Accurate and rapid measurements of thermodynamic properties of minerals by microcalorimetric method.

1.利用科研资助项目安装的差示扫描量热仪，测定了高压硅酸盐矿物的热容。为快速准确地计算差示扫描量热仪测得的热容，研制了微机数据处理系统。含辉石组分的石榴石固溶体在地幔过渡带的压温条件下是稳定的。用<Mg_4>本热容测量系统测量了<Si_4>&lt;O_（12）&gt; -<Mg_3><Al_2><Si_3>&lt;O_（12）&gt;体系中石榴石固溶体的热容，这一体系代表了过渡区的石榴石。实验结果表明，随着&lt;O_（12）&gt;组分的增加，石榴石固溶体在各温度下的热容变化不大<Mg_4><Si_4>。由热容数据估算了石榴石固溶体的Gruneisen参数和德拜温度.测量了在高压下稳定的硅酸盐和锗酸盐的焓。计算了MnSi中蔷薇辉石-单斜辉石-石榴石，<O_3>CaGe中硅灰石-石榴石-钙钛矿，CdGe中辉石-石榴石-钛铁矿<O_3><O_3><Mg_4>-钙钛矿，<Si_4>&lt;O_（12）&gt; - &lt;O_（12）<Mg_3><Al_2><Si_3>&gt;中辉石-石榴石的相变焓，并计算了上述相变的相边界，与相平衡实验确定的相边界基本一致。已经确定辉石（或辉石状）-石榴石转变通常具有平缓的正dP/dT斜率，而钛铁矿（或石榴石）-钙钛矿转变具有负斜率。

1. Heat capacities of high-pressure silicate minerals were measured by the differencial scanning calorimeter which was installed by the grant-in-aid for scientific research. The data processing system using the personal computor was made for rapid and accurate calculation of the heat capacity measured by the differencial scanning calorimeter. Garnet solid solutions containing pyroxene components are stable in the pressure-temperature conditions in the mantle transition zone. Heat capacities of the garnet solid solutions in the system <Mg_4> <Si_4> <O_(12)> - <Mg_3> <Al_2> <Si_3> <O_(12)> , which represent the garnets in the transition zone, were measured by the present heat capacity measurement system. It was observed that heat capacity of the garnet solid solution at each temperature changed very little with increasing <Mg_4> <Si_4> <O_(12)> component. The Gruneisen parameter and Debye temperature of the garnet solid solutions were estimated from the heat capacity data.2. Enthalpies of silicates and germanates stable at high pressures were measured. Enthalpies of transition of the silicates and germanates were obtained for the following systems:(1) rhodonite-clinopyroxene-garnet transitions in MnSi <O_3> , (2) wollastonite-garnet-perovskite transitions in CaGe <O_3> , (3) pyroxenoid-garnet-ilmenite-perovskite transitions in CdGe <O_3> , (4) pyroxene-garnet transition in the system <Mg_4> <Si_4> <O_(12)> - <Mg_3> <Al_2> <Si_3> <O_(12)> .Phase boundaries for the above transitions were calculated from the measured enthalpies.They were almost consistent with the boundaries determined by the phase equilibrium experiments. It was established that the pyroxene(or pyroxenoid)- garnet transitions have generally gentle positive dP/dT slopes, while the ilmenite (or garnet)-perovskite transitions have negative slopes.