Tucano Gold Project - Amapá
The Tucano site is located in Amapá State in northern Brazil, covering approximately 2,500 km 2 of mostly contiguous exploration licences and a mining concession. The nearest major populated centre to the Tucano site is Macapá, situated on the northern bank of the Amazon River (Figure 1).
Road access to the site is via 100 km of paved road from Macapá to Porto Grande followed by 116 km of unpaved road. The site is just north of the equator, with annual rainfall averaging 2,370 mm. The Tucano Mine site is currently powered by a 13.8 KVa substation sourced from the Caoraci Nunes hydroelectric power station in Porto Grande.
Figure 1. Location plan of Tucano Gold Project
History of the Project
Gold mineralisation was discovered at Tucano in 1994 by Anglo American who completed intensive exploration from 1995 to 2002. A feasibility study by AngloGold on the oxide resources was completed in October 2002. The property was acquired by EBX Gold Ltd ( EBX) in May 2003. EBX carried out a feasibility study based on the AngloGold feasibility study for the oxide mineral resources and produced a pre-feasibility study for the mining of the sulphide mineral resources. The property was acquired by Wheaton River Minerals Ltd. (which later merged with Goldcorp Inc.) in January 2004. The Operational License for the Tucano mining concession was issued on 25 February 2005. On 15 February 2007, Peak Gold Ltd (which later merged with New Gold) entered into an agreement with Goldcorp Inc. ( Goldcorp) to acquire the Tucano mine. The company completed the acquisition on April 3, 2007. Mine construction was initiated in July of 2004 and gold production commenced in late 2005. The Tucano Mine was operated as an open-pit and heap leach operation by MPBA until 2 January 2009, when surface mining operations were suspended and the mine was placed on a care and maintenance basis. Particularly instrumental in the decision to cease operations at the end of 2008 was the increasing occurrence of transition material in the pits and the inability to process this material economically under the current processing set-up. The transition material is mineralisation at the bottom of the strongly oxidized boundary that has not been weathered as much as the upper saprolite. It is much harder and thus requires drilling and blasting and additional primary crushing. It is also less amenable to heap leaching.
Exploitation of the oxide mineral reserves to the cessation of mining operations at the end of 2008 was by conventional open-pit mining and heap leaching of agglomerated crushed ore. Operations carried out in 2008 were in the Taperebá AB, Taperebá C and Urucum pits.
Mining from two small pits at Taperebá D was completed in 2006. To the end of 2008, total life-of-mine production was in excess of 8.8 million tonnes of ore mined with production of approximately 292,000 ounces of gold.
Figure 2. Plan showing location of Tucano gold deposits and interpreted geology
Geology
The Tucano Mine area is located within the Guyana Craton in what has been described as the Maroni-Itacaiunas Mobile Belt, a tectonic unit running from Venezuela through the Guyanas and into Amapá and Para States. The western part of the area is underlain by basement gneiss and the balance is underlain by ortho-amphibolite and meta-sedimentary rocks of the Vila Nova Group. These units are intruded by granitic pegmatites, diabase dykes and gabbro.
Gold mineralisation is associated with iron and carbonate-rich units of the chemical sedimentary unit known as the William Formation, within the Vila Nova Group. This unit comprises of a basal calc-magnesian domain of carbonate schist and calcsilicates, and an iron domain of banded iron formations ( BIF). The locus for the mineralisation on the property comprising the Tucano mine site is a north-south shear zone exhibiting intense hydrothermal alteration, particularly silicification and sulphidation, bearing auriferous pyrrhotite and pyrite. The alteration is most intense in BIF, followed by amphibolite, carbonate schist and calc-silicate rocks.
The mineralisation occurs in a series of deposits over a 7 km strike length of the shear zone (Figure 2).
The Urucum deposit (Figure 3) is in the northern part of the zone and Taperebá is in the southern part. Higher grades are associated with the more intensely hydrothermally altered rocks. Deep tropical weathering and oxidation has produced near-surface saprolitic mineral deposits overlying the primary sulphide mineralisation. The primary mineralisation consists of a series of sulphide-bearing lenses which strike north and north-northwest, and dip 60 to 80 o east except for the western zone in Taperebá AB1 pit which dips shallowly 45° west. Individual lenses achieve a thickness of between 5 and 25 metres. Sulphide content ranges from 5% to 10% and is mostly pyrrhotite and pyrite. Chalcopyrite, sphalerite, galena, arsenopyrite and marcasite occur in lesser amounts. Sulphides are found also as disseminations and fracture fillings on the margins of the mineralised bodies. Gold occurs as free gold, not tied into the crystal lattice of the sulphide minerals (and, is therefore more easily liberated during processing). Intense tropical weathering, reaching down 100 to 130 metres, has formed saprolite consisting mainly of iron oxides and hydroxides, clay and silica. These saprolite bodies follow the strike, dip and plunge of the massive sulphides. As well, extensive blankets of gold-bearing colluvium, up to 10 metres thick made up of laterite/saprolite fragments in a ferruginous clay-sand mix, overlie the saprolite. Together, gold-bearing saprolite and colluvium are referred to as "oxide mineralisation".
Gold deposits such as those at Tucano are typically encountered in greenstone belts of meta-sedimentary/volcanic rocks in Archaean-Proterozoic terranes worldwide and, specifically, in the Guyana Shield areas north of Brazil. Locally, some mineralised zones indicate high temperature hydrothermal activity with skarn-type characteristics.
Resources and development potential
Mineral resources for the Tucano project are divided into open pit and underground resources based on detailed scoping level analysis of cost inputs to derive cut off grades. Total resources for the project are 54.6 Mt @ 1.65 g/t gold for 2.9 Moz. This includes open pit resources totalling 26.3 Mt @ 1.45 g/t gold for 1.2 Moz based on optimised pit shells using a US$1,000 gold price from the three main deposits of Urucum, Taperebá AB and Taperebá C (Figure 2). The open pit resources are based on optimised pit shells using a US$1,000 gold price. Metallurgical testwork completed to date indicates free milling oxide and sulphide ore with expected recoveries of between 90 and 95%. A conventional CIL processing facility to liberate the gold is considered to be the most appropriate extraction technique.
Figure 3. Urucum Long Section with optimised pit shell and drill hole pierce points.
Figure 4. Tapereba AB Long Section with optimised pit shell and drill hole pierce points.
Exploration Potential
The Tucano project covers approximately 2,500 km 2 of highly prospective and sparsely explored greenstone terrain. In the near mine area significant exploration potential exists along the 7 km strike of the three deposits of Urucum, Tapereba AB and Tapereba C in the gap between the deposits where only limited drilling is present. Significant exploration upside also exists in the deeper untested plunges of the main ore bodies. Several other targets have been identified in the near mine area within trucking distance of the plant including the Duckhead prospect where diamond drill intersections including 23.1 m @ 93.1 g/t gold from 80.9 m and 5.85 m @ 100.3 g/t from 130 m have been obtained.
Figure 5. Tucano project location map
Regionally there are numerous geochemical and geophysical targets that remain sparsely explored and very little drilling has been completed outside of the Tucano near mine area. Of particular note is the Sucuriju prospect located 35 km to the northwest where a 9 km long north striking surface geochemical anomaly of comparable size to the Tucano Mine footprint is at a very early stage of exploration (Figure 5). Extensive Garimpeiro alluvial workings indicate significant gold enrichment in this area. A large coincident resistivity and chargeability anomaly has been generated by an Induced Polarisation ( IP) survey over the southern portion of the Suricuju prospect in an area covered by duricrust laterite on a topographic high.
Considerable exploration potential also exists within the tenement package for extensions of the iron ore mineralisation with extensive occurrences of the same Banded Iron Formation ( BIF) unit which hosts the active iron ore mining area operated by Anglo American.
Infrastructure
The Tucano project has significant infrastructure in place associated with the open pit and heap leach operation which was placed on care and maintenance in January 2009. All three deposits have established mining and haul road access including a fully operational and well maintained mining fleet with a capacity to mine 3 million tonnes of ore and 12 million tonnes of waste per year. Existing infrastructure also includes grid power, airstrip, accommodation village, workshops and a gold extraction circuit that will be incorporated into the new plant design.
Royalty
The Tucano project contains significant deposits of Hematite Iron Ore hosted in an extensive Banded Iron Formation that occurs throughout the greenstone belt. Anglo American plc and Cliffs Natural Resources Inc commenced an open pit mining operation and beneficiation plant in December 2007 and is ramping up to a projected 6.5 Mtpa of pellet and sinter feed production (from 2009 estimated levels of 3.0Mtpa) which is anticipated to occur between 2011 and 2012. The mining concession that makes up the Amapá Iron Ore Project is located immediately southeast of the Tucano gold deposits and is hosted in the same Banded Iron Formation (Figure 2). A 1% gross iron ore revenue royalty (net of 2% federal tax) over the Amapá Iron Ore Project mining concession is currently in place.