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Conference Paper: Granitic gneisses and gneissic granites from the Central Terrane of the Chinese Altai Orogen: zircon ages and tectonic significance

TitleGranitic gneisses and gneissic granites from the Central Terrane of the Chinese Altai Orogen: zircon ages and tectonic significance
Authors
Issue Date2006
PublisherJohn Wiley & Sons, Inc..
Citation
The 2006 Western Pacific Geophysics Meeting (WPGM), Beijing, China, 24-27 July 2006. In EOS (Online), 2006, v. 87 n. 36, abstract V25A-06 How to Cite?
AbstractThe granitic gneiss and gneissic granite are two major components of the Central Terrane of the Chinese Altai Orogen. The former is intruded by the latter and is considered to have Sinian or Ordovician ages. Samples of the granitic gneiss and gneissic granite were collected from the western part of the Central Terrane. Both of these rock types have granitic compositions with arc affinities, but can be chemically distinguished. For example, the granitic gneisses are characterized by high Mg, Ni, and Cr contents. Zircon U- Pb isotope analyses by LA-ICP-MS indicate that the granitic gneisses and gneissic granites were crystallized at 470-500 Ma and 380-420 Ma, respectively. Inherited zircons with Neoproterozoic ages are common and 2.5 Ga zircons also occur in the granitic gneisses, but only one gneissic granite sample contain some Neoproterozoic inheritance zircons. Amphibolites and greenschists also occur in the study area. These rocks are envisaged as metamorphic volcanic rocks and they have island arc geochemical features. Zircons separated from a amphibolite sample give 400 Ma U-Pb ages. Based on these results and geochemical data, we propose that an undefined Precambrian continental block with significant amount of Neoproterozoic rocks along its margin was intruded by the protolith of the granitic gneisses at 470-500 Ma in a continental magmatic arc environment. On the other hand, the gneissic granites were formed in an island arc environment about 100 Ma later, as evidenced by the absence of Neoprterozoic inheritance zircons and the contemporaneous island arc volcanism. This study is supported by Hong Kong RGC (HKU7040/04P).
DescriptionSession - The Ion, Laser, and Electron Probe Revolution: Microanalytical Dating of Geological Samples III: abstract no. V25A-06
Persistent Identifierhttp://hdl.handle.net/10722/117360
ISSN
2015 SCImago Journal Rankings: 0.434

 

DC FieldValueLanguage
dc.contributor.authorSun, Men_HK
dc.contributor.authorYuan, Cen_HK
dc.contributor.authorXiao, Wen_HK
dc.contributor.authorLong, Xen_HK
dc.contributor.authorXia, Xen_HK
dc.contributor.authorHan, Cen_HK
dc.contributor.authorLin, Sen_HK
dc.date.accessioned2010-09-26T07:13:13Z-
dc.date.available2010-09-26T07:13:13Z-
dc.date.issued2006en_HK
dc.identifier.citationThe 2006 Western Pacific Geophysics Meeting (WPGM), Beijing, China, 24-27 July 2006. In EOS (Online), 2006, v. 87 n. 36, abstract V25A-06-
dc.identifier.issn2324-9250-
dc.identifier.urihttp://hdl.handle.net/10722/117360-
dc.descriptionSession - The Ion, Laser, and Electron Probe Revolution: Microanalytical Dating of Geological Samples III: abstract no. V25A-06-
dc.description.abstractThe granitic gneiss and gneissic granite are two major components of the Central Terrane of the Chinese Altai Orogen. The former is intruded by the latter and is considered to have Sinian or Ordovician ages. Samples of the granitic gneiss and gneissic granite were collected from the western part of the Central Terrane. Both of these rock types have granitic compositions with arc affinities, but can be chemically distinguished. For example, the granitic gneisses are characterized by high Mg, Ni, and Cr contents. Zircon U- Pb isotope analyses by LA-ICP-MS indicate that the granitic gneisses and gneissic granites were crystallized at 470-500 Ma and 380-420 Ma, respectively. Inherited zircons with Neoproterozoic ages are common and 2.5 Ga zircons also occur in the granitic gneisses, but only one gneissic granite sample contain some Neoproterozoic inheritance zircons. Amphibolites and greenschists also occur in the study area. These rocks are envisaged as metamorphic volcanic rocks and they have island arc geochemical features. Zircons separated from a amphibolite sample give 400 Ma U-Pb ages. Based on these results and geochemical data, we propose that an undefined Precambrian continental block with significant amount of Neoproterozoic rocks along its margin was intruded by the protolith of the granitic gneisses at 470-500 Ma in a continental magmatic arc environment. On the other hand, the gneissic granites were formed in an island arc environment about 100 Ma later, as evidenced by the absence of Neoprterozoic inheritance zircons and the contemporaneous island arc volcanism. This study is supported by Hong Kong RGC (HKU7040/04P).-
dc.languageengen_HK
dc.publisherJohn Wiley & Sons, Inc..-
dc.relation.ispartofEOS (Online)en_HK
dc.rightsEOS (Online). Copyright © John Wiley & Sons, Inc..-
dc.titleGranitic gneisses and gneissic granites from the Central Terrane of the Chinese Altai Orogen: zircon ages and tectonic significanceen_HK
dc.typeConference_Paperen_HK
dc.identifier.emailSun, M: minsun@hku.hken_HK
dc.identifier.emailYuan, C: yuanchao@gig.ac.cnen_HK
dc.identifier.emailLong, X: lxp_79@sina.comen_HK
dc.identifier.emailXia, X: xpxia@hotmail.comen_HK
dc.identifier.authoritySun, M=rp00780en_HK
dc.description.naturelink_to_OA_fulltext-
dc.identifier.hkuros128548en_HK
dc.identifier.volume87-
dc.identifier.issue36, abstract V25A-06-
dc.publisher.placeUnited States-

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