A multi-sill magma plumbing system beneath the axis of the East Pacific Rise

作者：Marjanovic Milena^*; Carbotte Suzanne M; Carton Helene; Nedimovic Mladen R; Mutter John C; C****es Juan Pablo

来源：Nature Geoscience, 2014, 7(11): 825-829.

DOI：10.1038/NGEO2272

Upper oceanic crust at fast-to intermediate-spreading mid-ocean ridges is thought to form from the intrusion and eruption of magma accumulated within a mid-crustal reservoir present beneath the ridge axis(1-3). However, the mechanisms for formation of the lower crust are debated(4-8). Observations from pieces of ancient oceanic crust exposed on land ophiolites - imply that multiple small magma lenses exist throughout the lower crust at mid-ocean ridges and help form the crust(4,6,7), yet seismic data have imaged only a single lens beneath the innermost axial zones of various mid-ocean ridges(1-3). Here we use high-fidelity seismic data to image the crust beneath the East Pacific Rise. We identify a series of reflections below the axial magma lens that we interpret as magma lenses in the upper part of the lower crust. These reflections are present between 9 degrees 20%26apos; and 9 degrees 57%26apos; N and are located up to 1.5 km below the axial magma lens. From the geometry and amplitude of the reflections in a zone beneath a recent volcanic eruption(9), we infer that magma drained from a lower lens helped replenish the axial magma lens above and, perhaps, contributed to the eruption. Our data indicate that a multi-level complex of magma lenses is present beneath the East Pacific Rise and probably contributes to the formation of both the upper and lower crust.

• 出版日期2014-11