Characteristics and Genetic Significance of High Temperature Granulite Xenoliths in Cenozoic Volcanic Rocks, Tengchong,Western Yunnan Province, China
Lin Musen
Peng Songbai
Qiao Weitao
Li Changnian
Xu Haijun
Abstract：Researches on the Cenozoic volcanic rocks of the Mangbang Formation in the Mangbang area of the Tengchong block, South China,reveals many granulite xenoliths of felsic granulite and two-pyroxene granulite in trachyandesite. The granulite xenoliths range 3-5 cm in diameters,featured with aligned formation and blastic texture. Equilibrium temperature and pres-sure estimates for the felsic granulite xenoliths and two-pyroxene granulite xenoliths are 869-969°C,0.94-1.00 GPa and 841-972°C respectively,indicating that they are high temperature granulites. The crystallization temperature and pressure of trachyandesite phenocryst is 1008-1059 C,1.26 -1.33 GPa,indicating that they were formed in and originated from the low-er crust to the top of the upper mantle. Electron backs catter diffraction (EBSD) analyses of two-pyroxene granulite xenoliths show that orthopyroxene and clinopyroxene have obvious lattice preferred orientation (LP0),and the main slip systems are: (010) [001] and (100) [001],(010) [001] respectively. The deformation mechanism is dislocation creep,which indicates that granulite xenoliths experienced a strong plastic deformation and metamorphism. The discovery of high temperature granulite in Cenozoic volcanic rocks suggests that Tengchong Cenozoic magmatic activity may be related with volcanic magamatism and high temperature metamorphism in the lower crustal caused by post-collisional extensional collapse,delamination and slab break-off after subduction and collision of the Indian Plate and the Tengchong block.
Keywords：Tengchong blockCenozoic trachyandesiteHigh-temperature granulite xenolithequilibrium temperature and pressureelectron backscatter diffractionmicro-fabricpetrology
Publication Date：2014-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 807-819 )