Phase equilibria and metamorphic evolution of glaucophane-bearing UHP   eclogites from the Western Dabieshan Terrane, Central China

doi:10.1111/j.1525-1314.2010.00884.x

CORC > 北京大学 > 地球与空间科学学院

	Phase equilibria and metamorphic evolution of glaucophane-bearing UHP eclogites from the Western Dabieshan Terrane, Central China
	Wei, C. J. . ; Li, Y. J. . ; Yu, Y. ; Zhang, J. S.
刊名	journal of metamorphic geology
	2010
关键词	eclogite phase equilibrium P-T path western Dabieshan P-T PATH EFFECTIVE BULK-COMPOSITION CALCULATED MINERAL EQUILIBRIA SUBDUCTED CONTINENTAL-CRUST ULTRAHIGH-PRESSURE ROCKS NORTH QILIAN OROGEN EAST-CENTRAL CHINA NW CHINA THERMODYNAMIC MODEL MIXING PROPERTIES
DOI	10.1111/j.1525-1314.2010.00884.x
英文摘要	Glaucophane-bearing ultrahigh pressure (UHP) eclogites from the western Dabieshan terrane consist of garnet, omphacite, glaucophane, kyanite, epidote, phengite, quartz/coesite and rutile with or without talc and paragonite. Some garnet porphyroblasts exhibit a core-mantle zoning profile with slight increase in pyrope content and minor or slight decrease in grossular and a mantle-rim zoning profile characterized by a pronounced increase in pyrope and rapid decrease in grossular. Omphacite is usually zoned with a core-rim decrease in j(o) [=Na/(Ca + Na)]. Glaucophane occurs as porphyroblasts in some samples and contains inclusions of garnet, omphacite and epidote. Pseudosections calculated in the NCKMnFMASHO system for five representative samples, combined with petrographic observations suggest that the UHP eclogites record four stages of metamorphism. (i) The prograde stage, on the basis of modelling of garnet zoning and inclusions in garnet, involves P-T vectors dominated by heating with a slight increase in pressure, suggesting an early slow subduction process, and P-T vectors dominated by a pronounced increase in pressure and slight heating, pointing to a late fast subduction process. The prograde metamorphism is predominated by dehydration of glaucophane and, to a lesser extent, chlorite, epidote and paragonite, releasing similar to 27 wt% water that was bound in the hydrous minerals. (ii) The peak stage is represented by garnet rim compositions with maximum pyrope and minimum grossular contents, and P-T conditions of 28.2-31.8 kbar and 605-613 degrees C, with the modelled peak-stage mineral assemblage mostly involving garnet + omphacite + lawsonite + talc + phengite + coesite +/- glaucophane +/- kyanite. (iii) The early decompression stage is characterized by dehydration of lawsonite, releasing similar to 70-90 wt% water bound in the peak mineral assemblages, which results in the growth of glaucophane, j(o) decrease in omphacite and formation of epidote. And, (iv) The late retrograde stage is characterized by the mineral assemblage of hornblendic amphibole + epidote + albite/oligoclase + quartz developed in the margins or strongly foliated domains of eclogite blocks due to fluid infiltration at P-T conditions of 5-10 kbar and 500-580 degrees C. The proposed metamorphic stages for the UHP eclogites are consistent with the petrological observations, but considerably different from those presented in the previous studies.; Geology; SCI(E); EI; 27; ARTICLE; 6; 647-666; 28
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/155834]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Wei, C. J. .,Li, Y. J. .,Yu, Y.,et al. Phase equilibria and metamorphic evolution of glaucophane-bearing UHP eclogites from the Western Dabieshan Terrane, Central China[J]. journal of metamorphic geology,2010.
APA	Wei, C. J. .,Li, Y. J. .,Yu, Y.,&Zhang, J. S..(2010).Phase equilibria and metamorphic evolution of glaucophane-bearing UHP eclogites from the Western Dabieshan Terrane, Central China.journal of metamorphic geology.
MLA	Wei, C. J. .,et al."Phase equilibria and metamorphic evolution of glaucophane-bearing UHP eclogites from the Western Dabieshan Terrane, Central China".journal of metamorphic geology (2010).