Origin of Kimberlite Magma

金伯利岩岩浆的起源

基本信息

批准号：
62470049
负责人：
ARIMA Makoto
金额：
$ 3.84万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

项目摘要

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

该项目的目的是确定金伯利岩成分（被认为接近原生金伯利岩岩浆成分）的相平衡，并检查北美出现的几种金伯利岩的化学和稳定同位素特征。总结如下： 1. 对南非 Wesselton 矿的隐晶质金伯利岩成分进行的高压实验（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、方解石和钙钛矿相平衡，而斜辉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。可以用来解释金伯利岩岩浆中这些相的不相容性。部分熔融衍生的不同矿物学的含方解石的上地幔物质… 更多 2. 加拿大安大略省皮克顿和瓦蒂湖的侏罗纪时代的云母超镁铁质岩脉，在矿物学上由橄榄石-金云母-方解石-蛇纹石-尖晶石组成。从结构关系和C同位素来看，岩脉中轻稀土元素的富集与CO2含量相对较高，是原生岩浆相。岩脉为浅成相金伯利岩。 3. 富钡金云母产于安大略省上加拿大矿金伯利岩中的地幔来源的金云母中。金云母的化学特征表明，云母是由涉及Ba-的地幔交代作用形成的。地幔来源的金云母中的 Ba/K 范围与大陆碱性火山岩和地幔来源的捕虏体中的 Ba/K 范围相当，这表明金云母可能是 Ba 的主要储集层。上地幔.少