Resolving Deep Critical Zone Architecture in Complex Volcanic Terrain
Resolving Deep Critical Zone Architecture in Complex Volcanic Terrain
复制标题
解决复杂火山地形中的深层关键带结构
DOI：
10.1029/2019jf005189
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
J. Chorover
中科院分区：
文献类型：
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作者：
B. Moravec;Alissa White;R. Root;Andres Sanchez;Y. Olshansky;B. Paras;B. Carr;J. McIntosh;J. Pelletier;C. Rasmussen;W. Holbrook;J. Chorover
关键带（CZ）结构，包括矿物、元素和充满流体的孔隙的空间分布，在地质时间尺度上演化，这是由自上而下的气候强迫和自下而上的地质控制造成的。气候和岩性可能会在地下结构中留下印记，作为地球物理、地球化学、矿物学和生物数据集中依赖于深度的趋势。由于风化剖面是过去环境条件的产物，预测模型的开发需要了解气候强迫和CZ过程演变的地质模板的相对作用。在具有高初始基岩孔隙度和独特沉积和热液蚀变历史的复杂火山地形中这样做特别具有挑战性。为了解析Valles Caldera National Preserve（NM，USA）流纹岩集水区的CZ结构，本研究将地球物理学、钻探和实验室分析相结合，生成深度分辨孔隙度、地球化学和矿物学数据集，深度>40 m。定量X射线衍射分析表明，局部矿物转化控制复杂的化学富集/贫化（τ）模式。使用线性判别分析，关键变量可以将复杂的分层地质分离为离散区域。当代，基质主导的风化过程和现代水文通量主要发生在风化剖面的顶部15 m内。这一地带被不完全的原生矿物风化和喷发后风化和交代作用所覆盖。基质风化向断裂面风化的转变是由移动速度较慢、停留时间较长的大气沃茨在深部的深层渗流驱动的。通过改变初始条件和风化轨迹，地质遗产是地下景观如何演变和发挥作用的关键因素。
Critical zone (CZ) structure, including the spatial distribution of minerals, elements, and fluid‐filled pores, evolves on geologic time scales resulting from both top‐down climatic forcing and bottom‐up geologic controls. Climate and lithology may be imprinted in subsurface structure as depth‐dependent trends in geophysical, geochemical, mineralogical, and biological datasets. As the weathering profile is as much (or more) a product of past environmental conditions, development of predictive models requires understanding the relative roles of climatic forcing and the geologic template on which CZ processes evolve. Doing so in complex volcanic terrains with high initial bedrock porosity and distinct depositional and hydrothermal alteration histories is particularly challenging. To resolve CZ structure in a rhyolitic catchment in the Valles Caldera National Preserve (NM, USA), this study combined geophysics, drilling, and laboratory analyses to produce depth‐resolved porosity, geochemistry, and mineralogy datasets to >40 m in depth. Quantitative X‐ray diffraction analysis showed that local mineral transformations control complex chemical enrichment/depletion (τ) patterns. Using linear discriminant analysis, key variables enabled separation of complex‐layered geology into discrete zones. Contemporary, matrix‐dominated weathering processes and modern hydrologic fluxes occur dominantly within the top 15 m of the weathering profile. This zone is convoluted by incomplete primary mineral weathering and overprinted by post‐eruption weathering and metasomatism. Matrix weathering transitions to fracture surface weathering driven by deep percolation of slower moving, longer residence time meteoric waters at depth. By altering initial conditions and weathering trajectory, geologic legacy is a critical factor in how this subsurface landscape evolved and functions.