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Article: Melting of newly formed mafic crust for the formation of Neoproterozoic I-type granite in the Hannan region, South China

TitleMelting of newly formed mafic crust for the formation of Neoproterozoic I-type granite in the Hannan region, South China
Authors
KeywordsColor figures
Tables
Issue Date2009
PublisherUniversity of Chicago Press. The Journal's web site is located at http://www.journals.uchicago.edu/JG
Citation
Journal Of Geology, 2009, v. 117 n. 1, p. 54-70 How to Cite?
AbstractNeoproterozoic magmatism in the Hannan region at the northwestern margin of the Yangtze Block is characterized by numerous felsic plutons associated with minor mafic-ultramafic intrusions. The felsic plutons are either adakitic or normal-arc granitic in composition. The adakitic plutons are ∼735 Ma in age and are interpreted as having formed by partial melting of a thickened lower mafic crust. Among the normal-arc-related felsic plutons, the Tianpinghe pluton is the largest and has a SHRIMP zircon U-Pb age of 762 ± 4 Ma, older than the adakitic plutons in the region. Rocks from the Tianpinghe pluton have relatively high SiO2 (67.1-70.1 wt%) and K2O+ Na 2O (7.8-8.6 wt%) and relatively low MgO (0.7-1.3 wt%) and Al 2O3 contents (14.5-15.6 wt%), with Al2O 3/(CaO + K2O + Na2O) (A/CNK) values ranging from 0.95 to 1.08. They have arc-affinity trace-element compositions that are characterized by enrichment of large-ion lithophile elements and depletion of high-field-strength elements (Nb, Ta), with strong positive Pb and negative Ti anomalies. They have a narrow range of εNd(t) values (+0.15 to - 1.76) and relatively high zircon eHf values (+0.6 to - 8.3). These geochemical features are typical of I-type granites. The rocks from the Tianpinghe pluton have relatively young single-stage and two-stage Hf model ages (1.01-1.31 and 1.31-2.01 Ga, respectively), suggesting that the pluton was generated by partial melting of newly formed basaltic rocks. On the basis of its arc-related geochemical affinity and its emplacement before voluminous adakitic magmatism but after mafic-ultramafic intrusions, the Tianpinghe pluton is considered to be Neoproterozoic arc granite formed during a period of crustal growth and reworking. Generation of the later adakitic plutons suggests that the crustal thickness increased to more than 50 km by mafic magma underplating. © 2009 by The University of Chicago. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/58662
ISSN
2015 Impact Factor: 2.58
2015 SCImago Journal Rankings: 1.344
ISI Accession Number ID
Funding AgencyGrant Number
National Natural Science Foundation of China40873027
Chinese Academy of Science
University of Hong Kong
Funding Information:

This work was substantially supported by grants from the National Natural Science Foundation of China (40873027), the Chinese Academy of Science (2005), and a Chinese 973 project matching fund from the University of Hong Kong. We are grateful to Allen Kennedy for SHRIMP dating, Xiao Fu for x-ray fluorescence analyses, Gao Jian-Feng for ICP-MS analyses, and Liu He and Zhao Xin-Fu for zircon Lu-Hf analyses. Cheng Wei is also thanked for his assistance in the field.

References

 

DC FieldValueLanguage
dc.contributor.authorZhao, JHen_HK
dc.contributor.authorZhou, MFen_HK
dc.date.accessioned2010-05-31T03:34:36Z-
dc.date.available2010-05-31T03:34:36Z-
dc.date.issued2009en_HK
dc.identifier.citationJournal Of Geology, 2009, v. 117 n. 1, p. 54-70en_HK
dc.identifier.issn0022-1376en_HK
dc.identifier.urihttp://hdl.handle.net/10722/58662-
dc.description.abstractNeoproterozoic magmatism in the Hannan region at the northwestern margin of the Yangtze Block is characterized by numerous felsic plutons associated with minor mafic-ultramafic intrusions. The felsic plutons are either adakitic or normal-arc granitic in composition. The adakitic plutons are ∼735 Ma in age and are interpreted as having formed by partial melting of a thickened lower mafic crust. Among the normal-arc-related felsic plutons, the Tianpinghe pluton is the largest and has a SHRIMP zircon U-Pb age of 762 ± 4 Ma, older than the adakitic plutons in the region. Rocks from the Tianpinghe pluton have relatively high SiO2 (67.1-70.1 wt%) and K2O+ Na 2O (7.8-8.6 wt%) and relatively low MgO (0.7-1.3 wt%) and Al 2O3 contents (14.5-15.6 wt%), with Al2O 3/(CaO + K2O + Na2O) (A/CNK) values ranging from 0.95 to 1.08. They have arc-affinity trace-element compositions that are characterized by enrichment of large-ion lithophile elements and depletion of high-field-strength elements (Nb, Ta), with strong positive Pb and negative Ti anomalies. They have a narrow range of εNd(t) values (+0.15 to - 1.76) and relatively high zircon eHf values (+0.6 to - 8.3). These geochemical features are typical of I-type granites. The rocks from the Tianpinghe pluton have relatively young single-stage and two-stage Hf model ages (1.01-1.31 and 1.31-2.01 Ga, respectively), suggesting that the pluton was generated by partial melting of newly formed basaltic rocks. On the basis of its arc-related geochemical affinity and its emplacement before voluminous adakitic magmatism but after mafic-ultramafic intrusions, the Tianpinghe pluton is considered to be Neoproterozoic arc granite formed during a period of crustal growth and reworking. Generation of the later adakitic plutons suggests that the crustal thickness increased to more than 50 km by mafic magma underplating. © 2009 by The University of Chicago. All rights reserved.en_HK
dc.languageengen_HK
dc.publisherUniversity of Chicago Press. The Journal's web site is located at http://www.journals.uchicago.edu/JGen_HK
dc.relation.ispartofJournal of Geologyen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subjectColor figures-
dc.subjectTables-
dc.titleMelting of newly formed mafic crust for the formation of Neoproterozoic I-type granite in the Hannan region, South Chinaen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0022-1376&volume=117&issue=1&spage=54&epage=70&date=2009&atitle=Melting+of+Newly+Formed+Mafic+Crust+for+the+Formation+of+Neoproterozoic+I-Type+Granite+in+the+Hannan+Region,+South+Chinaen_HK
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hken_HK
dc.identifier.authorityZhou, MF=rp00844en_HK
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1086/593321en_HK
dc.identifier.scopuseid_2-s2.0-61849147827en_HK
dc.identifier.hkuros167320en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-61849147827&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume117en_HK
dc.identifier.issue1en_HK
dc.identifier.spage54en_HK
dc.identifier.epage70en_HK
dc.identifier.isiWOS:000263061900005-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridZhao, JH=11140043500en_HK
dc.identifier.scopusauthoridZhou, MF=7403506005en_HK
dc.identifier.citeulike4005422-

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