Back to Abstract Index
Paper Number: 150
Cao, H., Xu, Z.Q.,
Xu, C.P. and Li G.X.
State Key Laboratory for Continental Tectonics and Dynamics,
Institute of Geology, Chinese Academy of Geological Sciences, Beijing
100037, China. Caohui@cags.ac.cn
___________________________________________________________________________
Constrain the absolute age of multiple deformation and metamorphic
events is one of the hotspots in geochronology study. This study using
FIAs (foliation intersection axes preserved within porphyroblasts)
measurement technology, combined with garnet Lu-Hf and in situ monazite
U-Pb dating to determine the two stages deformation recorded in garnet
and plagioclase porphyroblast, in Tuolemuchang, North Qilian, China. The
early deformation events recorded in garnet porphyroblast is 512.3±2.7Ma
and the younger one recorded in plagioclase porphyroblast no early than
481.0±2.3 Ma, with NE-SW horizontal bulk shortening. Combined with the
results of previous studies on Hf and U-Pb isotopic analysis， 512.3±2.7
Ma garnet Lu-Hf age is considered as the growth time of garnet during
the subduction process of Qilian ocean. The garnet Lu-Hf isotope system
weren’t affected by Younger metamorphism and deformation obviously.
Combine with microstructure analysis, garnet Lu-Hf age can provide
useful constrain for early stage deformation.
