Zircon and allanite U-Pb TIMS dating in vaugnerites from the Calzadilla Pluton, Salamanca (Spain): the role of mantle magmatism and post-magmatic subsolidus overprint

F. J. LÓPEZ-MORO, R. L. ROMER, M. LÓPEZ-PLAZA, M. GÓNZALEZ SÁNCHEZ

Abstract


Basic to intermediate high-K, high-Mg mantle-derived rocks occur throughout the Iberian Massif and are particularly important in the Tormes Dome, where vaugnerites form several stocks and small plutons. One of the largest and geochemical most variable among these plutons is the Calzadilla Pluton in the Tormes Dome that crystallized at 318 ± 1.4 Ma (Bashkirian; U-Pb TIMS zircon). This age reveals that the vaugnerite pluton was emplaced during the transition from late D2 extensional deformation to early D3 contractional deformation (319 to 317 Ma). Large-scale extension in the area resulted on one hand in extensive anatexis in the crust due to quasi-isothermal decompression and mica-dehydration melting and on the other hand in upwelling of the mantle, which induced partial melting of the enriched domains in the lithospheric mantle. Extension is the driving reason why crustal and mantle melts were coeval. The U-Pb ID-TIMS age of allanite is not related to the emplacement or cooling of the Calzadilla vaugnerite, but seems to be related to a younger subsolidus overprint ca. 275 Ma that on the scale of the Central Iberian Zone corresponds to a period of hydrothermal alteration including episyenite formation and W-bearing deposit formation.

Keywords


Vaugnerite; Zircon; Allanite; U-Pb dating; Subsolidus overprint; Ledesma

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DOI: http://dx.doi.org/10.1344/%25x

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Geologica Acta (ISSN-1695-6133)
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