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

(1)由次固体关系程度推断出的冈山花岗岩体的冷却过程位于宫崎县的冈山花岗岩体是一个由单一岩浆室固化成带性深部岩体的。我们检查了从屋顶边界到身体内部的亚固体反应纹理（如myrmekite和perthite）的发展程度。(1)触点处myrmekite的平均宽度从10 μm逐渐增大到950 m处的100 μm。(2)斑长岩中钠长石片层宽度从10 μm增加到230 μm。(3)钠长石片层体积分数由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，奥圭马的尸体已经从屋顶有效地冷却下来。我们不能从壁面接触中检测到亚固反应程度的系统变化。我们还利用斜长石-角闪石地温计估算了亚固相反应进行的持续时间。持续时间估计在接触面顶部为15-25年，接触面以下950米处为150-300年。(2)花岗质体系中扩散控制熔体生长的实验我们进行了非平衡条件下的熔融实验，以了解地壳的部分熔融过程。通过实验得到了熔解动力学的基本数据。我们研究的体系是水晶石-钠长石-石英-H2O、正长石-石英-钠长石-H2O及其部分体系。主要结果如下：(1)在m，elt层中存在浓度梯度，表明熔体生长受扩散控制。(2)根据抛物线型生长速率规律，可以估计出控制速率物种的扩散系数。

(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.