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Subsolidus re-equilibration and diffusion during melting process of the granitic system

花岗岩体系熔融过程中的固相线再平衡和扩散

基本信息

批准号：
14340164
负责人：
NISHIYAMA Tadao
金额：
$ 4.03万
依托单位：
Kumamoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340164/
关键词：
granite subsolidus myrmeklite perthite diffusion kinetics parabolic growth rate law melt

项目摘要

(1)Cooling process of the Okueyama granitic body deduced from the extents of subsolidus reationsThe Okueyama granititc body situated in Miyazaki Prefecture represents a single magmatic chamber solidified to a zonal plutonic body. We examined the extents of development of subsolidus reaction textures such as myrmekite and perthite from the roof boundary towards the interior of the body. (1)The mean width of myrmekite increases systematically from 10 μm at the roof contact to 100 μm at 950 m below the contact. (2)The width of albite lamella in perthite increases similarly from 10 μm to 230 μm. (3)The volume fraction of albite lamella increases fiom 0.013 to 0.278. (4)The spacing between the albite lamella increases from 35 μm to 138 μm. These lines of evidence show that the Okueyma body has been cooled effectively from the roof. We could not detect the systematic change of the extent of subsolidus reactions from the wall contact.We also estimated the duration during which the subsolidus reactions had been progressing, by employing plagioclase -hornblende geothermometer. The durations are estiomated to be 15-25 years at the roof contact and 150-300 yeras at 950 m below the contact.(2)Experiments on the diffusion -controlled melt growth in granitic systemsWe carried out melting experiments under non-equilibrium conditions to understnad the partial melting process of the crust. We got basic data on the melting kinetics by the experiments. The systems we examined are sanidine -albite -quartz -H2O, orthoclase -quartz -albite -H2O, and their partial systems. Main results are : (1)We found concentration gradients in the m,elt layers, which suggest diffusion -controlled melt growth. (2)We can estimate diffusion coefficients of the rate-controlling species based on the parabolic growth rate law.

（1）从次固相反应的程度推断奥重山花岗岩体的冷却过程位于宫崎县的奥重山花岗岩体是一个单一的岩浆房，凝固成一个带状的深成岩体。我们研究了从屋顶边界到身体内部的subsolidus反应纹理，如myrmekite和条纹长石的发展程度。（1）从顶板接触面处的10 μm到接触面下950 m处的100 μm，myrmeite的平均宽度呈系统性增大。（2）条纹长石中钠长石片层的宽度从10 μm增加到230 μm。（3）钠长石片层的体积分数从0.013增加到0.278。（4）钠长石片层间距由35 μm增大到138 μm。这些证据表明，Okueyma身体已经从屋顶有效冷却。我们不能从壁面接触中探测到固相线下反应程度的系统变化，我们还用斜长石-角闪石地质温度计估算了固相线下反应进行的时间。在接触面以下950 m处，持续时间为150-300年。（2）花岗质系统中扩散控制熔体生长的实验为了了解地壳的部分熔融过程，我们进行了非平衡条件下的熔融实验。通过实验获得了熔融动力学的基本数据。我们研究的体系是透长石-钠长石-石英-H_2O、正长石-石英-钠长石-H_2O及其部分体系。主要结果有：（1）在熔体层中发现了浓度梯度，这表明熔体生长是扩散控制的。(2)We可以根据抛物线生长速率定律估算速率控制物种的扩散系数。