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Grain size is usually small (larger crystals in the matrix are 1–2 mm in size). The orthogneisses show lenticular grains that are slightly larger (2–3 mm) than the minerals in the quartz-feldspathic matrix, whereas others contain mineral aggregates (mostly made of quartz and feldspar) that show similar structure. Single-mineral lenses of feld- spar with augen structure suggest a micro-porphyritic texture in the igneous protolith. Some of the felsic gneisses include green amphibole and biotite in their matrix. Paragneisses are less abundant and are augen- free and mica-rich (biotite and white mica) (Figure 5(b)). No mafic rocks were observed within these. The absence of mafic rocks makes it difficult to interpret this ensemble as oceanic or transitional crust. Potential protoliths for the lithologies grouped into this unit (sedi- mentary and felsic igneous rocks) represent typical counterparts of continental crust sensu lato , although alternative options cannot be ruled out due to the lim- ited exposure of this unit. 3.2. Mafic-ultramafic Unit: Mérida Ophiolite The Mérida Massif contains an exposure of mafic and ultramafic rocks that have been grouped into a single tectonostratigraphic unit due to its contrasting compo- sition and consistent structural position (see below) relative to surrounding lithologies. This unit contains coarse-grained (isotropic) gabbros-diorites (Figure 5(c)), layered metagabbros with mafic cumulates (Figure 5 (d)), coarse-grained metagabbros-diorites (Figure 5(c)), pegmatitic gabbros, doleritic dikes (Figure 5(c)), amphi- bolites, garnet-bearing amphibolites (Figure 5(e)), banded amphibolites (Figure 5(e)), hornblendites (Figure 5(f)), metaperidotites (serpentinites after Figure 3. Geological map showing the distribution of tectonostratigraphic units of the Mérida Massif, and idealized lithological column of the Mafic-ultramafic Unit (Mérida Ophiolite). 4 R. D. FERNÁNDEZ ET AL. &KDSWHU