Relationships between granitoids and mineral deposits: three-dimensional modelling of the Variscan Limousin Province (NW French Massif Central)
C. Le Carlier de Veslud, M. Cuney, J. J. Royer, J. P. Floc'h, L. Améglio, P. Alexandrov, J. L. Vigneresse, P. Chèvremont, Y. Itard, 2000. "Relationships between granitoids and mineral deposits: three-dimensional modelling of the Variscan Limousin Province (NW French Massif Central)", The Fourth Hutton Symposium on the Origin of Granites and Related Rocks, Bernard Barbarin, William Edryd Stephens, Bernard Bonin, Jean-Luc Bouchez, David Barrie Clarke, Michel Cuney, Hervé Martin
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Multidisciplinary three-dimensional modelling, involving geophysical, structural and geochemical data, has been used to study the relationships between magmatism, tectonics, fluid circulation and mineralisation in the northern Limousin, and to provide P–T–Z–t paths constrained by the available dating. The ore deposit occurrence displays little spatial relationship with granites emplaced in the 360–320 Ma period, probably because the low global permeability and tectonic regime did not allowed vertical fluid exchanges to be established. In contrast, the change in the tectonic regime induced by the delamination of the lower lithosphere (320–300 Ma), and characterised by the passage to general extension, has played a major metallogenic role. However, the ore deposit processes appear to be specific to each metal. Most of the W-Sn deposits appear to be synchronous with rare metal granites emplacement, at c. 310 Ma, that allowed the focus of fluids of different origins towards the apex of plutons. In contrast, for Au and U, the whole mineralisation process covers several tens of millions of years. It is controlled by the regional tectonic evolution of the Limousin area during the same period, and especially by a rapid exhumation of the ductile crust which occurred in the 310–300 Ma period.