Kent GM, Singh SC, Harding AJ, Sinha MC, Orcutt JA, Barton PJ, White RS, Bazin S, Hobbs RW, Tong CH, Pye JW
Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla 92093, USA.
Nature. 2000 Aug 10;406(6796):614-8. doi: 10.1038/35020543.
Quantifying the melt distribution and crustal structure across ridge-axis discontinuities is essential for understanding the relationship between magmatic, tectonic and petrologic segmentation of mid-ocean-ridge spreading centres. The geometry and continuity of magma bodies beneath features such as overlapping spreading centres can strongly influence the composition of erupted lavas and may give insight into the underlying pattern of mantle flow. Here we present three-dimensional images of seismic reflectivity beneath a mid-ocean ridge to investigate the nature of melt distribution across a ridge-axis discontinuity. Reflectivity slices through the 9 degrees 03' N overlapping spreading centre on East Pacific Rise suggest that it has a robust magma supply, with melt bodies underlying both limbs and ponding of melt beneath large areas of the overlap basin. The geometry of melt distribution beneath this offset is inconsistent with large-scale, crustal redistribution of melt away from centres of upwelling. The complex distribution of melt seems instead to be caused by a combination of vertical melt transport from the underlying mantle and subsequent focusing of melt beneath a magma freezing boundary in the mid-crust.
量化跨洋中脊轴部间断处的熔体分布和地壳结构，对于理解大洋中脊扩张中心的岩浆、构造和岩石学分段之间的关系至关重要。诸如重叠扩张中心等特征下方的岩浆体的几何形状和连续性，会强烈影响喷发熔岩的成分，并可能有助于深入了解地幔流动的潜在模式。在此，我们展示了大洋中脊下方地震反射率的三维图像，以研究跨洋中脊轴部间断处熔体分布的性质。穿过东太平洋海隆北纬9度03分重叠扩张中心的反射率切片表明，它有强大的岩浆供应，熔体位于两翼下方，且在重叠盆地的大片区域下方有熔体聚集。这种偏移下方熔体分布的几何形状与熔体从上升中心大规模地壳再分配的情况不一致。相反，熔体的复杂分布似乎是由来自下地幔的垂直熔体传输以及随后熔体在中地壳岩浆凝固边界下方的聚焦共同造成的。
