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Article: Controls on the PGE distribution of Permian Emeishan alkaline and peralkaline volcanic rocks in Longzhoushan, Sichuan Province, SW China
Title | Controls on the PGE distribution of Permian Emeishan alkaline and peralkaline volcanic rocks in Longzhoushan, Sichuan Province, SW China | ||||||||||
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Authors | |||||||||||
Keywords | Emeishan Flood basalts Petrogenesis Platinum-group elements SW China Tephrite | ||||||||||
Issue Date | 2008 | ||||||||||
Publisher | Elsevier 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? | ||||||||||
Abstract | The ~ 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 Identifier | http://hdl.handle.net/10722/58711 | ||||||||||
ISSN | 2023 Impact Factor: 2.9 2023 SCImago Journal Rankings: 1.491 | ||||||||||
ISI Accession Number ID |
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 Field | Value | Language |
---|---|---|
dc.contributor.author | Qi, L | en_HK |
dc.contributor.author | Wang, CY | en_HK |
dc.contributor.author | Zhou, MF | en_HK |
dc.date.accessioned | 2010-05-31T03:35:27Z | - |
dc.date.available | 2010-05-31T03:35:27Z | - |
dc.date.issued | 2008 | en_HK |
dc.identifier.citation | Lithos, 2008, v. 106 n. 3-4, p. 222-236 | en_HK |
dc.identifier.issn | 0024-4937 | en_HK |
dc.identifier.uri | http://hdl.handle.net/10722/58711 | - |
dc.description.abstract | The ~ 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.language | eng | en_HK |
dc.publisher | Elsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/lithos | en_HK |
dc.relation.ispartof | Lithos | en_HK |
dc.subject | Emeishan | en_HK |
dc.subject | Flood basalts | en_HK |
dc.subject | Petrogenesis | en_HK |
dc.subject | Platinum-group elements | en_HK |
dc.subject | SW China | en_HK |
dc.subject | Tephrite | en_HK |
dc.title | Controls on the PGE distribution of Permian Emeishan alkaline and peralkaline volcanic rocks in Longzhoushan, Sichuan Province, SW China | en_HK |
dc.type | Article | en_HK |
dc.identifier.openurl | http://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+China | en_HK |
dc.identifier.email | Zhou, MF:mfzhou@hkucc.hku.hk | en_HK |
dc.identifier.authority | Zhou, MF=rp00844 | en_HK |
dc.description.nature | link_to_subscribed_fulltext | - |
dc.identifier.doi | 10.1016/j.lithos.2008.07.012 | en_HK |
dc.identifier.scopus | eid_2-s2.0-55849097312 | en_HK |
dc.identifier.hkuros | 167318 | en_HK |
dc.relation.references | http://www.scopus.com/mlt/select.url?eid=2-s2.0-55849097312&selection=ref&src=s&origin=recordpage | en_HK |
dc.identifier.volume | 106 | en_HK |
dc.identifier.issue | 3-4 | en_HK |
dc.identifier.spage | 222 | en_HK |
dc.identifier.epage | 236 | en_HK |
dc.identifier.isi | WOS:000261680100003 | - |
dc.publisher.place | Netherlands | en_HK |
dc.identifier.scopusauthorid | Qi, L=7202149924 | en_HK |
dc.identifier.scopusauthorid | Wang, CY=38362490600 | en_HK |
dc.identifier.scopusauthorid | Zhou, MF=7403506005 | en_HK |
dc.identifier.issnl | 0024-4937 | - |