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Article: The Kanasi potassic magnesian-rich dacites, Altai, northwestern Chinese: Metasomatism by the melts of subducted sediments

TitleThe Kanasi potassic magnesian-rich dacites, Altai, northwestern Chinese: Metasomatism by the melts of subducted sediments
Authors
KeywordsAltai Orogen
High-Mg Andesite
Nd Isotope
North Xinjiang
Volcanic Rocks
Issue Date2010
Citation
Scientia Geologica Sinica, 2010, v. 45 n. 1, p. 12-29 How to Cite?
AbstractPotassic magnesian-rich dacites occur to the south of the Kanasi, Altai, northwestern Chinese. U-Pb dating of zircons from these rocks yields an early Devonian age of 411 ± 4 Ma. The dacites are enriched in SiO 2 (64.71 ̃ 67.77 wt%), MgO (3.28 ̃ 3.53 wt%) and K 2O (2.12 ̃ 2.75 wt%), and depleted in Na 2O (1.70 ̃ 1.85 wt%). The rocks have low CaO content(1.12 ̃ 1.28 wt%), high Al 2O 3 content (14.12 ̃ 15.33 wt%) and K 2O/Na 2O ratios (1.2 ̃ 1.6), and ASI indexes larger than 1.8, indicating features of peraluminous potassic calc-alkali igneous rocks, which are clearly different to primitive High-Mg andesites. The dacites possess moderate Cr(134 × 10 -6 ̃ 153 × 10 -6), Co(17.5 × 10 -6 ̃ 18.7 × 10 -6), and Ni (72 × 10 -6 ̃ 81 × 10 -6) contents. These rocks are enriched in LREEs, large ion lithophile elements(e.g. Rb, K) and high field strength element (e. g. U, Th, Pb) with moderate Sr, Ba, and "TNT" ( Ta, Nb, Ti) negative anomalies, showing geochemical characteristics of igneous rocks in subduction zone. Their high Mg #(51.7 ̃ 52.5) and low ε Nd(t)ratios(-4.6 ̃ -4.2) imply partial melting of metasomatic peridotites in the mantle wedge. The relative high Ba/La, Pb/La and low Th/Yb, Nb/Y ratios suggest that the metasomatism of mantle peridotites was predominated by the melts of subducted sediments. Therefore, the above geochemistry indicates that the potassic magnesian-rich dacites were originated from the partial melting of metasomatic mantle peridotites mainly altered by the melts of subducted sediments, showing an active continental margin in the Devonian. In addition, the timing of the potassic magnesian-rich dacites provides a good constrain on the minimum depositional age of the underlying Habahe group and suggests the sediments of the group deposited before the early Devonian.
Persistent Identifierhttp://hdl.handle.net/10722/151307
ISSN
2015 SCImago Journal Rankings: 0.206
References

 

DC FieldValueLanguage
dc.contributor.authorWang, Yen_US
dc.contributor.authorYuan, Cen_US
dc.contributor.authorLong, Xen_US
dc.contributor.authorSun, Men_US
dc.contributor.authorXiao, Wen_US
dc.date.accessioned2012-06-26T06:20:23Z-
dc.date.available2012-06-26T06:20:23Z-
dc.date.issued2010en_US
dc.identifier.citationScientia Geologica Sinica, 2010, v. 45 n. 1, p. 12-29en_US
dc.identifier.issn0563-5020en_US
dc.identifier.urihttp://hdl.handle.net/10722/151307-
dc.description.abstractPotassic magnesian-rich dacites occur to the south of the Kanasi, Altai, northwestern Chinese. U-Pb dating of zircons from these rocks yields an early Devonian age of 411 ± 4 Ma. The dacites are enriched in SiO 2 (64.71 ̃ 67.77 wt%), MgO (3.28 ̃ 3.53 wt%) and K 2O (2.12 ̃ 2.75 wt%), and depleted in Na 2O (1.70 ̃ 1.85 wt%). The rocks have low CaO content(1.12 ̃ 1.28 wt%), high Al 2O 3 content (14.12 ̃ 15.33 wt%) and K 2O/Na 2O ratios (1.2 ̃ 1.6), and ASI indexes larger than 1.8, indicating features of peraluminous potassic calc-alkali igneous rocks, which are clearly different to primitive High-Mg andesites. The dacites possess moderate Cr(134 × 10 -6 ̃ 153 × 10 -6), Co(17.5 × 10 -6 ̃ 18.7 × 10 -6), and Ni (72 × 10 -6 ̃ 81 × 10 -6) contents. These rocks are enriched in LREEs, large ion lithophile elements(e.g. Rb, K) and high field strength element (e. g. U, Th, Pb) with moderate Sr, Ba, and "TNT" ( Ta, Nb, Ti) negative anomalies, showing geochemical characteristics of igneous rocks in subduction zone. Their high Mg #(51.7 ̃ 52.5) and low ε Nd(t)ratios(-4.6 ̃ -4.2) imply partial melting of metasomatic peridotites in the mantle wedge. The relative high Ba/La, Pb/La and low Th/Yb, Nb/Y ratios suggest that the metasomatism of mantle peridotites was predominated by the melts of subducted sediments. Therefore, the above geochemistry indicates that the potassic magnesian-rich dacites were originated from the partial melting of metasomatic mantle peridotites mainly altered by the melts of subducted sediments, showing an active continental margin in the Devonian. In addition, the timing of the potassic magnesian-rich dacites provides a good constrain on the minimum depositional age of the underlying Habahe group and suggests the sediments of the group deposited before the early Devonian.en_US
dc.languageengen_US
dc.relation.ispartofScientia Geologica Sinicaen_US
dc.subjectAltai Orogenen_US
dc.subjectHigh-Mg Andesiteen_US
dc.subjectNd Isotopeen_US
dc.subjectNorth Xinjiangen_US
dc.subjectVolcanic Rocksen_US
dc.titleThe Kanasi potassic magnesian-rich dacites, Altai, northwestern Chinese: Metasomatism by the melts of subducted sedimentsen_US
dc.typeArticleen_US
dc.identifier.emailSun, M:minsun@hku.hken_US
dc.identifier.authoritySun, M=rp00780en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-77954015822en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-77954015822&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume45en_US
dc.identifier.issue1en_US
dc.identifier.spage12en_US
dc.identifier.epage29en_US
dc.publisher.placeChinaen_US
dc.identifier.scopusauthoridWang, Y=35320615500en_US
dc.identifier.scopusauthoridYuan, C=35241599200en_US
dc.identifier.scopusauthoridLong, X=14012199100en_US
dc.identifier.scopusauthoridSun, M=25932315800en_US
dc.identifier.scopusauthoridXiao, W=7202456615en_US

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