2. |
- Saji, N. S., et al.
(författare)
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Hadean geodynamics inferred from time-varying 142Nd/144Nd in the early Earth rock record
- 2018
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Ingår i: Geochemical Perspectives Letters. ; 7, s. 43-48
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Tidskriftsartikel (refereegranskat)abstract
- Tracking the secular evolution of 142Nd/144Nd anomalies is important towards understanding the crust-mantle dynamics in the early Earth. Excessive scatter in the published data, however, precludes identifying the fine structure of 142Nd/144Nd evolution as the expected variability is on the order of few parts per million. We report ultra-high precision 142Nd/144Nd data for Eoarchean and Palaeoarchean rocks from the Isua Supracrustal Belt (SW Greenland) that show a well-resolved 142Nd/144Nd temporal variability suggesting progressive convective homogenisation of the Hadean Isua depleted mantle. This temporally decreasing 142Nd/144Nd signal provides a direct measure of early mantle dynamics, defining a stirring timescale of <250 Myr consistent with vigorous convective stirring in the early mantle. The 142Nd/144Nd evolution suggests protracted crustal residence times of ~1000-2000 Myr, inconsistent with modern-style plate tectonics in the Archean. In contrast, a stagnant-lid regime punctuated by episodes of mantle overturns accounts for the long life-time estimated here for the Hadean proto-crust.
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3. |
- Wielandt, J. Wolfram, et al.
(författare)
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Self-Assembly of Square-Planar Halide Complexes of Trimethylphosphine-Stabilized Diphenyl-Arsenium, -Stibenium, and -Bismuthenium Hexafluorophosphates*
- 2016
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Ingår i: Australian Journal of Chemistry. ; 69:5, s. 524-532
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Tidskriftsartikel (refereegranskat)abstract
- Square-planar halide complexes in which four trimethylphosphine-stabilized diphenyl-stibenium or -bismuthenium ions surround a central halide ion in discrete centrosymmetrical structures of C4h symmetry have been isolated and their structures determined by X-ray crystallography. The structures are stabilized by electrostatic interactions between the halide ion and four positively charged trimethylphosphine-stabilized diphenyl-stibenium or -bismuthenium ions, as well as four edge-to-face phenyl–phenyl embraces above and below the plane containing the nine main group elements. The parent halide-free trimethylphosphine-stabilized diphenyl-arsenium, -stibenium, and -bismuthenium hexaflurophosphate complexes have also been prepared and structurally characterized.
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