Expedition 368X Preliminary Report: South China Sea Rifted Margin

Abstract

rock composition and assessment of melting processes and age of crystallization. The combination of such analyses will contribute to geochemical or thermomechanical modeling that will constrain mantle origin and melting processes leading to the formation of these basalts.

Mantle upwelling beneath the South China Sea and links to surrounding subduction systems

“…1 a). Major advances in the last several years are providing new insights into the SCS-mantle dynamics, through regional seismic imaging of the upper mantle [ 1 , 2 ], unprecedented IODP drilling expeditions (349/367/368/368X) [ 3 – 5 ] that obtained the oceanic basement basalt samples for the first time, geochemical analyses of the SCS-mantle source compositions [ 6 – 8 ] and geodynamic modeling [ 9 , 10 ]. Furthermore, new geological mapping, seismic imaging [ 11 , 12 ] and IODP drilling [ 13 , 14 ] have revealed evidence for significantly greater magma production at the northern SCS rifted margin, in comparison to the magma-poor end-member of the Atlantic rifted margins.…”

Mantle Heterogeneity and Melting Processes in the South China Sea: Thermal and Melting Models Constrained by Oceanic Crustal Thickness and Basalt Geochemistry

“…The REE pattern of site U1500 is similar to E‐MORB (Figure S2c). The postcruise geochemistry data of U1500 and U1503 have not yet been released (Childress et al., 2019). In this study, the numerical model results are mainly constrained by MORBs of sites U1431, U1433, and U1434 near fossil spreading ridges.…”

“…have not yet been released (Childress et al, 2019). In this study, the numerical model results are mainly constrained by MORBs of sites U1431, U1433, and U1434 near fossil spreading ridges.…”

“…The igneous oceanic crust near fossil spreading ridges was first sampled by IODP Expedition 349 at site U1431 in the east subbasin and sites U1433 and U1434 in the SW subbasin (Expedition 349 Scientists, 2014). At the northern margin of the east subbasin, mid‐ocean ridge basalt (MORB) samples were recovered at sites U1500 and U1502 by IODP Expeditions 367/368 (Jian et al., 2018; Sun et al., 2018), and at site U1503 by IODP Expedition 368X (Childress et al., 2019). These drilling expeditions form a transect crossing the continent‐ocean boundary (COB) (Figure 1).…”

“…Site U1502 was flooded by remnants of continental lithosphere, which recorded the magmatism during the final stage of continental rifting and breakup (Larsen et al., 2018). Sites U1500 and U1503 sampled the oceanic crust formed during the incipient seafloor spreading (Childress et al., 2019; Yu & Liu, 2020). The bulk‐rock major and trace element contents of site U1500 are selected from Yu and Liu (2020).…”