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Article: EPMA U-Th-Pb monazite and SHRIMP U-Pb zircon geochronology of high-pressure pelitic granulites in the Jiaobei massif of the North China Craton

TitleEPMA U-Th-Pb monazite and SHRIMP U-Pb zircon geochronology of high-pressure pelitic granulites in the Jiaobei massif of the North China Craton
Authors
Issue Date2008
PublisherAmerican Journal of Science. The Journal's web site is located at http://www.ajsonline.org
Citation
American Journal Of Science, 2008, v. 308 n. 3, p. 328-350 How to Cite?
AbstractThe Jiaobei massif constitutes the southern segment of the Paleoproterozoic Jiao-Liao-Ji belt in the Eastern Block of the North China Craton, and contains high-pressure (HP) mafic and pelitic granulites. The HP pelitic granulites contain four distinct mineral assemblages: Garnet + kyanite + biotite + muscovite + rutile (M1), garnet + kyanite + ternary-feldspar + biotite + muscovite + rutile (M2), garnet + sillimanite + biotite + perthite + anti-perthite (M3), and biotite + muscovite + sillimanite + plagioclase (M4), of which M2 is a typical HP pelitic assemblage. The origin of these HP granulites is important for understanding the tectonic evolution of the Jiao-Liao-Ji Belt, but the timing of the HP event still remains unknown. This study applied the EPMA U-Th-Pb monazite and SHRIMP U-Pb zircon dating techniques to determine the metamorphic ages of the HP pelitic granulites in the Jiaobei massif. CL images and Th/U ratios show that all monazite and zircon grains in the analyzed samples are of metamorphic origin. Eighty-two EPMA analyses on 16 monazite grains from two samples yielded three age groups at 1895 to 1882 Ma, 1814 to 1813 Ma and 1706 to 1692 Ma, and the ages of 16 SHRIMP analyses on 14 zircon grains from one sample range from 1864 to 1803 Ma. The oldest ages of 1895 to 1882 Ma were yielded from high-Y monazite grains enclosed in garnet and sillimanite pseudomorph after kyanite, and thus interpreted as the time of the HP (M2) granulite-facies metamorphism. The EPMA monazite ages of 1814 to 1813 Ma and SHRIMP zircon ages of 1864 to 1803 Ma are interpreted as the approximate ages of the post-HP granulite-facies metamorphism (M3), most probably resulting from the exhumation of the HP granulites to the medium-pressure granulite-facies levels. The youngest age group of 1706 to 1692 Ma obtained from low-Y monazite grains in the matrix can be interpreted as the age of late cooling and retrograde metamorphism (M4) that occurred when the HP pelitic granulites were exhumed to the upper crust. The presence of Paleoproterozoic HP mafic and pelitic granulites in the southern segment of the Jiao-Liao-Ji Belt suggests that the evolution of the Jiao-Liao-Ji Belt in the Eastern Block of the North China Craton must have been involved in subduction- or collision-related tectonic processes.
Persistent Identifierhttp://hdl.handle.net/10722/151252
ISSN
2015 Impact Factor: 3.566
2015 SCImago Journal Rankings: 2.104
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorZhou, Xen_US
dc.contributor.authorZhao, Gen_US
dc.contributor.authorWei, Cen_US
dc.contributor.authorGeng, Yen_US
dc.contributor.authorSun, Men_US
dc.date.accessioned2012-06-26T06:19:21Z-
dc.date.available2012-06-26T06:19:21Z-
dc.date.issued2008en_US
dc.identifier.citationAmerican Journal Of Science, 2008, v. 308 n. 3, p. 328-350en_US
dc.identifier.issn0002-9599en_US
dc.identifier.urihttp://hdl.handle.net/10722/151252-
dc.description.abstractThe Jiaobei massif constitutes the southern segment of the Paleoproterozoic Jiao-Liao-Ji belt in the Eastern Block of the North China Craton, and contains high-pressure (HP) mafic and pelitic granulites. The HP pelitic granulites contain four distinct mineral assemblages: Garnet + kyanite + biotite + muscovite + rutile (M1), garnet + kyanite + ternary-feldspar + biotite + muscovite + rutile (M2), garnet + sillimanite + biotite + perthite + anti-perthite (M3), and biotite + muscovite + sillimanite + plagioclase (M4), of which M2 is a typical HP pelitic assemblage. The origin of these HP granulites is important for understanding the tectonic evolution of the Jiao-Liao-Ji Belt, but the timing of the HP event still remains unknown. This study applied the EPMA U-Th-Pb monazite and SHRIMP U-Pb zircon dating techniques to determine the metamorphic ages of the HP pelitic granulites in the Jiaobei massif. CL images and Th/U ratios show that all monazite and zircon grains in the analyzed samples are of metamorphic origin. Eighty-two EPMA analyses on 16 monazite grains from two samples yielded three age groups at 1895 to 1882 Ma, 1814 to 1813 Ma and 1706 to 1692 Ma, and the ages of 16 SHRIMP analyses on 14 zircon grains from one sample range from 1864 to 1803 Ma. The oldest ages of 1895 to 1882 Ma were yielded from high-Y monazite grains enclosed in garnet and sillimanite pseudomorph after kyanite, and thus interpreted as the time of the HP (M2) granulite-facies metamorphism. The EPMA monazite ages of 1814 to 1813 Ma and SHRIMP zircon ages of 1864 to 1803 Ma are interpreted as the approximate ages of the post-HP granulite-facies metamorphism (M3), most probably resulting from the exhumation of the HP granulites to the medium-pressure granulite-facies levels. The youngest age group of 1706 to 1692 Ma obtained from low-Y monazite grains in the matrix can be interpreted as the age of late cooling and retrograde metamorphism (M4) that occurred when the HP pelitic granulites were exhumed to the upper crust. The presence of Paleoproterozoic HP mafic and pelitic granulites in the southern segment of the Jiao-Liao-Ji Belt suggests that the evolution of the Jiao-Liao-Ji Belt in the Eastern Block of the North China Craton must have been involved in subduction- or collision-related tectonic processes.en_US
dc.languageengen_US
dc.publisherAmerican Journal of Science. The Journal's web site is located at http://www.ajsonline.orgen_US
dc.relation.ispartofAmerican Journal of Scienceen_US
dc.titleEPMA U-Th-Pb monazite and SHRIMP U-Pb zircon geochronology of high-pressure pelitic granulites in the Jiaobei massif of the North China Cratonen_US
dc.typeArticleen_US
dc.identifier.emailZhou, X: chouxiw@163.comen_US
dc.identifier.emailZhao, G: gzhao@hkucc.hku.hken_US
dc.identifier.emailSun, M: minsun@hku.hk-
dc.identifier.authorityZhao, G=rp00842en_US
dc.identifier.authoritySun, M=rp00780en_US
dc.description.naturelink_to_OA_fulltexten_US
dc.identifier.doi10.2475/03.2008.06en_US
dc.identifier.scopuseid_2-s2.0-48749115840en_US
dc.identifier.hkuros144307-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-48749115840&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume308en_US
dc.identifier.issue3en_US
dc.identifier.spage328en_US
dc.identifier.epage350en_US
dc.identifier.isiWOS:000257038900007-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridZhou, X=7410090761en_US
dc.identifier.scopusauthoridZhao, G=7403296321en_US
dc.identifier.scopusauthoridWei, C=7401657811en_US
dc.identifier.scopusauthoridGeng, Y=7103277827en_US
dc.identifier.scopusauthoridSun, M=25932315800en_US

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