Investigating novel metasomatic processes at the Ilimaussaq Complex, South Greenland

南格陵兰岛Ilimaussaq杂岩的kakortokites展示了世界级的灰白色榴石正长岩分层。每一韵律层均为亚水平向，自1160 Ma前形成以来未发生变形。它们含有含有高经济价值元素（如Zr、Ta、Nb和稀土元素）的双溶族矿物。层理的成因和矿物的富集存在广泛的争议。广泛的交代蚀变和热液叠印使情况进一步复杂化。本博士项目的基本目的是限制宏观层理是否可以归因于岩浆或交代/热液过程，以及这对矿物富集的影响程度。全文共分三章，主要内容为：(1)研究了岩浆岩、晚期交代岩和热液岩的岩石地球化学特征；交代蚀变对矿物学的地球化学影响；(3)利用稳定同位素地球化学方法确定引起蚀变的交代流体的来源。这项工作将进一步提高我们对层状侵入体的形成及其具有重要经济意义的金属矿床的认识。

The kakortokites of the Ilimaussaq Complex in South Greenland demonstrate world-class layering in agpaitic nepheline syenites. Each rhythmic layer is sub-horizontal in aspect and considered undeformed since their formation ~1160 Ma ago. They host eudialyte group minerals which contain elements of high economic value (e.g., Zr, Ta, Nb, and rare earth elements). The origin of the layering and mineral enrichment is widely debated. This is further complicated by widespread metasomatic alteration and hydrothermal overprint. The fundamental aim of this PhD project is to constrain whether the macroscale layering can be attributed to magmatic or metasomatic/hydrothermal processes and to what extent this had on the mineral enrichment. The thesis comprises three chapters, respectively focusing on: (1) the petrology and geochemistry of the magmatic, late-stage metasomatic, and hydrothermal phases from within the kakortokites; (2) the geochemical effects of the metasomatic alteration on the mineralogy; and (3) the source of the metasomatic fluids responsible for the alteration using stable isotope geochemistry. This work will further improve our understanding on the formation of layered intrusions and their economically important metal ore deposits.