Summary:
PGDM (Pilar de Goiás Desenvolvimento Mineral) consists of four mines, 3 underground mines: Pilar, Maria Lázara & Caiamar, 1 open pit development project: Três Buracos.
Underground - Pilar
Pilar mineralization is an orogenic gold system type, in metasedimentary rocks of Pilar Greenstone Belt. Mining in Pilar is concentrated in two mineralized zones:
- HG1: Fault and fill veins with hydrothermal halo in chlorite and graphite schists. Thickness between 0.8m and 1.5m;
HG2: Hydrothermal altered chlorite schists with quartz veining. Thickness between 0.5m and 30m, average of 10m.
HG1 and HG2 mineralisations are set in a very continuous context, covering an area with a strike length of 3.3km, a width of 2.6km. Mineralization system is opened to SE and down-dip.
Underground - Maria Lazara
Pilar mineralization is an orogenic gold system type, in metasedimentary rocks of Pilar Greenstone Belt. Mining in Pilar is concentrated in two mineralized zones:
- HG1: Fault and fill veins with hydrothermal halo in chlorite and graphite schists. Thickness between 0.8m and 1.5m;
- HG2: Hydrothermal altered chlorite schists with quartz veining. Thickness between 0.5m and 30m, average of 10m.
HG1 and HG2 mineralisations are set in a very continuous context, covering an area with a strike length of 3.3km, a width of 2.6km. Mineralization system is opened to SE and down-dip.
Underground - Caiamar
Gold mineralization at Caiamar occurs in four parallel zones and in a set of small ore shoot-like structures related to a transpressional shear zone. Diamond drilling has outlined zones of steeply plunging gold mineralization within an area with a strike length of approximately 1.4 km, a vertical extent measuring 600m, and thicknesses ranging from one metre to 20m.
Open Pit - Tres Buracos (under development)
Tres Buracos open-pit deposit comprises the Pilar HG2 mine structure outcropping. Gold is mineralized over a strike length of approximately 1.7km, a width of 1.0km, and a thickness of between 25m and 60m.
Gold mineralization at the Pilar and Guarinos Greenstone Belts is typical of orogenic gold deposition. The mineralization is related to, and controlled by, major faults and shear zones. At the Pilar mine, these structures are mainly low angle thrust faults and at Guarinos, they are mainly high angle transpressional structures and boudins, both probably related to the final stages of Archean-Paleoproterozoic deformation.
Strong silicification and sulphidation are the main forms of hydrothermal alteration. Host rocks and most carbonaceous meta-sedimentary rocks are well silicified and contain shear-related quartz veins. Arsenopyrite is the main sulphide related to the gold mineralization, while pyrite, and minor chalcopyrite, and pyrrhotite are also present. Gold is present both as free grains in clusters related to quartz veining, and in association with arsenopyrite and other sulphides.
Mineralization at the Pilar mine is located in three main zones:
• HG1 (Basal zone): the most continuous and important style of mineralization in the deposit. The Bazal zone is controlled by carbonaceous schists and intercalated chlorite schists. It is hosted on the basal contact of the chlorite schist with the graphite schist.
• HG2 (Upper zone): an important zone with similar volume to HG1 but with lower grades. The zone is essentially controlled by quartz veins inside the chlorite schists. It is located in the hangingwall portion of the main thrust fault.
• HG3 (Upper zone): the smallest and most discontinuous zone at the Pilar deposit, with location and average grades similar to HG2.
The upper zone is continuous along the Pilar – Três Buracos trend, with a width of up to 60 m. This zone is characterized by the presence of thin quartz veins and associated sulphides, mostly pyrite.
The basal zone is characterized by strong silicification and sulphidation. Arsenopyrite, the main sulphide, commonly constitutes up to 5% of the rock. The basal zone averages 10 m wide and is continuous along the main trend. The highest grades are closely associated with high sulphide (arsenopyrite) and quartz content and are associated with structurally controlled mineralized shoots distributed along the trend.
Mineralization at Maria Lázara is hosted by silicified biotite-chlorite-sericite schists and with quartz veins concordant with the main foliation. These schists show an average thickness of 2.0 m in diamond drill holes and mine openings. The mineral assembly contains sericite, chlorite, biotite, tourmaline, albite, quartz, and sulfides, mainly arsenopyrite with minor pyrite, pyrrhotite, sphalerite, galena, and chalcopyrite. The schists exhibit a porphyroblastic texture, containing porphyroblasts of garnet and occasionally magnetite. Native gold occurs associated with arsenopyrite and quartz or quartz-albite veins.
Diamond drilling has outlined an area of gold mineralization with a strike length of 3.6 km, a width of 720 m, and a thickness ranging from less than one metre to ten metres.
Gold mineralization at the Caiamar mine occurs in four parallel zones and in a set of small shoot-like structures related to a transpressional shear zone. They are described as follows:
• Zone A0: small zones of discontinuous mineralization not related to hydrothermal alteration, hosted by quartz-biotite-graphite schist.
• Zone A1: the most important and continuous zone in the deposit. The zone is hosted in a hydrothermally altered meta-greywacke and the mineralization is associated with quartz-albite-arsenopyrite veinlets. Contains small, scattered higher-grade zones associated with porphyritic intrusions.
• Zone A2: similar setting and slightly less tonnage than zone A1. It is separated from A1 by an amphibolitic metasediment. Contains small, scattered higher-grade zones associated with porphyritic intrusions.
• Zone A3: small, scattered patches of mineralization in a similar environment to A1 and A2.
Diamond drilling has outlined zones of steeply plunging gold mineralization within an area with a strike length of approximately 1.4 km, a vertical extent measuring 600 m, and thicknesses ranging from one metre to 20 m.