地球物理学进展 ›› 2018, Vol. 33 ›› Issue (1): 19-24.doi: 10.6038/pg2018AA0233

• 固体地球物理及空间物理学(大气、行星、地球动力学、重磁电及地震学、地热学) • 上一篇    下一篇

钾长石与斜长石变形机制的不同步性

党嘉祥1(),周永胜1   

  1. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
  • 收稿日期:2017-07-15 修回日期:2018-01-03 出版日期:2018-02-20 发布日期:2018-07-03
  • 作者简介:党嘉祥,男,1981年生,2007年在中国地震局地质研究所获得硕士学位,从事高温高压岩石力学研究.(E-mail: dangjiaxiang@ies.ac.cn)
  • 基金资助:
    国家自然基金(41604072)和中央级公益性科研院所基本科研业务专项(IGCEA1611)

Asynchronism of deformation mechanism between K-feldspar and plagioclase

DANG Jia-xiang1(),ZHOU Yong-sheng1   

  1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2017-07-15 Revised:2018-01-03 Online:2018-02-20 Published:2018-07-03

摘要:

本文通过总结天然变形钾长石和斜长石的变形机制研究成果,斜长石和花岗岩的脆塑性转化、钙长石集合体高温流变以及钠长石的实验变形研究成果.综合分析发现钾长石和斜长石变形机制具有温压条件的不同步性:在低于绿片岩相条件下两种长石均表现为脆性碎裂,相应的实验室变形条件为<850 ℃;在绿片岩相条件下,钾长石以碎裂变形为主,斜长石以晶内塑性变形为主,对应实验室变形温度约为900~950 ℃;在角闪岩相温压条件下,斜长石以动态重结晶为主,而钾长石表现为塑性变形为主,同时发生出溶,该变形特征在实验室条件下的变形温度需要>1000 ℃.影响斜长石流变性质的主要因素为粒度和结构水含量,粒度的减小将引起变形机制从位错蠕变向扩散蠕变转化,结构水含量增加导致激活能减小.结构水(羟基)和动态重结晶的细粒化均对长石的流变起到明显的弱化作用.

Abstract:

This paper reports the different deformation mechanism between K-feldspar and plagioclase under the same pressure and temperature condition based on previous field studies of deformed K-fieldspar and plagioclase,brittle-plastic experimental deformation of anorthite, albite, plagioclase and granite. Below greenschist grade (<850 ℃ in laboratory), both feldspars deformed by pervasive cataclasis.At greenschist condition (900~950 ℃ in laboratory), K-feldspar deformed mainly by fractures, and intracrystalline plastic deformation happened in plagioclase grains. At amphibolite condition (>1000 ℃ in laboratory), plagioclase is mainly fine-grained by recrystallization, and K-feldspar shows plastic deformation and exsolution happened. The major factors influence rheological strength of plagioclase are grain-size and trace water content. Reduce of grain-size leads to mechanism of creep changes from dislocation to diffusion and active energy is decreased with exist of trace water. Then, feldspar creep could be weakened by grain reduce induced by recrystallization or accompanied with trace water in shear zone.

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