Drill through the intact ocean crust
image: Thermal-Mechanical Processes Beneath Mid-Ocean Ridges: Decompression Melting, Melt-Residue Segregation, and Lithospheric Accretion Across Fast- and Slow-Spreading Regimes
Credit: Yaoling Niu
The formation and composition of oceanic crust remain central yet unresolved questions in plate tectonics. While seismic data suggest a globally uniform crustal thickness (~6 km), petrological evidence from slow-spreading ridges reveals extensive exposures of serpentinized mantle peridotites, contradicting the assumption of purely magmatic origins. These discrepancies underscore the need to reevaluate the nature of the Moho, traditionally interpreted as a magmatic boundary but potentially reflecting serpentinization fronts within the mantle.
The study integrates geochemical, geophysical, and thermal modeling to demonstrate that spreading rate governs mantle melting efficiency and crustal architecture. Fast-spreading ridges (e.g., East Pacific Rise) exhibit robust magmatism, forming thick gabbroic layers, while slow-spreading systems (e.g., Mid-Atlantic Ridge) show serpentinite-dominated crust due to inadequate melt supply and seawater-driven hydrothermal alteration. Critically, oceanic core complexes—unique to slow-spreading ridges—are reinterpreted as diapirs of buoyant serpentinites, reshaping understanding of crust-mantle interactions.
This work emphasizes the urgency of drilling intact oceanic crust to validate these hypotheses, particularly through China’s forthcoming D/V Meng Xiang and international collaborations. By addressing seismic-petrological mismatches and redefining the Moho’s nature, the study advances plate tectonics theory and sets priorities for future exploration, including targeted drilling in the Pacific’s fast-spreading crust. The work entitled “Do we really need to drill through the intact ocean crust?” was published on Geoscience Frontiers (published on Oct 22, 2024).