Accurate determination of phase equilibrium diagrams by calorimetric measurements of high pressure silicate minerals and applications to structure of the earth's mantle.

通过高压硅酸盐矿物的量热测量准确确定相平衡图及其在地幔结构中的应用。

• 批准号: 62540618
• 负责人: AKAOGI Masaki
• 金额: $ 1.54万
• 依托单位: Kanazawa University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1987
• 资助国家: 日本
• 起止时间: 1987 至 1989
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-62540618/
• 关键词: High pressure experiments; Calorimetry; Mantle; Phase transition; Silicate; Phase equilibrium; Enthalpy; Refinement; エンタルピー; 高圧合成; 相平衡図; 熱力学; High pressure experiments; Calorimetry; Mantle; Phase transition; Silicate; Phase equilibrium; Enthalpy; Refinement; エンタルピー; 高圧合成; 相平衡図; 熱力学

The important scientific results of this research project are summarized as follows.1. Enthalpies of the olivine-modified spinel-spinel transitions in the system Mg_2SiO_4-Fe_2SiO_4 were measured by high temperature calorimetric techniques. The phase diagrams calculated form the present thermochemical data are not well consistent with those by Ringwood and Major (1970) and Kawada (1977), but agree very well with that determined with precise high pressure experiments by Katsura and Ito (1989). From the calculated phase diagrams, it is concluded that the olivine-modified spinel transition occurs at about 390-410 km in the mantle, while the modified spinel-spinel transition at about 490-540 km. Temperatures at 390 and 650 km are estimated to be 1400 and 1600 ﾟC, respectively.2. Enthalpy of the pyroxene-garnet transition in the system Mg_4Si_4O_<12>-Mg_3Al_2 Si_3O_<12> was measured by the same calorimetric techniques. The calculated phase diagram was in good agreement, with that by high pressure experiments by Akaogi and Akimoto (1977), when the pressure scale was revised. It was concluded from the phase diagram that the pyroxene-garnet transition in the mantle occurs gradually with depth in the depth range of about 300-500 km and shows no sharp seismic velocity discontinuity.3. High pressures over 18 GPa were generated by using new Bridgman-anvils (26 mm in diameter) with sintered diamond tips. The transition of beta-Zn_2SiO_4 to ZnSiO_3 ilmenite plus ZnO was examined using these new anvils.4. From the measured enthalpies of the pyroxene-ilmenite transition in ZnSiO_3 and of the disproportionation of Ni_2SiO_4 spinel, these phase equilibrium boundaries were calculated thermodynamically.

该研究项目的重要科学结果总结如下1。通过高温calolimetric技术测量了系统MG_2SIO_4-FE_2SIO_4中橄榄石修饰的尖晶石旋转型转变的焓。计算出的相图本热化学数据与Ringwood和Major（1970）和Kawada（1977）的热化学数据不太一致，但与Katsura和Ito（1989）的精确高压实验确定的相一致。从计算出的相图中可以得出结论，橄榄石修饰的尖晶石转变发生在地幔中约390-410 km，而修饰的尖晶石旋转旋转过渡则在约490-540 km处。 390和650公里处的温度估计分别为1400和1600 c。通过相同的Calolimetric技术测量了系统MG_4SI_4O_2>的系统MG_4SI_4O_2> -MG_4SI_4O_2> -MG_4SI_4O_2>的焓。计算出的相图非常一致，与Akaogi和Akimoto（1977）的高压实验进行了良好的一致性。从相图得出的结论是，地幔中的辉石 - 晶状体跃迁逐渐在约300-500 km的深度范围内逐渐发生，并且没有明显的地震速度不连续性。3。通过使用新的Bridgman-Anvils（直径26毫米）和烧结的钻石尖端，产生了超过18 GPA的高压。使用这些新的Anvils.4检查了Beta-Zn_2Sio_4向Znsio_3 iLmenite和ZnO的过渡。4。从ZnSIO_3中的辉石 - 硅酸盐过渡的测得的焓和Ni_2Sio_4尖晶石的不成比例中，这些相等的边界是热力学计算的。