Behavioral differences between weathering and pedogenesis in a subtropical humid granitic terrain: Implications for chemical weathering intensity evaluation
Behavioral differences between weathering and pedogenesis in a subtropical humid granitic terrain: Implications for chemical weathering intensity evaluation
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亚热带湿润花岗岩地形风化和成土作用之间的行为差异：化学风化强度评估的意义
DOI：
10.1016/j.catena.2021.105368
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发表时间：
2021-08
期刊：
影响因子：
6.2
通讯作者：
Zhang Shuo
中科院分区：
文献类型：
--
作者：
Mei Haowei;Jian Xing;Zhang Wei;Fu Hanjing;Zhang Shuo
大陆风化在地球表面的演变中起着至关重要的作用，它连接地球的各个球体，塑造地貌，调节化学循环和全球气候。在某些情况下，风化层风化研究理想地假设连续和渐进的自下而上的物理化学变化趋势。为了验证这一假设，我们的目标是在亚热带季风气候为主的地区（中国东南部）的花岗岩风化层配置文件。我们目前的矿物学，岩相学和地球化学数据，从土壤，腐岩和基岩样品，以表征物理和化学蚀变。岩石学和矿物学结果表明，斜长石和钾长石都被耗尽，高岭石是主要的新形成的矿物相在表土样品，揭示了强烈的化学风化的风化。然而，这些表层土壤样品的化学蚀变指数要低得多（CIA，CA。64-67）的值比下面的氧化土壤样品（CIA值范围为65-80）。一些化学固定元素，如Al，Ti，Zr和Hf，在表土样品中被耗尽，但在氧化土样品中相对富集。这是由于细粒矿物的垂直沥滤和迁移（例如，高岭石、伊利石和锆石）。此外，所分析的表土样品中K和P元素相对丰富，这很可能是由于明显的生物固定过程。疏松、多孔和生物表土中的这些物理和生物过程可能是导致CIA值意外低的原因。我们的研究结果表明，复杂的物理，化学和生物变化的土壤和风化和成土过程之间的差异行为，特别是在热带-亚热带高降雨区。该案例研究还强调了岩石学和矿物学代用指标对风化层剖面和硅质沉积物化学风化强度评价的重要性。
Continental weathering plays a crucial role in the evolution of the Earth’s surface by linking Earth's spheres, shaping landscapes and regulating chemical cycles and global climate. Regolith weathering studies in some cases ideally assume successive and progressive bottom-up physicochemical variation trends. To validate this assumption, we target a granitic regolith profile in a subtropical monsoon climate-dominated region (southeast China). We present mineralogical, petrographic and geochemical data from soil, saprolite and bedrock samples to characterize physical and chemical alterations. The petrographic and mineralogical results indicate that both plagioclase and K-feldspar are depleted and kaolinite is the major neoformed mineral phase in top-soil samples, revealing intensive chemical weathering on the regolith. However, these top-soil samples have much lower chemical index of alteration (CIA, ca. 64–67) values than the underlying oxidized-soil samples (CIA values ranging 65–80). Some chemically immobile elements, such as Al, Ti, Zr and Hf, are depleted in top-soil samples but are comparatively enriched in oxidized-soil samples. This is attributed to vertical leaching and translocation of fine-grained minerals (e.g., kaolinite, illite and zircon) through the soils. Furthermore, the analyzed top-soil samples are comparatively rich in elements K and P, which are most likely due to the evident biological fixation process. These physical and biological processes in the unconsolidated, porous and biotic top-soil layer can be responsible for the unexpected low CIA values. Our findings demonstrate the complex physical, chemical and biological alterations on soils and the differential behaviors between weathering and pedogenic processes, especially for those tropical–subtropical high rainfall regions. This case study also highlights the importance of petrographic and mineralogical proxies to chemical weathering intensity evaluation for regolith profiles and siliciclastic sediments.
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影响因子：
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作者：
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影响因子：
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影响因子：
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