Detachment‐Fault Structure Beneath the TAG Hydrothermal Field, Mid‐Atlantic Ridge, Revealed From Dense Wide‐Angle Seismic Data

Abstract

The Trans‐Atlantic Geotraverse (TAG) field on the Mid‐Atlantic Ridge is one of the largest currently active seafloor hydrothermal fields known. An underlying detachment is inferred to maintain TAG's long‐lived hydrothermal discharge, but the detachment lacks a widespread corrugated surface. We used dense wide‐angle seismic data to define TAG's detachment structure at a finer scale than has previously been possible. We generated two P‐wave velocity profiles of the shallow section of the detachment using first‐arrival travel‐time tomography, preconditioned by downward continuation. Our results reveal a low‐angle detachment, dipping at ∼15° (±5°) at 5 km east of the ridge axis, and evidence for uplifted lower‐crustal gabbro in the footwall. Increasing footwall velocities southward suggest a more intense exhumation of deep‐seated rocks, showing the detachment's geometry changes along the ridge axis. We conclude the detachment is a complex 3‐D structure, and a young system without a dome‐shaped footwall can exhumes deep‐seated crustal rocks.