Petrology of the Teijeiro area: part of the Early Palaeozoic high-grade metamorphic Sobrado/Teijeiro complex (Galicia, NW Spain)

The high-grade metamorphic Sobrado-Teijeiro complex forms part of the peripheral belt of the Ordenes basin. The fault-bounded elliptical complex consists of a central unit of highly serpentinized ultramafic rocks, surrounded by (partly retrograded) mafic granulite facies rocks, highgrade paragneisses and orthogneisses. The area studied comprises the northern part of the complex. Here the ultramafic rocks are almost completely serpentinized and only in a few specimens relics of olivine, clinopyroxene, orthopyroxene and amphibole have been found. Paragneisses, consisting of K-feldspar, plagioclase, quartz, biotite, muscovite and garnet, form a rim around the mafic and ultramafic rocks. Coarse-grained orthogneisses, belonging to two different bodies, form the outermost parts of the complex. Mafic rocks occur in between the serpentinites and the paragneisses. Several phases of metamorphism and deformation can be discerned. A first phase of metamorphism under conditions of the clinopyroxenealmandine subfacies gave rise to a granoblastic-polygonal fabric consisting of rather jadeite-rich clinopyroxene, garnet and plagioclase. During a second phase of metamorphism, preceded and accompanied by deformation, recrystallization of the original assemblage and growth of brown hornblende at the expense of clinopyroxene occurred, giving rise to blastomylonitic and granulitic textures. Further retrogradations took place under amphibolite and greenschist facies conditions. This sequence of events resulted in a rather heterogeneous unit, ranging from essentially nonaltered granofelses, via blastomylonites to amphibolites and greenschists in which hardly any relics of high-grade minerals are encountered.