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Article: Geochemistry and Nd isotopic composition of the Early Paleozoic flysch sequence in the Chinese Altai, Central Asia: evidence for a northward-derived mafic source and insight into Nd model ages in accretionary orogen

TitleGeochemistry and Nd isotopic composition of the Early Paleozoic flysch sequence in the Chinese Altai, Central Asia: evidence for a northward-derived mafic source and insight into Nd model ages in accretionary orogen
Authors
KeywordsAccretionary orogen
Flysch
Geochemistry
Nd isotope
Provenance
Issue Date2012
PublisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/jcr
Citation
Gondwana Research, 2012, v. 22 n. 2, p. 554-566 How to Cite?
AbstractAlthough Nd isotopic composition of sedimentary rocks is considered as a useful tool to trace the provenance, their Nd model age (T DM) is usually misused to discuss the timing of crustal formation in accretionary orogen. In the Central Asian Orogenic Belt, an Early Paleozoic flysch sequence extensively occurs in the Chinese Altai and adjacent western Mongolian terranes. Sedimentary rocks in the northwestern Chinese Altai were collected from the flysch sequence for geochemical and Nd isotopic studies. Although these rocks show different geochemical characteristics (e.g., arenaceous and argillaceous), they all have relatively low CIA (Chemical Index of Alteration) values (49-75), indicating a relatively weak weathering source or the absence of compositionally mature alumina-rich minerals produced by chemical weathering processes. Their relatively high ICV (Index of Compositional Variability) values (0.95-1.35) reveal an immature source and indicate that these rocks were probably deposited in an active tectonic setting. The sedimentary rocks from the flysch sequence have high MgO, Sc, Co and low Y, Nb, which suggest significant addition of mafic rocks into the source. Modeling based on Nb-Cr and Zr-MgO contents displays nearly 20% to 50% addition of mafic materials. In combination with the age and distribution of mafic rocks in the Chinese Altai and adjacent terranes, a northward-derived mafic source is recommended for the sedimentary sequence. Although the sedimentary rocks have Nd model ages (T DM=1.44-1.57Ga) older than Devonian granites (T DM=1.6-1.1Ga), young detrital zircons from the sediments and inherited zircons from the granites (450-500Ma) suggest a mixed source consisting of both old crust components and juvenile or less evolved crustal components. This reveals that Nd model ages (T DM) of metasedimentary rocks and igneous rocks can hardly provide close constrains on the timing of crustal formation in accretionary orogen. With the progresses in adjacent western Mongolian terranes, a tectonic scenario dominated by subduction-accretionary process is suggested to interpret the formation of the Early Paleozoic flysch sequence in the Chinese Altai and adjacent terranes. © 2011 International Association for Gondwana Research.
Persistent Identifierhttp://hdl.handle.net/10722/151314
ISSN
2015 Impact Factor: 8.743
2015 SCImago Journal Rankings: 4.949
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorLong, Xen_US
dc.contributor.authorYuan, Cen_US
dc.contributor.authorSun, Men_US
dc.contributor.authorXiao, Wen_US
dc.contributor.authorWang, Yen_US
dc.contributor.authorCai, Ken_US
dc.contributor.authorJiang, Yen_US
dc.date.accessioned2012-06-26T06:20:28Z-
dc.date.available2012-06-26T06:20:28Z-
dc.date.issued2012en_US
dc.identifier.citationGondwana Research, 2012, v. 22 n. 2, p. 554-566en_US
dc.identifier.issn1342-937Xen_US
dc.identifier.urihttp://hdl.handle.net/10722/151314-
dc.description.abstractAlthough Nd isotopic composition of sedimentary rocks is considered as a useful tool to trace the provenance, their Nd model age (T DM) is usually misused to discuss the timing of crustal formation in accretionary orogen. In the Central Asian Orogenic Belt, an Early Paleozoic flysch sequence extensively occurs in the Chinese Altai and adjacent western Mongolian terranes. Sedimentary rocks in the northwestern Chinese Altai were collected from the flysch sequence for geochemical and Nd isotopic studies. Although these rocks show different geochemical characteristics (e.g., arenaceous and argillaceous), they all have relatively low CIA (Chemical Index of Alteration) values (49-75), indicating a relatively weak weathering source or the absence of compositionally mature alumina-rich minerals produced by chemical weathering processes. Their relatively high ICV (Index of Compositional Variability) values (0.95-1.35) reveal an immature source and indicate that these rocks were probably deposited in an active tectonic setting. The sedimentary rocks from the flysch sequence have high MgO, Sc, Co and low Y, Nb, which suggest significant addition of mafic rocks into the source. Modeling based on Nb-Cr and Zr-MgO contents displays nearly 20% to 50% addition of mafic materials. In combination with the age and distribution of mafic rocks in the Chinese Altai and adjacent terranes, a northward-derived mafic source is recommended for the sedimentary sequence. Although the sedimentary rocks have Nd model ages (T DM=1.44-1.57Ga) older than Devonian granites (T DM=1.6-1.1Ga), young detrital zircons from the sediments and inherited zircons from the granites (450-500Ma) suggest a mixed source consisting of both old crust components and juvenile or less evolved crustal components. This reveals that Nd model ages (T DM) of metasedimentary rocks and igneous rocks can hardly provide close constrains on the timing of crustal formation in accretionary orogen. With the progresses in adjacent western Mongolian terranes, a tectonic scenario dominated by subduction-accretionary process is suggested to interpret the formation of the Early Paleozoic flysch sequence in the Chinese Altai and adjacent terranes. © 2011 International Association for Gondwana Research.en_US
dc.languageengen_US
dc.publisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/jcren_US
dc.relation.ispartofGondwana Researchen_US
dc.subjectAccretionary orogenen_US
dc.subjectFlyschen_US
dc.subjectGeochemistryen_US
dc.subjectNd isotopeen_US
dc.subjectProvenanceen_US
dc.titleGeochemistry and Nd isotopic composition of the Early Paleozoic flysch sequence in the Chinese Altai, Central Asia: evidence for a northward-derived mafic source and insight into Nd model ages in accretionary orogenen_US
dc.typeArticleen_US
dc.identifier.emailYuan, C: yuanchao@gig.ac.cnen_US
dc.identifier.emailSun, M: minsun@hku.hk-
dc.identifier.emailCai, K: caikd@hku.hk-
dc.identifier.emailJiang, Y: ydjiang@hku.hk-
dc.identifier.authoritySun, M=rp00780en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1016/j.gr.2011.04.009en_US
dc.identifier.scopuseid_2-s2.0-84863877675en_US
dc.identifier.hkuros205438-
dc.identifier.volume22-
dc.identifier.issue2-
dc.identifier.spage554-
dc.identifier.epage566-
dc.identifier.isiWOS:000307602000015-
dc.publisher.placeNetherlandsen_US
dc.identifier.scopusauthoridJiang, Y=36657132100en_US
dc.identifier.scopusauthoridCai, K=14011943800en_US
dc.identifier.scopusauthoridWang, Y=37762225700en_US
dc.identifier.scopusauthoridXiao, W=7202456615en_US
dc.identifier.scopusauthoridSun, M=25932315800en_US
dc.identifier.scopusauthoridYuan, C=35241599200en_US
dc.identifier.scopusauthoridLong, X=14012199100en_US

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