Origin of Kimberlite Magma

该项目的目的是确定金伯利岩成分的相平衡，这种成分被认为接近于金伯利岩的初级岩浆成分，并检查在北美出现的几种金伯利岩的化学和稳定同位素特征。本研究的结果总结如下：1。对南非Wesselton矿一隐晶金伯利岩组成进行的高压实验（10-40 kb,100-1500℃）表明，该金伯利岩组成在上地幔条件下可能与橄榄石、斜辉石、尖晶石、方解石和钙钛矿等矿物组合平衡。蒙脱石在相对较低的压力下发生，而斜辉石在较高的压力下稳定性有限。实验中monticelite和斜辉石的不亲和性可以用来解释金伯利岩中这些相的不亲和性。金伯利岩岩浆可能是部分熔体衍生的含方解石的上地幔物质，具有不同的矿物学。…更多加拿大安大略省皮克顿和瓦尔蒂湖侏罗纪时代的云母超镁铁质岩脉，矿物学上由橄榄石-辉绿石-方解石-蛇纹石-尖晶石组成。岩脉表现出明显的轻稀土元素富集和相对高的CO2。从结构关系和碳同位素组成来看，方解石在岩脉中属于原生岩浆相。岩脉为浅成相金伯利岩。3. 富钡绿云母产于安大略省上加拿大矿金伯利岩的地幔源捕虏体中。该绿云母具有高BaO（高达4.3 wt.%）、高Mg、Na和低Ti的特点。云母的化学特征表明，云母是由富钡、富碱、贫钛含水流体的地幔交代作用形成的。幔源云母中Ba/K的变化范围与陆相碱性火山岩和幔源捕虏体中Ba/K的变化范围相当，表明幔源云母可能是上地幔中Ba的主要储集层。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