This report describes the results of the geological assessment activities of Brexia Resources’ El Bagre project,located in rural area of themunicipality of the same name, in Antioquia. This project sought to define the potential for the occurrence of a major Au deposit in the sector veins through a series of geological exploration activities and analysis of the information collected. The results of these activities are described in the relevant chapters.
2. Project description and location
The project is located in an area belonging to the municipality of El Bagre, Department of Antioquia, Republic of Colombia, about 200 km to the NE of the city of Medellin, departmental capital (See Figure 1). The project is 28 km from the NE of the municipal head of El Bagre, on land belonging to the greens of La Arenosa, Santa Bárbara, Santa Barbarita and Rio Viejo.
The project comprises a mining title, HHQK-01, from 1746 Ha, whose coordinates are shown in Table 1..
Table 1. Coordinates of the polygon vertices of the mining title HHQK-01
|Point||X (East)||Y (North)|
Figure 1. Location of the project.
3. Accessibility, climate, local resources, infrastructure and physiography
Access to the project is made from the municipality of El Bagre, which is reached by air on daily flights operated by a local airline from Medellin (flight time 1 hour), or by land from the same departmental capital, by the paved road leading to the Atlantic Coast; in Caucasia the detour is taken uncovered (two hours) to El Bagre.
From El Bagre you must go by river to the hamlet of Rio Viejo (50 minutes), and from there you take a horseshoe path (1.5 hours in beast) up to 2 kms before the hamlet of El Tupe, where Brexia Resources has a temporary camp.
Figure 2. Project location detail, with mining title polygon. Taken from IGAC Plates 83 and 94, scale 1:100,000 escala 1:100.000
3.2. Climate and vegetation
The climate of the area is warm-tropical, with an average temperature of 37oC, high relative humidity and altitudes between 50 to 150 meters above sea level. The following types of plant cover are presented:
- Natural forest intervened: the main extractive activity is generated in the logging of timber species, which allows the forest to preserve its functional characteristics, predominantly primary species.
- Secondary natural forest: It is the result of intensive logging and burning processes for agricultural and livestock purposes. It constitutes advanced sucessional states in which the tree component prevails over the herbaceous.
- Rastrojos: This type of coverage arises with posterity to the establishment of crops and paddocks once they have been abandoned.
- Pastures: They are located as tufts mixing with areas of intervened and secondary natural forest. They are basically dedicated to livestock activity.
- Miscellaneous: Areas resulting from the farm such as banana crops, maize, beans, cassava and a declining trend of illicit crops.
Illegal mineral activity is common in the region, resulting in uncontrolled intervention of forests and paddocks, as well as affected streams of water.
Figure 3. Illegal exploitation in La Arenosa sector
Figure 4. Landscape in El Tupe. In the foreground, remnants of illegal exploitation, in the background you can see vegetation of paddocks, stubble and natural forest.
The fauna and flora of the region is very diverse, with vegetation divided into primary natural forests, man-made natural forests, stubble, pastures for livestock and miscellaneous for agriculture (cassava, banana and fruit trees). According to IGAC’s «Land Classification Map byAbilitytoUse», the following areas in the area are distinguished (the following text was taken from the Geomines report,2011):
- Zone 4hs-2: as limiters of use there are short floods, high water table, imperfect drainage, strong acidity and low fertility; as a recommendation of use is presented Livestock and agriculture with crops tolerant to excess moisture. It is locally associated with areas of alluvial specially reworked towards the floodplains of the El Tupe and La Arenosa rava.
- Zone 4ps-2: Strongly inclined earrings, moderate susceptibility to erosion and mass movements, strong acidity, high saturation of aluminum, low fertility; local light erosion and occasionally surface stoniness; can be associated with surfaces located on the metamorphic rocks present towards the WNW of the mining title. It is recommended to adopt Agriculture activities with specific crops of semi-forest or dense, livestock in improved pastures and livestock.
- Zone 4s-2: moderately inclined slopes, moderate susceptibility to erosion and mass movements, light erosion, surface stonyness, strong acidity, high saturation of aluminum and low fertility are observed; it can be locally correlated with some sectors associated with the lithology of the Batolith of Segovia. The adoption of Agriculture with specific crops of semi-forest or dense livestock in improved pastures is presented as recommendations.
- Zone 7p-5: Moderately steep slopes can be observed towards the high and middle parts of the mountainous foothills present in the sector; moderate and light erosion; high susceptibility to erosion and mass movements (cow’s foot); excess moisture in some sectors; strong acidity, high aluminum content and low fertility; for these characteristics should be implemented (according to IGAC) arborization activities with producing protective forests, wildlife and water conservation, and fauna and flora.
Figure 5. Landscape and land use in the project. Upstairs, left: I’m on my way to El Tupe. Upstairs, der: Rio Viejo. Below, left: stubble on the way to the project. Below, der: plain without intervention in La Arenosa.
3.3. Local Resources and Infrastructure
The municipality of El Bagre comprises an area of 1563 km2,the town has the basic services (water and light), health care centers, educational centers, supermarkets, hotels and airport (El Tomín) with a daily flight from the city of Medellin. Mobile phone coverage is available in the town centre and in some areas of the city.
Figure 6. Left: panoramas of El Bagre. Right, up: horseshoe path to the project; right, down: Camp El Tupe.
The project is entered by river upstream of the Nechí River, which in winter times becomes flowing; later by a wide horseshoe path built by backhoes working alluvial mining in the area starting from Rio Viejo farmhouse, where the company has a camping area. The Brexia Resources camp in El Tupe has basic water and light service through a gasoline power generation plant. The camp facilities have basic amenities.
The project is located on the eastern flank of the Cordillera Central. The study area is regionally correlated with the so-called «El Bagre-Nechi Erosion Surface» consisting of an anthropic erosion surface (artisanal mining) and river.
Figure 7. Panoramas of the physiography of the project area. Above: view of the camp area. Below: view of the Nechí River, on the way to the camp.
Topographically the area is flat to wavy with hills of gentle, elongated slopes and rounded peaks. High slope slopes and deep drains are presented near the foothills of the San Lucas mountain. The mountainous areas are characterized by high slope slopes and deep and well-defined drainage; with a strong local slope dynamics represented by mass removal, carcavation, retation and concentrated surface erosion, which locally produces coluvial and mixed deposits towards the lower slopes towards contact with alluvial quaternary deposits (Geomines, 2011). On plutonic rocks is generated saprolith and residual soils, on which geoforms are generated as hills of medium to long slopes with strong to moderate slopes, and rounded top.
The project was originally initially focused for potential barrage exploitation. Although it was known that the alluvial within the mining title had been exploited informally for an indeterminate time, it was hoped that the flood without intervening and, even the re-worked,trabajadowould still have importantresources economically from Au. With such an approach it was offered by the project owners to Tribeca,which hired consulting firm Snowden to evaluate the project. Snowden reported in a sample taken in a reworked barrage a concentration of 2 gr/ton, and recommended, based on these values, to acquire the project. Exploration activities initially focused on determining the potential of the remaining floods did not confirm the values reported by Snowden, so the report was revalued, finding that there was an error on their part in calculating the concentration of the floods, closer to values of 0.2 g/m3..
Subsequent activities sought to determine Au’s potential in veta in the project. Several samples were carried out in 2011 and 2012, led by Brexia Resources directly or through third parties (companies such as Drilling and Topograhy and Geominas). No formal holdings of any kind directed by Brexia Resources have been carried out. Informal mining activity has been detected in the work area, not authorized by the company.
5. Geological Framework
5.1. Regional Geology
The mining title is located on the eastern flank of the Central mountain range. In this sector two geological domains limited by the Otú Fault, known as Tahamí and Chibcha lands (Restrepo and Toussaint, 1988), are recognized, as shown in Figure 9..
The Tahamí terrain, west of the Otú fault, consists of quartz-feldsparic and alumonic neises, and green and moscovitical schist, grouped as Cajamarca Complex (Maya and González, 1995). The radiometric ages in zirconia indicate a orogenic event during the Late Triassic, in the case of neis de Nechí a metamorphism on tax 236.6 + 4.4 Ma (Restrepo et al, 2011)
Figure 9. Regional geological map (taken from Geomines, 2011).
The Chibcha terrain, to the east of the Otú Fault, consists of quartz-feldsopathic gneises, amphibolites and precambrian marbles, grouped in the unit known as Gneis de San Lucas (Clavijo et al, 1995). The age of metamorphism is considered proterozoic compared to the Neises and Amphibolites of Tierradenth date back to 1360 + 270 M.a (Gonzales, 2001)
These rocks are intruded by the so-called Batolith of Segovia, of Jurassic age, an elongated body in the north-south direction, consisting of diorites, with wide textural and compositional variations to diorites, gabros and granodiorites. Rocks belonging to such a unit generally have a high degree of meteorization. It commonly has basic diques and silyses intruding the Batolith. Locally there are shear areas with predominant management milonitization N-S (Londoño et al, 2009). The age of this body is 170 + M.a. (Feininger et al,1972 in Gonzales 2001)
The Tarazá Formation and Caucasian Formation are made up of low-consolidated sandstones and conglomerates of the Neogen, as well as recent floods also exist in the area.
At the regional level, the most important structural features are the Fallas de Otú and El Bagre.
The text of this chapter was taken from the report made for Brexia Resources by Geominas (2011).
Lithologically the study area consists of a metamorphic sequence with intercalation ofquartz-sericitic and quartzite shale associated with rocks of the Cajamarca Complex, arranged mainly towards the NW area of the HHQK-01 title, in contact with plutonic rocks type granodiorites related to the Batolith of Segovia located in zones E, NE and South of the title. Although a mainly failed contact between these lithodemas (Falla El Bagre) has been suggested in the study area, these units have irregular intrusive contact, but with a general N-S tendency, with the presence of contact halo represented by rocks with recrystallization, epidotization, caolinitization and pyritization such as «alterations by zone» and»cornubianitization»ofthese from the batolith, generally preserving the internal structure (foliation) of the metamorphic rock object of thermal metamorphism.
There are also quaternary materials of variable extent and thickness coverage consisting of torrential-trend alluvials, mixed deposits and some small slope deposits located on the slopes of mountainous geoforms. On quaternary deposits, especially alluvial deposits present towards the margins of larger drains, advanced artisanal mining has been present. These units are described below and their distribution can be seen in the Geological Plan.
They are distributed to the W zone of the study area, especially encompassing a large front to the NW vertex of the title. They are rocks of fine grain and medium to dark greenish gray, with marked foliation, very resistant, locally recrystallized by overimposed thermal metamorphism processes, and with alterations associated with intermediate argilic zone such as epidotization, silicification and pyritization. Among its main minerals are quartz, plagioclase and sericite-Moscovite. Its texture varies from fine foliation to banded and massive, with local crenulation. The foliation has a general orientation between N30-60E with buzations between 35o and 85o to the SE, although it has local variations indicating the existence of minor folds within the sequence. Locally there are lenses consistent with foliation, and milky quartz diche to translucent grey, usually oblique to this, with local insulated sulphides in both the fitted structure and the backrests; the latter usually present centimeter quartzic veneers parallel to the dam (Photographs 33 to 38); also subordinately present andesitic-dacitic dichesembedded within the cornubianitized rock resulting from a possible late phase of mineralization with remaining batolith fluids, these manifest superficially as massive tabular structures. On cornubianas it is possible to appreciate collation of massive and foliated rocks of the same composition, possibly the product of thermal involvement of cuarcitas-squistos collation, for this case usually occurs in the areas of epidotization and pyritization (10-15%) compared to the batolyte increased concentration of sulphites scattered in the mass sections.
In some sectors centimeter zones were identified to very few meters of graphite black shale within this unit, which appear to correspond to areas of intense shear within a possible mylonitic zone,theoretically they could correspond to amphibolic lenses within the metamorphic sequence with an overimposed dynamic metamorphism.
On the other hand, small manifestations of marbles (usually not mapped to the work scale) were determined, which were «uncovered» when performing old mining work with retro on the El Tupe ravine.
They are associated with the so-called Batolith of Segovia (Photographs 39 to 45), with a main composition of Qzo+Plag/Feld (NaNa mainly)+biotita/moscovita (according to its composition)+-Amphiboles; present local milonitization. On this litodema is given rise to residual soils and highly oxidized thick saprolites. saprolitos Outcrops occur with moderate to high diclassation
For this rock has been observed both regionally and locally, which presents itself as»fit»of the veins of greatest economic interest within the mining district; in the area the mouth of «Don Honorio», «Alberto» and «La Arenosa» share this same behavior.
The presence of recent catchment deposits covering some sectors of the slopes of the sector is common; the presence of slope deposits with surface blocks on high gradient slopes is also common. Its thickness and composition is variable, and in close proximity to alluvial deposits it conforms to these mixed deposits where delimitation is difficult and unreliable; in addition, anthropic intervention generates geomorphological alteration of these materials.
On the study area, alluvial deposits of torrential affinity represented by 2 or three conglomeric sedimentation pulses prevail, interspersed with levels of sands and alms of average thickness of 1-3 mts.,given from a suspension sedimentation (the burdeny levels have an average thickness of 2 mts.);it can be cited thataccording to the informal mining activities developed on the area, oral references of settlers and miners of the sector, and cateos carried out on the front of alluvial exploration (barequeo) it was observed that the highest concentration level of Au libre is presented in the suprayacent alluvial in erosive discord to the base, which corresponds mostly in the area covered by alluvial to granodiorite rock to meteorized diorite and residual soils from this rock. Also observed locally are the presence of paleosuelos, logs and organic matter moistified between the different sedimentation pulses especially towards the ceiling of fine materials.
The level of interest has a matrix clastos ratio: 60-40% to 70-30%, and is made up of light grey to yellowish brown sandy material, with concentrated local oxidation, hard consistency and high humidity, often defining the water table of the spine. The lithics correspond to rocks of hypoabisal (aphaitic) and plutonic affinity mainly, angular to sub-covered low sphericity, with average diameters of 10 cm. The presence of primary sedimentation structures is diffuse by prevailinga chaotic arrangement of the lithic within the matrix(Qft)at slight inverse gradation, with sporadic planar beds and incipient to marked imbrication; with regard to the latter point, it should be noted that a statistical study of paleocurrents could be of vital importance to know approximately the trajectory of the paleochannel that deposited the alluvial with the highest gold content, providing future exploration routes for the unworked alluvials (very few in the sector).
Restrictedly, in an area of very little extension are possible levels of old terrace, which could well suggest mounds of anthropic intervention of removed materials; in much of the area of alluvial nature you can see topographic depressions associated and analogous to «open pits» flooded,productof the abandonment of localized ore extraction.
The main type of deposit of the project consists of quartz veins related to a mesothermal type environment,with mineralization temperatures between 200oC-300oC and depths less than 2 km structurally controlled. The main target of the project are quartz veins embedded in diooritic rock – granodiorítica. Quartz is massive in type and usually with oxidation (sulfide remnant), with spot and heterogeneous occurrence of sulfides in which Free Au is generally not visible. The spatial continuity of the veins is limited: field observations point to a noticeable irregularity in the thickness (maximum 0.8 m), shape, arrangement and continuity in course (side) and in buzation (depth) of the veins, presenting»puncture»and loss of the vein. It is common in the many illegal veta farms in the sector that operations are abandoned because in depth both the tenor and thickness of the vein are diminished. These characteristics make it very difficult to define the potential of veins.
For reference: at the regional level the La Yé Mine (about 30 kms to the S of the project) is the most important mining operation near the area. There is being exploited a vein of milky quartz one to 4 meters thick and direction 330-350/SW with mineralization of sulphides and free gold and / or associated with them. The normally observed content in quartz veins is 3% metallic minerals, mainly pyrite (70%) in addition to Galena, Esfalerita and calcopyrite. Although generally speaking the type of mineralization is similar, similar thicknesses have not been observed within the project. In this mine the mining programme is strongly affected by irregularity in veins.
Regionally the work area is located within the vetoform manifestations of the Bagre-Nechí Mining district, limited in its southern part by the Segovia-Remedios Mining District, with decades of gold production and currently one of the most productive gold areas in Colombia. Towards the NE of the study area is the south bolivar region, with the Santa Rosa and San Martin de Loba mining districts, which currently include prospective geological zones for gold deposits. Some general aspects can be compared between the project area and the districts mentioned:
Geology: the study area has a close relationship with The Segovia-Remedios deposits. Both districts are divided litostructurally by the Otú-Pericosfault: Eastern Block and Western Block. The eastern block is formed by a metamorphic sequence intruded by the batolith of Segovia, composed of diorites-granodiorites with some manifestations of basic aphyanitic- porphyritic diques. The western block is basically associated with the Cajamarca complex, consisting of Gneis, marbles and amphibolites. Pleasure deposits related to recent floods are presented in the two blocks. The South of Bolivar presents a metamorphic base in discordant contact with volcanosediments -sedimentary of Jurassic-Cretaceous age, with some Jurassic igneous intrusions of the Batolith of volcano Norosi (granodioritas-dioritas), strategically and lithologically associated with the Batolith of Segovia.
Rock box: theJurassic-age Jurassic igneous rocks type granodiorita-diorita constitute the box rock in the areas of Segovia-Remedios and bagre (the Batolith of Segovia), and for the south of Bolívar (Batolito de Norosí). The two lythologies represent the same unit only as with different names. The mineralizations for the three districts are basically of the same composition: quartz-pyrite as the main assembly, in lower percentage calcopyrite, esfalerite and galena. Gold is freely or associated with sulfide-enriched areas. Scheelita is located in the veins of Segovia associated with the areas of contact metamorphism.
Structural geology: A structural relationship with direction N45-65W/30-40E corresponding to the Cogote system in Segovia-Remedios, and the BA-10056, BA-10023 veins of the El Bagre project is presented. It should be noted that each zone has a structural local mineralization system possibly associated with regional guidelines.
The geological characteristics of the district-related project at the regional level are mentioned in Table 2..
|SEGOVIA-REMEDIOS||PROJECT EL BAGRE||SUR DE BOLIVAR (Associated with the san lucas mountain)|
|Mining District||DMSR(Segovia Remedios Mining District||Bagre-Nechi mining district as alluvial deposits with manifestations of vetoform gold.||Santa Rosa Mining DistrictSmer mining district San Martin de Loba|
|Location||Northeast of Antioquia, on the eastern flankof Colombia’s central school, 200 km from the city of Medellin.||28 km to the NE of the municipality of Bagre in the vicinity of the hamlet el Tupe and the Pisingos sector via to Arenal. On the eastern flank of the Cordillera Central.||The mountain range of St. Luke is the northern culmination of the central mountain range. Delimited by the valleys of the Magdalena and Cauca rivers.|
|Geology||The mining district is divided into two lithostructural blocks, limited by the Otú- Pericos fault, the eastern block and the western block, the eastern block consists of Gneis, Marbles, Amphibolites (precapic) intruded by the Batolith of Segovia (Jurasico), while the Western block consists of Gneis quartz feldsopers, Aluminians, and quartzites, marbles and Amphibolites associated with the Cajamarca complex intruded by the Batolito de Santa Isabel and La Culebra. Taken from Restrepo and Toussaint,1988.||The geology of this sector is basically composed of two types of lithologies a metamorphic sequence (quartz-sericitic and quartzite cysts) to the NW of the study area associated with the Cajamarca Complex and plutonic igneous rocks type granodiorites with textural variations related to the Batolith of Segovia, located at E, NE and south of the title. Both litologies are presented in failed contact.||Geologically it is comprised of three units:1. Metamorphic base composed of gneis migmatites, precambrian age.2. Diorites and granodiorites belonging to the Jurassic-age Batolith of Norosi.3. Volcanosedimentary rocks (intermediate lavas, ignimbrites, ashes, lapilli and bombs) in stratigraphic contact with metamorphic rocks.|
|Regional Structures||The structural domain of the area is marked by the Otú-Pericos regional fault system with a synestro-lateral kinematic character with N-S to N10W domain with local variations N30W.||The main structural range corresponds to the Otú-Pericos Fault system with an izquierdo lateral displacement with a domain on the N-S.
Fails The left side kinematic bagre and an N20W course. Falla Nus considers it a course failure in the direction of N10W.
|Several important structural features occur:
· Ne-SW failure affecting metamorphic and volcano-sedimentary rocks.
· Swinging directed by a failure in the direction of N-S
|Mineralization and alteration||Mainly pyrite-quartz, in lower percentage sperite, galena, calcopyrite.||Quartz-pyrite, galena, calcopyrite, au libre||Pirita, galena, calcopyrite, sprig associated with gold. Au libre|
|Mineralization Structures||4 fracturing systems associated with the Otú-Pericos Fault: 1. Silence System: N10-30E, mineralized dams and backrests2. Vertical System: N45W/70E, no dams but strong fracturing3. Cogote System: N45-60W/35-30E, 6 different veins4. Providence System: N70E/50E, veins backed by porphyritic dams||4 main quartz veins for the project area:1. BA-10038 (N70W/38NE) thick between 20 and 50 cm.2. BA-10056 (veta Don Alberto) with an address of N65W/35NE and a thickness of 20 to 60 cm3. BA-10308 (N70E/85SE) set of quartz veins-venillas with thicknesses between 20 and 50 cm.4. BA-10023 (Honorio vein) with an orientation of N45W/25NE and thicknesses of 10 to 80 cm.||Veins are controlled by a pre-existing fault system in two directions: 1. N5-20E, with an extensional NNE.2 domain. N55-70E, with a dislocated NWW structural domain relative to the other system. Subsequently affected by sinestrolateral bearing movements and NW-SE extensional buzations.|
|Rock Box||The rock box for this deposit are the rocks of the Batolith of Segovia (system of veins in the batolith)||The rock box for the Project are the igneous diorite-granodiorite and quartzdiorite rocks associated with the Batolith of Segovia with a system of hydrothermal veins.||Intrusive igneous diorite and granodiorite rocks for phylonian deposits. Mineralization spread in pyroclastic rocks with effusive input|
|Deposit Type||Mesothermal (T-200-C-300oC and at depths less than 2 km) tectonically controlled||Mesotermal (T-200-C-300-C and at depths less than 2 km).||Epithermal (BS) Quartz-adularia-sericite.Mesothermal.|
|Mining History||It is related to mineralizing structures: – Mina Silencio, Sandra K and San Nicolás – Sistema Silencio- Pomarrosa and Cecilia – Vertical system – Cogote and Marmajillo – Sistema Cogote- Mina Providencia- Providencia System||Veta la Ye: direction N20W/52SW with an average thickness of one meter with variations. Veta el Carmen: with an N5E/45SE layout and an average thickness of 1.2 mt.||Artisan mining|
|Mining Companies||Greater Colombia Gold||Brexia Resources License HHQK-01Mineros S.A||Minatura, Grupo de Bullet S.A.S|
Au’s mineralization in the project is related to a system of quartz veins and veins in predominant directions N55-65W/ 35NE, N45W/25NE, with thicknesses between 0.2 to 0.8 mt for veins and <5 mm for venillas, fitted into the Batolith of Segovia (granodiorites and diorites (Qz+Pl+An+Bt)). The mineralization is of sulphide (pyrite, calcopyrite, galena) with some traces of gold little visible in hand sample, presenting a pyrite-quartz mineralogical assembly. Areas with enrichment in amorphous patches of sulfides and also totally sterile areas can be seen in quartz veins. In some segments of the rock box is exhibited sulfide spread <1% as well as millimeter pyrite venes < 5mm polydirectional accompanied by oxides, but generally the box rock does not present mineralization, being very limited the alteration of it. Locally pyrite spread in traces was observed, but this is not common or results in important precious metal or base content.
Areas with chlorrhythization – silicification – epidotization alterations occur mainly in the backrests (top-bottom) of mineralized fractures or weakness planes. Swarm-like structures by leaching of sulfides occurs in the most superficial parts of veins.
No Au mineralization associated with metamorphic rocks was found. Locally the occurrence of veins embedded in rocks of this type was reported, but this was not confirmed. Small-scale pleasure deposits are also found within the project.
Brexia Resources has run several regional and detailed mapping and sampling campaigns since 2010. An initial reconnaissance campaign, with general mapping, photo-return and site-specific sampling, was conducted by Brexia Resources through local company Drilling & Topography.. This company took 15 surface samples within the project, corresponding to vein chip, rock chip, concentrate and a rolled block. Results of 13 of these samples (no analysis of two of these) indicate Au content from <1 to 19 g/ton in on-site samples, and 48 g/ton in the rolling sample. Unfortunately, the review of the information found no reliability in the geographical location of the samples or in the sampling methodology, so this data is not included in the analysis.
A subsequent campaign run by Geominas in 2011 focused on determining the potential of veins and floods. Sampling was carried out in both outcrops and apiks (for alluvials and saprolitized or fresh rock below them), and samples were also taken in retracted and concentrated alluvial alluvials in situ, to determine potential (see Table 3).
For 2012 a drilling program was carried out that included the sampling selected: all intervals of the first well and selected intervals of the next six were sampled.
To identify veins with spatial continuity, deeply projected surface planes were generated from the heading and buzzling of each point at which a field vein had been identified. The available detailed information generated by the company T&D was used for surveying. Each plane was generated its surface trace, which was taken as a basis for spatially checking the continuity of the structures in the field.
This information was compared with other identified traits, such as differences in slopes in the area and guidelines observed in satellite images. The idea was to compare the surface trace of the projected veins, considering that a structural discontinuity (failure, fracture, vein for example) can be reflected in variations of the topography. The information analyzed was verified in the field, seeking continuity in the structures interpreted on the surface.
In general, little continuity was observed in the veins within the project. Projected surface traces of veins could rarely be tracked and/or confirmed in the field and depth (with drilling – see corresponding chapter of Drilling). Individual measurements of field veins generally had no correlation with other points taken. Only four veins with continuity in surface and depth could be identified; the nomenclature of the cartography stations corresponds to the ID of the cartography stations.
- Veta BA-10023: also called «Veta de Honorio», orientation 315o/25o
- Veta BA-10056: also called «Veta de Alberto», orientation 295/35
- Veta 03_NOV: also called «Veta de los Ilegales», orientation 39/9
- Veta 10037, orientation 145/60
Figure 20. Trace on the surface of veta BA-10023 («Veta de Honorio») towards the center of the title, with measurements of structures taken in the field. Note the correspondence between the guideline and the measurements.
Figure 21. Surface traces of the four identified veins and orientation of planes measured in El Bagre veins, central sector of the title. Note the correspondence of the vein orientations with traces in this sector.
Only information from these defined veins shall be taken into account for potential calculation purposes. The others will not be taken into account due to the lack of confirmation of their spatial continuity.
The samples taken were sent for analysis at the SGS lab. No important Cu, Pb or Zn content was found in the samples analyzed. The summary of the results of the analyses for Au and Ag is indicated in Table 4 and Table 5..
|Au||Total Samples||Samples analyzed||Samples with >1 g/ton||Samples with >5 g/ton||Au_prom||Au_lowest||Au_Highest|
|Ag||Total Samples||Samples analyzed||Samples with >5 g/ton||Samples with >10 g/ton||Ag_prom||Ag_lowest||Ag_Highest|
According to the results shown, it can be concluded that:
- Au’s tenors in the veins within the project have a maximum of 6 g/ton.
- The vast majority of vein samples have Au grades less than 1 g/ton.
- No high Au contents were observed in the rock box.
- High Au content is present in alluvial concentrates. However, calculating the actual tenor in the floods results in much smaller content.
- Ag’s contents have behavior similar to that of the Au.
The results of the samples do not reflect the contents of Au that have been reported in the project, nor would they justify the constant presence of illegal operations. It was considered that, due to the nature of mineralization, the concentration of sulfides and oxides to which gold is associated is heterogeneous, so point sampling is not representative. Therefore, additional sampling was performed at two sites, seeking to collect at least 100 kg of sample to minimize bias produced by the heterogeneous distribution of free gold in the vein. The procedure used for sampling was as follows:
- Sample channel over the vein at the points.
- Advance of the socavón 2 m, before starting sampling.
- Manual classification of the material, Ganga: sterile material; Mena: Material with the presence of oxides, sulfide and possible gold content.
- Homogenization and quarteting, of each of the materials. Half of the quartet is the sample and another half is the counter-sample.
- Weight and registration of the fractions of ore and bargain obtained in the quartet.
- This is repeated until at least 150 kg of ore and 150 of bargain is completed.
The procedure included the separation of «mena» and «ganga» according to their visually detectable physical characteristics, a procedure used by local miners, and which optimizes the benefit in their artisanal process. For the éste purposes of this sampling, this separation sought to know the contents of Au and Ag within the vein itself.
The samples were sent for analysis in the UIS lab. Sample results were extrapolated according to their weight and ratio of mena-ganga at the sampling site to determine the total tenor of the vein.
The summary of the analysis and the final result are shown in Table 6. The determination of the total tenor of the vein sample was made as follows:
- Each sample consists of two subsamples: one from Mena and one from Ganga.
- Each subsample (ore and bargain) was determined to be concentration separately.
- Au’s weight for the Mena subsample was determined by a simple three-rule: according to the concentration per tonne, it was calculated how many grams of Au there were in the corresponding subsample.
- The same procedure was performed for the Ganga Subsample.
- The Au weight of the subsamples was added, in order to determine the weight content of the total sample.
- With the total of Au contained in the total sample (i.e. the Au contained in the Mena subsample plus the Au contained in the bargain subsample) the tenor of the total sample was determined by rule of three.
- The same procedure was applied for Ag’s wording.
|UIS Laboratory Results|
|Tenor Subsample Mena 1||5.18 g/ton||5.49 g/ton|
|Mena Subsample Weight 1||0.237 Ton||0.237 Ton|
|Au contained in Subsample Mena 1||1,229 gr||1,302 gr|
|Tenor Subsample Ganga 1||0.00 g/ton||14.50 g/ton|
|Weight Subsample Ganga 1||0.322 Ton||0.322 Ton|
|Au contained in Subsample Ganga 1||0.000 gr||4,662 gr|
|Total Au Sample Content 1||1,229 gr||5,964 gr|
|Total Tenor in Sample 1||2.20 g/ton||10.67 g/ton|
|Tenor Subsample Mena 2||4.70 g/ton||1.53 g/ton|
|Mena Subsample Weight 2||0.150 Ton||0.150 Ton|
|Au content in Mena 2||0.705 gr||0.230 gr|
|Tenor Subsample Ganga 2||0.00 g/ton||12.00 g/ton|
|Ganga Subsample Weight 2||0.250 Ton||0.250 Ton|
|Au contained in Subsample Ganga 2||0.000 gr||3,000 gr|
|Total Au Sample Content 2||0.705 gr||3,230 gr|
|Total Tenor in Sample 2||1.76 g/ton||8.07 g/ton|
According to the above, a tenor of between 1.76 – 2.2 g/ton of Au was obtained and between 8.08 – 10.7 Ag for these veins, a tenor that can be extrapolated for the project. Although the uncertainty of extrapolating this grade should be considered for all veins in the project based on two samples, this content is normal as observed and point samples taken. For example, illegal miners process only the material called «Mena», manually sorting what they extract from the vein, and obtain approximately 1 Castilian (4.6 g) per tonne.
The drilling campaign in El Bagre sought to confirm in depth the continuity of the veins identified on the surface. Seven core recovery wells were drilled into the project, executed by Perforando Ltda.
A total of 120 samples were taken in 200.10 meters (total well depth). At intervals 54.35-54.95 (sample EB00226), 55.75-56.27 (sample EB00229) and 107.25-107.53 (sample EB000285) quartz veins with thicknesses between 20 cm to 50 cm are observed, milky white occasionally presence of pyrite-calcopyrite fine and in small amorphous patches.
For the EB-DRI002 well, 10 samples were taken in 200 meters of drilling, located at intervals 26.70-27.20, 40.1-40.40, 54.20-54.60, 60-60.39, 67.09-67.49, 97.05-97.95, 105.12-105.57, 172.52-173.15, 181.2-181.82, 195.70-196.15. These intervals are differentiated by their significant mineralization, mineralized or sterile quartz veins and hydrothermal alterations of chloritic type and silicification..
Figure 26. EB-DRI001 Well Section, with expected projections of Veta BA-10056. Cut a lower quartz vein to the expected depth. A quartz occurrence towards the base of the well does not correlate with any known structure.
Figure 27.. Well EB-DRI002. a. Free gold <1 mm. b. Failure smooth with presence of hematite. c. Presence of hematite in quartz vein. d. and f. quartz veins. e. aphaitic rock dam and quartz vein in fitting rock (quartzdiorite).
In the EB-DRI003 well it presents several representative areas of interest with mineralization of fine disseminated sulphides and in small amorphous patches with replacement of millimetric quartz venilleum, quartz veins with thicknesses up to 30cm accompanied by mineralization in the upper and lower backrests, silicification in various sectors of the drilling core and fault zones filled with salbanda and fine pyrite. A total of 22 samples were taken in 199 meters of drilling at intervals 30.5-32.28; 34.12-34.86; 35.02-35.88; 36.08-36.59.
The EB-DRI004 well with a depth of 160.60, is initially composed of a thin yellowish to reddish brown soil with clay-sandy texture and quartz subredonderated clasts (0-5.3 with perdida loss of 1.95), followed by a saprolith and saprolitized rock with rings of concentrations of maficos minerals by meteorization and veneers of manganese oxides? (5.5-21.4 with perdida loss of 7.55 meters). Between the meters 21.4 to 160.60 roca fresca a fresh rock is observed with tenuous textural variations of fine to medium grain, speckled with granodioritic classification corresponding to the Batolith of Segovia, presenting a replacement of sterile and mineralized quartz veins-venillas (pyrite-calcopyrite-galena) with thicknesses from 0.2cm to 20 cm.
Intrusive granodioritic igneous rock has sporadic areas of disseminated sulfide mineralization <3% (pyrite-calcopyrite-galena-calcosine, amorphous patches and Pyrite veneers <2mm usually accompanied by silicification and chloritization with some fracturing zones identified by stretch marks and fault mirrors with a preferential angle varying between 30o to 40o.
For this well 11 samples were taken at intervals 33.8-34.7; 35.5-36.2; 41.25-41.86; 45.15-45.82; 87.2-87.74; 97.47-97.87; 105.49-106.04; 120.1-120.51; 122-123.55; 154.1-154.3; 155.3-155.7.
In the range 45.15-45.82 (sample EB-DRI00356) a quartz vein of 20cm thick with mineralized bottom and upper backrest is highlighted.
Figure 30. EB-DRI004 well. A. Quartz vein with their respective backrests, range 45-15-45.82 (sample EB-00356). B. Granodioritic rock in the range 32.40-35.45 with millimeter Qz venes, area of fracture and disseminated mineralization and in specific concentrations of Py-Cpy
The well perdida consists of a clayey-sandy reddish brown soil with slight foliation (0-23.9 with loss of 14 meters) preserving two sterile quartz veins 10 and 15 cm thick continuing with saprolith and saprolitized rock (23.9-55). From metro 55 to the end of well you have fresh faneritic igneous rock of grainyoritic type with occasional mineralization<1%, in disseminated form and in aefatic concentrations linked to chloritic alteration and silicification.
Between the range 70 to 80.1 an intense fracturing area with disseminated mineralization is observed and in small concentrations of pyrite, calcopyrite, arsenopyrite?, varying the degree of percentage in the rock from 1% to 3%.
Quartz veneers are located only in the range 57 to 60 with millimeter thicknesses without the presence of mineralization.
This well sampled 4 intervals corresponding to the areas of greatest interest at 59.30-59.84; 72.05-73; 77.7-78.2; 80.41-81.86.
Figure 31. EB-DRI005 well. A. Fine grain granodiorite with quartz silicification and venilleo zones. B. Fracture zone with loss of 0.35 meters. C. Top of the well (soil) preserving two sterile quartz veins; lost in the range of 2.05 mt.D. Qz millimeter venilleo replaced in fresh rock in the range 76.30-76.80.
The EB-DRI006 well contains 100 meters: the 0-19 meter stretch is made up of a reddish-brown clay-sandy soil with 5% subredonderated quartz clasts, followed by saprolitized igneous rock with preservation of plag-maficos as well as a sterile 10 cm quartz vein and some point oxide concentrations.
Between the interval 19 – 40mt is observed a granodiorite with segregation of mafia minerals,speckled, mineralization mainly pyrite-calcopyrite in disseminated form, venillas and in specific concentrations. At the same time it exhibits millimeter quartz veneers-veins up to 2cm accompanied by fine pyrite in several directions.
From metro 40 to the end of the logueada part are fractures at intervals 40-40.5; 40.7-40.9; 41.1-42.3; 45-46.2; 47-47.4; 48.3-48.5; 48.8-.50.3; 63.9-65.4; 67.5-68; 72.65-74.25 and a fault zone with a vertical displacement of a quartz veneers (51.6-52).
8 rock samples were taken at intervals 30.94-31.45; 31.45-32.10; 33.7-34.1; 37.8-38.9; 41.9-42.4; 43.6-44.25; 67.8-68.52; 71.37-72.75.
Figure 32. EB-DRI006 well. A. Silicified and mineralized granodiorite with pyrite in disseminated form, area of slight fracturing at the end of the interval. B. Interval 46.80-49.69 corresponding to an intense fracturing zone affecting the igneous rock
The first 14 meters consist of red saprolith and thick quartz-plagioclase clasts and granodiorite-like saprolithized rock with quite a loss. The remaining 9.8 meters are basically fresh granodiorite with some areas of silicification, mild fracturing and sulfide spread only in the range 22-23.2 mt..
Based on the processed information, the following criteria were defined for estimating potential resources:
- Tonnage calculations will be made for the four veins with confirmed continuity. The other points will not be taken into account for an estimate of potential resources.
- Due to the irregular nature of the veins and the difficulty in interpolating thicknesses, degrees and continuity, unique values will be assumed for each parameter.
- According to the information observed, a MIN case shall be defined as follows: thickness of 0.3 m (may be smaller as observed in the field, but an average is assumed), with 1.5 g/ton of Au and 5.3 g/ton of Ag (considering a factor of 3.5 in relation to Ag/Au), projecting 50 m on the course from points with measurement on the vein, and 50 m on the buzamiento.
- A MID case will be defined as follows: thickness of 0.5 m (may be smaller as observed in the field, but an average is assumed), with 2.0 g/ton of Au and 7.0 g/ton of Ag (considering a factor of 3.5 in ag/Au ratio), projecting 100 m on the course from points with measurement on the vein, and 100 m on the buzamiento.
- A MAX case will be defined as follows: thickness of 0.8 m (may be smaller as observed in the field, but an average is assumed), with 3.5 g/ton of Au and 12.3 g/ton of Ag (considering a factor of 3.5 in ag/Au ratio), projecting 200 m on the course from points with measurement on the vein, and 200 m on the buzamiento.
- A density of 2.7 Ton/m3 was considered..
Course projections may seem conservative, but they reflect the observed behavior of veins. Such projections were measured on physical planes. The results of the estimated potential resources are shown in the following tables.
|Min||Course Length||Buzamiento length||Thickness||Tonnage|
|Total Tons||27,945 Ton|
|Total Grams of Au||41,918 Gr|
|Total Ounces of Au||1,348 Oz Au|
|Total Grams of Ag||146,711 Gr|
|Total Ounces of Ag||4,717 Oz Ag|
|Mid||Course Length||Buzamiento length||Thickness||Tonnage|
|Total Tons||187,650 Ton|
|Total Grams of Au||375,300 Gr|
|Total Ounces of Au||12,066 Oz Au|
|Total Grams of Ag||1,313,550 Gr|
|Total Ounces of Ag||42,232 Oz Ag|
|Max||Course Length||Buzamiento length||Thickness||Tonnage|
|Total Tons||1,118,880 Ton|
|Total Grams of Au||2,237,760 Gr|
|Total Ounces of Au||71,946 Oz Au|
|Total Grams of Ag||13,706,280 Gr|
|Total Ounces of Ag||440,667 Oz Ag|
75,946 Oz by Au
Estimated Price US$1,194 May 6, 2015. Total US$85,903,524
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