Network of off-axis melt bodies at the East Pacific Rise

Constraints on the accretion of the gabbroic lower oceanic crust from plagioclase lattice preferred orientation in the Samail ophiolite

“…In order to explain inferred cooling rates through the 800 • isotherm of ∼1 • C/yr that are faster than predicted in models of hydrothermal convection, they suggested that some samples may have been emplaced as off-axis sills, where host-rock temperatures were markedly colder. This interpretation is consistent with recent seismic imaging of mid-crustal melt bodies several kilometers off-axis at both Juan de Fuca ridge (Canales et al, 2009) and the East Pacific Rise (Canales et al, 2012).…”

Sill to surface: Linking young off-axis volcanism with subsurface melt at the overlapping spreading center at 9°03′N East Pacific Rise

“…Likewise, geophysical studies have provided evidence for the presence of off-axis melt bodies (e.g., Canales et al, 2009Canales et al, , 2012Durant and Toomey, 2009), but until the AT15-17 survey (see also ), it has not been possible to directly link lava age, geochemistry, and petrology with seafloor and seismic imaging, since such a broad range of multidisciplinary data are only rarely collectively available in submarine settings. At the most fundamental level, this connection between off-axis magmatism and volcanism demonstrates that off-axis volcanism can be sourced from off-axis magma bodies at certain tectonic settings (cf., Sohn and Sims, 2005).…”

Diverse magma flow directions during construction of sheeted dike complexes at fast- to superfast-spreading centers

“…Although adjacent dikes with distinct geochemistries record the nearly contemporaneous existence of multiple melt reservoirs in the axial region, they do not indicate the physical location or temporal relationships of these distinct zones of melt. Seismic data reveal that the AMC along most of the fastto superfast-spreading EPR axis has variable seismic character and fine-scale discontinuities (Kent et al, 1993a;Hooft et al, 1997;Singh et al, 1998;Carbotte et al, 2013). These variations imply the presence of distinct melt lenses from ∼2 to 15 km in length along the ridge separated by ∼1.5 to 20 km long crystal mush zones (Singh et al, 1998;Carbotte et al, 2013).…”

“…Seismic data reveal that the AMC along most of the fastto superfast-spreading EPR axis has variable seismic character and fine-scale discontinuities (Kent et al, 1993a;Hooft et al, 1997;Singh et al, 1998;Carbotte et al, 2013). These variations imply the presence of distinct melt lenses from ∼2 to 15 km in length along the ridge separated by ∼1.5 to 20 km long crystal mush zones (Singh et al, 1998;Carbotte et al, 2013). In some places, seismic data also image distinct melt lenses at deeper levels within the low-velocity zone below the AMC and farther off-axis (Singh et al, 2006;Canales et al, 2009Canales et al, , 2012.…”

“…This reflector is interpreted as the top of an axial magma chamber (AMC), and although it appears relatively continuous, variations in S-wave velocity imply varying proportions of melt within the AMC along the EPR axis (Singh et al, 1998). Recent surveys along the EPR resolve present-day discontinuities of the AMC and characterize discrete melt lens segmentation that coincides spatially with distinct lava compositions at the surface (Carbotte et al, 2013). Spatial correlation of these data is considered to indicate that two recent eruptions were fed by vertical magma transport from three discrete melt lenses.…”