The reaction mechanism of weathering of chlorite, an important rock-forming phyllosilicate, is not well understood in natural settings. 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.

绿泥石是一种重要的成岩层状硅酸盐，其风化反应机制在自然环境中尚不清楚。在这项工作中，我们在美国阿巴拉契亚山脉（页岩山）的一个小型页岩下伏流域研究了从深层原岩到腐泥再到土壤的富铁绿泥石的风化。我们发现，绿泥石中 Fe(II) 的氧化总是发生在矿物夹层溶解之前。黄铁矿和绿泥石的氧化开始于地下水位附近，跨越上集水山脊下的狭窄深度区间，但远低于地下水位，跨越山谷下的宽深度区间。我们假设这些模式可以通过山脊和山谷之间的水文和地球化学差异来解释：含氧水在山脊下垂直下降（一维流），

地球化学和矿物学特征表明，富铁绿泥石在页岩山的转变是由 Fe(II) 的氧化引发的。接下来，层间氢氧化物片溶解形成羟基夹层蛭石，然后形成蛭石。在转变过程中，Mg 和 Fe 被释放到溶液中，Fe 在孔隙空间中以针铁矿的形式重新沉淀。通过大气水的渗透将氧气输送到地下深处被认为可以控制页岩山绿泥石的初始转变。许多富含 Fe(II) 的矿物的风化可能是由氧化引发的，这种氧化是由地下氧气输送速率介导的。