Magma Rheology, Transport, and Eruption: Field, Experiments and Models

该研究计划包括火山学中3个不同但互补的主题。A）硅酸盐熔体粘度模型：Redux* 粘度是控制岩浆运输和喷发的最重要的物理性质。2008年，我们发表了预测天然含水硅酸盐熔体粘度的“GRD模型”。虽然被广泛认为是最好的模型，但由于使用该模型的科学家越来越多，新的第二代模型已经过时。新模型将：i）更准确（相对于实验数据库），ii）跨越更宽范围的熔体组成（例如，金伯利岩），iii）导致更高的压力，iv）添加挥发性CO2，和v）允许铁作为两种物质Fe 3+和Fe 2+。最重要的是，该模型将基于亚当斯-吉布斯理论的合作松弛的熔体，它连接运输（粘度）和热力学性质（熵，热容）。由此产生的模型将捕获地球和其他行星上发现的几乎所有硅酸盐熔体，并具有更强的理论基础，可以预测其他热化学性质。B）熔岩穹丘的流变行为：实验和模型 * 岩浆流变学是理解和预测火山喷发类型和强度的关键。火山系统的岩石力学是一个新的、动态的、高度竞争的研究领域;它位于岩石力学和实验火山学领域之间的界面。本实验的目的是建立在火山喷发的升高条件下的火山物质的流变特性。由此产生的数据集被用来建立本构方程，预测自然岩浆的流动作为应力，应变率，温度和晶体含量的函数。本构关系是更复杂和准确的火山爆发模型的关键。**C）流化火山系统中的颗粒吸附 * 在上升和喷发过程中，岩浆通常会变成高速、富含气体、载有颗粒的悬浮液。这些环境支持“磨损”，即，剧烈的、持续的颗粒-颗粒相互作用，导致颗粒尺寸减小和悬浮货物的重塑。天然火山沉积物中晶体和岩石碎片的形状和表面性质直接影响岩浆运输和喷发的条件，包括流动状态（层流与湍流），上升速度和停留时间。我们将用实验来研究在与火山系统相当的条件下气体和流体射流的磨损。实验阐明的机制和磨损率作为粒子密度，能量和时间的函数。我们的目标是创建一个范例，使用属性的“研磨”（即磨损）岩性和晶体在火山沉积物中推断运输和喷发条件。

This research program comprises 3 distinct but complementary themes in volcanology.******A) A Model for Silicate Melt Viscosity: Redux***Viscosity is the most important physical property governing transport and eruption of magma. In 2008, we published the "GRD model" for predicting the viscosity of natural hydrous silicate melts. Although widely accepted as the best model available, due to the increasing diversity of scientists using the model a new 2nd generation model is overdue. The new model will: i) be more accurate (relative to the experimental database), ii) span a wider range of melt compositions (e.g., kimberlite), iii) account for higher pressures, iv) add the volatile CO2, and v) allow for iron as both species Fe3+ and Fe2+. Most importantly, the model will be based on the Adams-Gibbs theory for cooperative relaxation of melts, which connects transport (viscosity) and thermodynamic properties (entropy, heat capacity). The resulting model will capture virtually all silicate melts found on Earth and other planets, and have a stronger theoretical basis allowing for prediction of other thermochemical properties.******B) Rheological behaviour of lava domes: Experiments & models***Magma rheology is key to understanding and predicting the styles and intensities of volcanic eruption. The Rock Mechanics of Volcanic Systems is a new, dynamic, and highly competitive area of research; it lies at the interface between the fields of rock mechanics and experimental volcanology. The goal of this experimentation is to establish the rheological properties of volcanic materials at the elevated conditions attending volcanic eruption. The resulting datasets are used to build constitutive equations that predict the flow of natural magmas as a function of stress, strain-rate, temperature, and crystal content. The constitutive relationships are key to more sophisticated and accurate modelling of volcanic eruptions. ******C) Particle Attrition in Fluidized Volcanic Systems***During ascent and eruption, magmas commonly become high velocity, gas-rich, particle-laden suspensions. These environments support “attrition” - that is, vigorous, sustained particle-particle interactions causing grain size reduction and reshaping of the suspended cargo. The shapes and surface properties of crystals and rock fragments in natural volcanic deposits directly inform on the conditions attending magma transport and eruption, including, flow regime (laminar vs. turbulent), ascent velocity, and residence time. We will use experiments to study attrition in gas and fluid jets at conditions comparable to volcanic systems. The experiments elucidate the mechanisms and rates of attrition as a function of particle density, energy, and time. Our goal is to create a paradigm for using the properties of the "milled” (i.e. attrited) lithics and crystals in volcanic deposits to infer transport and eruption conditions.