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Petrology, Metamorphic P-T Paths and Zircon U-Pb Ages for Paleoproterozoic Mafic Granulites from Xuanhua, North China Craton
- Source :
- Journal of Earth Science. 30:1197-1214
- Publication Year :
- 2019
- Publisher :
- Springer Science and Business Media LLC, 2019.
-
Abstract
- The studied mafic granulites are located at Xiwangshan, Xuanhua region in the north of the Trans-North China Orogen (TNCO), occurring as lens within tonalite-trondhjemite-granodiorite (TTG) gneisses in the eastern part of the Xiwangshan area. The rocks contain the representative granulite-facies minerals such as garnet, clinopyroxene, orthopyroxene, plagioclase, amphibolite, rutile and quartz, and also well-developed melt pseudomorph and antiperthite. Although the prograde metamorphic stage (M1) cannot be retrieved due to rare preservation of pre-peak-stage mineral associations, three distinct mineral assemblages that formed in different metamorphic stages can be identified, based on petrography and mineralogy characteristics. The peak stage (M2) is characterized by Grt2+Cpx2+Amp2+Pl2+Rt+melt pseudomorphs, and a post-peak decompression stage (M3) contains a mineral assemblage of Grt3+Opx3+ Cpx3+Amp3+Pl3, while a later-retrogression stage (M4) is featured by coronas of Amp4+Pl4 surrounding garnet. By calculating metamorphic P-T conditions using THERMOCALC, stage M2 was constrained to be 13.2–14.8 kbar and 1 050–1 080 °C, and M3 recorded P-T conditions of 5.7–7.3 kbar and 825–875 °C, while M4 yielded P of ~5 kbar and T of ~660 °C, consistent with amphibolite facies metamorphism. Taking into account of all these petrological data, we propose that the mafic granulite experienced a high-pressure (HP) and ultra-high temperature (UHT) granulite-facies metamorphism during the peak metamorphism, which was accompanied with a clockwise P-T path. U-Pb dating of metamorphic zircons in the granulites yields two groups of ages at 1 853±14 and 1 744±44 Ma, respectively. We suggest that the older age corresponded to the HP-UHT metamorphism, while the younger age represented an retrograde metamorphic event during cooling.
- Subjects :
- 020209 energy
Metamorphic rock
Metamorphism
02 engineering and technology
010502 geochemistry & geophysics
Granulite
01 natural sciences
0202 electrical engineering, electronic engineering, information engineering
General Earth and Planetary Sciences
Mafic
Pseudomorph
Petrology
Metamorphic facies
Geology
0105 earth and related environmental sciences
Zircon
Gneiss
Subjects
Details
- ISSN :
- 1867111X and 1674487X
- Volume :
- 30
- Database :
- OpenAIRE
- Journal :
- Journal of Earth Science
- Accession number :
- edsair.doi...........b0acd2560138feaffe95bda6aac6b8c9