RT Journal Article
T1 Polycyclic metamorphic evolution of the Sierra Albarrana Schists (SW Iberian Massif): From low-pressure Ordovician rifting to medium-pressure Variscan overprint
A1 Solís Alulima, Byron Ernesto
A1 López Carmona, Alicia
A1 Abati Gómez, Jacobo
A1 Rojas Agramonte, Yamirka
A1 Bousquet, Romain
A1 González del Tánago y del Río, José
AB This study presents new information on the polycyclic metamorphic evolution of the Sierra Albarrana Domain (SW Iberian Massif) obtained through a comprehensive assessment of mineral assemblages and petrological modelling (P–T–X pseudosection approach). The pelitic schists in this domain depict the uncommon paragenesis St-Grt-And together with And-Grt-Sil-bearing schists. The first assemblage has been accurately reproduced by pseudosection modelling using the whole rock composition directly analysed by XRF. In contrast, early attempts to model And-Grt-Sil-bearing schists were not as successful. Fe3+ can be a critical element influencing the phase relations in pelites. For this reason, we investigated the influence of the effective amounts of Fe3+ to estimate the oxidation estate during the metamorphism by computing a series of P/T–X pseudosections to explore whether somewhere in P–T–X space the matrix association can be reproduced.The Sierra Albarrana Domain recorded a regional low-pressure metamorphic event accompanied by a complex structural evolution, probably related with the Middle Cambrian-Lower Ordovician rifting developed in the NW Gondwanan margin. This episode has been constrained at ∼4 kbar and 580 °C in the St-Grt-And pelitic schists. Related granitic magma pulses contributed to a local thermal increase of the extending crust (preserved in the And-Grt-Sil-bearing schists), where temperature reaches up to 595 °C. This area shows the syntaxial replacement of coarse-grained andalusite porphyroblasts by sillimanite. This was followed by exhumation, characterised by decompression at ∼2 kbar and 510 °C. After the main pre-Variscan Buchan-type regional metamorphism, a localised medium-pressure metamorphic event, limited to granitic pegmatites and concordant ky-bearing quartz segregation veins was recorded, possibly due to the tectonic thickening corresponding to the Variscan cycle.
PB Elsevier Science B.V., Amsterdam
SN 0024-4937
YR 2023
FD 2023-05
LK https://hdl.handle.net/20.500.14352/73105
UL https://hdl.handle.net/20.500.14352/73105
LA eng
NO Ministerio de Economía y Competitividad
NO Ministerio de Ciencia e Innovación
NO Universidad Complutense de Madrid
DS Docta Complutense
RD 3 oct 2024