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。采用解析和数值相结合的方法，本研究的目标是调查各种非平衡的非线性地球化学系统，这些系统都有一个共同的主线：它们构成了在与地球化学相关的环境中的非线性反应迁移现象的表现形式。更具体地说，我将致力于回答这些问题：“是什么原因导致许多矿藏呈现出复杂的空间模式，即它们的化学成分沿着核心到边缘的剖面(振荡分带)或跨矿物集合体(周期性降水)变化？从对这些模式的分析中，我们能从这些矿床的成因条件中了解到什么？例如，我们能否开发出古气候情景来解释东地中海沉积物中存在周期性的黄铁矿降水带？从航空照片中观察到的北部针叶林中有趣的大型森林年轮模式的形成是什么地球化学过程？”火山系统提供了富含远离平衡的非线性过程的地球化学复杂系统的其他例子。我将致力于回答以下问题：“岩浆系统中的气泡在猛烈喷发的发展过程中扮演了什么角色？我们能用浮石氧化作为估算火山羽流的温度历史和冷却速度(地球测速)的指标吗？”

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 that all are linked by a common thread: they constitute manifestations of non-linear reactive transport phenomena in geochemically relevant settings. More specifically, I will contribute to answer these questions: "What causes many mineral deposits to exhibit complex spatial patterns, whereby their chemical composition varies along a core-to-rim profile (oscillatory zoning) or across a mineral aggregate (periodic precipitation)? What can we learn about the genesis conditions of these deposits from the analysis of these patterns? For instance, can we develop paleo-climatic scenarios that explain the presence of periodic precipitation bands of pyrite in sediments of the Eastern Mediterranean? What are the geochemical processes leading to the formation of the intriguing large forest rings patterns, observed in the boreal forest from aerial photographs?" Volcanic systems provide other examples of geochemical complex systems rich in far-from-equilibrium non-linear processes. I will contribute to address the following questions:" What is the role played by gas bubbles in magmatic systems in the development of violent eruptions? Can we use pumice oxidation as a proxy for estimating the temperature history and cooling rate of a volcanic plume (geospeedometry)?"