Constraints on the Crystallization of Degassing Magmas: An Experimental Study of Crystal Nucleation and Growth Kinetics

火山爆发的类型在很大程度上取决于当上升的岩浆到达浅层时，挥发性成分从熔体中溶出和物理分离的能力。研究岩浆供应速率之间的相互关系的管道从深层次的水库，同喷发脱气，并在喷口的岩浆排放速率是至关重要的，我们的理解控制喷发风格。 脱气导致H2O饱和的硅酸盐熔体结晶，这一过程的结果可能会被火山学家利用，以更好地了解岩浆脱气历史。 为了解释压力-时间路径使用天然火山产品的基质晶体纹理，我们需要了解在这种情况下晶体成核和生长的动力学，这是本提案的重点。我们建议把重点放在有趣的方面结晶动力学的地质和火山学意义的多组分系统。 我们将研究成核在合成和天然玻璃隔离不同的因素（如晶化相的种子和少量的非化学计量的氧化物）在天然熔体的非均质成核的影响。 将使用组合物作为快速减压实验中的变量来检查成核速率的表面能和熔体粘度的相对重要性。 该项目的目标是量化长石成核和生长动力学由于成分（而不是热）过饱和，比较结果，现有的理论，并开发模型的晶体结构的发展在一系列的压力-时间路径相关的火山过程。

HammerEAR-0087463The styles of volcanic eruptions are determined in large part by the ability of volatile components to exsolve and physically separate from the melt when the ascending magma reaches shallow levels. Study of the interrelationships between magma supply rate to the conduit from deep-seated reservoirs, syn-eruptive degassing, and magma discharge rate at the vent is critical to our understanding of controls on eruptive style. Degassing causes H2O-saturated silicate melts to crystallize, and the results of this process may be exploited by volcanologists for greater understanding of magmatic degassing history. In order to interpret pressure-time paths using the groundmass crystal textures of natural volcanic products, we need to understand the kinetics of crystal nucleation and growth under such circumstances, and that is the focus of this proposal. We propose to focus on the intriguing aspects of crystallization kinetics in a multicomponent system of geologic and volcanological significance. We will study nucleation in synthetic and natural glasses to isolate the effects of different factors (such as seeds of the crystallizing phase and minor amounts of nonstoichiometric oxides) on heterogeneous nucleation in natural melts. The relative importance of surface energy and melt viscosity for nucleation rate will be examined using composition as a variable in rapid decompression experiments. The goal of this project is to quantify feldspar nucleation and growth kinetics due to compositional (rather than thermal) supersaturation, compare the results to available theories, and develop models of crystal texture development over a range of pressure-time paths relevant to volcanic processes.