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Article: Elemental and Sr-Nd-Pb isotopic geochemistry of Late Paleozoic volcanic rocks beneath the Junggar basin, NW China: Implications for the formation and evolution of the basin basement

TitleElemental and Sr-Nd-Pb isotopic geochemistry of Late Paleozoic volcanic rocks beneath the Junggar basin, NW China: Implications for the formation and evolution of the basin basement
Authors
KeywordsHeterogeneous basement
Junggar basin
Late Paleozoic volcanic rocks
Lava geochemistry
NW China
Oceanic crust
Sr-Nd-Pb isotopes
Issue Date2007
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/jseaes
Citation
Journal Of Asian Earth Sciences, 2007, v. 29 n. 5-6, p. 778-794 How to Cite?
AbstractThe basement beneath the Junggar basin has been interpreted either as a micro-continent of Precambrian age or as a fragment of Paleozoic oceanic crust. Elemental and Sr-Nd-Pb isotopic compositions and zircon Pb-Pb ages of volcanic rocks from drill cores through the paleo-weathered crust show that the basement is composed mainly of late Paleozoic volcanic rock with minor shale and tuff. The volcanic rocks are mostly subalkaline with some minor low-K rocks in the western Kexia area. Some alkaline lavas occur in the central Luliang uplift and northeastern Wulungu depression. The lavas range in composition from basalts to rhyolites and fractional crystallization played an important role in magma evolution. Except for a few samples from Kexia, the basalts have low La/Nb (<1.4), typical for oceanic crust derived from asthenospheric melts. Zircon Pb-Pb ages indicate that the Kexia andesite, with a volcanic arc affinity, formed in the early Carboniferous (345 Ma), whereas the Luliang rhyolite and the Wucaiwan dacite, with syn-collisional to within-plate affinities, formed in the early Devonian (395 and 405 Ma, respectively). Positive ε Nd(t) values (up to +7.4) and low initial 87Sr/ 86Sr isotopic ratios of the intermediate-silicic rocks suggest that the entire Junggar terrain may be underlain by oceanic crust, an interpretation consistent with the juvenile isotopic signatures of many granitoid plutons in other parts of the Central Asia Orogenic Belt. Variation in zircon ages for the silicic rocks, different Ba, P, Ti, Nb or Th anomalies in the mafic rocks, and variable Nb/Y and La/Nb ratios across the basin, suggest that the basement is compositionally heterogeneous. The heterogeneity is believed to reflect amalgamation of different oceanic blocks representing either different evolution stages within a single terrane or possibly derivation from different terranes. © 2006 Elsevier Ltd. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/72682
ISSN
2015 Impact Factor: 2.647
2015 SCImago Journal Rankings: 1.393
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorZheng, Jen_HK
dc.contributor.authorSun, Men_HK
dc.contributor.authorZhao, Gen_HK
dc.contributor.authorRobinson, PTen_HK
dc.contributor.authorWang, Fen_HK
dc.date.accessioned2010-09-06T06:44:07Z-
dc.date.available2010-09-06T06:44:07Z-
dc.date.issued2007en_HK
dc.identifier.citationJournal Of Asian Earth Sciences, 2007, v. 29 n. 5-6, p. 778-794en_HK
dc.identifier.issn1367-9120en_HK
dc.identifier.urihttp://hdl.handle.net/10722/72682-
dc.description.abstractThe basement beneath the Junggar basin has been interpreted either as a micro-continent of Precambrian age or as a fragment of Paleozoic oceanic crust. Elemental and Sr-Nd-Pb isotopic compositions and zircon Pb-Pb ages of volcanic rocks from drill cores through the paleo-weathered crust show that the basement is composed mainly of late Paleozoic volcanic rock with minor shale and tuff. The volcanic rocks are mostly subalkaline with some minor low-K rocks in the western Kexia area. Some alkaline lavas occur in the central Luliang uplift and northeastern Wulungu depression. The lavas range in composition from basalts to rhyolites and fractional crystallization played an important role in magma evolution. Except for a few samples from Kexia, the basalts have low La/Nb (<1.4), typical for oceanic crust derived from asthenospheric melts. Zircon Pb-Pb ages indicate that the Kexia andesite, with a volcanic arc affinity, formed in the early Carboniferous (345 Ma), whereas the Luliang rhyolite and the Wucaiwan dacite, with syn-collisional to within-plate affinities, formed in the early Devonian (395 and 405 Ma, respectively). Positive ε Nd(t) values (up to +7.4) and low initial 87Sr/ 86Sr isotopic ratios of the intermediate-silicic rocks suggest that the entire Junggar terrain may be underlain by oceanic crust, an interpretation consistent with the juvenile isotopic signatures of many granitoid plutons in other parts of the Central Asia Orogenic Belt. Variation in zircon ages for the silicic rocks, different Ba, P, Ti, Nb or Th anomalies in the mafic rocks, and variable Nb/Y and La/Nb ratios across the basin, suggest that the basement is compositionally heterogeneous. The heterogeneity is believed to reflect amalgamation of different oceanic blocks representing either different evolution stages within a single terrane or possibly derivation from different terranes. © 2006 Elsevier Ltd. All rights reserved.en_HK
dc.languageengen_HK
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/jseaesen_HK
dc.relation.ispartofJournal of Asian Earth Sciencesen_HK
dc.subjectHeterogeneous basementen_HK
dc.subjectJunggar basinen_HK
dc.subjectLate Paleozoic volcanic rocksen_HK
dc.subjectLava geochemistryen_HK
dc.subjectNW Chinaen_HK
dc.subjectOceanic crusten_HK
dc.subjectSr-Nd-Pb isotopesen_HK
dc.titleElemental and Sr-Nd-Pb isotopic geochemistry of Late Paleozoic volcanic rocks beneath the Junggar basin, NW China: Implications for the formation and evolution of the basin basementen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=1367-9120&volume=29&issue=5-6&spage=778&epage=794&date=2007&atitle=Elemental+and+Sr–Nd–Pb+isotopic+geochemistry+of+Late+Paleozoic+volcanic+rocks+beneath+the+Junggar+basin,+NW+China:+Implications+for+the+formation+and+evolution+of+the+basin+basementen_HK
dc.identifier.emailSun, M:minsun@hku.hken_HK
dc.identifier.emailZhao, G:gzhao@hkucc.hku.hken_HK
dc.identifier.authoritySun, M=rp00780en_HK
dc.identifier.authorityZhao, G=rp00842en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.jseaes.2006.05.004en_HK
dc.identifier.scopuseid_2-s2.0-33847229763en_HK
dc.identifier.hkuros127574en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-33847229763&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume29en_HK
dc.identifier.issue5-6en_HK
dc.identifier.spage778en_HK
dc.identifier.epage794en_HK
dc.identifier.isiWOS:000245564700015-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridZheng, J=48961536100en_HK
dc.identifier.scopusauthoridSun, M=25932315800en_HK
dc.identifier.scopusauthoridZhao, G=7403296321en_HK
dc.identifier.scopusauthoridRobinson, PT=7403720506en_HK
dc.identifier.scopusauthoridWang, F=7501311273en_HK

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