Rutile_zircon_melt assemblages, key to understand processes in mafic layered intrusions: examples from the Bushveld Complex, South Africa

本研究的重点是系统调查的金红石，锆石，并在岩石中相关的熔融包裹体的勒斯滕堡层状套件（RLS）的布什费尔德杂岩，和相关的卫星侵入体（Uitkomst岩浆导管），目的是了解这些组合的形成和组成的（超）镁铁质岩石的系统学，并获得新的信息过程中岩浆房演化。这包括有关母岩浆的来源和成分的信息，以及从最早的积云结晶（由铬铁矿中的金红石熔融包裹体反映）到非常晚的积云内熔融阶段（由锆石中的金红石-锆石对和相关熔融包裹体反映）结晶期间的物理化学条件（P-T-X-t-冷却速率）。此外，锆石和金红石接触变质岩将进行研究，以获得有关流体诱导HFSE动员和均匀化由于布什维尔德加热，以及这些元素的可能摄入到RLS的信息。在这方面，锆石和金红石将研究其结构背景，分带模式，微量元素组成，矿物包裹体，和U-Pb-Hf-O同位素。熔融包裹体中的锆石，和金红石含熔体包裹体中的铬铁矿将另外进行研究，以量化RLS结晶过程中的熔体分馏，并估计锆石，金红石和熔体之间的分配系数。

This study focus on the systematic investigation of rutile, zircon, and associated melt inclusions in rocks of the Rustenburg Layered Suite (RLS) of the Bushveld Complex, and a related satellite intrusion (Uitkomst magma conduit) with the aim to understand the systematics of the formation and composition of these assemblages in (ultra)mafic rocks, and to obtain new information about processes during magma chamber evolution. This comprises information about the source(s) and composition(s) of the parental magma(s), and physical-chemical conditions (P-T-X-t-cooling rates) during crystallisation from the earliest cumulus crystallisation (reflected by rutile-melt inclusions in chromite), to the very late intra-cumulus melt stage (reflected by rutile-zircon pairs and related melt inclusions in zircon). In addition, zircon and rutile from contact metamorphic rocks will be studied, in order to gain information about fluid induced HFSE-mobilization and -homogenization due to Bushveld heating, and about a possible uptake of these elements into the RLS. In this respect zircon and rutile will be investigated for their textural context, zoning patterns, trace element compositions, mineral inclusions, and U-Pb-Hf-O isotopes. Melt inclusions in zircon, and rutile-bearing melt inclusions in chromite will additionally be studied in order to quantify melt fractionation during RLS crystallisation, and to estimate partitioning coefficients between zircon, rutile and melt.