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Mehlich 3 as an indicator of grain nutrient concentration for five cereals in sub-Saharan Africa
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Weathering of chlorite from grain to watershed: The role and distribution of oxidation reactions in the subsurface
The reaction mechanism of weathering of chlorite, an important rock-forming phyllosilicate, is not well understood in natural settings. Here, in this work we investigated the weathering of Fe-rich chlorite from deep protolith to saprock to soil across a small shale-underlain watershed in the Appalachian Mountains, USA (Shale Hills). We found that oxidation of Fe(II) in chlorite always occurs prior to dissolution of the interlayers of the mineral. The oxidation of pyrite and chlorite commence near the water table across narrow depth intervals under the upper-catchment ridges, but well below the water table across wide depth intervals under the valley. We hypothesize that these patterns can be explained by hydrological and geochemical differences between the ridge and the valley: oxygenated water descends sub-vertically (1D flow) under the ridge, while under the valley, oxygen-depleted water moves upward to the stream and laterally out of the watershed in the subsurface (3D flow). Geochemical and mineralogical characterization indicates that the transformation of Fe-rich chlorite at Shale Hills is initiated by the oxidation of Fe(II). Next, the interlayer hydroxide sheet dissolves to form hydroxy-interlayered vermiculite and then vermiculite. During the transformation, Mg and Fe are released into solution and Fe is reprecipitated as goethite in pore space. Delivery of oxygen to the deep subsurface by infiltration of meteoric water is thought to control the initial transformation of chlorite at Shale Hills. It is possible that weathering of many Fe(II)-rich minerals is initiated by oxidation as mediated by rates of subsurface oxygen delivery.
Microspectroscopy reveals dust-derived apatite grains in acidic, highly-weathered Hawaiian soils
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Effect of grain size and precipitates on hydrogen embrittlement susceptibility of nickel alloy 718
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Crystal grain size effects and crystallinity dynamics during supersonic particle impacts
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The development of grain resolved stress fields around notch tips in soft-textured zirconium polycrystals: A three-dimensional synchrotron X-ray diffraction study
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Non-destructive determination of phase, size, and strain of individual grains in polycrystalline photovoltaic materials
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Fatigue crack propagation in fine-grained magnesium under low temperature tension-tension cyclic loading
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Grain boundary network plasticity: Reduced-order modeling of deformation-driven shear-coupled microstructure evolution
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