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harzburgites) (Figure 6(a)) and minor silicic dikes intruding the gabbroic protoliths (Figure 3). It lacks felsic and intermediate igneous rocks, and paraderived lithologies. No cross-cutting relationships have been observed between pristine igneous rocks and the rest of metamorphic rocks of this unit. But on the other hand, some exposures provide evidence that the foliated metamorphic rocks of this unit resulted from deformation and metamorphism of igneous rocks along shear zones (e.g. amphibolites after gabbros; Figure 5(c)). Therefore, the whole ensemble represents a heterogeneously strained and variably recrystallized mafic-ultramafic complex. The age of crystallization of some mafic rocks of this ensemble was dated at 580–570 Ma (U-Pb in zircon), while their geochemical composition shows negative anomalies in Nb, Ti, and Ta relative to REE and, compared to present-day N-MORB, they have higher 87 Sr/ 86 Sri ratios and lower ڙ Nd values (Brandrés et al ., 2004). Ultramafic rocks, such as strongly foliated serpenti- nites (Figure 6(a)), occur at different levels across struc- ture within this unit, and they are usually related to sections where the mafic constituents show higher strain (Figure 5(d,e)). Poorly strained gabbros-diorites preserve primary igneous textures (not described here). Poorly strained rocks typically occur away from the ultramafites, their strain being markedly heterogeneous, even at the outcrop scale (Figure 5(c)). This mafic-ultramafic ensemble represents tectonic slices of lower crust and upper mantle (serpentinites), and is collectively referred to as the Mérida Ophiolite. It might represent slices of lower continental crust (more mafic in composition), but given the lack of metasedi- mentary rocks and/or felsic-intermediate rocks to con- form with the relatively felsic composition expected for the lower continental crust in many regions of the world (e.g. Hacker et al . 2015), and the presence of slices of metaperidotite that are in turn typical of obducted Figure 4. Cross-sections showing the current structure of the tectonostratigraphic units of the Mérida Massif. (a) Cross-section normal to the trace of Variscan folds and faults. (b) Cross-section subparallel to shear direction of Cadomian shear zones and showing the Cadomian nappe pile of the Mérida Massif. Cenozoic cover is not represented. INTERNATIONAL GEOLOGY REVIEW 5 Tectonostratigraphy of the Mérida Massif