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在压力4.0到17.5GPa、温度1200℃到1400℃范围,研究了模拟地幔岩成分中的辉石-石榴子石相转变。相转变大多出现在14～16GPa压力范围,单相铝亏损的石榴子石(镁铁榴石)在16GPa压力以上变得稳定。根据本实验和其他最近实验资料计算了地幔岩的矿物组合、密度、地震波速随深度的变化。所得到的密度和地震波速度剖面在550Km深度范围和根据地震观测所建立的模型相吻合。如果证实在550km到650km之间存在有一高密度、高速度梯度带确定,则可能表明镁铁榴石有新的相转变和或存在某种程度的化学不均匀性。
The pyroxene-garnet phase transitions in the composition of simulated mantle rocks were studied at pressures ranging from 4.0 to 17.5 GPa and temperatures ranging from 1200 ° C to 1400 ° C. Most of the phase transitions occurred in the pressure range of 14-16 GPa. Single-phase aluminum-depleted garnet (Mg-Fe-garnet) stabilized above 16 GPa. Based on this experiment and other recent experimental data, the mineral assemblage, density and velocity of seismic wave with depth of mantle rock are calculated. The resulting densities and seismic velocity profiles coincide with the models established from the seismological observations at a depth of 550 km. If it is confirmed that there is a high-density, high-velocity gradient band between 550 km and 650 km, it may indicate that the magnesia has a new phase transition and / or some degree of chemical inhomogeneity.