Penedono gold(-bearing granite-hosted quartz veins) prospect: the place, the history and the deposit
Penedono (Viseu district, northern Portugal) is home to a gold(-bearing granite-hosted quartz veins) prospect, currently being explored and evaluated by the Penedono consortium (Canadian Colt Resources and Brazilian Contécnica) – http://www.coltresources.com/en/santo-antónio.
The Santo António Experimental Mining Licence (EML) in North-Eastern Portugal covers a total area of 35.34 km2. This concession was granted to a joint venture between Colt and Brazilian company, Contecnica, in which the latter will be the operator (Press Release: September 4, 2012). The granting of this concession follows on the exploration project undertaken by Colt in the Penedono concession between 2007 and 2012.
The area is mostly underlain by multi-phase granitic intrusions of the Variscan tectonic cycle (Upper Paleozoic), which host a number of known gold deposits of the “Reduced Intrusion Related” type. These can consist of either individual veins such as at Sendim; clusters of quartz veins such as at Santo António (13 veins), Ferronha and Dacotim (3 main veins each); or sheeted vein systems with or without associated greisen envelopes, such as respectively at Turgueira and Marofa. Some tungsten mineral (wolframite) can also be present in these mineralized structures (e.g. Santo António, Turgueira) which can perhaps originate by-product tungsten production.
Mining activity in the area dates back to Roman times, when gold was produced from Santo António, Ferronha and Dacotim. Small scale artisanal tungsten (wolframite) mining took place in the area during the 1940’s and 1950’s. Gold mining attempts were also undertaken in the mid 20th Century from Ferronha, Dacotim and particularly Santo António. The latter was exploited by the Companhia das Minas de Ouro de Penedono in the 1950’s, having produced a total of around 11,000 ounces of gold from a total of 105,000 tons of ore (ROM) extracted from underground mining along veins # 2 and 3, and to a minor extent veins # 7 and 13.
The 1950’s Santo António mining plant never achieved an acceptable level of gold recovery and as a result the ca. 100,000 m3 of tailings material still existing at the Santo António mine are believed to host gold that may be recoverable using more modern methods.
During the experimental mining period the Joint Venture’s activity will focus on: trial open pit mining at Turgueira; recovery of gold from the Santo António tailings; excavation of a new adit to access and de-water the Santo António underground workings and recover for pilot metallurgical testwork blasted ore left in the old galleries; and continuing evaluation drilling of the vein deposits.