DOI: 10.1038/ngeo2019
论文题名: Delamination and recycling of archaean crust caused by gravitational instabilities
作者: Johnson T.E. ; Brown M. ; Kaus B.J.P. ; Vantongeren J.A.
刊名: Nature Geoscience
ISSN: 17520894
出版年: 2014
卷: 7, 期: 1 起始页码: 47
结束页码: 52
语种: 英语
英文摘要: Mantle temperatures during the Archaean eon were higher than today. As a consequence, the primary crust formed at the time is thought to have been extensive, thick and magnesium rich, and underlain by a highly residual mantle. However, the preserved volume of this crust today is low, implying that much of it was recycled back into the mantle. Furthermore, Archaean crust exposed today is composed mostly of tonalite-trondhjemite-granodiorite, indicative of a hydrated, low-magnesium basalt source, suggesting that they were not directly generated from a magnesium-rich primary crust. Here we present thermodynamic calculations that indicate that the stable mineral assemblages expected to form at the base of a 45-km-thick, fully hydrated and anhydrous magnesium-rich crust are denser than the underlying, complementary residual mantle. We use two-dimensional geodynamic models to show that the base of magmatically over-thickened magnesium-rich crust, whether fully hydrated or anhydrous, would have been gravitationally unstable at mantle temperatures greater than 1,500-1,550C. The dense crust would drip down into the mantle, generating a return flow of asthenospheric mantle that melts to create more primary crust. Continued melting of over-thickened and dripping magnesium-rich crust, combined with fractionation of primary magmas, may have produced the hydrated magnesium-poor basalts necessary to source tonalite-trondhjemite-granodiorite melts. The residues of these processes, with an ultramafic composition, must now reside in the mantle. © 2014 Macmillan Publishers Limited. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/106428
Appears in Collections: 气候减缓与适应 科学计划与规划
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作者单位: Institute for Geoscience, University of Mainz, Mainz 55099, Germany; Department of Geology, University of Maryland, College Park, MD 20742, United States; Department of Earth Sciences, University of Southern California, CA, 90089-0740, United States; Department of Geology and Geophysics, Yale University, New Haven, CT, 06511, United States
Recommended Citation:
Johnson T.E.,Brown M.,Kaus B.J.P.,et al. Delamination and recycling of archaean crust caused by gravitational instabilities[J]. Nature Geoscience,2014-01-01,7(1)