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

(1)从固相线作用范围推论的奥江山花岗岩体的冷却过程位于宫崎县的奥江山花岗岩体代表了一个凝固成带状深成体的单一岩浆室。我们检查了从屋顶边界到身体内部的亚固相线反应纹理（例如 myrmekite 和 perthite）的发展程度。 (1)磁力石的平均宽度从顶板接触处的10 μm系统性地增加到接触面以下950 m处的100 μm。 (2)钠长石片层宽度同样从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)钠长石片层间距从35μm增加到138μm。这些证据表明，奥奎玛的遗体已从屋顶有效冷却。我们无法从壁接触处检测到次固相线反应程度的系统变化。我们还通过使用斜长石-角闪石地温计估计了次固相线反应进行的持续时间。预计顶板接触面的持续时间为15-25年，接触面以下950 m处的持续时间为150-300年。(2)花岗岩体系中扩散控制熔体生长实验为了解地壳部分熔融过程，开展了非平衡条件下的熔融实验。通过实验我们得到了熔化动力学的基本数据。我们研究的体系是箭碱-钠长石-石英-H2O、正长石-石英-钠长石-H2O以及它们的部分体系。主要结果是： (1)我们发现熔体层中存在浓度梯度，这表明熔体生长受扩散控制。 (2)我们可以根据抛物线增长率定律来估计速率控制物种的扩散系数。

(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.