Multicomponent Diffusion and Speciation Reactions of Major Melt Components, High Field Strength Elements, and Ligands in Haplogranite Melt

三个项目将评估或利用硅酸盐熔体中扩散的质量传输，以更好地了解花岗岩液体的性质。在项目I中，我们将完成近平衡和远平衡条件下含水花岗岩熔体结晶的自洽热力学、动力学和迁移模型。数学算法现在大多已经开发出来，我们最近完成了大量的实验，这些实验为花岗岩体系的结晶动力学提供了约束。项目二解决了一个简单但耐人寻味的问题，即花岗岩熔体如何通过熔体中的扩散(即一旦失去共晶晶界接触)而变得均匀？初步实验表明，碱的快速扩散促进了碱性长石组分在整个熔体中达到平衡比例，然后在碱性长石组分与石英熔融产生的二氧化硅之间发生混合。项目三将处理关于成矿金属(例如Nb、Ta、Sn、W、Zr、Hf和REE)和潜在配体(卤素F和Cl以及H、B、P的氧离子)之间关系的长期假设。不仅将测试物种形成的情况，还将得出可能熔体物种的化学计量比以及它们的扩散系数。项目III的结果将阐明氧以外的阴离子在多大程度上增加或降低成矿金属在熔体中的溶解度。

London & DewersEAR-0124179Three projects will assess or utilize mass transport by diffusion in silicate melts to better understand the properties of granitic liquids. In Project I, we will complete a self-consistent thermodynamic, kinetic, and transport model for the crystallization of water-bearing granite melts under near- and far-from-equilibrium conditions. The mathematical algorithms are now mostly developed, and we have recently completed a large number of experiments that provide constraints on the kinetics of crystallization in the granite system. Project II addresses a simple but intriguing question, namely how do granitic melts become homogeneous by diffusion through the melt (i.e., once eutectic grain-boundary contacts are lost)? Preliminary experiments indicate that rapid diffusion of alkalis promotes the attainment of an equilibrium proportion of alkali feldspar components throughout the melt, and that mixing then occurs between this alkali feldspar component and silica derived from the melting of quartz. Project III will address longstanding presumptions about the relationships among ore-forming metals (e.g., Nb, Ta, Sn, W, Zr, Hf, and REE) and potential ligands (halogens F, and Cl, and oxyanions of H, B, P). Not only will the case for speciation be tested, but the stoichiometry of the probable melt species, along with their diffusion coefficients, will be derived. The results of Project III will elucidate the extent to which anions other than oxygen enhance or decrease the solubility of ore-forming metals in melt.