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The Vila Nova pluton is a small, Pre-Variscan granitic body that intruded rocks of the Central Iberian
Zone near the contact with the Ossa Morena Zone and is affected by several shear zones and faults. Its
contact metamorphic aureole is constituted by micaschist with porphyroblasts in the outer zone and
hornfels in the inner zone. Small metasedimentar xenoliths are dispersed all over the body. The pluton
has a great mineralogical heterogeneity with pronounced variations in muscovite/biotite and plagioclase/
microcline contents and is classified as granite, granodiorite or tonalite. It is a leucogranite, highly
peraluminous (A/CNK = 1.31 – 1.64), magnesian and calc-alkaline to alkaline-calcic. The variation diagrams
show curvilinear trends with silica. Eu/Eu* = 0.47 – 0.77 and there is a slight enrichment in LREE
relative to HREE. The normalized diagrams indicated dominantly crustal granite, related to subduction.
U-Pb isotopic data of zircon and monazite gives 540-542 Ma age.
Five granitic rocks, concentrically disposed from core to rim, were distinguished in the Castelo Branco
pluton. U-Pb-Th electron microprobe monazite ages from granitic rocks are similar and ranging between
297-303 Ma. The granitic rocks from Castelo Branco pluton are 310 ± 1 Ma old, obtained by U-Pb
(ID-TIMS) in separated zircon and monazite crystals, indicating a similar emplacement age for all granitic
rocks of the pluton. Initial 87Sr/86Sr isotopic ratios and εNd310 and δ18O values suggest three distinct pulses
of granitic magma and that they are derived from partial melting of heterogeneous metasedimentary
materials. The other granitic rocks are related by magmatic differentiation and show small variations in
(87Sr/86Sr)310, εNd310 and δ18O. The granitic pluton of Castelo Branco shows a rare reverse zoning.
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