%0 Journal Article
%T Mineralogical Characteristics of Garnet in Garnet Mica Schist and Its Tectonic Significance in the Tongbai Section of the Shangdan Fault Zone
%A Shenglian Ren
%A Chuanzhong Song
%A Jiahao Li
%J Open Journal of Geology
%P 13-27
%@ 2161-7589
%D 2015
%I Scientific Research Publishing
%R 10.4236/ojg.2015.51002
%X Studies on the
metamorphism and deformation conditions of rocks in the suture zone are good
ways to discuss the orogenic process and mechanism. The microstructure and
ultramicrostructure features of minerals are true embodiment of formation
environment of the orogenic belt. Based on the study of microstructure,
ultramicrostructure deformation characteristic and compositional zonation of
garnets in garnets-mica schists in the Tongbai mountain, east section of the
Shangdan fault zone, the results show that the three types of garnets have
suffered various states of plastic deformation. The dynamic recrystallization
of garnets is due to the subgrain growth and boundary migration. The
dislocations are mainly free dislocation and dislocation walls. The free
dislocation density ¦Ñ = 6.14 ¡Á 108/cm2,
and dislocation movement are mainly slips; slip planes are 1/2 <111>
{110} and <100> {001}. Garnet microprobe analysis shows that it belongs
to almandine, and reflects it has undergone epidote-amphibolite to amphibolite
facies metamorphism. Compositional zonation of garnet shows that the rocks had experienced
progressive metamorphism. First metamorphic environment was continuous
temperature-pressure and in mid-term there were two non-synchronous transient
cooling and decompression processes, and it finally underwent decompression and
warming process of the thermal relaxation environment. The formation condition
of garnet-mica schist is estimated: T = 562¡ãC - 617¡ãC, and P = 0.77 - 1.02 GPa.
The differential stress is 0.511 GPa and strain rate is 4.97536 ¡Á 10-10 m/s. After systemic analysis, a
conclusion is drawn that the plastic deformation mode, deformation mechanism
and formation environment of garnets are
%K The Tongbai Area
%K The Shangdan Fault Zone
%K Metamorphism and Deformation
%K Compositional Zonation of Garnet
%K Dislocation
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=53513