Accessory mineral geochemistry in high-T systems

问题：不相容的微量元素模式（例如REE）通常用于模拟高温地质系统中的过程。然而，辅助矿物可能控制不相容的微量元素分布。因此，在将地球化学建模应用于地质过程时，了解微量元素和辅助矿物的地球化学之间的联系至关重要。目的：了解高温地质系统中伴生矿物对全岩模式的地球化学影响。这将首先集中于对地壳熔体形成的初步检查，以及不同成分的母岩和由此产生的熔体之间各种辅助矿物和不相容微量元素的分布。研究大型岩浆侵入体中不相容元素的地球化学演化，为目前仅存在锆石和磷灰石的微量元素数据库提供辅助矿物组成数据库。这将使本研究结果与岩浆和高温变质系统中辅助矿物地球化学和不相容微量元素行为的已建立模型进行更好的比较。方法：拟议的研究将开发和应用微分析技术，以满足拟议的研究目标，利用现有的和新开发的ICP-MS技术，以Chicoutimi大学的新设施为中心。已经确定了在Cap l'Aigle和St. fulence的优秀实地研究区域，并将提供各种各样的母岩和熔体类型。意义：将痕量元素地球化学记录与辅助矿物分布联系起来，将有助于更好地理解不相容元素的行为，从而有助于建立更准确的全岩系统地球化学模型。还将提供辅助矿物分布系数和浓度的数据库。

The Problem: Incompatible trace-element patterns (e.g. REE) are commonly used to model processes in high-temperature geologic systems. However, accessory minerals such may control incompatible trace-element distributions. Thus, understanding the link between the geochemistry of trace-elements and accessory minerals is crucial when applying geochemical modeling to geologic processes. The Objectives: To understand the geochemical influence of accessory minerals on whole-rock patterns in high-temperature geological systems. This will begin by focusing on an initial examination of crustal melt formation and the distribution of various accessory minerals and incompatible trace-elements between the parent rocks of different compositions and the resulting melts. The geochemical evolution of incompatible elements in large magmatic intrusions will also be studied to provide a database of accessory mineral compositions to augment and expand trace-elements databases which currently only exist only for zircon and apatite. This will allow a better comparison of the results of this research with established models for accessory mineral geochemistry and incompatible trace-element behavior in both magmatic and high-temperature metamorphic systems. Methodology: The proposed research will develop and apply micro-analytical techniques to meet the proposed research objectives using existing and newly developed ICP-MS techniques, centered around a new facility at the University du Québec a Chicoutimi. Excellent field study areas at Cap à l'Aigle and St. Fulgence, Québec have been identified and will provide access to a wide variety of parent rock and melt types. Significance: Linking the trace-element geochemical record with accessory mineral distributions will contribute to a significantly better understanding of incompatible element behavior, which in turn will allow more accurate geochemical models for whole-rocks system to be developed. A database of accessory mineral distribution coefficients and concentrations will also be made available.