DOI: 10.1016/j.epsl.2020.116217
论文题名: Slab-controlled elemental–isotopic enrichments during subduction initiation magmatism and variations in forearc chemostratigraphy
作者: Yu M. ; Dilek Y. ; Yumul G.P. ; Jr ; Yan Y. ; Dimalanta C.B. ; Huang C.-Y.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 538 语种: 英语
中文关键词: forearc chemostratigraphy
; ophiolites
; South China Sea
; subduction initiation magmatism
; Sulu Sea
; West Philippine
英文关键词: Silicate minerals
; Zircon
; Chemostratigraphy
; Magmatisms
; ophiolites
; South China sea
; Sulu Sea
; West Philippine
; Isotopes
; chemostratigraphy
; enrichment
; forearc basin
; isotopic analysis
; magmatism
; Oligocene
; ophiolite
; seafloor spreading
; slab
; subduction
; uranium-lead dating
; zircon
; Pacific Ocean
; Philippines
; South China Sea
; Sulu Sea
英文摘要: Supra-subduction zone (SSZ) ophiolites formed in forearc settings and the Izu–Bonin–Mariana (IBM) in-situ forearc show conversions from normal mid-ocean ridge basalt (MORB) to boninitic affinities, which are widely interpreted as rules for the evolving chemical geodynamics of subduction initiation magmatism (SIM). Nevertheless, forearc sequence generated by subduction initiation need not always include boninitic rocks. Here we reconstruct a forearc chemostratigraphy without boninitic affinity based on the Central Palawan and Amnay (CPA) ophiolites of the west Philippines to show diversity in melt evolution of SIM. Zircon U–Pb dating on the MORB-type Amnay gabbros reveal a 10 m.y. of seafloor spreading from 33 to 23 Ma. These ages together with the progressively enriched zircon in-situ oxygen isotopes (δ18O= 1.62–10.1‰) and whole rock elemental and Nd–Hf isotopic signatures ([La/Yb]N= 0.19–3.45; Nb/Yb= 0.07–5.24; εNd= 2.1–10.2; εHf= 11.2–24.1) indicate that the depleted MORB mantle (DMM)-type source of the Amnay ophiolite was getting enriched by fluxing of aqueous slab fluid in the early stage followed by addition of adakitic and Nb-enriched slab melts in the later stage. This distinct mantle evolution together with higher εHf at a given εNd of the Amnay mafic samples than the contemporaneous South China Sea (SCS) oceanic samples do not support previous interpretation that the Amnay ophiolite was a fragment of the SCS. However, the 33–23 Ma Amnay ophiolite can be the younger part of the 34 Ma forearc-type Central Palawan ophiolite, and both (i.e. the CPA ophiolites) represent on-land fragments of the NW Sulu Sea. We propose that the 34–23 Ma CPA ophiolites and the NW Sulu Sea constitute forearc basin of the late Oligocene–middle Miocene island arc–backarc basin duo of the Cagayan Ridge and SE Sulu Sea, associated with subduction of the Cretaceous to Eocene Proto-SCS since 34 Ma. The CPA ophiolites lack boninite but show geochemical progression from normal to enriched MORB affinities, whose melt evolution differs from that of the IBM SIM. We attribute the differences in SIM and variations in forearc chemostratigraphy to the subduction of a younger slab with thick terrigenous sediment cover of the Proto-SCS versus an older slab with thin pelagic sediment cover of the Pacific Plate. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165370
Appears in Collections: 气候变化与战略
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作者单位: State Key Laboratory of Marine Geology, Tongji University, Shanghai, 200092, China; Key Laboratory of Ocean and Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China; Department of Geology & Environmental Earth Science, Miami University, Ohio, 45056, United States; Cordillera Exploration Company Incorporated, NAC Tower, Bonifacio Global City, Taguig, Metro Manila 1634, Philippines; National Institute of Geological Sciences, University of the Philippines, Diliman, 1101, Philippines
Recommended Citation:
Yu M.,Dilek Y.,Yumul G.P.,et al. Slab-controlled elemental–isotopic enrichments during subduction initiation magmatism and variations in forearc chemostratigraphy[J]. Earth and Planetary Science Letters,2020-01-01,538