La Mina is a porphyry gold-copper project located 45km southwest of Medellin in the Antioquia region of Colombia. La Mina is currently in the resource stage, with ongoing exploration and drilling at the site.
The project is being developed by Bellhaven Copper & Gold, an exploration company based in Canada.
The La Mina exploration area covers 1,794ha in mountainous topography at an elevation ranging between 1,600m and 2,000m. The site is accessed through paved and improved dirt roads. Power, water and labour are readily available at the site.
Gold-copper project geology
La Mina lies in the Middle Cauca belt of Colombia, which hosts significant porphyry gold deposits such as AngloGold’s La Colosa and Sunward Resources’ Titiribi.
La Mina flanks the intrusive centres associated with porphyry-type mineralisation and alteration. Gold and copper are found disseminated in volcanic rocks, sub-volcanic breccias and porphyries at shallow level.
Mineralisation of La Mina project
The mineralisation at the intrusive centres comprise of quartz, magnetite, pyrite, chalcopyrite, plagioclase, amphibole and phenocrysts.
A ZTEM (airborne electromagnetic) survey was completed over the La Mina project area in December 2012. The survey was conducted by Geotech, a Canadian geophysical survey company.
The ZTEM survey was carried out to identify and define the porphyry style mineralisation at La Mina. The survey will also add to the current understanding of geophysical properties related to known porphyries at La Mina.
The ZTEM airborne survey results are expected by the middle of 2013. Condor Consulting is assisting Geotech for modelling and interpretation of the survey results.
La Mina project history
Resource exploration at La Mina dates back to 2002. Drilling at La Mina was carried out in mid 2006 by a joint venture between AngloGold Ashanti and B2Gold (formerly Bema Gold) with six drill holes at La Cantera, one of the porphyry deposit of La Mina.
Bellhaven Copper & Gold acquired La Mina in 2010.
Scott E Wilson Consulting (SEWC) prepared the technical report of the La Mina project for the company, describing the geology, mineralisation and exploration potential at La Mina. The report was published in 2011.
Reserves at La Mina copper-gold mine
As of July 2012 estimates, inferred resources at La Mina were 1.6 million ounces (moz) of gold averaging at a grade of 0.62g/t Au, and 419 million pounds (mlbs) of copper at an average grade of 0.24% Cu.
La Cantera accounted for 1.009moz of gold grading 0.77g/t Au and 279.8mlbs copper grading 0.31% Cu.
The Middle Zone accounted for 0.594moz of gold grading 0.47g/t Au and 139.4mlbs copper grading 0.71% Cu.
La Mina gold-copper mine development details
The Esperanza copper-gold project, situated in the Sierra Gorda district of Antofagasta, northern Chile, is jointly owned by Antofagasta Minerals (70%) and Marubeni Corporation (30%).
The La Mina resource development project currently consists of exploration at four identified porphyry gold-copper targets, namely La Cantera, Middle Zone, El Limon and La Garrucha. Seven other discrete targets have also been identified, which are yet to be drilled.
Bellhaven continued drilling and exploration at La Cantera from mid 2010. A total of 8,032m of drilling in 25 holes was completed by the end of 2011. The mineral resource of the La Cantera deposit was announced in September of 2011. Mineralisation at La Cantera is not significant, but higher grade copper and gold occurs near the surface.
The Middle Zone is the second porphyry deposit to have advanced to the resource stage. It is located 400m north of La Cantera. A total of 14,159m of drilling through 39 holes was complete at the Middle Zone as of May 2012. Higher grade mineralisation (up to 0.7 g/t Au) occurs within 250m beneath the surface at the Middle Zone.
El Limon and La Garrucha are the other two discoveries yet to be advanced to resource stage. El Limon is located 300m north of the Middle Zone resource. The first hole at El Limon was drilled in April 2011. Six holes were drilled at La Garrucha, which is located 700m east of La Cantera deposit, in late 2011. Four of these holes showed higher grade mineralisation of up to 0.85g/t Au.
Drilling activities were concentrated at El Limon towards the end of 2012. The exploration plan at La Mina for the first half of 2013 involved aggressive drilling at La Garrucha as well as Cristalina, which is a recent discovery located approximately 500m south of La Cantera.