Beinlich Andreas, Austrheim Håkon, Mavromatis Vasileios, Grguric Ben, Putnis Christine V, Putnis Andrew
The Institute for Geoscience Research (TIGeR), Department of Applied Geology, Curtin University, Perth, WA, 6845, Australia.
Physics of Geological Processes (PGP), University of Oslo, 0316, Oslo, Norway.
Nat Commun. 2018 Feb 12;9(1):634. doi: 10.1038/s41467-018-03039-9.
The chemical composition of the continental crust cannot be adequately explained by current models for its formation, because it is too rich in Ni and Cr compared to that which can be generated by any of the proposed mechanisms. Estimates of the crust composition are derived from average sediment, while crustal growth is ascribed to amalgamation of differentiated magmatic rocks at continental margins. Here we show that chemical weathering of Ni- and Cr-rich, undifferentiated ultramafic rock equivalent to ~1.3 wt% of today's continental crust compensates for low Ni and Cr in formation models of the continental crust. Ultramafic rock weathering produces a residual that is enriched in Ni and also silica. In the light of potentially large volumes of ultramafic rock and high atmospheric CO concentrations during the Archean, chemical weathering must therefore have played a major role in forming compositionally evolved components of the early Earth's crust.
目前关于大陆地壳形成的模型无法充分解释其化学成分，因为与任何一种提出的机制所产生的情况相比，大陆地壳中的镍和铬含量过高。地壳成分的估计来自平均沉积物，而地壳生长则归因于大陆边缘分异岩浆岩的合并。我们在此表明，相当于当今大陆地壳1.3 wt%的富含镍和铬的未分异超镁铁质岩石的化学风化，弥补了大陆地壳形成模型中镍和铬含量的不足。超镁铁质岩石风化产生的残余物富含镍和二氧化硅。鉴于太古宙时期可能存在大量超镁铁质岩石以及高浓度的大气二氧化碳，因此化学风化必定在早期地球地壳成分演化组分的形成过程中发挥了主要作用。
