OLIVINE-MODIFIED SPINEL-SPINEL TRANSITIONS IN THE SYSTEM MG2SIO4-FE2SIO4 - CALORIMETRIC MEASUREMENTS, THERMOCHEMICAL CALCULATION, AND GEOPHYSICAL APPLICATION
OLIVINE-MODIFIED SPINEL-SPINEL TRANSITIONS IN THE SYSTEM MG2SIO4-FE2SIO4 - CALORIMETRIC MEASUREMENTS, THERMOCHEMICAL CALCULATION, AND GEOPHYSICAL APPLICATION
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DOI：
10.1029/jb094ib11p15671
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发表时间：
1989-11-10
期刊：
影响因子：
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通讯作者：
NAVROTSKY, A
中科院分区：
文献类型：
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作者：
AKAOGI, M;ITO, E;NAVROTSKY, A
采用高温溶液量热法研究了Mg2SiO4‐fe2sio4体系中橄榄石（α）‐修饰尖晶石（β）‐尖晶石（γ）的转变。测定了mg2sio4在975 K时的β - γ和α - γ跃迁焓，以及fe2sio4在298 K时的α - γ跃迁焓。γ固溶体的混合焓为正。根据这些热化学数据计算了高压和高温下的相关系，包括对α、β和γ固溶体非理想性影响的校正。计算的相图与Katsura和Ito最近的实验结果吻合得很好。α−(Mg0.89, Fe0.11) 2sio4在地幔约400 km深度（间隔约18（±5）km）不经过α+γ相场而通过α+β区转变为β， 390 km深度和650 km深度的温度分别约为1673和1873 K，假设为绝热地热。
The olivine(α)‐modified spinel(β)‐spinel (γ) transitions in the system Mg2SiO4‐Fe2SiO4were studied by high‐temperature solution calorimetry. Enthalpies of the β‐γ and a α‐γ transitions in Mg2SiO4at 975 K and of the α‐γ transition in Fe2SiO4at 298 K were measured. The γ solid solution showed a positive enthalpy of mixing. Phase relations at high pressures and high temperatures were calculated from these thermochemical data including correction for the effect of nonideality of α, β, and γ solid solutions. The calculated phase diagrams agree well with those determined experimentally by Katsura and Ito very recently. The α − (Mg0.89, Fe0.11)2SiO4transforms to β through a region of α+β without passing through the α+γ phase field at around 400 km depth in the mantle with an interval of about 18(±5) km. Temperatures at 390 and 650 km depths are estimated to be about 1673 and 1873 K, respectively, assuming an adiabatic geotherm.