Department of Geology, University of Maryland, College Park, MD 20742, USA.
Science. 2011 Apr 1;332(6025):88-91. doi: 10.1126/science.1202221.
The permeability of the upper mantle controls melt segregation beneath spreading centers. Reconciling contradictory geochemical and geophysical observations at ocean ridges requires a better understanding of transport properties in partially molten rocks. Using x-ray synchrotron microtomography, we obtained three-dimensional data on melt distribution for mantle peridotite with various melt fractions. At melt fractions as low as 0.02, triple junctions along grain edges dominated the melt network; there was no evidence of an abrupt change in the fundamental character of melt extraction as melt fraction increased to 0.2. The porosity of the partially molten region beneath ocean ridges is therefore controlled by a balance between viscous compaction and melting rate, not by a change in melt topology.
上地幔的渗透性控制着扩张中心下方熔体的分异。为了协调大洋脊上存在的矛盾的地球化学和地球物理观测结果，我们需要更好地理解部分熔融岩石中的输运性质。我们使用同步加速器 X 射线微断层扫描技术，获得了具有不同熔体分数的地幔橄榄岩中熔体分布的三维数据。在熔体分数低至 0.02 的情况下，晶界处的三叉点控制着熔体网络；当熔体分数增加到 0.2 时，没有证据表明熔体提取的基本特征发生了突然变化。因此，大洋脊下地幔部分熔融区的孔隙度是由粘性压实和熔融速率之间的平衡控制的，而不是由熔体拓扑结构的变化控制的。
