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group lie in the range 8.4–10.2, whereas in the metato- nalite most vary between 2.1 and 7.9, although one zircon gives a positive value of 9.9 and another a negative value of −10.8 (Figures 11a and 11b). Zircon analyses from metagabbro OM-2 fall in the MORB- depleted mantle field and can be considered to have crystallized from gabbroic magmas derived directly from a depleted mantle source. Furthermore, the relative homogeneity of the Hf isotopic composition in the zircon grains and the contemporary and juvenile char- acter of the main isotopic sources confirm an orthomag- matic origin. Hence, the analysed zircon grains were very likely derived directly from the mafic magma from which the gabbroic rocks crystallized. This is consistent with the U-Pb age determined for the protolith of metagab- bro OM-2. In the metatonalite OM-1, most analyses show crustal or mixed isotopic sources, confirming their more complex generation with the participation of materials Figure 11. a) Initial Ɛ Hf (t) versus age diagram combining the U-Pb and Lu-Hf isotope data of zircons analyzed in metagabbro OM-2 and metatonalite OM-1. The evolution trend of MORB ( 176 Lu/ 177 Hf = 0.02; Blichert-Toft and Albarède 2008) is shown, as well as the depleted mantle evolution and the chondritic uniform reservoir (CHUR). b) Initial Ɛ Hf (t) versus age diagram for zircons of samples OM- 2 and OM-1 showing the evolution trend of Cadomian, Mesoproterozoic, Paleoproterozoic and Archean crusts. Abbreviations and other trends are as in a). The common present-day crustal evolution trend ( 176 Lu/ 177 Hf = 0.0113; Taylor and McLennan 1985; Wedepohl 1995) is also shown. 18 R. ARENAS ET AL. &KDSWHU