Using PERPLE_X and garnet isopleth thermobarometry we tested whether Permian metasediments, orthogneisses, and amphibolitized eclogites from the Nevado-Filábride Complex in the western Sierra Nevada (Betics, Spain) underwent the same high-pressure metamorphism, or whether the different lithologies were tectonically emplaced after metamorphism as is commonly assumed. Our results highlight the role of some accessory minerals, especially small inclusions of Ti-bearing phases (mainly titanite and rutile) in garnet, in the thermobarometric estimates and indicate the presence of several populations of garnets in the orthogneisses—recording different stages of the prograde and retrogressive Alpine metamorphic path—in addition to pre-Alpine garnets. The schists also contain two populations of garnet: rare detrital grains and metamorphic crystals. Despite the scarcity of key phases proving that the orthogneisses and metasediments experienced high-pressure conditions, this study yields a number of lines of evidence suggesting that both rock types followed a clockwise pressure-temperature path similar to the eclogites, reaching peak pressures of 2.0–2.2 GPa for temperatures of 550–600 °C, and that the lithologies were all in contact prior to the high-pressure Alpine event.
↵1We will use the term pre-magmatic because of the difficulties in differentiating detrital phases (e.g., old zircon cores), restites, or metamorphic phases entrained with the melt, from the source rocks and possible contamination at upper crustal levels.
↵2We have obtained chemical maps from all garnets shown in Figures 5–7, and the profiles were obtained with the more appropriate orientation for showing the possible chemical variations between cores and rims. The analyzed points were selected from the BSE images to avoid the contribution of the inclusions.
↵3Apatite from the biotite gneisses is interpreted as a metamorphic phase in the source rock from which the granitic melt derives, which was entrained with the melt.
- © 2015 Mineralogical Association of Canada