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Abstract: The Early Ordovician Oledo pluton consists of four distinct granodioritic to granitic phase (G1–G4), which intruded a Cambrian schist-metagraywacke complex, but were themselves intruded by a Late Carboniferous pluton. ID-TIMS U–Pb ages for zircon and monazite from these granitic rocks indicate emplacements within a short period of time at 479–480 Ma. Granodiorite G1 is the most deformed rock with shear zones and deformation at the border. G1 and G3 contain fine-grained biotite tonalite and biotite granodiorite microgranular enclaves, which are darker and richer in mafic minerals than the host granodiorites. The geological, mineralogical, geochemical and Sr, Nd and O isotopic data show that tonalitic and granodioritic enclaves and host G1 are of I-type and were related predominantly by a fractional crystallization process. Least-square analysis of major elements and modelling of trace elements indicate that granodioritic enclaves and host G1 could be derived from the tonalitic enclave magma by fractional crystallization of plagioclase, grunerite, biotite and ilmenite. Granodiorite G2 is of hybrid origin. Most variation diagrams for granodioritic enclaves and host G3 granodiorite and their biotites show linear trends. Modelling of major and trace elements of granodioritic enclaves indicate that they result from mixing of relatively primitive granodiorite magma with magma derived from crustal melting. Tonalitic enclaves correspond to globules of a more mafic relatively primitive magma. Granite G4 has the most pronounced crustal signature and is of S-type. [Copyright &y& Elsevier]

Ion microprobe (SIMS) dating of zircon from the Miranda do Douro orthogneiss, Central Iberian Zone, Hercynian Iberian belt, defines an Early Ordovician U-Pb age of 496.0 ± 2.6 Ma (195 % conf., MSWD = 1.14) for magmatic zircon crystallization in its granitic protolith. The age contrasts with an earlier, conventional (ID-TIMS) U-Pb zircon age of 618 ± 9(95 % conf.) Ma, now thought to be an artefact of the complex zircon population. Individual SIMS ages for zircon from the rock range from 2700 to 180 Ma and comprise inherited and magmatic zircon, both concordant and common Pb-enriched, and younger, reset ages. The ID-TIMS study seems to have misinterpreted this heterogeneous population as a cogenetic suite consisting of magmatic zircon and its age-reset equivalents produced by recent Pb loss. The 496 ± 3 Ma SIMS age represents the weighted average for 26 magmatic zircon domains located by careful inspection of cathodoluminescence, secondary electron and optical microscopy images of ∼ 700 individual zircon crystals. Inherited zircon is widespread, ranging in age from 2700 to 550 Ma, with age clusters, which are statistically indistinguishable from those known from pre-Hercynian granitic basement material elsewhere in the Central Iberian Zone. Including the present age information, 582 ± 4 Ma (95 % conf., MSWD = 1.02, n = 13) and 619 ± 9 Ma (95 % conf., MSWD = 0.93, n = 7) appear as prevailing inherited zircon age components in basement intrusions in the Central Iberian Zone. [ABSTRACT FROM AUTHOR]

Soft-bodied preservation is common in the Cambrian but comparatively rare in the Ordovician. Here, a new deposit preserving soft-bodied fossils is reported from the Middle Ordovician (Dapingian-Darriwilian) upper Valongo Formation of northern Portugal. The deposit contains the first known occurrences of soft-bodied fossils from the Middle Ordovician (Dapingian-Darriwilian) of Portugal and is the first Ordovician example of soft-tissue preservation involving carbonaceous films from the Iberian Peninsula. It also represents the lone deposit of soft-bodied fossils from the Middle Ordovician of northern Gondwana. Thus temporally, it lies between the exceptional deposits of the Lower Ordovician of Fezouata (Morocco) and the Upper Ordovician of the Soom Shale (South Africa); it also serves as a biogeographic link between these and the various Ordovician soft-bodied deposits in Laurentia. The soft-bodied fossils come from the deep-water slates of the upper part of the Valongo Formation and include a discoidal fossil questionably referable to Patanacta, wiwaxiid sclerites, and a possible pseudoarctolepid arthropod.