Validity of the microboudin method for palaeo-stress analysis: application to extraordinarily long sodic amphibole grains in a metachert from Aksu, China

This paper deals with microboudin structures of sodic amphibole in a metachert collected from the Aksu terrane, Xinjiang, China. The pre-boudinage sodic amphibole grains of the metachert have large aspect ratios of up to 100, providing a rare opportunity to test the validity of the microboudin method for palaeo-stress analysis. The test was performed by comparing the measured proportions of boudinaged grains at aspect ratios of 2–25 with the theoretically predicted proportions, and the comparison was statistically revealed to be excellent. This result further supports the reliability of the microboudin method.