Evolution of Intraplate Magmas: An Experimental Approach

板内岩浆岩套的岩石通常在组成上差异较大，但在时间和空间上却同时发生。这些套装分为碱性和拉斑岩类型，每种类型都形成了独特的化学趋势。这项工作特别关注这些套件类型中的三种：1。来自大陆和海洋岛屿环境的高规范碱性岩石；2. 2 .洋岛拉斑岩及伴生岩；大陆拉斑岩及其伴生的演化岩石，以及与元古代块状斜长岩伴生的独特套岩，从高铝辉长岩到铁闪长岩（高铁；高铁/镁）到费亚理花岗岩。关于这三种类型的套件成员之间的关系，或者连接这些套件类型的任何可能的关系，还有很多未知。我们将继续在不同压力和含水量条件下对三种类型的组份进行分步结晶实验模拟，以提供其组成演化的约束条件。三种套类型中演化最慢的岩浆似乎都来自相似的拉斑玄武岩。如果这三种类型确实有共同的起源，那么进化程度更高的成员的趋势差异必然主要是由次要因素引起的，如分馏压力、减压历史或挥发性成分的差异。将继续进行实验以探索这种可能性。导致熔化的条件与每组中观察到的岩石成分最接近，将应用于其他组类型，试图将它们从标准路径转移到与所施加条件最相关的路径次平行的趋势上。这方面的成功将对热点地区和早裂陷地区的岩浆生成和演化过程产生深远的影响。

Lindsley and NekvasilEAR-0003443Rocks of within-plate magmatic suites commonly show a wide range in composition, yet occur together in time and space. These suites fall into alkalic and tholeiitic types, each forming distinctive chemical trends. This work focuses specifically on three of these suite-types: 1. hy-normative alkalic rocks from both continental and ocean-island settings; 2. ocean-island tholeiites and associated rocks, and 3. continental tholeiites and their associated evolved rocks, together with the distinctive suites associated with Proterozoic massif anorthosites, ranging from high-Al gabbro through ferrodiorite (high-Fe; high Fe/Mg) to fayalite granite. Much remains unknown about the relationship among the suite-members of these three types or any possible relationship linking these suite-types. We will continue experimental simulation of step-wise fractional crystallization under variable conditions of pressure and water content for the three suite-types in order to provide constraints on their compositional evolution. The least-evolved magmas from each of the three suite-types appear to emanate from a similar tholeiitic basalt. If the three suite-types indeed share a common parentage, then the differences in trends of the more evolved members must have arisen primarily from secondary factors such as differences in pressure of fractionation, decompression history, or volatile content. Experiments will be continued that explore this possibility. The conditions leading to melts that simulate most closely the observed rock compositions within each suite will be applied to the other suite-types in attempt to divert them from their standard path and onto trends subparallel to the path most relevant to the conditions imposed. Success in this would have far-ranging implications about the processes at work in magma generation and evolution in hot-spot and early-rifting settings.