Origin of Kimberlite Magma

该项目的目的是确定一种被认为接近原生金伯利岩岩浆成分的金伯利岩组分的相平衡，并研究北美几种金伯利岩的化学和稳定同位素特征。本研究的研究结果总结如下：1.高压实验(10-40kb，100-1500℃)表明，在上地幔条件下，这种金伯利岩成分可以与橄榄石、单斜辉石、尖晶石、方解石和钙钛矿的矿物组合相平衡。单斜辉石在相对较低的压力下出现，而单斜辉石在较高的压力下稳定性有限。单斜辉石和单斜辉石在实验中的不相容可以用来解释金伯利岩中这些相不相容的原因。金伯利岩浆可能是Deverse矿物学中方解石上地幔物质的部分熔融产物。…加拿大安大略省Picton和Varty Lake侏罗纪时期的云母超镁铁质岩脉，其矿物学组成为橄榄石-金云母-方解石-蛇纹石-尖晶石。这些岩脉表现出明显的轻稀土元素富集性，结合相对较高的二氧化碳。从结构关系和碳同位素组成来看，岩脉中的方解石是主要的岩浆相。岩脉为浅成金伯利岩。3.富钡金云母产于安大略省上加拿大矿山金伯利岩中的地幔包体中。金云母具有高BaO(高达4.3wt.%)、高镁、高钠、低钛的特征。金云母的化学特征表明，云母是由地幔交代作用形成的，经历了富Ba、富碱、贫钛的水合流体。地幔来源的金云母中的Ba/K值范围与陆源碱性火山岩和地幔包体中的值相当，表明金云母可能是上地幔中Ba的主要储集层。较少

The aims of this project are to determine the phase equilibrium of a kimberlite composition, which is thought to be close to a primary kimberlite magma composition, and to examine chemical and stable isotopic characteristics of several kimberlites occurring in North American. The results of this study are summarized as following.1. High pressure experiments (10-40 kb,100-1500 C) on an aphanitic kimberlite composition from the Wesselton Mine, South Africa, indicate that this kimberlite composition could be equilibrated with a mineral assemblage of olivine, clinopyroxene, spinel, calcite, and perovskite at upper mantle conditions. Monticellite occurs at relatively lower pressures while clinopyroxene stability is limited at higher pressures. The untipathy of monticellite and clinopyoxene in the experiments may be used to explain the incompatibility of these phases in kimberlites. Kimberlite magmas could be partial melts derived calcite-bearing upper mantle material of deverse mineralogy. … More 2. Micaceous ultramafic dikes of Jurassic age from Picton and Varty Lake, Ontario, Canada, consist mineralogically of olivine-phlogopite-calcite-serpentine-spinel. The dikes exhibit pronounced enrichments of light rare earth elements combined relatively high CO2. Calcite in the dikes is a primary magmatic phases, from textural relations and C-isotopic compositions. The dikes are hypabyssal facies kimberlite. 3. Barium-rich phlogopite occurs in a mantle derived xenolith incorporated into the Upper Canada Mine Kimberlite, Ontario. The phlogopite is characterized by high BaO (up to 4.3 wt.%) with a high Mg, Na, and low Ti. The chemical characteristics of the phlogopite suggest that the mica has been formed by mantle metasomatism involving Ba- and alkali-rich, Ti-poor hydrous fluids. A range of Ba/K in mantle derived phlogopites is comparable with that in the continental alkali volcanic rocks and in the mantle derived xenoliths, suggesting that phlogopite may be a principal reservoir for Ba in the upper mantle. Less