显微构造现象-3.1

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Fractured and rotated grains
antithetic
synthetic
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Sigma and Delta clasts
Sigma clast
Delta clast
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Complex clasts
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Mica fish
S-surface
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变斑晶

Controversy about whether porphyroblasts rotate or not. Use patterns of internal fabric (Si) versus matrix fabric (Se). Porphyroblast overgrew older structure & did not rotate or rotating while overgrowing fabric getting transposed. Get opposite sense of shear depending on interpretation.
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3）变形纹
石英变形纹出现的方位在温度压力坐标上的分布 柱面变形纹
次底面Ⅱ变形纹 次底面Ⅰ变形纹 底面变形纹
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4）石英光轴组构图确定滑移系和形成的温压环境
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2 动力学分析问题
1） 主应力方位： 利用石英变形纹确定主应力方位
锐角法
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利用双晶纹确定主应力方位
如方解石的双晶纹与应力方位有一定的关系，e双晶纹滑移最有利的应力方位是 压缩轴C和拉伸轴T都在双晶纹和光轴组成的平面内，与e双晶面成45°角。 因为方解石光轴与e双晶面法线为26 °角，压缩轴C与光轴之间的夹角为71 ° ， 压缩轴C和拉伸轴T之间夹角为90 ° 。
Rotation or preservation of older fabric?
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Pressure Shadows

Mineral fibers grow adjacent to grains in pressure shadows on flank of deformed grains. Pressure shadows parallel the axis of instantaneous extension and will be parallel to the shear zone for coaxial deformation, oblique for non-coaxial deformation.
Steady-state appears at medium to large deformation.
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3）应变分析 定量计算岩石变形后应变量的大小，以及由此 进一步计算剪切带的体积变化和位移量，是 显微构造研究的重要内容之一。 A Flinn图解，主要用来表示无体积变化的平面 应变。Flinn参数k=(a-1)/(b-1) 其中a=(1+e1)/(1+e2), b=(1+e2)/(1+e3). a,b≧1,而(1+e1)=x, (1+e2)=y, (1+e3)=z，分别代表 应变椭球体的长轴，中间轴和短轴。
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2）差应力值大小 位错密度法
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亚晶粒法
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动态重结晶新颗粒
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Prerequisite
Steady state means that strain rate does not change in an increment of strain if , T, and P do not change (Porier, 1985).
Plagioclase rims on garnet
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雁列脉

Form perpendicular to direction of maximum instantaneous extension (i.e. unlike other strain sense markers, veins "lean" in opposite direction to shear zone boundary) Older veins will be sheared into sigmoidal shape and cross cut by younger veins forming in accordance with instantaneous strain ellipse
显微构造现象、分析方法与应用
应用
刘俊来 中国地质大学
2012-03-15
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1 变形温度计问题
1）变形（机械）双晶
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2）变形机制 与变形机制组合
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矿物晶体内平直的或是成长透镜状的薄 层纹，厚约0.1~2μm。其折射率和双 折射率与主晶不同，消光位与主晶稍 有偏差。其成因是位错滑移产生的。 Carter(1971)年将石英中变形纹与C轴 之间的夹角大小分为四类： （1）底面变形纹，变形纹面法线与C轴 之间的夹角为0~5°； （2）次底面Ⅱ变形纹，变形纹面法线与 C轴之间的夹角为 6°~15°。 （3）次底面Ⅰ变形纹，变形纹面法线与 C轴之间的夹角为16°~30°。 （4）柱面变形纹，变形纹面法线与C轴 之间的夹角为81°~90°。
Sheath folds - form lineation in direction of shear.
Байду номын сангаас
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组构型式
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谢 谢！
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S-C fabrics
S C
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C’ or extensional shear bands
C’
S
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多米诺或书斜式构造
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多米诺与剪切条带式破裂

Rigid inclusions in the shear zone may be sliced-up on faults If fractures are subparallel to the shear zone, faults are synthetic If fractures are at high angle to shear zone the faults are typically antithetic
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En echelon sigmoidal veins in a brittle-ductile shear zone, Cornwall.
Fibers in veins
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Folds

Asymmetrical folds may or may not indicate shear sense.
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(1+e1)=x (1+e2)=y (1+e3)=z
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Flinn图解
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B 应变量计算
(1)利用有限应变的测量的主应变计算剪切应变.
(2)利用剪切带内面理与剪切带边界之间的夹 角计算
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心对心法
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雁列脉
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3 剪切指向标志
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S-C Fabrics
Shear surfaces (C-surfaces) - discrete thin zones of high shear strain in the main shear zone Cross-cut foliation (S-fabric) within the shear zone C-surfaces are oriented subparallel to the shear zone boundary Foliation is deflected into parallelism with shear band generating a sigmoidal shape