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题名: A trace element perspective on the source of ocean island basalts (OIB) and fate of subducted ocean crust (SOC) and mantle lithosphere (SML)
作者: Niu, YL; Wilson, M; Humphreys, ER; O'Hara, MJ
收录类别: SCIE
出版日期: 2012-06
刊名: EPISODES
卷号: 35, 期号:2, 页码:310-327
出版者: GEOLOGICAL SOC INDIA
出版地: BANGALORE
英文摘要: We analyze the first-order observations, basic concepts and explicit/implicit assumptions built into the three major hypotheses for the enriched component(s) in the source of ocean island basalts (OIB) in terms of incompatible trace elements: (1) subducted ocean crust (SOC), (2) subducted continental sediments, and (3) mantle metasomatism. SOC is compositionally too depleted (i.e., [La/Sm](N) <1) to be the major source material for OIB that are highly incompatible element enriched (e.g., [La/Sm](N) >>1). We cannot rule out the,contribution of continental sediments as an enriched OIB source component; however, except for two known cases that are yet to be further investigated, there is no convincing evidence for any significant sediment contribution to the petrogenesis of global OIB. Continental materials through subduction erosion can certainly contribute to mantle compositional heterogeneity and may contribute towards some enriched component in OIB source regions. Overall, OIB are not only enriched in incompatible elements, but also enriched in the progressively more incompatible elements, with their inferred source material being variably more enriched than the primitive mantle. These observations require that the OIB sources are pre-enriched by low-degree (Low-F) melt metasomatism. The interface between the growing oceanic lithosphere and the top of the seismic low velocity zone (LVZ) represents a natural peridotite solidus and is the ideal site for major low-F melt induced metasomatism. The similar to 70 Myr history of oceanic lithosphere growth to its flail thickness of similar to 90 km records the history of mantle metasomatism, resulting in the deep portion of the oceanic lithosphere being an important enriched geochemical reservoir. We argue that ancient subducted metasomatized mantle lithosphere (SML) provides the major source component for OIB. The metasomatic agent is an H2O-CO2-rich silicate melt derived from within the LVZ. Upward migration and concentration of the melt at the lithosphere-LVZ interface (i.e., the lithosphere-asthenosphere boundary or LAB) results in chemical stratification in the LVZ with the deeper portion being more depleted (i.e., DMM), providing the source for MORB. The widespread metasomatized peridotites, pyroxenites and hornblendites from xenolith suites exhumed from the deep lithosphere (both oceanic and continental) and in orogenic peridotite massifs confirm the role of a low-F silicate melt phase as the metasomatic agent. The SOC, if subducted into the lower mantle, will be too dense to return in bulk to the upper mantle source regions of oceanic basalts, and may have contributed to the two large low shear wave velocity provinces (LLSVPs) at the base of the mantle beneath the Pacific and Africa over Earth's history.
作者部门: [Niu, Yaoling] Lanzhou Univ, Sch Earth Sci, Lanzhou 730000, Peoples R China ; [Niu, Yaoling] Univ Durham, Dept Earth Sci, Durham DH1 3LE, England ; [Wilson, Marjorie] Univ Leeds, Sch Earth & Environm, Leeds LS2 9JT, W Yorkshire, England ; [Humphreys, Emma R.] Univ Bristol, Dept Earth Sci, Bristol BS8 1RJ, Avon, England ; [O'Hara, Michael J.] Aberystwyth Univ, Inst Geog & Earth Sci, Aberystwyth SY23 3DB, Dyfed, Wales
通讯作者: Niu, YL (reprint author), Lanzhou Univ, Sch Earth Sci, Lanzhou 730000, Peoples R China.
学科分类: Geology
文章类型: Article
所属项目编号: Leverhulme Trust ; Durham University ; China University of Geosciences in Beijing ; Peking University ; Chinese 111 Project [B07011] ; Chinese NSF [91014003, 41130314]
所属项目名称: 国家自然科学基金项目 ; 高等学校学科创新引智计划(111计划)
项目资助者: NSFC ; MOE ; SAFEA
语种: 英语
ISSN号: 0705-3797
WOS记录号: WOS:000315559200002
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内容类型: 期刊论文
URI标识: http://ir.lzu.edu.cn/handle/262010/120618
Appears in Collections:地质科学与矿产资源学院_期刊论文

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Recommended Citation:
Niu, YL,Wilson, M,Humphreys, ER,et al. A trace element perspective on the source of ocean island basalts (OIB) and fate of subducted ocean crust (SOC) and mantle lithosphere (SML)[J]. EPISODES,2012,35(2):310-327.
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