Toronto Geological Discussion Group
Abstract: The Rovina Valley Project (RVP) in west-central Romania lies within the historic gold-mining district known as the ‘Golden Quadrilateral’ (GQ) with estimated +55 Moz of gold (Au) produced since the Roman period. Historic gold production has come from low-to-intermediate sulfidation epithermal deposits hosted in Neogene volcanic and subvolcanic, intermediate calc-alkaline rocks. Since opening-up to western exploration companies, a further 25 Moz gold-only resources in epithermal mineralization have been defined. The GQ is also host to copper (Cu)-porphyry deposits of similar age which can occur in proximity to the epithermal gold mineralization.
Carpathian Gold Inc. began exploration drilling in 2006 on the RVP and to date has drilled over 136,000 meters discovering and defining one Cu-Au porphyry deposit; and two Au-Cu porphyry deposits. These deposits, named from north to south, Rovina, Colnic and Ciresata deposits, define a 7km-long NNE trend. Drilling in 2008 discovered the ‘blind’ Ciresata Au-rich porphyry where mineralization starts 50-100m below the surface. Gold grade and contained Au ounces increase from north to south with the Colnic and Ciresata porphyries classified as Au-rich porphyries; a new porphyry class for the Golden Quadrilateral District.
In July 2012, Carpathian Gold announced a NI 43-101 compliant resource estimate update for the RVP which is currently being utilised in a Prefeasibility Study that is designing a central ore-processing plant for the three deposits. On a consolidated basis, in the measured + indicated resource contains 7.2 million ounces Au and 1.4 billion pounds of Cu (10.84 Moz Au-equivalent1) within 406 million tonnes at average grade of 0.55 g/t Au and 0.16% Cu using base-case cut-off grades1 (NI 43-101 Technical Report August, 2012). Importantly, each of the three Au-Cu porphyry deposits has a higher-grade core that vectors outward toward lower grade. As an example, at the Ciresata deposit, at the higher cut-off grade of 1.0 g/t Au-equivalent1, the measured + indicated resource includes 65 million tonnes at 1.01 g/t Au and 0.18% Cu. Gold grades are locally higher in Ciresata as indicated in drill hole RGD-17 which intersected 244 meters with 1.70 g/t Au and 0.22% Cu.
The high Au grade of Ciresata and Colnic make them unique to the Golden Quadrilateral and comparable to the Au-rich porphyry deposits of the Maricunga porphyry belt in Chile (Sillitoe, 2000). The discovery of Au-rich porphyries at RVP highlights the value of applying new exploration models to an old district.
1 Resource estimate base case cut-off grades are 0.35 g/t Au eq. for Colnic, 0.25% Cu eq for Rovina, both of which are amenable to open-pit mining and 0.65 g/t Au eq. for the Ciresata deposit which is amenable to underground bulk mining. Gold equivalent (Au eq.) determined by using a gold price of US$1,370 per ounce and a copper price of US3.52/lb representing the 3-year trailing average price at July 2012. Metallurgical recoveries are not taken into account for Au eq.
© Copyright 2018 Toronto Geological Discussion Group