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Couto, H., Roger, G., Moelo, Y. & Sodre-Borges, F. (2016) Sb and Au mineralizations in the Variscan Durico-Beira area (north Portugal): litho-stratigraphic and structural controls. 16th International Multidisciplinary Scientific Geoconference, Sgem 2016: Science and Technologies in Geology, Exploration and Mining, Vol I Sofia. 
Added by: Richard Baschera (2017-03-06 13:30:33)   Last edited by: Richard Baschera (2017-03-06 13:36:46)
Type de référence: Chapitre/Section
Numéro d'identification (ISBN etc.): 978-619-7105-55-1
Clé BibTeX: Couto2016
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Mots-clés: antimony, evolution, gold, shear zones, Variscan ore deposits, volcanic rocks
Créateurs: Couto, Moelo, Roger, Sodre-Borges
Éditeur: Stef92 Technology Ltd (Sofia)
Collection: 16th {International} {Multidisciplinary} {Scientific} {Geoconference}, {Sgem} 2016: {Science} and {Technologies} in {Geology}, {Exploration} and {Mining}, {Vol} {I}
Consultations : 2/548
Indice de consultation : 4%
Indice de popularité : 1%
The Sb and Au mineralizations of the Durico Beirao Mining district are located in the Central-Iberian Zone of the Variscan orogen. Two types of auriferous mineralizations were distinguished: Sb-Au and Au-As. Two gold free/poor types are also present: Pb-Zn-(Ag) and W-Sn. Controls of mineralizations include structural and litostratigraphic features. There exists also a genetic relation with hidden granitic apexes. Country rocks of the area consist of Cambrian to Carboniferous metasediments, acid and basic volcanics, subvolcanics and Variscan granites. Two main episodes of folding, one ante-Stephanian and the other one post-Stephanian, are recognized. The major ante-Stephanian structure is the Valongo Anticline, N 150-160 degrees E trending with axial plunge toward NW. Another prominent structural feature is the sinistral "Douro Shear Zone" (DSZ), along the western limb of the Valongo Anticline. Carboniferous basins are settled up all along this structure. Several shear-zones sub-parallel to the DSZ crosscut the studied area, notably the "Santa Justa Shear-Zone" (SJSZ) along the hinge zone of the Valongo Anticline. Volcanic rocks linked to a rifting at the Cambrian-Ordovician transition seem also associated to shear zones. Pegmatitic, aplitic, microgranitic and doleritic sills are frequently emplaced in the same fractures, with spatial relationship with mineralizations. The most evident lithostratigraphic control concerns the Au-As mineralization hosted by the Floian succession composed of quartzites, slates, wakes, ironstones with intercalations of volcano-sedimentary layers, along the Eastern limb and in the nose of the Valongo Anticline. Most of the Sb-Au veins occur west of the Western limb of the Valongo Anticline. Deposits are hosted by competent successions: mainly conglomerates, quartzites and slates, with acid and basic volcanics and diabases (weathered dolerites) intercalations of Cambrian age (Montalto Formation), and in some cases by the Carboniferous basal breccia and the overlying wackes. More recently a relationship between Upper Ordovician glacigenic rocks of Sobrido Formation (Hirnantian age) and Au-Sb-As anomalies was reported. The most marked structural control is the alignment of most of the Sb-Au deposits at short distances from the DSZ, in the Montalto Formation domain, of Cambrian age, West of the Valongo Anticline. SJSZ along Montalto Formation in the core of Anticline also controls Sb mineralizations. Another structural control was evidenced along the Eastern limb of the Valongo anticline, in Au-As and Sb-Au deposits: the mineralized veins are emplaced in sub-vertical faults in the hinge zones of anticlines associated with the major folding, subsequently affected by deformation.
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