Sandia National Laboratories, PO Box 5800, Albuquerque, New Mexico 87185, USA.
Nat Commun. 2012 Feb 21;3:685. doi: 10.1038/ncomms1684.
Lateral metre-scale periodic variations in porosity and composition are found in many dolomite strata. Such variations may embed important information about dolomite formation and transformation. Here we show that these variations could be fossilized chemical waves emerging from stress-mediated mineral-water interaction during sediment burial diagenesis. Under the overlying loading, crystals in higher porosity domains are subjected to a higher effective stress, causing pressure solution. The dissolved species diffuse to and precipitate in neighbouring lower porosity domains, further reducing the porosity. This positive feedback leads to lateral porosity and compositional patterning in dolomite. The pattern geometry depends on fluid flow regimes. In a diffusion-dominated case, the low- and high-porosity domains alternate spatially with no directional preference, while, in the presence of an advective flow, this alternation occurs only along the flow direction, propagating like a chemical wave. Our work provides a new perspective for interpreting diagenetic signatures in sedimentary rocks.
许多白云岩地层中都存在横向米级规模的孔隙度和成分周期性变化。这些变化可能蕴含着有关白云岩形成和转化的重要信息。本文研究表明，这些变化可能是在埋藏成岩作用过程中，由应力介导的矿物-水相互作用产生的化学波化石。在上方覆压下，高孔隙度域中的晶体承受更高的有效应力，导致压溶作用。溶解物质扩散并在相邻的低孔隙度域中沉淀，进一步降低了孔隙度。这种正反馈导致白云岩中出现横向孔隙度和成分模式。图案几何形状取决于流体流动状态。在扩散主导的情况下，低和高孔隙度域空间上交替，没有方向偏好，而在存在平流的情况下，这种交替仅沿流动方向发生，像化学波一样传播。我们的工作为解释沉积岩中成岩特征提供了新的视角。
