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：
10.31223/osf.io/qhtb6
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发表时间：
2020-08
影响因子：
4.9
通讯作者：
A. Lipp;O. Shorttle;E. Sperling;J. Brocks;D. Cole;P. Crockford;Lucas Del Mouro;K. Dewing;Stephen Q. Dornbos;J. Emmings
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文献类型：
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作者：
A. Lipp;O. Shorttle;E. Sperling;J. Brocks;D. Cole;P. Crockford;Lucas Del Mouro;K. Dewing;Stephen Q. Dornbos;J. Emmings
大陆地壳的组成记录了一段由构造作用造成的建造和由物理和化学侵蚀造成的破坏的历史。定量限制如何火成添加剂和化学风化已经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。我们已经提取了时间趋势的沉积物原岩成分和风化强度的最大的可用汇编的沉积物的主要元素成分，约15,000个样品从4.0 Ga到现在。为此，我们使用了一种新的分析方法，同时反演整个沉积物的原岩组成和风化强度。我们发现，平均太古代上大陆地壳是二氧化硅丰富，并有类似的现代大陆的成分多样性。这与早太古代或更早的板块构造的开始是一致的。在太古代，化学风化在封存CO2方面的效率比随后的时间段高出约25%。自2.0 Ga以来，在较长的时间尺度（> 0.5 Ga）上，地壳风化强度基本保持不变。在较短的时间尺度在中生代，风化的强度与全球气候状态，一致的硅酸盐风化作用的反馈，在CO2出气的变化。
The composition of continental crust records a history of construction by tectonics and destruction by physical and chemical erosion. Quantitative constraints on how both igneous addition and chemical weathering have modified the continents bulk composition are essential for understanding the evolution of geodynamics and climate. We have extracted temporal trends in sediments protolith composition and weathering intensity from the largest available compilation of sedimentary major-element compositions, of ~ 15,000 samples from 4.0 Ga to the present. To do this we used a new analytical method which inverts whole sedimentary compositions for protolith composition and weathering intensity simultaneously. 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 was ~ 25 % more efficient at sequestering CO2 than in subsequent time periods. Since 2.0 Ga, over long (> 0.5 Ga) timescales, the crustal weathering intensity has remained largely constant. On shorter timescales over the Phanerozoic, the intensity of weathering is correlated to global climate state, consistent with silicate weathering feedback acting in response to changes in CO2 outgassing.