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

这项研究将探讨交代流体和上地幔组合之间的同位素和化学作用机制。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，对新母细胞、碎斑细胞和未重结晶相进行REE、LILE(Ba，Sr，Rb，Na，K)和HFSE(Ti，Nb，Zr，Hf，Ta)的分析，以识别不相容的微量元素地球化学与再结晶的关系。还将研究与织构变化相关的氧化态的可能变化。将对橄榄石和斜方辉石的斑石和新成岩的分离物进行同位素测量(~(87)Sr/~(86)Sr和~(143)Nd/~(144)Nd)，以确定同位素组成是否随粒度系统变化。此外，还将确定石榴石、单斜辉石以及可能的次要物相(如氧化物或云母)的同位素测量结果，以便将整个数据集与玄武岩中的石榴石和尖晶石二辉橄榄岩的数据结合起来。这一研究将有助于加深对导致交代作用的上地幔过程的理解。

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.