Origin of Kimberlite Magma

该项目的目的是确定金伯利岩成分的相平衡，这被认为是接近原始金伯利岩岩浆成分，并检查化学和稳定同位素特征的几个金伯利岩发生在北美。本研究的结果总结如下.对南非Wesselton矿隐晶质金伯利岩成分的高压实验（10-40 kb，100-1500 C）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。镁橄榄石在相对较低的压力下出现，而单斜辉石的稳定性在较高的压力下受到限制。实验中发现的单斜辉石和钙镁橄榄石的不相容性可以用来解释金伯利岩中这两个相的不相容性。金伯利岩岩浆可能是部分熔融形成的含方解石的上地幔物质，其矿物学类型多样。 关于我们 2.加拿大安大略皮克顿湖和瓦提湖侏罗纪云母超镁铁质岩脉的矿物组成为橄榄石-金云母-方解石-蛇纹石-尖晶石。脉岩表现出明显的轻稀土元素的富集结合相对较高的CO2。从结构关系和碳同位素组成来看，脉岩中的方解石为原生岩浆相。脉岩为浅成相金伯利岩。3.富钡金云母存在于地幔衍生捕虏体中，该捕虏体被纳入安大略上加拿大矿金伯利岩中。金云母的特征是高BaO（高达4.3wt.%）镁钠含量高钛含量低金云母的化学特征表明，云母已形成地幔交代，涉及Ba和碱，富Ti贫含水流体。幔源金云母的Ba/K值与大陆碱性火山岩和幔源包体的Ba/K值相当，表明金云母可能是上地幔Ba的主要储集体。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