RPG: An Investigation of the Effects of Recrystallization Processes on the Metasomatism of Mantle Peridotites

本研究将探讨交代流体与上地幔组合之间的同位素和化学相互作用机制。来自南非金伯利岩和美国西南部碱性玄武岩的捕虏体样本被选为研究对象。利用电子探针和SIMS相结合的方法，对新生母细胞、斑岩碎屑和非重结晶相进行REE、LILE （Ba、Sr、Rb、Na、K）和HFSE （Ti、Nb、Zr、Hf、Ta）的分析，探讨不相容微量元素地球化学与重结晶的关系。与结构变化相关的氧化态可能的变化也将被研究。同位素测量（87Sr/86Sr和143Nd/144ND）将对斑岩和橄榄石和正辉石的新母细胞分离物进行测定，以确定同位素组成是否随晶粒大小系统性地变化。此外，还将测定石榴石、斜辉石和少量相（即氧化物或云母）的同位素，以便将整个数据集与玄武岩中石榴石和尖晶石的数据结合起来。这项研究将增加对导致交代作用的上地幔过程的认识。

The proposed research will investigate the mechanism of isotopic and chemical interaction between metasomatic fluid and upper mantle assemblages. Xenolith samples from South African kimberlites and alkali basalts for the southwestern United States have been chosen for study. Neoblasts, porphyroclasts, and non-recrystallized phases will be analyzed for REE, LILE (Ba, Sr, Rb, Na, K) and HFSE (Ti, Nb, Zr, Hf, Ta) by a combination of electron microprobe and SIMS to discern the relationship of incompatible trace element geochemistry to recrystallization. Possible variations in oxidation state associated with textural variations will also be investigated. Isotopic measurements (87Sr/86Sr, and 143Nd/144ND) will be made on separates of porphyrocalsts and neoblasts of olivine and orthopyroxene to determine whether isotopic compositions vary systematically with grain size. In addition, isotopic measurements for garnet, clinopyroxene, and when possible minor phases (i.e. oxides or mica) will be determined so that the total data set can be combined with data for garnet and spinel lherzolites from basalts. This investigation will add to the understanding of the upper mantle processes which result in metasomatism.