High-pressure polymorphs of olivine and enstatite are major constituent minerals in the mantle transition zone （MTZ）. The phase transformations of olivine and enstatite at pressure and temperature conditions corresp...High-pressure polymorphs of olivine and enstatite are major constituent minerals in the mantle transition zone （MTZ）. The phase transformations of olivine and enstatite at pressure and temperature conditions corresponding to the lower part of the MTZ are import for understanding the nature of the 660 km seismic discontinuity. In this study, we determine phase transfor- mations of olivine （MgSi204） and enstatite （MgSiO3） systematiclly at pressures between 21.3 and 24.4 GPa and at a constant temperature of 1600~C. The most profound discrepancy between olivine and enstatite phase transformation is the occurency of perovskite. In the olivine system, the post-spinel transformation occures at 23.8 GPa, corresponding to a depth of 660 km. In contrast, perovskite appears at 〈23 GPa （640 km） in the enstatite splitting of the 660 km seismic discountinuity under eastern China. system. The -1 GPa gap could explain the uplifting and/orsplitting of the 660 km seismic discountinuity under eastern China.展开更多
This paper studied some properties of PdSwr phase related to 670 km discontinuities in detail, and theoretically processed a preliminary analysis to this phase. We discussed the relationships between the incident angl...This paper studied some properties of PdSwr phase related to 670 km discontinuities in detail, and theoretically processed a preliminary analysis to this phase. We discussed the relationships between the incident angle ih of PdSwr phase with its path, epicentral distance, travel-time and relative amplitude due to low velocity zone (LVZ) of upper mantle, and preliminarily pointed out the main characters of PdSwr phase recorded in seismogram. The PdSwr phase is concentrated in range of 13.5~96.5. When epicentral distance is greater than 33, the start point of PdSwr phase is relatively well distinguishable and could thus be determined more easily. When the epicentral distance is between 13.5 to 33, the triplication of PdSwr's travel-time curve could be slightly distinguished due to the low velocity zone and 220 km seismic velocity discontirluity of upper mantle. The relevant observed PdSwr phase should be in a more complex pattern and it should be more difficult to determine its start point展开更多
基金financially supported by the Sinoprobe-0801National Natural Science Foundation of China(Grant Nos.41002068&41174076)
文摘High-pressure polymorphs of olivine and enstatite are major constituent minerals in the mantle transition zone （MTZ）. The phase transformations of olivine and enstatite at pressure and temperature conditions corresponding to the lower part of the MTZ are import for understanding the nature of the 660 km seismic discontinuity. In this study, we determine phase transfor- mations of olivine （MgSi204） and enstatite （MgSiO3） systematiclly at pressures between 21.3 and 24.4 GPa and at a constant temperature of 1600~C. The most profound discrepancy between olivine and enstatite phase transformation is the occurency of perovskite. In the olivine system, the post-spinel transformation occures at 23.8 GPa, corresponding to a depth of 660 km. In contrast, perovskite appears at 〈23 GPa （640 km） in the enstatite splitting of the 660 km seismic discountinuity under eastern China. system. The -1 GPa gap could explain the uplifting and/orsplitting of the 660 km seismic discountinuity under eastern China.
文摘This paper studied some properties of PdSwr phase related to 670 km discontinuities in detail, and theoretically processed a preliminary analysis to this phase. We discussed the relationships between the incident angle ih of PdSwr phase with its path, epicentral distance, travel-time and relative amplitude due to low velocity zone (LVZ) of upper mantle, and preliminarily pointed out the main characters of PdSwr phase recorded in seismogram. The PdSwr phase is concentrated in range of 13.5~96.5. When epicentral distance is greater than 33, the start point of PdSwr phase is relatively well distinguishable and could thus be determined more easily. When the epicentral distance is between 13.5 to 33, the triplication of PdSwr's travel-time curve could be slightly distinguished due to the low velocity zone and 220 km seismic velocity discontirluity of upper mantle. The relevant observed PdSwr phase should be in a more complex pattern and it should be more difficult to determine its start point
