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Basalts and picrites from a plume-type ophiolite in the South Qilian Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic Plateau?
Zhang, Yuqi1; Song, Shuguang1; Yang, Liming1; Su, Li2,3; Niu, Yaoling4,5; Allen, Mark B.4; Xu, Xin1
2017-05-01
Source PublicationLITHOS
Volume278Pages:97-110
SubtypeArticle
AbstractOceanic plateaus with high-Mg rocks in the present-day oceanic crust have attracted much attention for their proposed mantle-plume origins and abnormally high mantle potential temperatures (T-p). However, equivalent rocks in ancient oceanic environments are usually poorly preserved because of deformation and metamorphism. Here we present petrological, geochronological and geochemical data for pillow lavas from Cambrian ophiolites in the Lajishan and Yongjing regions of the South Qilian Accretionary Belt (SQAB), from the southern part of the Qilian Orogen, northern China. Three rock groups can be identified geochemically: (1) sub-alkaline basalts with enriched mid- ocean ridge basalt (E-MORB) affinity; (2) alkaline basalts with oceanic island basalt (OIB) features, probably derived from partial melting of an enriched mantle source; and (3) picrites with MgO (18-22 wt%). Crnumbers [Cr-# = Cr/(Cr + Al)] of spinels from the picrites suggest 18-21% degree of partial melting at the estimated mantle potential temperature (Tp) of 1489-1600 degrees C, equivalent to values of Cenozoic Hawaiian picrites (1500-1600 degrees C). Zircons from one gabbro sample yielded a U-Pb Concordia age of 525 +/- 3 Ma, suggesting the oceanic crust formed in the Cambrian. Available evidence suggests that Cambrian mantle plume activity is preserved in the South Qilian Accretionary Belt, and influenced the regional tectonics: "jamming" of the trench by thick oceanic crust explains the emplacement and preservation of the oceanic plateau, and gave rise to the generation of concomitant Ordovician inner-oceanic island arc basalts via re-organisation of the subduction zones in the region. (C) 2017 Elsevier B.V. All rights reserved.
KeywordPicrites Cambrian Oceanic Plateau Trench Jam South Qilian Accretionary Belt Qilian Orogen
DOI10.1016/j.lithos.2017.01.027
Indexed BySCI
Language英语
WOS IDWOS:000399258500007
Citation statistics
Document Type期刊论文
Version出版稿
Identifierhttp://ir.qdio.ac.cn/handle/337002/137042
Collection海洋地质与环境重点实验室
Affiliation1.Peking Univ, Sch Earth & Space Sci, MOE Key Lab Orogen Belt & Crustal Evolut, Beijing 100871, Peoples R China
2.China Univ Geosci, Inst Earth Sci, Beijing 100083, Peoples R China
3.China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China
4.Univ Durham, Dept Earth Sci, Durham DH1 3LE, England
5.Chinese Acad Sci, Inst Oceanol, Qingdao 266071, Peoples R China
Recommended Citation
GB/T 7714
Zhang, Yuqi,Song, Shuguang,Yang, Liming,et al. Basalts and picrites from a plume-type ophiolite in the South Qilian Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic Plateau?[J]. LITHOS,2017,278:97-110.
APA Zhang, Yuqi.,Song, Shuguang.,Yang, Liming.,Su, Li.,Niu, Yaoling.,...&Xu, Xin.(2017).Basalts and picrites from a plume-type ophiolite in the South Qilian Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic Plateau?.LITHOS,278,97-110.
MLA Zhang, Yuqi,et al."Basalts and picrites from a plume-type ophiolite in the South Qilian Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic Plateau?".LITHOS 278(2017):97-110.
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