Fig. 12. Lower-hemisphere equal-area projections of the olivine fabrics in the garnet lherzolites. XZ is the sample section, X is the lineation, and Z is normal to the foliation. N is the number of analyzed olivine grains. J-index is the strength of the olivine fabric.
8 Conclusions
(1) The Yinggelisayi garnet lherzolites from South Altyn contain residual protolith minerals, and near-peak (M1), granulite-facies (M2) retrograde, and amphibolite-facies (M3) retrograde metamorphic mineral assemblages. The estimated P–T conditions of M1 and M2 are 2.52–3.08 GPa/1095–1136°C, and 1.31–1.80 GPa /851–893°C, respectively.
(2) The coarse-grained olivine porphyroblasts crystallized at the near-peak metamorphic stage (M1) during deep subduction of the continental crust and developed the B-type olivine fabric. The fine-grained olivine around the porphyroblasts recrystallized in decompression and retrograde metamorphism (M2) during exhumation, and developed the A-type olivine fabric.
(3) Distinct olivine fabrics developed during different stages of metamorphism and deformation, and the study of olivine fabric combining with metamorphic stages makes us better understand the metamorphism and deformation evolution history during deep subduction and exhumation of continental crust.