方向(x方向)呈不同角度(0°、30°、45°、60°、90°)钻取圆柱样品,并在Paterson气体介质高温高压流变仪上进行轴向压缩变形实验。实验条件设定为:围压约300 MPa、温度850~975℃、应变速率3×10^(-6)~10^(-4)s^(-1)。变形过程中,稳态加载差应力范围为69~576 MPa;岩石强度受与x方向夹角控制:沿x方向压缩时强度最大,从x方向到与x方向呈30°夹角时压缩强度快速降低(~36.6%),随后从30°到60°方向压缩强度缓慢降低,而沿y方向的压缩强度较60°方向略有回升。利用幂律流变方程拟合岩石力学数据时,去除850℃下压缩方向为y方向和900℃下压缩方向为x方向的两个稳态差应力σ>300 MPa(围压)的数据后,获得的视应力指数na为4.9~7.9,且随温度升高而减小。显微结构观察显示,黑云母出现弯曲、褶皱现象,颜色变暗、解理模糊、颗粒细化,并发生脱水反应,同时诱导长石和石英部分熔融。结合视应力指数na>3的结果,表明长英质糜棱岩的主要变形机制为位错滑移和位错攀移,在低温高应力条件下伴随有脆性破裂的参与。
To investigate the influence of lineation on the strength of felsic mylonite,cylindrical samples were extracted from the foliation plane(xy plane)at varying angles(0°,30°,45°,60°,and 90°)relative to the lineation direction(x direction).Axial compression deformation experiments were then performed using a Paterson gas-medium high-pressure,high-temperature rheometer under the following conditions:confining pressure of approximately 300 MPa,temperatures ranging from 850 to 975,and strain rates℃℃between 3×10^(-6)and 10^(-4)s^(-1).During the deformation process,the steady-state differential stress varied from 69 MPa to 576 MPa.The rock strength was found to be dependent on the angle relative to the x direction:the compressive strength was highest in the x direction and decreased sharply(~36.6%)from the x direction to a 30°angle relative to x.From 30°to 60°,the compressive strength gradually declined,with a slight increase observed in the y direction compared to the 60°orientation.By fitting the rock mechanical data to a power-law rheological equation and excluding two steady-state differential stressσ>300 MPa(confining pressure)data points at 850℃in the y direction and 900 in the℃x direction,an apparent stress exponent na ranging from 4.9 to 7.9 was obtained,which decreased with increasing temperature.Microstructural analyses revealed bending,folding,darkening,blurring of cleavage,and grain refinement in biotite,indicative of dehydration and partial melting of feldspar and quartz.Combined with an apparent stress exponent na>3,these results indicated that the dominant deformation mechanisms in the studied felsic mylonite were dislocation glide and climb,with brittle fracturing occurring under low temperature and high stress conditions.
作者
张洪通
郑小东
姜哲轩
李建峰
宋茂双
ZHANG Hongtong;ZHENG Xiaodong;JIANG Zhexuan;LI Jianfeng;SONG Maoshuang(State Key Laboratory of Deep Earth Processes and Resources,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;University of Chinese Academy of Sciences,Beijing 100049,China;Chinese Academy of Sciences Center for Excellence in Deep Earth Science,Guangzhou 510640,Guangdong,China)
出处
《大地构造与成矿学》
北大核心
2025年第4期925-936,共12页
Geotectonica et Metallogenia
基金
国家自然科学基金面上项目(42374122、42172243)
广东省自然科学基金面上项目(2022A1515011000)联合资助。
关键词
线理
长英质糜棱岩
应力指数
位错蠕变
lineation
felsic mylonite
stress exponent
dislocation creep
