Department of Earth and Planetary Science, University of New Mexico, Albuquerque, NM, USA.
Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL, USA.
Science. 2014 Jun 13;344(6189):1265-8. doi: 10.1126/science.1253358.
The high water storage capacity of minerals in Earth's mantle transition zone (410- to 660-kilometer depth) implies the possibility of a deep H2O reservoir, which could cause dehydration melting of vertically flowing mantle. We examined the effects of downwelling from the transition zone into the lower mantle with high-pressure laboratory experiments, numerical modeling, and seismic P-to-S conversions recorded by a dense seismic array in North America. In experiments, the transition of hydrous ringwoodite to perovskite and (Mg,Fe)O produces intergranular melt. Detections of abrupt decreases in seismic velocity where downwelling mantle is inferred are consistent with partial melt below 660 kilometers. These results suggest hydration of a large region of the transition zone and that dehydration melting may act to trap H2O in the transition zone.
地球地幔过渡带（410-660 公里深度）中矿物质的高储水能力意味着存在深层 H2O 储层的可能性，这可能导致垂直流动地幔的脱水熔融。我们通过高压实验室实验、数值模拟以及北美密集地震台阵记录的地震 P 波到 S 波转换，研究了从过渡带向下俯冲进入下地幔的影响。在实验中，含水的榴辉岩向钙钛矿和（Mg，Fe）O 的转变产生了粒间熔体。俯冲地幔下方推断存在的地震速度突然下降的检测结果与 660 公里以下的部分熔融一致。这些结果表明过渡带的一个大区域被水化，脱水熔融可能会将 H2O 困在过渡带中。
