Discovery and geology of the Roberto Gold Zone, Éléonore Project, Québec

CIM Vancouver 2006
Abstract The Éléonore property consists of 480 map-designated claims totalling 25,081.25 hectares (250.08 km2). It is located in the Ell Lake area in the eastern part of the Opinaca reservoir in the James Bay region of Québec, approximately 320 kilometres north of the town of Matagami. The property is accessible by boat, floatplane or helicopter, but is situated only 35 km away from secondary gravel roads connecting to the James Bay main highway.

The Opinaca area lies within the Superior Province of the Canadian Shield. The geology is dominated by a vast batholithic complex essentially composed of synvolcanic (2747-2710 Ma) and syntectonic (2710-2697 Ma) intrusions, indicative of voluminous and long-lived magmatic activity covering a span of 50 Ma. The area also includes typical Archean volcano-sedimentary assemblages of the La Grande sub-province which are overlain by paragneisses of the Opinaca sub-province. Metamorphism ranges from upper greenschist to amphibolite levels in the volcano-sedimentary assemblages while higher-grade facies up to granulite level characterize the Opinaca sub-province. The Éléonore property is centred on the Ell Lake intrusion, a small dioritic stock located in the contact zone between the La Grande and Opinaca sub-provinces. The intrusion is bounded mainly by quartzo-feldspathic sediments and conglomerates.

A regional reconnaissance work program led Virginia in the Opinaca area for the first time in 1996. Additional prospecting and reconnaissance programs conducted in the area by Virginia resulted in the discovery in June 2001 of several Au-Cu-Ag showings hosted by the Ell Lake diorite, including the Ell Lake showing, a former copper showing outlined by Noranda in 1964. Subsequent exploration campaigns identified further Au-Cu-Ag occurrences in the diorite intrusion and also discovered several Au-As-(Sb) showings in the sediments to the north.


The Roberto zone was discovered at the beginning of the summer 2004 campaign, while following up on a grab sample collected in the late fall of 2003 that had yielded assays of 10.25 g/t Au. Hand stripping and preliminary sampling of this showing yielded very encouraging results: up to 80.70 g/t Au in grab samples and 4.29 g/t Au over 12 m, including 6.16 g/t Au over 5 m in channel sampling. Further stripping and channel sampling of the showing returned very impressive results, including 9.35 g/t Au over 13 m, 18.5 g/t Au over 11 m and 15.52 g/t Au over 10 m. These results prompted a major mechanical stripping and mapping program and diamond drilling was initiated in early September 2004. Since then, drilling has been carried out on a continuous basis and more than 200 holes have been completed on the property. The Roberto-style mineralization consists of finely disseminated sulfides (5% pyrrhotite- arsenopyrite) and is associated with strong potassic (microcline-biotite) and brown tourmaline alterations of the sediments. The Roberto zone has yielded very impressive gold values at surface (up to 18.5 g/t Au over 11.0 metres in channel sampling) and in drilling (up to 18.85 g/t Au over 16.0 meters). Other similar parallel zones have also been discovered and a very fertile gold system has since been outlined over a distance of 1900 m and to a depth of 900 m and remains wide open in all directions. The Roberto deposit is a major gold discovery and its ultimate size has yet to be determined.

The Roberto discovery is a strong validation of Virginia’s long-term strategy to focus exploration in the virgin territories of Québec. Partnerships, portfolio diversification and generous tax-incentive programs from the Québec government have all been key elements that helped Virginia to maintain a long-term presence on the James Bay territory and to develop an excellent expertise, ultimately resulting in the discovery of the Roberto gold deposit.
Full Access to Technical Paper
PDF version for $20.00
Other papers from CIM Vancouver 2006