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Metamorphic evolution and geochronology of the Changshanzi area, Dunhuang Orogenic Belt, Northwest China
Pham Van Tho1; Wang Hao2; Zhang Qian1; Liu JiaHui1; Shi MengYan1; Li Zhen1; Wu ChunMing1
2018
Source PublicationACTA PETROLOGICA SINICA
ISSN1000-0569
Volume34Issue:9Pages:2773-+
AbstractMedium- to high-grade metamorphic supracrustal rocks are exposed in the Changshanzi area, northeastern Paleozoic Dunhuang Orogenic Belt, ca. 100km south of Guazhou City, Gansu Province, Northwest China. The Changshanzi metamorphic complex mainly consists of felsic gneiss, metapelitic granulite, amphibolite and high-pressure mafic granulite. Amphibolite and high-pressure mafic granulite occur as lenses or puddings (0. 5 similar to 15m in length) and are intercalated with the matrix ( felsic gneiss, metapelitic granulite) , and show typical block-in-matrix structure. Therefore, the Changshanzi area is in fact a tectonic melange. Two to three stages of metamorphic mineral assemblages are ubiquitously found in the high-pressure mafic granulite, amphibolite and metapelitic granulite. The prograde assemblage ( M1) is the inclusion assemblage preserved in the garnet porphyroblast, the metamorphic peak ( M2) assemblage includes the garnet and the matrix minerals, and the retrograde assemblage ( M3) consists of "white-eye socket" symplectite surrounding the garnet porphyroblast which were formed during tectonic exhumation. Clockwise metamorphic P-T paths were retrieved from the high-pressure mafic granulite, amphibolite and metapelitic granulite, which are generally believed to have been formed in subduction, collision and later tectonic exhumation. The retrograde P-T paths indicate nearly isothermal decompression and thus are ascribed to the western Alpine type, suggesting fast uplift in the tectonic exhumation stage. The peak metamorphism ( M2) belongs to the medium P/T series but the peak P-T conditions show large gaps. For high-pressure mafic granulite, the M2 P-T conditions were determined to be 790 similar to 870 degrees C/1. 29 similar to 1. 37GPa. For amphibolite, they are 680 similar to 685 degrees C/0. 89 similar to 0.97GPa. For metapelitic granulite, the M2 P-T conditions are estimated to be 860 similar to 880 degrees C/0. 90 similar to 1. 14GPa. The data suggest that these rocks were metamorphosed at different depths in the same one subduction channel, and later they amalgamated at shallower level in the uplift stage. SIMS U-Pb dating of metamorphic zircon suggests that the metamorphic event of the Changshanzi area possibly occurred at 419 similar to 417Ma, i. e. , Early Devonian.
KeywordMetamorphic P-T-t path Tectonic melange Geochronology The Changshanzi area Dunhuang Orogenic Belt
WOS KeywordZIRCON U-PB ; NORTHEASTERN TARIM CRATON ; ARCHEAN CONTINENTAL-CRUST ; HIGH-PRESSURE GRANULITES ; LU-HF ; PALEOZOIC SUBDUCTION ; TECTONIC MELANGE ; GARNET ; BLOCK ; THERMOBAROMETRY
Language英语
WOS Research AreaGeology
WOS SubjectGeology
WOS IDWOS:000456917900017
PublisherSCIENCE PRESS
Citation statistics
Cited Times:1[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.iggcas.ac.cn/handle/132A11/90531
Collection岩石圈演化国家重点实验室
Corresponding AuthorWu ChunMing
Affiliation1.Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing 100049, Peoples R China
2.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China
Recommended Citation
GB/T 7714
Pham Van Tho,Wang Hao,Zhang Qian,et al. Metamorphic evolution and geochronology of the Changshanzi area, Dunhuang Orogenic Belt, Northwest China[J]. ACTA PETROLOGICA SINICA,2018,34(9):2773-+.
APA Pham Van Tho.,Wang Hao.,Zhang Qian.,Liu JiaHui.,Shi MengYan.,...&Wu ChunMing.(2018).Metamorphic evolution and geochronology of the Changshanzi area, Dunhuang Orogenic Belt, Northwest China.ACTA PETROLOGICA SINICA,34(9),2773-+.
MLA Pham Van Tho,et al."Metamorphic evolution and geochronology of the Changshanzi area, Dunhuang Orogenic Belt, Northwest China".ACTA PETROLOGICA SINICA 34.9(2018):2773-+.
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