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Article: Geochemistry of the Early Paleozoic Baiyin Volcanic Rocks (NW China): Implications for the Tectonic Evolution of the North Qilian Orogenic Belt

TitleGeochemistry of the Early Paleozoic Baiyin Volcanic Rocks (NW China): Implications for the Tectonic Evolution of the North Qilian Orogenic Belt
Authors
KeywordsBasalt
Geochemistry
Plate tectonics
Subduction zones
Volcanic ash, tuff, etc.
Issue Date2005
PublisherUniversity of Chicago Press. The Journal's web site is located at http://www.journals.uchicago.edu/JG
Citation
The Journal of Geology, 2005, v. 113 n. 1, p. 83-94 How to Cite?
AbstractThe Qilian Mountains in NW China comprise the North Qilian Orogenic Belt, Central Qilian Block, and South Qilian Orogenic Belt. The North Qilian Orogenic Belt consists of the Northern and Southern terranes separated by a volcanic rock belt. This belt is composed mainly of felsic and mafic volcanic rocks. Volcanic rocks in the Baiyin area of the eastern part of the belt include rhyolites, rhyodacite, andesitic basalts, and basalts. New zircon U-Pb isotopic data yield a crystallization age of ca. 445 Ma for the rhyolite, 30 m.yr. younger than the associated basalts. The mafic volcanic rocks are relatively enriched in Th, Sr, and light rare earth element with (La/Yb) N ratios ranging from 4.2 to 5.6 and LaN ranging from 40 to 49, and depleted in high field strength elements, with high Th/Nb ratios (0.9-1.3). These features together with their εNd(T) values (-1.4 to +3.1) are consistent with a subduction-related origin, most likely in a mature island arc or an arc built on thin continental crust in an active continental margin. The felsic volcanic rocks show a calc-alkaline affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies and relatively high Th/Nb ratios (0.8-1.6). They have significantly high εNd(T) values (+4.4 to +7.7) relative to the mafic volcanic rocks. Such radiogenic Nd isotopic compositions rule out a crustal origin and indicate the derivation from a depleted mantle source in a volcanic arc environment. Therefore, the geochemistry of the mafic and felsic volcanic rocks demonstrates an Ordovician volcanic arc above a northward subduction zone. The northward drifting of the Central Qilian Block eventually resulted in the amalgamation of the Northern and Southern terranes to form the North Qilian Orogenic Belt in the Early Paleozoic. © 2005 by The University of Chicago. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/44686
ISSN
2015 Impact Factor: 2.58
2015 SCImago Journal Rankings: 1.344
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorWang, CYen_HK
dc.contributor.authorZhang, Qen_HK
dc.contributor.authorQuan, Qen_HK
dc.contributor.authorZhou, MFen_HK
dc.date.accessioned2007-10-30T06:07:44Z-
dc.date.available2007-10-30T06:07:44Z-
dc.date.issued2005en_HK
dc.identifier.citationThe Journal of Geology, 2005, v. 113 n. 1, p. 83-94en_HK
dc.identifier.issn0022-1376en_HK
dc.identifier.urihttp://hdl.handle.net/10722/44686-
dc.description.abstractThe Qilian Mountains in NW China comprise the North Qilian Orogenic Belt, Central Qilian Block, and South Qilian Orogenic Belt. The North Qilian Orogenic Belt consists of the Northern and Southern terranes separated by a volcanic rock belt. This belt is composed mainly of felsic and mafic volcanic rocks. Volcanic rocks in the Baiyin area of the eastern part of the belt include rhyolites, rhyodacite, andesitic basalts, and basalts. New zircon U-Pb isotopic data yield a crystallization age of ca. 445 Ma for the rhyolite, 30 m.yr. younger than the associated basalts. The mafic volcanic rocks are relatively enriched in Th, Sr, and light rare earth element with (La/Yb) N ratios ranging from 4.2 to 5.6 and LaN ranging from 40 to 49, and depleted in high field strength elements, with high Th/Nb ratios (0.9-1.3). These features together with their εNd(T) values (-1.4 to +3.1) are consistent with a subduction-related origin, most likely in a mature island arc or an arc built on thin continental crust in an active continental margin. The felsic volcanic rocks show a calc-alkaline affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies and relatively high Th/Nb ratios (0.8-1.6). They have significantly high εNd(T) values (+4.4 to +7.7) relative to the mafic volcanic rocks. Such radiogenic Nd isotopic compositions rule out a crustal origin and indicate the derivation from a depleted mantle source in a volcanic arc environment. Therefore, the geochemistry of the mafic and felsic volcanic rocks demonstrates an Ordovician volcanic arc above a northward subduction zone. The northward drifting of the Central Qilian Block eventually resulted in the amalgamation of the Northern and Southern terranes to form the North Qilian Orogenic Belt in the Early Paleozoic. © 2005 by The University of Chicago. All rights reserved.en_HK
dc.format.extent459510 bytes-
dc.format.extent2822 bytes-
dc.format.mimetypeapplication/pdf-
dc.format.mimetypetext/plain-
dc.languageengen_HK
dc.publisherUniversity of Chicago Press. The Journal's web site is located at http://www.journals.uchicago.edu/JGen_HK
dc.rightsThe Journal of Geology. Copyright © University of Chicago Press.en_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subjectBasalten_HK
dc.subjectGeochemistryen_HK
dc.subjectPlate tectonicsen_HK
dc.subjectSubduction zonesen_HK
dc.subjectVolcanic ash, tuff, etc.en_HK
dc.titleGeochemistry of the Early Paleozoic Baiyin Volcanic Rocks (NW China): Implications for the Tectonic Evolution of the North Qilian Orogenic Belten_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0022-1376&volume=113&issue=1&spage=83&epage=94&date=2005&atitle=Geochemistry+of+the+Early+Paleozoic+Baiyin+Volcanic+Rocks+(NW+China):+Implications+for+the+Tectonic+Evolution+of+the+North+Qilian+Orogenic+Belten_HK
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hk-
dc.identifier.authorityZhou, MF=rp00844-
dc.description.naturepublished_or_final_versionen_HK
dc.identifier.doi10.1086/425970-
dc.identifier.scopuseid_2-s2.0-13244286652-
dc.identifier.hkuros108773-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-13244286652&selection=ref&src=s&origin=recordpage-
dc.identifier.volume113-
dc.identifier.issue1-
dc.identifier.spage83-
dc.identifier.epage94-
dc.identifier.isiWOS:000226246000005-
dc.publisher.placeUnited States-
dc.identifier.scopusauthoridWang, CY=35849436700-
dc.identifier.scopusauthoridZhang, Q=35515964300-
dc.identifier.scopusauthoridQian, Q=7102168564-
dc.identifier.scopusauthoridZhou, MF=7403506005-

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