Basalts and picrites from a plume-type ophiolite in the South Qilian   Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic   Plateau?

doi:10.1016/j.lithos.2017.01.027

CORC > 北京大学 > 地球与空间科学学院

	Basalts and picrites from a plume-type ophiolite in the South Qilian Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic Plateau?
	Zhang, Yuqi ; Song, Shuguang ; Yang, Liming ; Su, Li ; Niu, Yaoling ; Allen, Mark B. ; Xu, Xin
刊名	LITHOS
	2017
关键词	Picrites Cambrian oceanic plateau Trench jam South Qilian accretionary belt Qilian Orogen NORTHERN TIBETAN PLATEAU QAIDAM UHPM BELT NW CHINA VOLCANIC-ROCKS TRACE-ELEMENTS FLOOD BASALTS CR-SPINEL HIGH-MG IUG RECLASSIFICATION GORGONA KOMATIITES
DOI	10.1016/j.lithos.2017.01.027
英文摘要	Oceanic 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.; National Natural Science Foundation of China [41572040]; Major State Basic Research Development Program [2015CB856105]; SCI(E); ARTICLE; 97-110; 278
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/473776]
专题	地球与空间科学学院
推荐引用方式 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.
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.
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 (2017).