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Chemical Kinetics and texture interpretation of rocks at high pressures and temperatures

高压高温下岩石的化学动力学和结构解释

基本信息

批准号：
60420016
负责人：
MORI Takeshi
金额：
$ 13.12万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1987
项目状态：
已结题

项目摘要

We have made researches on chemical kinetics of subsolidus reactions among rock-forming minerals at high pressures and temperatures, of both synthetic and natural rocks. As natural rock samples, the Horoman peridotites and basic metamorphic xenoliths at Kibi Plateau were chosen.The most important outcome of the analysis of garnet lherzolites synthesized at high pressures using a piston-cylinder type high pressure apparatus is the experimental demonstration of differential velocities among various subsolidus chemical reactions in the garnet lherzolite mineralogy. That is, the Ca-Mg-Fe redistribuion ,that is rathe simple reaction, took place everywhere in the minerals while such an Al-related reaction as the Tschermak substitution failed at the core. This phenomena, probably due to the relative complexity of reaction mechanisms, would be directly related to the differential closure temperatures among various geothermometers.The analysis of texture and mineral chemistry of natural rocks , in conjunction with the experimental study, led us to deeper understandings in the textures and formation histories of natural rocks. For example, we could decipher that the Horoman peridotites once belonged to the garnet lherzolite facies though the peridotites now totally lack traces of garnet lherzolite facies mineralogy.Future studies : The high pressure apparatus in our laboratory can maintain pressure in lengthy period. On this benefit, we paln to make as lengthy runs as possible so that subsolidus chemical kinetics can be further understood.

我们对合成岩石和天然岩石中的造岩矿物在高温高压下的固相线下反应进行了化学动力学研究。以Kibi高原的霍罗曼橄榄岩和基性变质捕虏体为天然岩石样品，采用活塞-圆筒式高压装置对高压合成的石榴石二辉橄榄岩进行了分析，最重要的结果是实验证明了石榴石二辉橄榄岩矿物学中各种固相线下化学反应之间的速度差。即Ca-Mg-Fe再分配反应，即简单的反应，在矿物的各个部位都发生了，而与Al有关的Tschermak置换反应，在矿物的核心部位却失败了。这一现象可能是由于反应机理的相对复杂性，与不同地质温度计之间的闭合温度差有直接关系。通过对天然岩石结构和矿物化学的分析，结合实验研究，加深了对天然岩石结构和形成历史的认识。例如，我们可以推断霍罗曼橄榄岩曾经属于石榴二辉橄榄岩相，尽管现在的橄榄岩完全没有石榴二辉橄榄岩相矿物学的痕迹。未来的研究：我们实验室的高压装置可以长时间保持压力。基于这一点，我们计划进行尽可能长的实验，以便进一步了解亚固相线化学动力学。