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.