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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Where fast weathering creates thin regolith and slow weathering creates thick regolith
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Where fast weathering creates thin regolith and slow weathering creates thick regolith

机译：快速风化产生稀疏的块状体，而慢速风化产生浓厚的块状体

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摘要

Weathering disaggregates rock into regolith - the fractured or granular earth material that sustains life on the continental land surface. Here, we investigate what controls the depth of regolith formed on ridges of two rock compositions with similar initial porosities in Virginia (USA). A priori, we predicted that the regolith on diabase would be thicker than on granite because the dominant mineral (feldspar) in the diabase weathers faster than its granitic counterpart. However, weathering advanced 20× deeper into the granite than the diabase. The 20×-thicker regolith is attributed mainly to connected micron-sized pores, microfractures formed around oxidizing biotite at 20m depth, and the lower iron (Fe) content in the felsic rock. Such porosity allows pervasive advection and deep oxidation in the granite. These observations may explain why regolith worldwide is thicker on felsic compared to mafic rock under similar conditions. To understand regolith formation will require better understanding of such deep oxidation reactions and how they impact fluid flow during weathering.
机译：风化作用将岩石分解成块石-破碎的或粒状的土壤物质，维持了陆地表面的生命。在这里，我们研究了如何控制在弗吉尼亚州（美国）的具有相似初始孔隙度的两种岩石组合物的脊上形成的重灰岩的深度。先验地，我们预测辉绿岩上的碎屑岩比花岗岩上的厚，因为辉绿岩中的主要矿物（长石）的风化速度比花岗岩中的长石。但是，风化作用使花岗岩比辉绿岩更深20倍。 20倍厚的重块岩主要归因于相连的微米级孔隙，氧化黑云母周围20m深度处形成的微裂缝以及长英质岩石中较低的铁（Fe）含量。这样的孔隙率允许花岗岩中普遍的对流和深度氧化。这些观察结果可以解释为什么在相似条件下，全球长石在长英质上比镁铁质岩厚。要了解重石灰石的形成，将需要更好地了解此类深度氧化反应及其在风化过程中如何影响流体流动。

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