In active volcanoes, petrological studies have been proven to represent a reliable approach to defining the depth conditions of magma transport and storage in the mantle and the crust. Based on fluid inclusion mineral geothermobarometry in mantle xenoliths, we propose a model for the recent magma plumbing system of the Island of El Hierro (Canary Islands). Studied peridotites are entrained in a lava flow from El Yulan Valley, which is part of the Rift volcanism activity at approximately 40-30 ka. Peridotites are spinel lherzolites, harzburgites and dunites equilibrated in the shallow mantle at pressures from 1.5 to 2 GPa. 800 to 950°C (LT peridotites). Manuscript Click here to download Manuscript Oglialoro et al revised.docx Click here to view linked References 2 and higher equilibration temperatures from 900 to 1100°C (HT peridotites). Microthermometry and Raman analyses of fluid inclusions show trapping of two distinct fluid phases: early Type I metasomatic CO2-N2 fluids (d = 1.19 g/cm 3), coexisting with silicate-carbonate melts, in LT peridotites; and late Type II pure CO2 fluids (d = 0.99 to 1.11 and 0.65-0.75 g/cm 3) in both LT and HT peridotites. Type I fluids represent metasomatic phases in the deep oceanic lithosphere (60-65 km) before the onset of magmatic activity, whereas Type II CO2 fluids testify for fluid trapping episodes during the ascent of xenoliths in host mafic magmas. Identification of magma accumulation zones through interpretation of Type II CO2 fluid inclusions and mineral geothermobarometry indicate the presence of a vertically stacked system of interconnected small magma reservoirs in the shallow lithospheric mantle from 22 to 36 km depth (or 0.67 to 1 GPa). This deeper magma accumulation region fed a short-lived magma storage region located in the lower oceanic crust at 10-12 km depth (or 0.26-0.34 GPa). According to our model, the 40-30 ka old volcanic activity of El Hierro is related to mantle magma dynamics, as also proposed for the 2011-2012 eruption. developed on the margin of the African Plate (Fig. 1a) (Robertson and Stillman 1979;