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Variscan shear zones and control of Sn-W, Au, U mineralizations in the Central-Iberian Zone in Portugal

Abstract

[Resumo] Propoese urna síntese sobre a génese dos cisalhamentos regionais e estruturas secundárias associadas nas diferentes fases colisionais, para o sector restricto da Zona Centro-Ibérica (Z.C.!.) da orogenia hercínica. Adoptam-se os conceitos de RAMSAY (1980) e SANDERSON &MARCHINI (1984) para enquadrar, respectivamente, a tipologia e cinemática destes cisalhamentos. Esboçase um cenário geral da geometria e cinemática das estructuras na Z.C.!., concomitantemente, com a evolu~ao dos cisalhamentos tangenciais nas fases precocese com os cisalhamentos transcorrentes nas fases tardias do orógeno. No quadro da associa~ao espacial das mineralizag:>es de Sn-W, Au e U aos cisalhamentos, define-se o controlo estrutural destas mineraliza~oes e procede-se a tentativa de hierarquizar as referidas mineralizag:>es da Z.C.!., conectando-as as diferentes fases de deformaçao da orogenia hercínica[Abstract] The tipology and kinematic evolution of the shear zones and related secondary structures in the Central Iberian Zone (Variscan orogeny) are stablished on the basis of the concepts expressed, respectively, by RAMSAY (1980) and SANDERSON & MARCHINI (1984). The geometry and kinematics of these structures are linked to the evolution of nappes in the preliminary deformation phases and with transcurrent shearing in the later deformation phases. The structural control and the spatial relationship of Sn-W, Au and U mineralizations by these shears, is defined. For each her cynian deformations phase it is made an atempt of hierarchyzation of these C.I.Z. mineralizations

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