The Pulacayo-Paca is a Joint Venture with Apex Silver of Denver, Colorado (American Stock Exchange symbol:SIL) to develop the Pulacayo Mine, the second-largest silver mine in the history of Bolivia with over 600 million ounces of past production, and the Paca project, a large dacitic dome with open-pit potential.
A Phase II drilling program is planned to outline a NI 43-101 compliant resource estimate and complete a bankable Feasibility Study in 2006.
The History of Pulacayo
The Pulacayo silver mine was discovered in 1883 and since then has produced about 678 million ounces of silver, 200,000 tons of zinc and 200,000 tons of lead, (ref Sergeomin – Bulletin No 30, 2002). It has been the second largest silver mine in Bolivia after Cerro Rico de Potosi and one of the most important in Latin America. Production came mainly from the exceedingly rich and non-outcropping Tajo vein system which was exploited down to a depth of over 1,000 meters. These veins split at shallow depths into a dense zone of veins and veinlets with stockworks and local disseminations, still containing according to Sergeomin in excess of 10 million tonnes grading 2.6% Zn, 1.3% Pb and 96 g/t Ag. In addition, Sergeomin state that silver lead and zinc could be extracted at low cost from the enormous waste dumps and tailings.
Revenue from the mine funded the first railway line to Bolivia, which connected the mine to the port of Antofagasta in Chile in 1888. In 1891 silver production reached 170,097 kgs (5.7 million ounces) and in 1923 the mine was flooded. It was subsequently dewatered in 1927 when Mauricio Hochschild took over the mine. After 1930 production increased considerably again and in 1951 concentrates were exported containing 68,843 kgs silver (2.3 million ounces), 18,652 tons of zinc, 3,191 tons of lead, 1,120 tons of copper and 15 kgs gold (500 ounces). In 1952 the mine was nationalized and exploited by Comibol. It was closed in 1958 when the average content of the ore was 10.5% Zn, 1.5% Pb, 0.9% Cu and 250 g/t Ag.
Pulacayo is an excellent example of a subvolcanic epithermal mineralized system and vertical zoning of mineralization is clearly visible. The mineralization is associated with the southern flank of a dacitic intrusive dome with surface dimensions of about 3x2 kilometers. In addition to the mined veins on the southern flank, there are also major siliceous and alunitic veins developed on the northern flank. Surface sampling of these shows anomalous silver values, but these have yet to be drilled. A second mineralized dacitic dome, the Paca dome outcrops some 4 kilometers to the north of Pulacayo. The mineralization at the Paca dome is associated with siliceous volcanic breccias, where it forms steeply dipping bodies and adjacent volcano-sedimentary units, where it is hosted in near surface shallowly dipping mantos. The main Tajo vein system at Pulacayo and the mineralization associated with the Paca dome were drilled by Apex Silver in the late 1990’s. They obtained interesting mineralized intercepts as described below:
Apogee Minerals have signed a joint venture agreement with Apex Silver over the Pulacayo-Paca project and plan to carry out exploration with the objectives of defining reserves at both Pulacayo and Paca, based on the mineralized intercepts obtained by Apex Silver. This will require infill drilling and modeling of these mineralized zones, metallurgical testing, etc. In addition, other mineralized targets associated with the two dacitic domes will be explored, in particular the undrilled system of siliceous and alunitic veining with which is associated anomalous silver content on the northern flank of the Pulacayo dome.
References:
Apex Silver Corporation, March 2003 report.
At Pulacayo Apex silver identified 5 objectives which were investigated with diamond drill holes. Of these 3 are different zones of the Tajo Vein, one on Vein 4 and the last on a silicified zone located north of the veins. They drilled 14 holes totaling 3,130 meters. They intercepted interesting grade mineralization in 2 blocks in the Tajo Vein, hosted in andesites.
Apex did metallurgical testing from samples of block B which showed flotation can produce concentrates of zinc with 3.30 kg/t Ag and concentrates of lead with 10.9 kg/t Ag.
In the Paca area they identified 4 drill targets and drilled 18 diamond holes totaling 3,448 meters and 5 R.C. holes totaling 896 meters. This defined 2 mineralised bodies, being a sub-vertical mineralized volcanic breccia which is open along strike and a near surface, shallowly dipping (manto) body following volcanic lithology. These bodies probably connect and are part of the same mineralized system. Both of these bodies need more drilling to prove up reserves and resources.
Apex did metallurgical testing of Paca mineralization, including leach testing and flotation. The initial leach testing gave extractions of about 60% and flotation gave recoveries of 39.9% in sediments and 80.2% in the intrusive.
Sergiomin; Boletin del Servicio Nacional de Geologia y Mineria. No 30, Ano 2002.
“The mushroom shaped complex of Pulacayo by far the most extensive (about 3x2 km) and enrichment of metals (precious and base), suffered a strong fracturing and hydrothermal alteration (especially in the margins of the apical veins) of siliceous, phyllic, argillic, peripheral propylitic and advanced argillic in the upper levels, particularly penetrative in sector S where the Pulacayo mineralization is found. Here a transversal set (W-E to WNW-ESE) and important vein system of more than 1,000 meters of vertical development controlled by regional tensional fractures, and which develops towards the surface into a system of dense zone of veins and veinlets with stockworks and local disseminations. The reserves of these still exceed 10 million tonnes with 2.6% Zn, 1.3% Pb, and 96g/t Ag, based on previous workings which were quickly abandoned due to the development at depth of much better and exceptionally rich blind polymetallic veins (cf. “bonanzas” of the famous Tajo vein). These have yielded approximately 20,000 t Ag, 200,000 t Zn and 200,000 t Pb p up until the present (according to Mignon 1989). This major silver vein system is the second largest in Bolivia after Cerro Rico de Potosi and one of the most important in Latin America. Also, an additional quantity of Ag, Au, Zn, Pb could be extracted at low cost from the enormous waste dumps and tailings accumulated during the period of exploitation.”
Ministerio de Minas Y Petroleo; Los Yacimientos Minerales Y de Hydrocarburos de Bolivia; Dr Federico Ahlfeld and Dr Alejandro Schneider-Scherbina; Special Bulletin No 5, 1964.
“The ancient and famous mineralised system, known also with the name Huanchaca (where the mineralisation was previously treated) was one of the greatest producers of silver in South America”
“Beneath the level of the San Leon tunnel, recently was opened the Tajo vein, one of the largest and richest in Bolivia, hosted in pyritised and silicified red shales. Contrary to the veins hosted in dacite, this vein dips to the north. Its length is 2,700 meters and average thickness is 1.10 meters, with local thickenings up to 6 meters.”
“In level 698 meters there are three large ore shoots with commercial mineralization and with a plunge of 30-45 degrees to the west. At this level the average grade of mineralization exploited is 14% Zn, 2% Pb, 0.5% Cu 0.1% Ag and indications of Au and Bi.
Pulacayo constitutes an excellent example of a subvolcanic epithermal mineralized system. As explained, the vertical zoning of mineralization is clearly visible.”
“In 1833 the miner Mariano Ramirez discovered poor outcrops. The history of the mine in the following years is related to Mr Aniceto Arce, later the President of Bolivia, who in 1856 formed the Company Huanchaca. At first they worked with little success. Then the mine first flourished with the formation of a new company Co Huanchaca de Bolivia) in 1873 with French capital. Between 1877 and 1892 US$46 million dollars value of silver was exploited. In 1877 the San Leon tunnel was completed and in 1888 the mine was connected to the port of Antofagasta by rail, the first rail line in Bolivia. In 1891 silver production reached 170097 kgs. In the following years the mine was flooded with hot water and gases on various occasions, the last time being 1923. A new stage of success started in 1927, the year in which Mauricio Hochschild took the mine and dewatered it.
After 1930 production was increased considerably because of treatment of the enormous dumps and tailings. Sphalerite was recovered by differential flotation (with 55% Zn) and a complex concentrate of Ag, Pb, Cu and Au was produced. In 1951 they exported concentrates with a content of 68843 kgs of Ag, 18652 tons of Zn, 3191 tons of Pb, 1120 tons of Cu and 15 kgs Au.
In 1952 the mine was nationalized and exploited by Comibol. In the following years the Ag content diminished considerably. In 1956 the average content of the ore was 10.5% Zn, 1.5% Pb, 0.9% Cu, and 0,025% Ag. The mine was closed in 1958.”