TY - JOUR T1 - Variable crustal production originating from mantle source heterogeneity beneath the South East Indian Ridge and Amsterdam‐St. Paul Plateau A1 - Sibrant,A.L.R. A1 - Maia,M. A1 - Mittelstaedt,E. A1 - Graham,D.W. AD - Univ Breset, Laboratoire Géosciences Océan, UMR6538 Plouzané , France AD - CNRS, Univ Brest, Laboratoire Géosciences Océan, UMR6538 Plouzané , France AD - Department of Geological Sciences, University of Idaho Moscow Idaho , USA AD - College of Earth, Ocean, and Atmospheric Sciences, Oregon State University Corvallis , USA UR - https://archimer.ifremer.fr/doc/00587/69863/ DO - 10.1029/2019GC008419 KW - ywords KW - oceanic plateaus KW - plume-ridge interaction KW - Amsterdam-St KW - Paul Plateau KW - South East Indian Ridge KW - geophysical and geochemical evidence N2 - The Amsterdam‐St. Paul (ASP) Plateau formed by interaction between the South East Indian Ridge (SEIR) and the ASP mantle plume during the last 10 Myr. The combined bathymetry and gravity‐derived crustal thickness anomalies along the present and paleoaxes of the SEIR atop the plateau indicate: (1) a thicker crust and shallower water depth along the southern part of segment I2 during much of the last 10 Myr; (2) an earlier decrease (~1.4 Ma) in crustal thickness along the southern part of I2 compared to the northern part (~0.9 Ma) during the most recent period of reduced magmatism; (3) a topographic transition at ~0.7 Ma and during the last 0.1 Myr; and (4) an approximately uniform crustal thickness (8 km) along the entire I2 segment today. These observations require spatial and temporal variations in magma production during construction of the ASP Plateau over the last 3 Myr. We propose that during periods of weaker plume magma flux, spatial variations in upper mantle temperature and composition are small, and lead to small variations in crustal thickness along‐axis. In contrast, during periods of stronger plume magma flux, spatial contrasts in upper mantle temperature and composition (fertility) are large, leading to significant variations in crustal thickness. Along‐axis variations of 3He/4He, Δ8/4Pb, K/Ti, and Na8 in “zero‐age” basalts indicate that there is a gradient in the underlying mantle material, from a “common” mantle plume component (Δ8/4Pb~60) stronger in the north to a DUPAL component (Δ8/4Pb~110) dominating in the south. Y1 - 2019/11 PB - American Geophysical Union (AGU) JF - Geochemistry Geophysics Geosystems SN - 1525-2027 VL - 20 IS - 11 SP - 4635 EP - 4653 ID - 69863 ER -