DOI: 10.1016/j.epsl.2020.116225
论文题名: Generation of Eoarchean continental crust from altered mafic rocks derived from a chondritic mantle: The ∼3.72 Ga Aktash gneisses, Tarim Craton (NW China)
作者: Ge R. ; Wilde S.A. ; Kemp A.I.S. ; Jeon H. ; Martin L.A.J. ; Zhu W. ; Wu H.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 538 语种: 英语
中文关键词: crust – mantle differentiation
; Eoarchean
; isotopes
; Tarim Craton
; TTG gneisses
英文关键词: Binary alloys
; Isotopes
; Neodymium alloys
; Rocks
; Silicate minerals
; Strontium alloys
; Structural geology
; Temperature
; Zircon
; Continental crusts
; Crustal recycling
; Eoarchean
; Isotopic systematics
; Mantle differentiation
; Metamorphic events
; Tarim Craton
; TTG gneisses
; Gallium
; Archean
; chemical alteration
; chondrite
; continental crust
; crust-mantle boundary
; differentiation
; geochemistry
; geochronology
; gneiss
; isotopic analysis
; mafic rock
; metamorphism
; China
; Tarim Block
英文摘要: Our understanding of crust – mantle evolution and geodynamics of the early Earth has been hampered by the scarcity of Hadean to Eoarchean rocks and by the almost ubiquitous isotopic disturbance of the oldest rocks. Here we present in-situ zircon U-Pb ages, O-OH and Lu-Hf isotopes, as well as whole-rock Sr-Nd-Hf-Pb isotopes for the recently identified Eoarchean Aktash gneisses in the Tarim Craton, NW China. The new age data confirm that the Aktash gneisses were formed at least by ∼3.72 Ga and were affected by two metamorphic events at ∼3.56 and ∼2.0 Ga, respectively. Whole-rock isotopic data show that the Sr-Nd-Hf-Pb isotopic systematics have all been variously disturbed by ∼2.0 Ga regional granulite facies metamorphism, resulting in decoupling of Nd-Hf isotopic systematics that is, in some samples, similar to that observed in SW Greenland. The least disturbed sample (16ALT67), however, yielded chondritic to slightly sub-chondritic whole-rock εNd (−0.3) and εHf (−0.9). This is consistent with the in-situ magmatic zircon εHf (weighted mean −0.2 to −1.8) for most samples of the Aktash gneisses, suggesting a mafic source derived from chondritic mantle with a short crustal residence time. Our data thus provide no evidence for the presence of an Eoarchean depleted mantle or a Hadean enriched crust, implying that early Earth crust – mantle differentiation was either limited or balanced by large-scale crustal recycling. In-situ zircon O–OH data show that metamorphism and later alteration tend to decrease the zircon δ18O of the Aktash gneisses, and the weighed mean δ18O of pristine magmatic zircons (6.2–6.3‰) from the least disturbed samples indicate that the mafic source was mildly altered at low temperature by the early hydrosphere, facilitating partial melting and formation of some of the earliest preserved continental crust known on Earth. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164981
Appears in Collections: 气候变化与战略
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作者单位: State Key Laboratory for Mineral Deposits Research, Institute of Continental Geodynamics, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210093, China; The Institute for Geoscience Research, School of Earth and Planetary Sciences, Curtin University, PO Box U1987, Perth, Western Australia 6845, Australia; School of Earth Sciences, University of Western Australia, Perth, Western Australia 6009, Australia
Recommended Citation:
Ge R.,Wilde S.A.,Kemp A.I.S.,et al. Generation of Eoarchean continental crust from altered mafic rocks derived from a chondritic mantle: The ∼3.72 Ga Aktash gneisses, Tarim Craton (NW China)[J]. Earth and Planetary Science Letters,2020-01-01,538