Quantitative Modeling of Infiltration in Layered Intrusions

像南非的布什维尔德杂岩和蒙大拿州的斯蒂尔沃特杂岩这样的火成岩侵入体拥有世界上大部分有经济价值的元素储量，如铬和铂族元素。 尽管经过了大量的研究，但令人惊讶的是，关于它们是如何结晶和分化的，仍然没有达成一致。所提出的研究的一个重要部分涉及扩展一个数值模型，该模型将平衡结晶程序（基于Ghiorso及其同事的MELTS算法）与包括McKenzie压实方程在内的一维热量和质量输运方程联系起来。该工作将扩展的领域的例子包括将尖晶石添加到该计划中，并调查层状侵入体中发生的具有经济意义的富铬层的形成。 在平行轨道上，我们将研究矿物-矿物微量元素分配的细节，以测试温度依赖性微量元素的浓度是否受结晶驱动的重结晶的影响。 具体而言，激光烧蚀ICP-MS和电子探针矿物测绘和散装矿物分析将测试矿物分区相关的纹理和/或模态variation.Finally，我们希望测试，如果一个可以推断出隐藏的侵入体几何形状从晶体尺寸分布（CSD）的数据。 这将通过将现有数据与新的下部和临界区样本进行比较来进行测试，其中下部在下盘海湾上异常厚（即，“Burgersfort Bugle”）以及低层和临界层与东部布什维尔德的底板岩石重叠的地方。 如果成功的话，这将进一步证明结构是在当地演变的，不一定是从其他地方运来的矿物的功能。

BoudreauEAR-0206905Igneous intrusions such as the Bushveld Complex of South Africa and the Stillwater Complex of Montana host much of the world's reserves of economically valuable elements such as chromium and the platinum-group elements. Although subject to numerous studies, there is still surprisingly little agreement on how they crystallized and differentiated. A significant part of the proposed study involves extending a numerical model that links an equilibrium crystallization routine (based on the MELTS algorithm of Ghiorso and coworkers) with one-dimensional heat and mass transport equations that include compaction equations of McKenzie. Examples of areas the work would be extended include the addition of spinels to the program and investigation of the formation of economically important chromite-rich layers that occur in layered intrusions. On a parallel track, we will look at details of mineral-mineral trace element partitioning to test if concentrations of temperature-dependent trace elements are affected by compaction-driven recrystallization. Specifically, laser ablation-ICP-MS and electron microprobe mineral mapping and bulk mineral analysis will test if mineral-mineral partitioning is correlated textural and/or modal variations.Finally, we wish to test if one can infer concealed intrusion geometry from crystal size distribution (CSD) data. This will be tested by comparing existing data with new Lower and Critical zone samples to be collected where the Lower is both unusually thick over footwall embayments (i.e., the "Burgersfort Bugle") and where the Lower and Critical zone onlap the floor rocks in the eastern Bushveld. If successful, this will further demonstrate that texture is locally evolved and not necessarily a function of minerals transported from elsewhere.