Measuring Trace Element Partition Coefficients Between Minerals and Basaltic Melts

LundstromEAR-0000924岩浆岩石学在过去20年里经历了观测地球化学数据的指数增长，导致我们对岩浆过程物理学的看法发生了根本变化。解释这些数据需要更好地了解微量元素是如何在地幔矿物和熔体之间分配的。该项目将提供单斜辉石或斜长石与潜在地幔熔体之间各种元素(稀土元素、高场强元素和大离子亲石元素)之间的相关微量元素分配数据。具体地说，它将通过集中于贫化的单斜辉石成分与贫化的玄武岩熔体之间的平衡来限制单斜辉石与与地幔熔融柱上部有关的熔体之间的分配系数。将特别注意熔体和晶体成分变化的影响。此外，该项目还将限制各种微量元素在斜长石和熔体之间的分配系数。在这种情况下，研究的熔体范围从玄武岩到安山岩。这些实验将在活塞式圆柱体装置或1气氛炉中进行，使用天然和合成的起始材料。实验将通过电子和离子微探针进行分析。结果将被参数化，目的是预测作为地幔熔融柱深度函数的微量元素分配行为。这些实验将提供必要的分配系数数据，以解释地球上各种构造制度的微量元素和铀系不平衡数据。所得数据将被纳入两相流的地球化学模型，以便进一步限制地幔中岩浆作用的物理过程。

LundstromEAR-0000924Igneous petrology has experienced an exponential increase in the number of observational geochemical data over the past 20 years, leading to fundamental changes in our view of the physics of magmatic processes. Interpreting these data requires a better understanding of how trace elements distribute themselves between mantle minerals and melts. This project will provide relevant trace element partitioning data for a wide range of elements (rare earth elements, high field strength elements, and large ion lithophile elements) between clinopyroxene or plagioclase and potential mantle melts. Specifically it will provide constraint on the partition coefficients between clinopyroxene and melt relevant to the upper portions of a mantle-melting column by focussing on depleted clinopyroxene compositions in equilibrium with depleted basaltic melts. Particular attention will be paid to the effects of variations in both melt and crystal composition. In addition, the project will constrain the partition coefficients for a variety of trace elements between plagioclase and melt. Melts examined in this case will range from basaltic to andesitic. The experiments will be performed in either a piston cylinder apparatus or a 1-atmosphere furnace using both natural and synthetic starting materials. Experiments will be analyzed by electron and ion microprobe. Results will be parameterized with the goal of predicting trace element partitioning behavior as a function of depth in mantle melting column. These experiments will provide needed partition coefficient data for interpreting trace element and uranium-series disequilibria data from a variety of tectonic regimes on the planet. The resulting data will be incorporated into geochemical models of two-phase flow in order to gain further constraint on the physics of magmatic processes in the mantle.