The composition and weathering of the continents over geologic time
The composition and weathering of the continents over geologic time
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DOI：
10.7185/geochemlet.2109
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发表时间：
2021-03-02
影响因子：
4.9
通讯作者：
Yang, J.
中科院分区：
文献类型：
--
作者：
Lipp, A. G.;Shorttle, O.;Yang, J.
大陆地壳的组成记录了构造的建设与物理和化学侵蚀的破坏之间的平衡。定量限制如何火成岩添加和化学风化改变了大陆的整体组成是必不可少的了解地球动力学和气候的演变。使用新的数据分析技术，我们已经提取了时间趋势的沉积物的原岩成分和风化强度的最大的可用汇编的沉积物主要元素组成：类似于15,000样品从4.0 Ga到现在。我们发现，平均太古代上大陆地壳富含二氧化硅，并有类似的组成多样性，现代大陆。这与太古代早期或更早的板块构造的开始是一致的。在太古代，化学风化封存类似于25%以上的CO2每质量侵蚀相同的风化强度比在随后的时间段，符合碳质量平衡，尽管太古代放气率较高，大陆暴露更有限。自2.0 Ga以来，在较长（>0.5 Gyr）的时间尺度上，地壳风化强度保持相对恒定。在中生代较短的时间尺度上，风化强度与全球气候状态相关，与响应CO2源或汇变化的风化反馈一致。
The composition of continental crust records the balance between construction by tectonics and destruction by physical and chemical erosion. Quantitative constraints on how igneous addition and chemical weathering have modified the continents' bulk composition are essential for understanding the evolution of geodynamics and climate. Using novel data analytic techniques we have extracted temporal trends in sediments' protolith composition and weathering intensity from the largest available compilation of sedimentary major element compositions: similar to 15,000 samples from 4.0 Ga to the present. We find that the average Archean upper continental crust was silica-rich and had a similar compositional diversity to modern continents. This is consistent with an early Archean, or earlier, onset of plate tectonics. In the Archean, chemical weathering sequestered similar to 25 % more CO2 per mass eroded for the same weathering intensity than in subsequent time periods, consistent with carbon mass balance despite higher Archean outgassing rates and more limited continental exposure. Since 2.0 Ga, over long (>0.5 Gyr) timescales, crustal weathering intensity has remained relatively constant. Onshorter timescales over the Phanerozoic, weathering intensity is correlated to global climate state, consistent with a weathering feedback acting in response to changes in CO2 sources or sinks.