Quantitative Modeling of Infiltration in Layered Intrusions

例如南非的布什维尔德杂岩和蒙大拿州的斯蒂尔沃特杂岩，拥有世界上许多具有经济价值的元素的储量，如铬和铂族元素。尽管有许多研究，但令人惊讶的是，关于它们是如何结晶和分化的，仍然几乎没有达成一致意见。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和同事的Melts算法)与一维热量和质量传输方程联系起来，其中包括McKenzie的压实方程。这项工作将扩展的领域包括将尖晶石添加到计划中，以及调查在层状侵入体中形成具有重要经济意义的富铬矿层。在平行的轨道上，我们将研究矿物-矿物微量元素分配的细节，以测试与温度相关的微量元素浓度是否受到压实驱动的重结晶的影响。具体地说，激光烧蚀-电感耦合等离子体质谱和电子探针矿物填图和大块矿物分析将测试矿物-矿物分配是否与结构和/或模式变化相关。最后，我们希望测试是否可以从晶体尺寸分布(CSD)数据中推断隐伏的侵入几何形状。这将通过将现有数据与将收集的新的下部和临界区样本进行比较来检验，其中下部在下部海湾(即“Burgersfort Bugle”)上异常厚，而在东部布什维尔德，下部和临界区与底岩重叠。如果成功，这将进一步证明纹理是在当地进化的，而不一定是从其他地方运输来的矿物的功能。

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.