A subduction influence on ocean ridge basalts outside the Pacific subduction shield

• Published in: Nature Communications
• Main Authors: Yang, A. Y., Langmuir, C. H., Cai, Y., Michael, P., Goldstein, S. L., Chen, Z.
• Format: Report
• Language: English
• Published: NATURE PORTFOLIO 2021
• Subjects: Science & Technology - Other Topics; Multidisciplinary Sciences; SOUTHWEST INDIAN RIDGE; TRACE-ELEMENT; HETEROGENEITY BENEATH; ISOTOPE EVIDENCE; SR ISOTOPE; MANTLE; CRUST; WATER; FLOW; ORIGIN; Arctic; Gakkel Ridge; Indian; Pacific
• Online Access: http://ir.gig.ac.cn/handle/344008/63067; https://doi.org/10.1038/s41467-021-25027-2

The plate tectonic cycle produces chemically distinct mid-ocean ridge basalts and arc volcanics, with the latter enriched in elements such as Ba, Rb, Th, Sr and Pb and depleted in Nb owing to the water-rich flux from the subducted slab. Basalts from back-arc basins, with intermediate compositions, show that such a slab flux can be transported behind the volcanic front of the arc and incorporated into mantle flow. Hence it is puzzling why melts of subduction-modified mantle have rarely been recognized in mid-ocean ridge basalts. Here we report the first mid-ocean ridge basalt samples with distinct arc signatures, akin to back-arc basin basalts, from the Arctic Gakkel Ridge. A new high precision dataset for 576 Gakkel samples suggests a pervasive subduction influence in this region. This influence can also be identified in Atlantic and Indian mid-ocean ridge basalts but is nearly absent in Pacific mid-ocean ridge basalts. Such a hemispheric-scale upper mantle heterogeneity reflects subduction modification of the asthenospheric mantle which is incorporated into mantle flow, and whose geographical distribution is controlled dominantly by a "subduction shield" that has surrounded the Pacific Ocean for 180 Myr. Simple modeling suggests that a slab flux equivalent to similar to 13% of the output at arcs is incorporated into the convecting upper mantle.