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Article: Akaz greenschist, West Kunlun: Within-plate basalt contaminated by continental crust origin of the Akaz greenschist (metabasalt), West Kunlun: Accreted seamount or continental rift basalt?

TitleAkaz greenschist, West Kunlun: Within-plate basalt contaminated by continental crust origin of the Akaz greenschist (metabasalt), West Kunlun: Accreted seamount or continental rift basalt?
Authors
KeywordsContinental Rift
Crustal Contamination
Gondwana
Greenschist
Seamount
Tarim
West Kunlun
Issue Date2005
PublisherChinese Academy of Sciences, Institute of Geology and Geophysics. The Journal's web site is located at http://www.ysxb.ac.cn/ysxb/ch/index.aspx
Citation
Acta Petrologica Sinica, 2005, v. 21 n. 1, p. 65-76 How to Cite?
AbstractThe Sinian-Early Cambrian Akaz greenschists (metavolcanic rocks) of West Kunlun, NW China was metamorphosed from mafic to andesitic rocks. They contain low to intermediate SiO 2 (42.3% - 64.7%), MgO (2.69% - 7.54%) and have wide range of TiO 2 (0.94% - 3.05%) and Fe 2O 3T(7.64% - 18.47%) contents, indicating a basaltic to andesitic protolith. These rocks possess high HFSE (e. g. Nb, Ta, Zr, Hf, Ti), REE (∑ REE = ∼ 407 μg/g) and Th (∼ 16 μg/g) contents, and are characterized by relatively high Ti/Y (183 - 673), Th/Yb (0.6 - 2.8) and low Hf/Ta (1.6 - 8.6) ratios. They are relatively LREE-enriched (La/Yb = 5.4 - 20), and except for two samples characterized by positive Nb-anomalies, most samples show variable negative Nb-anomalies (Nb/Nb* = ∼ 0.2) and exhibit transitional characteristics between within-plate and subduction-related basalts. The subduction-related characteristics preclude oceanic plateau, oceanic island and within-plate seamount basalts as the protolith; while their within-plate characteristics, together with the existence of positive Nb-anomaly samples, suggest that the metavolcanic rocks were not produced in destructive settings (island arc or active continental margin). In particular, their relatively high Gd/Yb ratios (1.4 - 3.2) distinguish clearly these rocks from island-arc tholeiites, and their relatively high Zr/Y (3.1 - 12), Ta/Yb (0.27 - 0.73) and relatively low Zr/Nb (mostly less than 12) are of strong continental within-plate characteristics, suggesting that the protolith of the greenschist was continental rift-related basalts probably contaminated by continental crust materials during their ascent. This indicates that the Akaz metavolcanic rocks were originally formed in a continental rift environment. The Akaz metavolcanic rocks, in combination with approximately coeval within-plate volcanic rocks in East Kunlun and North Qilian, suggest that the rifting of Tarim from Gondwana most likely occurred in Sinian or Early Cambrian. Based on this study and previous work, an amended model is proposed to interpret the Sinian to Early Paleozoic tectonic evolution of West Kunlun.
Persistent Identifierhttp://hdl.handle.net/10722/151160
ISSN
2015 Impact Factor: 1.234
2015 SCImago Journal Rankings: 0.892
References

 

DC FieldValueLanguage
dc.contributor.authorYuan, Cen_US
dc.contributor.authorSun, Men_US
dc.contributor.authorYang, JSen_US
dc.contributor.authorZhou, Hen_US
dc.contributor.authorZhou, MFen_US
dc.date.accessioned2012-06-26T06:17:56Z-
dc.date.available2012-06-26T06:17:56Z-
dc.date.issued2005en_US
dc.identifier.citationActa Petrologica Sinica, 2005, v. 21 n. 1, p. 65-76en_US
dc.identifier.issn1000-0569en_US
dc.identifier.urihttp://hdl.handle.net/10722/151160-
dc.description.abstractThe Sinian-Early Cambrian Akaz greenschists (metavolcanic rocks) of West Kunlun, NW China was metamorphosed from mafic to andesitic rocks. They contain low to intermediate SiO 2 (42.3% - 64.7%), MgO (2.69% - 7.54%) and have wide range of TiO 2 (0.94% - 3.05%) and Fe 2O 3T(7.64% - 18.47%) contents, indicating a basaltic to andesitic protolith. These rocks possess high HFSE (e. g. Nb, Ta, Zr, Hf, Ti), REE (∑ REE = ∼ 407 μg/g) and Th (∼ 16 μg/g) contents, and are characterized by relatively high Ti/Y (183 - 673), Th/Yb (0.6 - 2.8) and low Hf/Ta (1.6 - 8.6) ratios. They are relatively LREE-enriched (La/Yb = 5.4 - 20), and except for two samples characterized by positive Nb-anomalies, most samples show variable negative Nb-anomalies (Nb/Nb* = ∼ 0.2) and exhibit transitional characteristics between within-plate and subduction-related basalts. The subduction-related characteristics preclude oceanic plateau, oceanic island and within-plate seamount basalts as the protolith; while their within-plate characteristics, together with the existence of positive Nb-anomaly samples, suggest that the metavolcanic rocks were not produced in destructive settings (island arc or active continental margin). In particular, their relatively high Gd/Yb ratios (1.4 - 3.2) distinguish clearly these rocks from island-arc tholeiites, and their relatively high Zr/Y (3.1 - 12), Ta/Yb (0.27 - 0.73) and relatively low Zr/Nb (mostly less than 12) are of strong continental within-plate characteristics, suggesting that the protolith of the greenschist was continental rift-related basalts probably contaminated by continental crust materials during their ascent. This indicates that the Akaz metavolcanic rocks were originally formed in a continental rift environment. The Akaz metavolcanic rocks, in combination with approximately coeval within-plate volcanic rocks in East Kunlun and North Qilian, suggest that the rifting of Tarim from Gondwana most likely occurred in Sinian or Early Cambrian. Based on this study and previous work, an amended model is proposed to interpret the Sinian to Early Paleozoic tectonic evolution of West Kunlun.en_US
dc.languageengen_US
dc.publisherChinese Academy of Sciences, Institute of Geology and Geophysics. The Journal's web site is located at http://www.ysxb.ac.cn/ysxb/ch/index.aspxen_US
dc.relation.ispartofActa Petrologica Sinicaen_US
dc.subjectContinental Riften_US
dc.subjectCrustal Contaminationen_US
dc.subjectGondwanaen_US
dc.subjectGreenschisten_US
dc.subjectSeamounten_US
dc.subjectTarimen_US
dc.subjectWest Kunlunen_US
dc.titleAkaz greenschist, West Kunlun: Within-plate basalt contaminated by continental crust origin of the Akaz greenschist (metabasalt), West Kunlun: Accreted seamount or continental rift basalt?en_US
dc.typeArticleen_US
dc.identifier.emailSun, M: minsun@hku.hken_US
dc.identifier.emailZhou, MF: mfzhou@hkucc.hku.hken_US
dc.identifier.authoritySun, M=rp00780en_US
dc.identifier.authorityZhou, MF=rp00844en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-22744435612en_US
dc.identifier.hkuros108601-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-22744435612&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume21en_US
dc.identifier.issue1en_US
dc.identifier.spage65en_US
dc.identifier.epage76en_US
dc.publisher.placeChinaen_US
dc.identifier.scopusauthoridYuan, C=35241599200en_US
dc.identifier.scopusauthoridSun, M=25932315800en_US
dc.identifier.scopusauthoridYang, JS=8871818900en_US
dc.identifier.scopusauthoridZhou, H=7404741996en_US
dc.identifier.scopusauthoridZhou, MF=7403506005en_US

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