Nonlinear processes in geochemical systems

在自然界中，非线性复杂系统经常被驱使远离平衡。对于生物来说当然是这样，但对于许多在开放环境中发生化学反应的地球化学系统也是如此。这些系统可以由确定性过程、随机强迫(代表耦合到系统的环境的随机性质)或两者共同驱动。利用分析和数值相结合的方法，拟议研究的目标是调查各种非平衡的非线性地球化学系统，了解观察到的空间和时间模式，并查明环境波动(“噪声”)所起的作用。这项调查将有助于更好地了解所观察到的岩石和矿物花样的成因条件、沉积物中发生的过程(早期成岩作用)以及岩浆室中导致剧烈火山喷发的一些过程。更具体地说，我建议解决以下四类问题。我计划调查导致许多矿物系统呈现复杂分带模式的各种过程，据此，化学成分沿着核心到边缘的剖面(振荡分带-子项目I)或跨矿物集合体(周期性降水-子项目II)而变化。我还将调查在沉积物中发生的生物地球化学过程的传统反应-运输模型中没有考虑的影响(称为早期成岩作用-子项目III)。在子项目IV中，我将构建一个更完整的(成核/生长/聚集)模型，阐明气泡在岩浆室中所起的作用，并了解气泡动力学与剧烈火山喷发事件之间的联系。

In nature, nonlinear complex systems are often driven far from equilibrium. This is certainly true of living beings, but it is also the case for many geochemical systems, where chemical reactions occur in open environments. These systems may be driven by deterministic processes, stochastic forcing (representing the random nature of the environment coupled to the system), or both. Using a combination of analytical and numerical methods, the goal of the proposed research is to investigate a variety of non-equilibrium nonlinear geochemical systems, to understand the observed spatial and temporal patterns and to pinpoint the role played by environmental fluctuations ("noise"). This investigation will lead to a better understanding of the genesis conditions of observed patterns in rocks and minerals, of processes taking place in sediments (early diagenesis) and of some of the processes in magma chambers leading to violent volcanic eruptions. More specifically, I propose to address the following four classes of problems. I plan to investigate the various processes leading many mineral systems to exhibit complex zoning patterns, whereby the chemical composition varies along a core-to-rim profile (oscillatory zoning - subproject i) or across a mineral aggregate (periodic precipitation - subproject ii). I will also investigate effects that are not considered in conventional reaction-transport models of biogeochemical processes taking place in sediments (called early diagenesis - subproject iii). In subproject iv, I will construct a more complete (nucleation/growth/ aggregation) model clarifying the role played by gas bubbles in magma chambers, and to understand the links between the bubble dynamics and the event of violent volcanic eruptions.