Sill to surface: Linking young off-axis volcanism with subsurface melt at the overlapping spreading center at 9°03'N East Pacific Rise
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No young, off-axis, mid-ocean ridge lavas have yet been directly linked to underlying off-axis melt bodies. In this study, we present new measurements of 238U-230Th-226Ra-210Pb isotope compositions for a suite of lavas from the overlapping spreading center (OSC) at 9°03'N on the East Pacific Rise (EPR). These lavas span a large range of compositions, from basalt to dacite, and include both axial and off-axis samples recovered from a prominent, axis-parallel pillow ridge and a flat-topped seamount that overlie the westernmost extent of a 4-km-wide melt lens (Kent et al., 2000). We report 210Pb excesses in axial basalts and basaltic andesites, which we suggest results from gas-magma fractionation of 222Rn from 226Ra beneath dacite magmas. In addition, our U-series ages agree with visual observations, indicating that while most recent volcanic activity occurs at the spreading axis, active volcanism also occurs away from the axis. Specifically, the off-axis pillow ridge and seamount samples overlying the off-axis subsurface melt body have eruption ages of less than 8ka, and likely as young as 1ka, despite being located on crust that has a spreading age of ~75ka. The young ages of these lavas, combined with existing geological, geochemical and geophysical constraints, provide evidence for a genetic link between the pillow ridge and seamount lavas and the seismically imaged, underlying off-axis melt lens. This link demonstrates that off-axis volcanism does not necessarily come from a sub-axial magma body and can be sourced directly from off-axis magma bodies. © 2013 Elsevier B.V.
Published Version (Please cite this version)10.1016/j.epsl.2013.03.006
Publication InfoGirard, G; Klein, Emily M; Reagan, MK; Sims, KWW; Waters, CL; & White, SM (2013). Sill to surface: Linking young off-axis volcanism with subsurface melt at the overlapping spreading center at 9°03'N East Pacific Rise. Earth and Planetary Science Letters, 369-370. pp. 59-70. 10.1016/j.epsl.2013.03.006. Retrieved from https://hdl.handle.net/10161/8324.
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Professor of Earth and Ocean Sciences
Dr. Klein's research focuses on the geochemistry of oceanic basalts, using diverse tools of major, trace and isotopic analyses. Her research involves sea-going expeditions to sample and map the ocean floor.