Scientific Reports ( IF 3.8 ) Pub Date : 2019-03-14 , DOI: 10.1038/s41598-019-40819-9 W. Steven Holbrook , Virginia Marcon , Allan R. Bacon , Susan L. Brantley , Bradley J. Carr , Brady A. Flinchum , Daniel D. Richter , Clifford S. Riebe
As bedrock weathers to regolith – defined here as weathered rock, saprolite, and soil – porosity grows, guides fluid flow, and liberates nutrients from minerals. Though vital to terrestrial life, the processes that transform bedrock into soil are poorly understood, especially in deep regolith, where direct observations are difficult. A 65-m-deep borehole in the Calhoun Critical Zone Observatory, South Carolina, provides unusual access to a complete weathering profile in an Appalachian granitoid. Co-located geophysical and geochemical datasets in the borehole show a remarkably consistent picture of linked chemical and physical weathering processes, acting over a 38-m-thick regolith divided into three layers: soil; porous, highly weathered saprolite; and weathered, fractured bedrock. The data document that major minerals (plagioclase and biotite) commence to weather at 38 m depth, 20 m below the base of saprolite, in deep, weathered rock where physical, chemical and optical properties abruptly change. The transition from saprolite to weathered bedrock is more gradational, over a depth range of 11–18 m. Chemical weathering increases steadily upward in the weathered bedrock, with intervals of more intense weathering along fractures, documenting the combined influence of time, reactive fluid transport, and the opening of fractures as rock is exhumed and transformed near Earth’s surface.
中文翻译:
从穿过地球关键区域的65米深的井孔推断出的物理和化学风化之间的联系
随着基岩风化到重新定型(这里定义为风化的岩石,腐泥土和土壤),孔隙度增加,引导流体流动,并从矿物质中释放出养分。尽管对地球生命至关重要,但人们对于将基岩转化为土壤的过程了解甚少,尤其是在难以直接观察的深部重石块中。南卡罗来纳州卡尔霍恩临界区天文台的深达65米的钻孔为阿巴拉契亚花岗岩提供了完整的风化剖面的非常规通道。钻孔中位于同一位置的地球物理和地球化学数据集显示了联系在一起的化学和物理风化过程的非常一致的图景,作用于一个38米厚的重碎石,分为三层:多孔,高度风化的腐泥土;以及风化,破裂的基岩。数据表明,在深,风化的岩石中,主要矿物(斜长石和黑云母)开始在38 m深度,腐泥土基部以下20 m处开始风化,其物理,化学和光学性质会突然发生变化。从腐泥土到风化的基岩的过渡更为渐变,深度在11–18 m之间。化学风化作用在风化的基岩中稳定地向上增加,沿着裂隙的风化作用更加频繁,记录了时间,反应性流体运移和裂隙在岩石被挖掘并转换到地表附近时的综合影响。在11–18 m的深度范围内。化学风化作用在风化的基岩中稳定地向上增加,沿着裂隙的风化作用更加频繁,记录了时间,反应性流体运移和裂隙在岩石被挖掘并转换到地表附近时的综合影响。在11–18 m的深度范围内。化学风化作用在风化的基岩中稳定地向上增加,沿着裂隙的风化作用更加频繁,记录了时间,反应性流体运移和裂隙在岩石被挖掘并转换到地表附近时的综合影响。