serie NOVA TERRA nº 49

54 metamorphic event is considered to be related to the accretion of the arc to the southern margin of Laurussia, which facilitated imbrication of a basal sheet that subducted until the development of the HP – HT event. The metamorphic P – T conditions reached around 800 °C and 20 – 23 kb, obscuring preservation of tectonothermal events prior to the accretion of the arc to Laurussia. Nevertheless, Fernández-Suarez et al. (2002) identi fi ed a widespread metamorphic event dated at ca. 490 – 480 Ma in paragneisses of the lower sheet. This early event reached high-temperature and medium-pressure conditions, but its signi fi cance is uncertain. It may be related to the dynamics associated with the magmatic arc while it occupied a position at the periphery of Gondwana. The upper sheet (intermediate-pressure upper units) consists of medium- to low-grade metasedimentary sequences of problematic age, massifs of variably deformed and metamorphosed gabbros and granitoids, and a thick metagreywacke series occupying the upper- most position ( Fig. 3 ). Both gabbros and granitoids have typical volcanic arc compositions, and have been dated at c. 500 Ma. Abati et al. (1999) have dated (TIMS U – Pb zircons) the Monte Castelo gabbro (western part of the Órdenes Complex) at 499±2 Ma and the Corredoiras orthogneiss (easter part of the same complex) at 500±2 Ma. The upper sheet shows a widespread medium-pressure and variable low- to high-temperature event (see Abati et al., 2003 and references therein), with which most of the regionally distributed Fig. 3. Geological sketch and cross-section of the Órdenes and Cabo Ortegal complexes ( Martínez Catalán et al., 2002; Arenas et al., 2007 ), with the distribution of the main allochthonous terranes, the basal, ophiolitic and upper units. The position of the area represented in Fig. 4 is also shown. CD, Corredoiras detachment; CMD, Campo Marzo detachment; LFT, Lalín-Forcarei thrust; PCD, Ponte Carreira detachment; PSD, Pico Sacro detachment. 341 J.M. Fuenlabrada et al. / Gondwana Research 17 (2010) 338 – 351