Simultaneous determination of deviatoric stress tensors from polyphase calcite twin data: improvement and application

Abstract

It is a challenge to obtain the meaningful solution of deviatoric stress tensors from polyphase calcite twin data measured in multi-deformed rocks. Our paper advances current approaches that simultaneously determine stresses from polyphase twin data. Key refinements include the selection of the dimensionless stress space, the estimation of the dimensionless critical resolved shear stress (${\bar{\tau }}_c$), the definition of the stress criterion including ${\bar{\tau }}_c$, and the exclusion or inclusion of incompatible untwinned planes (IU). The improved simultaneous-determination method (ISDM) is applied to three series of two–three-phase IU-free synthetic datasets generated under imposed stresses. Stress results demonstrate that the ISDM is accurate in principal stress direction, stress ratio, and ${\bar{\tau }}_c$, although the ISDM including IU is a little more accurate than the ISDM excluding IU. For two-phase equally-sized synthetic datasets, the ISDM excluding IU is generally more accurate than existing similar methods. Applying both the ISDM and an existing similar method to a natural dataset reveals that the ISDM excluding IU yields the most reasonable stress solution.