DOI: 10.1016/j.epsl.2020.116627
论文题名: Evolution of the early to late Archean mantle from Hf-Nd-Ce isotope systematics in basalts and komatiites from the Pilbara Craton
作者: Hasenstab E. ; Tusch J. ; Schnabel C. ; Marien C.S. ; Van Kranendonk M.J. ; Smithies H. ; Howard H. ; Maier W.D. ; Münker C.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 553 语种: 英语
中文关键词: Archean
; komatiites
; La-Ce
; Lu-Hf
; Pilbara
; Sm-Nd
英文关键词: Binary alloys
; Cerium alloys
; Gallium
; Isotopes
; Magnesite
; Mixing
; Neodymium alloys
; Rocks
; Silicate minerals
; Stratigraphy
; Structural geology
; Ternary alloys
; Zircon
; Differentiation process
; Early evolution of the earth
; Isotope compositions
; Mafic-ultramafic rocks
; Mantle source region
; Mantle temperatures
; Radiogenic isotope systems
; Temporal evolution
; Hafnium alloys
; Archean
; basalt
; cerium
; hafnium
; komatiite
; lutetium
; mantle
; neodymium isotope
; rare earth element
; samarium
; tectonic evolution
; Australia
; Pilbara Block
; Western Australia
英文摘要: Inferences on the early evolution of the Earth's mantle can be deduced from long-lived radiogenic isotope systems such as 176Lu-176Hf and 147Sm-143Nd, for which both parent and daughter elements largely remain immobile at low metamorphic grades. However, it remains ambiguous when and to what extent mantle-crust differentiation processes had started in the Archean. For a better understanding of Archean mantle-crust evolution, we determined the initial 176Lu-176Hf, 147Sm-143Nd, and, in a new approach, the 138La-138Ce isotope compositions of a suite of Archean mafic-ultramafic rock samples from the 3.53-2.83 Ga old Pilbara Craton and 2.78-2.63 Ga old Fortescue Group in NW Australia. These rocks represent one of the best-preserved Archean successions worldwide and contain mafic-ultramafic rocks that were erupted during repeated and long-lived pulses of volcanism throughout much of the Archean. Mantle-derived mafic-ultramafic rock samples were collected from six major stratigraphic groups of the Pilbara Craton and the overlying Fortescue Group in order to characterize the parental mantle source regions of the lavas and to reconstruct the temporal evolution of the ambient mantle beneath this piece of cratonic lithosphere. In addition, we analyzed contemporaneous TTG-like igneous suites and interbedded sediments in order to reconstruct the lithospheric evolution of the Pilbara Craton. The Hf-Nd-Ce isotope data imply the onset of mantle-crust differentiation in the Pilbara Craton as early as ∼4.2 Ga, well prior to any of the preserved stratigraphy. Within error, coupled Ce-Nd-Hf isotope arrays all intersect chondritic values, implying that the Earth is of broadly chondritic composition, also for the 138La-138Ce isotope system. Mafic rocks usually yield strongly coupled εHf(i), εNd(i) and εCe(i) values that form a mixing line between an evolving depleted upper mantle composition and the primitive mantle value (εHf(i) ca. 0.0 to + 3.2, εNd(i) ca. +0.2 to +1.7 and εCe(i) ca. +0.3 to -0.1). As all Paleoarchean samples lack co-variations between Nb/Th with εHf(i) or εNd(i), contamination with an enriched crust is unlikely to explain this mixing trend. The most primitive mantle-like mafic samples show elevated GdN/YbN ratios (2.2-1.4), implying the involvement of a deep-rooted, near-primitive, upwelling mantle that was progressively mixed into the depleted upper mantle. In contrast to the mafic rocks, most, but not all komatiites are decoupled in their initial Hf-Nd-Ce isotope compositions, by having extremely radiogenic εHf(i) values at only moderately high εNd(i) and low εCe(i) values. This decoupling is best explained by the assimilation of mantle domains that underwent early melt depletion in the garnet stability field and evolved at high 176Lu/176Hf ratios but at moderate 147Sm/143Nd and 138La/138Ce ratios over time. The disappearance of rocks with decoupled Hf-Nd isotope compositions after ∼3.2 Ga is likely linked to decreasing mantle temperatures that were no longer able to melt such refractory mantle domains. Collectively, our new data for mafic rocks from the Pilbara Craton confirm the presence of long-term depleted mantle domains in the early Archean that are not sampled by the zircon Hf isotope record in the Pilbara Craton. © 2020 The Authors Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165500
Appears in Collections: 气候变化与战略
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作者单位: Institut für Geologie und Mineralogie, Universität zu Köln, Zülpicher Straße 49, Cologne, 50674, Germany; Abteilung Nuklearchemie, Universität zu Köln, Zülpicher Straße 45, Cologne, 50674, Germany; Australian Centre for Astrobiology, University of New South Wales, Kensington, NSW, 2052, Australia; Geological Survey of Western Australia, Mineral House, 100 Plain Street, East Perth, WA 6004, Australia; School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, United Kingdom
Recommended Citation:
Hasenstab E.,Tusch J.,Schnabel C.,et al. Evolution of the early to late Archean mantle from Hf-Nd-Ce isotope systematics in basalts and komatiites from the Pilbara Craton[J]. Earth and Planetary Science Letters,2021-01-01,553