TY - JOUR
T1 - Top boundary of the Dabie UHPM rocks, central China
AU - Qingchen, Wang
AU - Xiaohan, Liu
AU - Maruyama, Shigenori
AU - Bolin, Cong
N1 - Funding Information:
Acknowledgements--This work is financially supported by the National Natural Science Foundation of China. Prof. W. G. Ernst, Prof. J. G. Liou and Dr B. Hacker of Stanford University, U.S.A., are thanked for their helpful discussions. The authors also wish to thank two anonymous reviewers for their careful and instructive reviews.
PY - 1995/5
Y1 - 1995/5
N2 - The top boundary of the ultra-high pressure metamorphic (UHPM) rocks in the Dabie Mountains, central China, has been mapped. The results show that the top boundary of the UHPM rocks is occupied by flat-lying felsic gneiss, on which tonalitic gneiss rests. Petrological and mineralogical evidence indicates a wide P-T gap across the boundary with an estimated peak metamorphic P-T value of the UHPM rocks being >30 kbar and 800 ± 50°C, and that of the tonalitic gneiss around 11 kbar and 800°C. Their P-T-t paths are different. The former has a clockwise path and the latter is counterclockwise. This implies that the UHPM rocks at the bottom and the tonalitic gneiss on top have been structurally juxtaposed together. The top boundary, i.e. the contact between the UHPM rocks and tonalitic gneiss, shows characteristics of a ductile shear zone. Microscopically, feldspar and quartz in the shear zone are characterized by ductile deformation. In larger scale, the top boundary is undulating. Shear sense in the top boundary is a two-way direction. Only the latest shear sense measured with c-axes of quartz show a consistent direction of top-to-the-north. The study provides some constraints to the exhumation process of the Dabie UHPM rocks.
AB - The top boundary of the ultra-high pressure metamorphic (UHPM) rocks in the Dabie Mountains, central China, has been mapped. The results show that the top boundary of the UHPM rocks is occupied by flat-lying felsic gneiss, on which tonalitic gneiss rests. Petrological and mineralogical evidence indicates a wide P-T gap across the boundary with an estimated peak metamorphic P-T value of the UHPM rocks being >30 kbar and 800 ± 50°C, and that of the tonalitic gneiss around 11 kbar and 800°C. Their P-T-t paths are different. The former has a clockwise path and the latter is counterclockwise. This implies that the UHPM rocks at the bottom and the tonalitic gneiss on top have been structurally juxtaposed together. The top boundary, i.e. the contact between the UHPM rocks and tonalitic gneiss, shows characteristics of a ductile shear zone. Microscopically, feldspar and quartz in the shear zone are characterized by ductile deformation. In larger scale, the top boundary is undulating. Shear sense in the top boundary is a two-way direction. Only the latest shear sense measured with c-axes of quartz show a consistent direction of top-to-the-north. The study provides some constraints to the exhumation process of the Dabie UHPM rocks.
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U2 - 10.1016/0743-9547(94)00035-D
DO - 10.1016/0743-9547(94)00035-D
M3 - Article
AN - SCOPUS:0029539096
SN - 1367-9120
VL - 11
SP - 295
EP - 300
JO - Journal of Asian Earth Sciences
JF - Journal of Asian Earth Sciences
IS - 4
ER -