Inversion of polyphase calcite twin data for deviatoric stress tensors: 1. A novel numerical approach

• Published in: Journal of structural geology Vol. 128; p. 103873
• Main Authors: Shan, Yehua, Zheng, Jian, Liang, Xinquan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2019
• Subjects: Accuracy; Calcite twin; Inversion; Polyphase; Reduced stress; Stress tensor; Stress tensor; Reduced stress; Inversion; Accuracy; Calcite twin; Polyphase
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/j.jsg.2019.103873

A new inversion method is developed in this paper to estimate deviatoric stress tensors from a certain population of polyphase calcite twins. It is both to minimize the number of the common incompatible (twinned and untwinned) e-planes and to maximize the sum of the resolved shear stresses along the compatible twinned e-planes under each reduced stress. The genetic algorithm is employed to resolve this optimization problem. A series of two-phase, equally-mixed artificial datasets, generated under the prescribed stresses, were taken to demonstrate the feasibility of this method. Results indicate a strong tendency to have an increasing accuracy of reduced stress with the ascent of the prescribed maximum differential stress, the difference between the prescribed stresses, and the number of twinned calcite crystals, respectively. What is more, the maximum differential stress becomes sufficiently large to permit an accurate estimate of reduced stress, even though the prescribed stresses are intermediately similar to each other. However, the method assumes a constant critical resolved shear stress value to rescale the stress tensors, and does not consider the influence on the critical resolved shear stress value of strain hardening, grain size, and temperature. It takes an enormous amount of time in calculation. •A new stress inversion method for polyphase calcite twin data is proposed.•Both stress estimation and data separation are made at the same time.•Reduced stress accuracy increases with imposed maximum differential stress.