COLLABORATIVE RESEARCH: The Role of Exsolution Lamellae in the Rates and Mechanism of Dissolution of Plagioclase Feldspare

斜长石长石是自然界中储量丰富的原生矿物 是非碳酸盐岩中Ca和Na的重要来源 系统. 富钙和富钠两相共生 （出溶纹层）是斜长石中常见的特征， 然而，很少有研究评估它们在发病率中的作用， 化学计量和斜长石溶解机制。 的 拟议合作研究的目标是：（i）确定 出溶层流对反应速率和化学计量的影响 斜长石斜晶石，（ii）确定的影响， 优先风化层状相的解释， 使用表面敏感的光谱仪收集的数据， X射线光电子能谱（XPS）和（iii）检查 出溶相在钙优先释放中的潜在作用 从斜长石样品中收集的 分水岭实验室 校长之间的合作 调查人员将结合联合收割机的专业知识和必要的设施， 实现这些目标。 溶解实验将 在pH 4下使用分批pH stat、流通池进行，和 使用斜长石样品的柱状反应容器， 一个内容有和没有exsolution laminate。 此外，本发明还提供了一种方法， 来自流域实验室的斜长石样品将用于 表征和溶出度研究，以评价 自然系统中的出溶作用。 的表面 反应的矿物将使用扫描电子 显微镜（SEM-EDX）、X射线光电子能谱（XPS）和 高分辨率透射电子显微术（HRTEM-EDX， HRTEM-ED）。 本研究的结果将用于模拟 和斜长石溶解的化学计量学作为An的函数 在有和没有出溶相的矿物中的含量。 假设 关于斜长石溶解机制和 溶解过程中Ca相对于Si和Na优先释放 将进行实验室和流域风化测试 环境.

Plagioclase feldspars are abundant primary minerals in nature and represent an important source of Ca and Na in noncarbonate systems. Two phase intergrowths of calcic and sodic rich phases (exsolution lamellae) are common features in plagioclase feldspars, yet few studies have evaluated their role in the rates, stoichiometry and mechanisms of plagioclase dissolution. The objectives of the proposed collaborative study are to (i) determine the effects of exsolution lamellae on the rates and stoichiometry of plagioclase feldspars, (ii) determine the effect of preferentially weathered lamellar phases on the interpretation of data collected using surfaced sensitive spectroscopies such as x-ray photoelectron spectroscopy (XPS) and (iii) examine the potential role of exsolved phases in preferential release of Ca from plagioclase samples collected from well characterized watershed laboratories. Collaboration among the principal investigators will combine expertise and facilities necessary to accomplish these objectives. Dissolution experiments will be conducted at pH 4 using batch pH stat, flow through cell, and column reaction vessels using plagioclase samples over a range of an contents with and without exsolution lamellae. In addition, plagioclase samples from watershed laboratories will be used in characterization and dissolution studies to evaluate the potential role of exsolution lamellae in natural systems. The surfaces of reacted minerals will be characterized using scanning electron microscopy (SEM-EDX), x-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM-EDX, HRTEM-ED). Results from this study will be used to model the rate and stoichiometry of plagioclase dissolution as a function of An content in minerals with and without exsolved phases. Hypotheses concerning the mechanisms of plagioclase dissolution and the preferential release of Ca relative to Si and Na during dissolution will be tested for both laboratory and watershed weathering environments.