Quantitative Modeling of Infiltration in Layered Intrusions

像南非的Bushveld杂岩和蒙大拿州的Stillwater杂岩这样的火成岩侵入体，蕴藏着世界上许多具有经济价值的元素，如铬和铂族元素。尽管进行了大量的研究，但令人惊讶的是，关于它们是如何结晶和分化的，人们仍然没有达成一致意见。拟议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melt算法）与一维热量和质量传递方程（包括McKenzie的压实方程）联系起来。这项工作将扩展的领域包括将尖晶石添加到该计划中，并研究在层状侵入体中出现的具有重要经济意义的富铬铁矿层的形成。在平行轨道上，我们将研究矿物-矿物微量元素分配的细节，以测试依赖温度的微量元素浓度是否受到压实驱动的再结晶的影响。具体来说，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-矿物分配是否与纹理和/或模态变化相关。最后，我们希望测试是否可以从晶体尺寸分布（CSD）数据推断出隐藏的入侵几何形状。这将通过将现有数据与新收集的Lower和Critical带样本进行比较来进行测试，其中Lower和Critical带在下盘（即“Burgersfort Bugle”）上异常厚，并且Lower和Critical带位于Bushveld东部的底板岩石上。如果成功，这将进一步证明纹理是局部进化的，而不一定是来自其他地方的矿物质的功能。

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.