The Ediacaran strata of the Narcea Antiform from the West Asturian-Leonese Zone, known as the Narcea Slates or Mora Formation, deformed prior to deposition of the unconformably overlying Terreneuvian strata. They are subdivided into the Allande and Navelgas members. The former is intruded by Ediacaran granites, granodiorites, and gabbros (ranging from 605 ± 10 to 571 ± 5 Ma), along with associated dyke swarms, and represents Mg- and K-rich magmas associated with subduction zones sourced from a subcontinental heterogeneous lithospheric mantle. The Navelgas member contains ignimbrite levels, crystalline tuffs, basalts, rhyolites, and hyaloclastic breccias (ranging from 559 ± 3 to 556 ± 3 Ma), displaying a bimodal nature indicative of extension. Both suites reveal two main episodes of magmatic activity, separated by a gap of ca. 20 m.y., which links the transition from a prolonged Ediacaran subduction to the final establishment of extensional rifting conditions.