Japan Geoscience Union Meeting 2018

Presentation information

[EE] Oral

S (Solid Earth Sciences) » S-MP Mineralogy & Petrology

[S-MP36] Crust-Mantle Connections

Mon. May 21, 2018 10:45 AM - 12:15 PM A08 (Tokyo Bay Makuhari Hall)

convener:Yoshihiko Tamura(R & D Center for Ocean Drilling Science, Japan Agency for Maine-Earth Science and Technology), Osamu Ishizuka(Geological Survey of Japan, AIST), Chris Conway, Chairperson:Tamura Yoshihiko(JAMSTEC), Ishizuka Osamu

12:00 PM - 12:15 PM

[SMP36-06] Petrogenesis of enriched MORB from the Macquarie Ridge Complex

*Chris Conway1, Richard Wysoczanski2, Alexander Nichols4, Joel Baker3, Helen Bostock2 (1.National Museum of Nature and Science, 2.National Institute of Water and Atmospheric Research, 3.University of Auckland, 4.University of Canterbury)

Keywords:mid-ocean ridge basalt, petrogenesis, Macquarie Ridge Complex, E-MORB

The Macquarie Ridge Complex is an ideal site for examining magmatism at slow-spreading mid-ocean ridges due to the Miocene evolution from seafloor spreading to oblique convergence along the coincident Australia–Pacific plate boundary. We present whole-rock major and trace and glass volatile element data for volcanic samples collected from a 1200 km section of the extinct spreading ridge in order to investigate the dynamics of magma generation, ascent, and eruption in such settings. The sample suite can be divided into E-MORB lavas with moderate (La/SmN = 1.0–1.8) or high (La/SmN > 2.0) incompatible element enrichment. The latter type is consistent with being sourced from low-degree partial melts of enriched mantle domains. Furthermore, as indicated by their evolved geochemical compositions and CO2-H2O systematics, the source magmas underwent fractionation and degassing during stalled ascents, possibly due to ultraslow seafloor spreading rates.