Aeromagnetic mapping and geodynamic reconstruction of the Ediacaran Najd fault system in the Arabian Shield

• Geologic and aeromagnetic maps reveal the geometry of the Najd fault system. • Only the Ar-Rika fault zone displaces the Amar collisional front by 55–80 km. • The Halaban Suture reveals the shape of the collision front at ca. 620 Ma. Three major NW-trending fault zones are assigned to the Ediacaran Najd fault system in the exposed Proterozoic Arabian Shield of Saudi Arabia. The total left-lateral displacement along the three zones has been previously interpreted as ca. 250 km, and to project from the southeastern edge of the Arabian Shield to beneath the Phanerozoic cover rocks in Saudi Arabia. In this article, aeromagnetic and geological maps, geochronological data, and structural evidence are integrated in a new Ediacaran tectonic framework of the Arabian Shield. It indicates only the middle branch of Najd system, the Ar Rika–Qazaz, constitutes a major strike-slip fault zone with a left-lateral displacement ranging between 55 and 80 km as estimated at several locations. The fault zone became active at ca. 620/615 Ma when it broke across the NS-oriented collisional front of the Amar orogeny and ceased to move by ca. 560 Ma, or possibly later.