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Article: Controls on the PGE distribution of Permian Emeishan alkaline and peralkaline volcanic rocks in Longzhoushan, Sichuan Province, SW China

TitleControls on the PGE distribution of Permian Emeishan alkaline and peralkaline volcanic rocks in Longzhoushan, Sichuan Province, SW China
Authors
KeywordsEmeishan
Flood basalts
Petrogenesis
Platinum-group elements
SW China
Tephrite
Issue Date2008
PublisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/lithos
Citation
Lithos, 2008, v. 106 n. 3-4, p. 222-236 How to Cite?
AbstractThe ~ 260-Ma Emeishan large igneous province in SW China and northern Vietnam contains low-Ti tholeiitic basalts, high-Ti alkaline basalts and minor peralkaline volcanic rocks. The flood basalts in Longzhoushan, Sichuan Province, SW China, comprise four units, each of which has volcanic breccia at the base. From the base upward, rocks of Units 1 and 2 are high-Ti basalts with relatively high MgO (7.6-11.0 wt.%), TiO 2 (1.7-4.5 wt.%) and Ti/Y ratios (420-790). Unit 3 is composed of tephrites with lower MgO (0.87-6.2 wt.%), TiO 2 (0.96-2.14 wt.%) and Ti/Y ratios (190-530), whereas Unit 4 consists of basaltic andesites with moderate MgO (3.5-4.8 wt.%), TiO 2 (2.2-3.1 wt.%) and Ti/Y ratios (383-606). The high-Ti basalts may have been derived from an OIB-like mantle source and the basaltic andesites were probably generated by crustal contamination and fractionation of high-Ti basaltic magmas. The tephrites show high Nb/Y (1.2 to 2.7) and Th/Y (0.31 to 0.55) ratios, variable Zr/Hf ratios (40 to 49) and relatively low εNd(t) (- 0.7 to + 0.28) values, suggesting an asthenospheric mantle contribution modified by carbonate-rich fluids. The high-Ti basalts contain relatively high and variable PGE and their Cu/Pd ratios are relatively constant (compared to the tephrites) and vary from 8,500 to 86,000. We attribute such relative constancy of the Cu/Pd ratios to the presence of residual sulphide in the source of the high-Ti rocks and subsequent crystallization from S-undersaturated melts. The basaltic andesites have relatively high and constant Cu/Pd ratios (130,000-370,492) and the lowest PGE contents (average 0.12 ppb for Pd, 0.20 ppb for Pt), suggesting an earlier removal of sulfide due to crustal contamination before emplacement. The tephrites have PGE abundances (0.057 to 1.89 ppb for Pt and 0.11 to 2.10 ppb for Pd) higher than those for basaltic andesites, however, the Cu/Pd ratios (33,300 to 429,000) of the rocks are more variable than those for the basaltic andesites, suggesting that the tephrites may have undergone both S-saturated fractionation during emplacement of the magmas and weak removal of sulfides from the source magmas. Early fractionation of chromite together with removal of laurite and/or Os-Ir-Ru alloys from the parental magmas may be responsible for the negative Ru anomalies of the tephrites, high-Ti basalts and basaltic andesites. © 2008 Elsevier B.V. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/58711
ISSN
2015 Impact Factor: 3.723
2015 SCImago Journal Rankings: 2.920
ISI Accession Number ID
Funding AgencyGrant Number
"CAS Hundred Talents" Program from the Chinese Academy of Sciences
Chinese 973 project2007CB411401
National Natural Science Foundation of China40573049
Research Grant Council of Hong KongHKU7057/05P
Funding Information:

This study was Supported by the "CAS Hundred Talents" Program from the Chinese Academy of Sciences to Qi Liang, Chinese 973 project (2007CB411401), the National Natural Science Foundation of China (NSFC 40573049) and the Research Grant Council of Hong Kong (HKU7057/05P). We thank Ms. Xiao Fu for helping with the XRF analyses and two anonymous reviewers and the editor, Nelson Eby, for providing construction criticism.

References

 

DC FieldValueLanguage
dc.contributor.authorQi, Len_HK
dc.contributor.authorWang, CYen_HK
dc.contributor.authorZhou, MFen_HK
dc.date.accessioned2010-05-31T03:35:27Z-
dc.date.available2010-05-31T03:35:27Z-
dc.date.issued2008en_HK
dc.identifier.citationLithos, 2008, v. 106 n. 3-4, p. 222-236en_HK
dc.identifier.issn0024-4937en_HK
dc.identifier.urihttp://hdl.handle.net/10722/58711-
dc.description.abstractThe ~ 260-Ma Emeishan large igneous province in SW China and northern Vietnam contains low-Ti tholeiitic basalts, high-Ti alkaline basalts and minor peralkaline volcanic rocks. The flood basalts in Longzhoushan, Sichuan Province, SW China, comprise four units, each of which has volcanic breccia at the base. From the base upward, rocks of Units 1 and 2 are high-Ti basalts with relatively high MgO (7.6-11.0 wt.%), TiO 2 (1.7-4.5 wt.%) and Ti/Y ratios (420-790). Unit 3 is composed of tephrites with lower MgO (0.87-6.2 wt.%), TiO 2 (0.96-2.14 wt.%) and Ti/Y ratios (190-530), whereas Unit 4 consists of basaltic andesites with moderate MgO (3.5-4.8 wt.%), TiO 2 (2.2-3.1 wt.%) and Ti/Y ratios (383-606). The high-Ti basalts may have been derived from an OIB-like mantle source and the basaltic andesites were probably generated by crustal contamination and fractionation of high-Ti basaltic magmas. The tephrites show high Nb/Y (1.2 to 2.7) and Th/Y (0.31 to 0.55) ratios, variable Zr/Hf ratios (40 to 49) and relatively low εNd(t) (- 0.7 to + 0.28) values, suggesting an asthenospheric mantle contribution modified by carbonate-rich fluids. The high-Ti basalts contain relatively high and variable PGE and their Cu/Pd ratios are relatively constant (compared to the tephrites) and vary from 8,500 to 86,000. We attribute such relative constancy of the Cu/Pd ratios to the presence of residual sulphide in the source of the high-Ti rocks and subsequent crystallization from S-undersaturated melts. The basaltic andesites have relatively high and constant Cu/Pd ratios (130,000-370,492) and the lowest PGE contents (average 0.12 ppb for Pd, 0.20 ppb for Pt), suggesting an earlier removal of sulfide due to crustal contamination before emplacement. The tephrites have PGE abundances (0.057 to 1.89 ppb for Pt and 0.11 to 2.10 ppb for Pd) higher than those for basaltic andesites, however, the Cu/Pd ratios (33,300 to 429,000) of the rocks are more variable than those for the basaltic andesites, suggesting that the tephrites may have undergone both S-saturated fractionation during emplacement of the magmas and weak removal of sulfides from the source magmas. Early fractionation of chromite together with removal of laurite and/or Os-Ir-Ru alloys from the parental magmas may be responsible for the negative Ru anomalies of the tephrites, high-Ti basalts and basaltic andesites. © 2008 Elsevier B.V. All rights reserved.en_HK
dc.languageengen_HK
dc.publisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/lithosen_HK
dc.relation.ispartofLithosen_HK
dc.subjectEmeishanen_HK
dc.subjectFlood basaltsen_HK
dc.subjectPetrogenesisen_HK
dc.subjectPlatinum-group elementsen_HK
dc.subjectSW Chinaen_HK
dc.subjectTephriteen_HK
dc.titleControls on the PGE distribution of Permian Emeishan alkaline and peralkaline volcanic rocks in Longzhoushan, Sichuan Province, SW Chinaen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0024-4937&volume=106&issue=3-4&spage=222&epage=236&date=2008&atitle=Controls+on+the+PGE+distribution+of+Permian+Emeishan+alkaline+and+peralkaline+volcanic+rocks+in+Longzhoushan,+Sichuan+Province,+SW+Chinaen_HK
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hken_HK
dc.identifier.authorityZhou, MF=rp00844en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.lithos.2008.07.012en_HK
dc.identifier.scopuseid_2-s2.0-55849097312en_HK
dc.identifier.hkuros167318en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-55849097312&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume106en_HK
dc.identifier.issue3-4en_HK
dc.identifier.spage222en_HK
dc.identifier.epage236en_HK
dc.identifier.isiWOS:000261680100003-
dc.publisher.placeNetherlandsen_HK
dc.identifier.scopusauthoridQi, L=7202149924en_HK
dc.identifier.scopusauthoridWang, CY=38362490600en_HK
dc.identifier.scopusauthoridZhou, MF=7403506005en_HK

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