Volume strain and mass transport of tectonite: Implications for geology,with an example from the Gaoligongshan ductile shear zone

The mylonite from the Gaoligongshan ductile shear zone within the Nujiang fault, western Yunnan is markedly depleted in SiO₂, TiO₂, total Fe and H₂O, and enriched in CaO, MgO, Na₂O and K₂O. The development of the ductile shear zone has led to the alteration of the pre-existing gneiss into mylonite, with the mass and volume change of the original rocks of -29.48% and -26.86%, respectively. The analysis of volume strain and mass transport of tectonite is an intermediate link of the examination of structural chronology and fluid/rock ratios, and will be widely used in the estimation of shortening volumes of compressional structural zones and the resources.