方解石e-双晶的古应力分析:原理和展望

Paleostress Analyses of Calcite e-twins: Theory and Prospect

方解石e-双晶是在低温、低围压环境下发育的一种晶内塑性变形,广泛发育于亮晶灰岩和大理岩中。由于e-双晶的形成与地应力密切相关,与其相关的古应力分析原理得到了深入的研究,相继提出了两类分析方法,即图解法和反演法。通过方解石e-双晶的古应力分析,我们可以获得形成时的主应力方位、应力比,甚至绝对的差应力,因而该分析方法被广泛运用于未遭受明显构造变形的地区,如克拉通盆地、褶皱‒冲断带等。本文首先简单地回顾了方解石e-双晶古应力分析的研究历史,总结了图解法和反演法的基本原理,然后评价了影响这些方法的一些可能因素,如方法的局限性和数据的质量,最后指出今后在数据获取和多期数据反演两个方面值得进一步研究。

Calcite e-twin is a kind of low-temperature intracrystalline plasticity mechanism,which is commonly developed in sparitic limestone and marble.The principle of paleostress analyses related to e-twin is elucidated because the close relationship between twinning and crustal stress,and two kinds of analytical methods,graphical method and inversion method,were put forward in this contribution.Through paleostress analyses of calcite e-twin,we can obtain the orientation of principal stress,the stress ratio and even the absolute differential stress.Therefore,this method can be widely used in paleostress analyses of Craton basin,foreland basin,and fold-and-thrust belts,where host rock deformation is weak.In this paper,we briefly reviewed the research history of paleostress analyses of calcite e-twin,summarized the principles of graphic and inversion methods,then evaluated the possible factors(the limitations of the method and the quality of the data)affecting the accuracy of these methods,and lastly,two aspects of data acquisition and inversion of polyphase data are proposed for further study.