DOI: 10.1016/j.epsl.2018.09.011
Scopus记录号: 2-s2.0-85054303580
论文题名: Subducted Mg-rich carbonates into the deep mantle wedge
作者: Shen J. ; Li S.-G. ; Wang S.-J. ; Teng F.-Z. ; Li Q.-L. ; Liu Y.-S.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 503 起始页码: 118
结束页码: 130
语种: 英语
英文关键词: mantle wedge metasomatism
; Mg isotope
; O isotope
; subducted carbonates
; supercritical liquid
英文摘要: Recent studies have concluded that subducted calcium (Ca-) rich carbonates could be dissolved in slab-derived aqueous fluids and transported upwards into the shallow mantle wedge (75–120 km), while magnesium (Mg-) rich carbonates could be delivered to a greater depth (i.e., the mantle transition zone, ∼410 km), melted, and recycled into the convective upper mantle. However, it remains unknown whether or not Mg-rich carbonates can be transferred to the deep mantle wedge (>∼120 km) by subduction-zone fluids, which, if true, is important for tracing deep carbon. In this paper, we report a comprehensive mineralogical, geochemical, stable (Mg and O) and radiogenic isotopic (zircon U–Pb) study of garnet clinopyroxenites from the Maowu ultra-mafic massif (a slice of the mantle wedge) in the Dabie orogeny, Central China. Whole-rock and mineral trace elemental features and zircon U–Pb ages reveal evidence of mantle wedge metasomatism by a slab-derived melt or supercritical fluid from the subducted rutile-bearing eclogitic Paleo-Tethys oceanic crust, in addition to subsequent metamorphism occurring during the Triassic collision between the South and North China blocks. Combined with the results of previous works, the high Th/U ratios of both whole rocks and metasomatized zircons with no oscillatory zoning lead us to infer that a supercritical liquid rather than a melt was the metasomatic agent during oceanic subduction at peak conditions (5.3–6.3 GPa and ∼800 °C, 160–190 km). Abundant carbonate mineral inclusions (including calcite, dolomite and magnesite) and the high δ18OVSMOW values of the metasomatized zircons (up to 12.2‰) indicate that sedimentary carbonates were leached by the supercritical fluid. Furthermore, whole-rock δ26Mg values (−0.99‰ to −0.65‰) that are lower than normal mantle values (−0.25±0.07‰) imply that the incorporated carbonates contain not only calcites but also a certain amount of dolomites (approximately 1–10 wt.% of the metasomatic supercritical liquid). The dissolved Mg-rich carbonates in the slab-derived supercritical liquid could effectively modify the Mg isotope composition of the deep mantle wedge. Our study represents a critical step towards achieving a broad understanding of the behaviours of recycled carbonate during slab subduction. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109624
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: CAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China; State Key Laboratory of Geological Processes and Mineral Resources, China, University of Geosciences, Beijing, 100083, China; Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, United States; State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China; State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
Recommended Citation:
Shen J.,Li S.-G.,Wang S.-J.,et al. Subducted Mg-rich carbonates into the deep mantle wedge[J]. Earth and Planetary Science Letters,2018-01-01,503