Characterization of diverse origins for orthopyroxene in ultramafic rocks

最近发现一些上地幔橄榄岩由于富硅熔体与周围地幔相互作用而富正辉石。此外，一些来自太古宙克拉通的榴辉岩包体失去了富含硅的熔融部分。最近对Kaapvaal克拉通橄榄岩捕虏体的研究表明，橄榄岩中存在不同的正辉石微量元素组成，这些橄榄岩由于与富硅交代熔体反应而经历了高度的部分熔融和正辉石结晶。本项目将研究来自不同成岩背景的天然橄榄岩正辉石。不同成岩史（如熔体耗尽后的残余、橄榄岩与俯冲相关熔体或堆积结晶的反应）的正辉石微量元素组成的差异，将有助于理解上地幔二氧化硅富集的过程。此外，将进行初步的高压和高温实验，分析正辉石中微量元素在部分熔融和熔体/岩石相互作用中的行为。

Some upper mantle peridotites have recently been found to be strongly enriched in orthopyroxene due to interaction of silica-rich melt with surrounding mantle. Additionally, some eclogite xenoliths from Archaean Cratons have lost a silica-rich melt fraction. Recent findings on Kaapvaal Craton peridotite xenoliths point towards different orthopyroxene trace element compositions in peridotite which previously experienced high degree partial melting and orthopyroxene crystallization due to reaction with silica-rich metasomatic melts. This project will examine naturally occurring peridotitic orthopyroxene from different petrogenetic settings. Differences in the trace element composition of orthopyroxene with different petrogenetic histories (e.g. residues after melt depletion, reaction of peridotite with subduction-related melt or cumulate crystallization) will help understanding the process of silica enrichment of the upper mantle. Additionally, preliminary high pressure and high temperature experiments will be conducted analysing the behaviour of trace elements in orthopyroxene during partial melting and melt/rock interactions.