The Rio Grande Rise: microcontinent, mantle plume, or both? - Starts at 2:00 pm
A plume origin for the Rio Grande Rise (RGR) is debated. Significant doubts have arisen because in 2012 and 2013, Japanese and Brazilian researchers using Japan's research ship Yokosuka and its manned submersible Shinkai 6500 recovered samples of granite, gneiss and silica-rich metamorphic rocks. The RGR could therefore represent a continental sliver, or a large igneous province (LIP) that was emplaced in the late Cretaceous after the opening of the South Atlantic. The interplay between the RGR and the nearby Jean Charcot Seamount Chain (JCSC) is also not understood. During a recent expedition of the RV Maria S. Merian (MSM82), we dredge sampled rocks from the JCSC and the RGR and measured two seismic refraction profiles across the RGR where it is bisected by a long rift graben. Our main questions are (1) is the RGR a microcontinent or a hotspot track or both and (2) is the JCSC a hotspot trail. The combination of geochronological, geochemical and geophysical information will provide a unique window on the relation between mantle plumes, continental fragments and the evolution of LIPs. I will discuss the MSM82 Expedition in the context of our recent suggestion that the distribution of hotspot volcanism in the southeast Atlantic expresses interaction between deep mantle plumes, shallow plate tectonics and asthenosphere processes.
https://www.munich-geocenter.org/events/seminars/frontiers-in-earth-sciences-25/tba-3
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The Rio Grande Rise: microcontinent, mantle plume, or both? - Starts at 2:00 pm
Abstract
A plume origin for the Rio Grande Rise (RGR) is debated. Significant doubts have arisen because in 2012 and 2013, Japanese and Brazilian researchers using Japan's research ship Yokosuka and its manned submersible Shinkai 6500 recovered samples of granite, gneiss and silica-rich metamorphic rocks. The RGR could therefore represent a continental sliver, or a large igneous province (LIP) that was emplaced in the late Cretaceous after the opening of the South Atlantic. The interplay between the RGR and the nearby Jean Charcot Seamount Chain (JCSC) is also not understood. During a recent expedition of the RV Maria S. Merian (MSM82), we dredge sampled rocks from the JCSC and the RGR and measured two seismic refraction profiles across the RGR where it is bisected by a long rift graben. Our main questions are (1) is the RGR a microcontinent or a hotspot track or both and (2) is the JCSC a hotspot trail. The combination of geochronological, geochemical and geophysical information will provide a unique window on the relation between mantle plumes, continental fragments and the evolution of LIPs. I will discuss the MSM82 Expedition in the context of our recent suggestion that the distribution of hotspot volcanism in the southeast Atlantic expresses interaction between deep mantle plumes, shallow plate tectonics and asthenosphere processes.
