STRATEGY IN COLOMBIA
Exploration Potential for World-class Gold Deposits
Soma has created a unique opportunity by using a small miner mill to create an excellent local relationship, allowing access to exploration at its Zara concessions. In addition, Soma has closed the purchase of Operadora S.A.S., which includes a mine, an operating plant, exploration drill rigs an experienced team of operators, engineers and geologists, further adding to the landholding.
Zara Concessions - El Limon Mine and Mill
22,990 ha with exploration permits in place
200+ tpd small miner mill (expanded from 50 tpd tested up to 150 tpd at 85% recovery) - crushing, grinding, gravity, float, leach, Merrill-Crowe, smelting
To date, 13 illegal mines have been "formalized" through a government-sponsored program, which has created social, environmental, economic and legal solutions
Initial exploration target: 746,000 ounces Au averaging 5.9 grams/tonne
1-year drill plan: 231,000 ounces Au averaging 7.7 grams/tonne
Subsequent years targeting 250,000 ounces/year
Soma's strategy: ramp up small miner production and develop inferred resource within El Limon zone for in-house base production
450 tpd plant currently operating - crushing, grinding, gravity, float, leach, Merrill–Crowe, smelting
4,634 ha in concessions (contiguous to Zara)
Existing reserves for approximately 2 years (potential 10+ years)
Nechi (61km from La Ye): M&I – 48,600 oz at 4.9 g/mt and Inf – 85,700 oz at 6.5 g/mt (approx. 5 years of feed)
The fault corridor of OTU, Pericos and El Bagre has generated multiple high-grade and high-ounces mines. Previosuly, the surrounding areas were inaccessible due to the resistance from small miners. The area between Nechi and Segovia has produced over 18M ounces of gold without considering informal mining which is estimated to be 2-3 times the formal production. It is one of the most prolific and under-explored land packages in the world
The El Bagre, El Limon and Nechí projects lie within the Central Cordillera of the Andes Mountains. In the Bagre-Nechí gold mining district the vast majority of historical gold production to date has come from alluvial deposits within river basins, including the Nechí River. In addition to alluvial gold, structurally controlled mesothermal gold-silver and sulphide-bearing quartz vein lode deposits are hosted within intrusive rocks.
Nechí and El Bagre are two examples of such mineralization. The mineralized veins at Nechí are hosted within the Mesozoic-aged Segovia batholith and mineralized veins at El Bagre are hosted within the Carboniferous aged El Carmen intrusive. The veins average approximately one metre in thickness and extend for up to five kilometres.
The El Bagre underground mining concessions lie within the Central Cordillera, one of the three physiographic subdivisions (Central, Western, and Eastern Cordillera) of the Andes Mountains in northern South America. The area is part of the Bagre-Nechí mining district that includes gold mineralization within the Bagre, Zaragoza and Nechí regions. The vast majority of historical gold production comes from alluvial deposits within the river basins, including the Nechí River.
In addition to alluvial gold, vein-type gold mineralization is present and can be followed for up to three kilometres. Mineralization is hosted within intrusive rocks observed near Nechí, El Bagre, and Zaragoza.
At El Bagre, the veins of La Ye, Mangos, and Cordero are hosted in shear zones with fragile ductile deformation within carboniferous granite rocks of the El Carmen stock. At the regional level, the main structure to the west is the sinistral Otú fault system which trends north-south to north-northwest near the municipality of Zaragoza. El Limon and the bulk of Soma’s Zara concessions are on the Otú fault. This fault which brings into contact carboniferous plutonic rocks from the El Carmen stock with metamorphic Permo-Triassic rocks grouped regionally as the Cajamarca Complex.
The Otú fault is the most northern expression of the Otú-Pericos fault system. To the east is the El Bagre fault, interpreted regionally as an overrun fault, which brings the Segovia batholith into contact with Precambrian metamorphic rocks grouped in the San Lucas Gneiss. To the southeast are volcano-sedimentary deposits of Segovia and to the north are the sedimentary rocks of the Caucasia Formation, the Tarazá Formation, and the recent deposits of the Nechí and Tiguí rivers, which mask the trace of the Otú fault and cover discordantly the granite rocks of the Segovia batholith and El Carmen stock.
PROJECT: EL LIMÓN
Geology and Mineralization
In the area, there are two zones of metamorphic rocks, one of feldespathic-aluminic gneisses and the other associated to the Cajamarca Complex rocks. There are also granitic bodies associated to Cretaceous magmatism. Gneisses and schists occur in bundles which are elongated in an N-S course; they cover the entire area and they are intruded into the NW by a stock of granodioritic composition and small dikes of porphyry andesitic composition.
The area features Quaternary deposits; the largest ones are located on the creeks called Juan Vara, Sardina and Culebra. The main structure present in the area is the Otu Fault that crosses the area from North to South, the control over the Juan Vara creek is relevant. The known vein systems of the region extend up to 2-3 km in length with plunging high-grade ore shoots central to the vein and surrounded by a lower grade halo. Vein dips are typically around 30-40°, and occasionally sub-vertical.
The mineralization of El Limon mine is embedded in the quartz-feldespathic gneisses. The gold occurs in a milky quartz vein, to the west of Otu Fault, its approximate course is N10E/40W, with average thickness of 0.40 m. These features are very consistent in an extension of almost 400m on the course and 350m in the dip direction.
Typical production grades of the region range 8-12 g/t Au diluted. However, higher-grade mines also exist, such as Quintana and El Limon mines at 15-20 g/t Au diluted. Vein widths are typically below 1m, although both the hanging wall and footwall zones can contain appreciable economic mineralization within the high-grade cores. The structure is continuous, except for a series of reverse faults, with displacements ranging from 0.2 up to 40 and 60 meters, of which the main ones are El Limon and Leonel Faults, and to the north the 5N and the Victoria faults.
Gold mineralization is related to sulphide contents, mainly pyrite, with smaller amounts of galena, sphalerite and tetrahedrite, usually occurring as clear strips with a thickness ranging from 2 to 5 mm, and they comprise from 7% to 12% in volume. Occasionally the strip structure is replaced by distributions of sulfides which are more irregular or uneven. Pyrite is the first most common and abundant ore, present in the form of aggregates of anhedral and subhedral crystals. Tetrahedrite is the second most abundant ore; usually it occurs in anhedral crystals. Gold is the most important metal; it appears in the form of grains in native state or electrum, normally encapsulated with galena and in the form of inclusions in pyrite crystals, but not always. The particle size is distributed in ranges from 1 to 120 microns, occasionally above 200 microns.
Gold – silver ratio is 1:1.2; the mineralization is normally contained within quartz veins, it is very rare to find quantities of gold directly in the host rock. The tenor of gold appears to relate to the quantity of sulphides, preferably related to the presence of sphalerite and galena.
Underground mining at El Limon is restricted by the size of the main winch (located underground) to 100tpd. The strategy to remedy this is to take the shaft vertically up to surface and then install a new winch at the top of the shaft.
In addition the company plans to gain economies of scale by buying in ore. Nearly 60 independent gold mining operations are located in very close proximity to the El Limon production facility. Many of these are operating on Soma Gold’s concession territory. These operators are being targeted as sources of ore to be purchased by Soma Gold and fed into the milling operation of the company.
The material mined by the small local miners is very similar in nature to the material being mined at El Limon.
The economic model of the processing of the third party ore is that the local miners are paid 35-42.5% of the assayed gold in the rock delivered to the mill, based on the current price of gold. The final product sold by El Limon is gold/silver doré from this comingled ore.
The existing process set-up at El Limon consists of two-stage crushing, milling, gravity, flotation, cyanidation, Merrill-Crowe precipitation and smelting.
The crushing plant historically operated one shift per day at 10-12 tonnes per hour but has capacity of 20 tonnes per hour, providing sufficient crushed rock to feed the mill. The crushing plant consists of a jaw crusher, cone crusher, vibrating screen and associated belts and bins. A nominal 3/4” product is supplied to the mill.
The crushing plant consists of a jaw crusher, cone crusher, vibrating screen and associated belts and bins.
Work is ongoing to survey and assay the four levels of historical working where “room and pillar” mining method was used and the historical tailings. During the time the processing plant was being rehabilitated, underground development work was undertaking, opening two new working faces on Levels 6 and 7.
El Limon is at cash flow break-even at production of 62 TPD producing 450 ounces per month.
El Limon restarted limited production in June 2016 but due to some manufacturer’s defects on a long lead time item, the installation of the second ball mill was delayed. The original start up at El Limon occurred in May/June of 2017, after a US$7mn rehabilitation and plant upgrade at the crushing plant via the installation of a second ball mill, a new thickener, new flotation circuit and an upgraded CIP process circuit. Mill throughput was increased to 200tpd for mined rock and 400tpd for milled rock and tailings.
The mine is currently focusing on four main development projects, including three new mine mouths:
Level 9 of El Limon is a development project to deepen the lowest levels of the mine past the El Limon fault. The project to date has rehabilitated 140 meters of existing drift, re-established internal hoisting, and all utilities and advanced 32 meters of development passing and establishing ground support in the fault zone. 83 meters of waste development remains before drifting and raises begin in the vein for 320 meters of development to establish the first two production stopes
Renacer is a new mine mouth for the El Limon mine. A new mine mouth with concreted metal archways was established and development in the main decline advanced 22 meters with 60 meters remaining , before beginning 440 meters of drifting and raises in the vein for 440 meters to establish the first two production stopes
Alacran is a modernization project on a formalized mine with support in engineering, design, and supervision from the company.
The 70 meters of the existing access incline were straightened by new excavation, and 120 meters of drift rehabilitated. The incline is being extended and 15 meters remain.
Construction is almost completed on a truck loadout with the new hoist. Once completed, work will begin on 340 meters of development in the vein to establish the first two production stopes
Diamantina is a modernization project on a formalized mine with support in engineering, design, and supervision from the Company. The mine mouth has been re-established with a concreted metal archway and 95 meters of incline rehabilitation including re-excavation of 15 meters. 50 meters of incline extension remain before drifting and raises begin in the vein for 190 meters of development to establish the first production stope
In the first quarter of 2019 plant through-put averaged 43 tpd, averaging 3.6 g/t. In 3Q19 plant through-put averaged 36.82 tpd and the gold grade was averaging 3.6 grams per ton.
The company’s expectation is to increase both feed quantity and grade through development at the El Limon Mine and 3rd party miners reaching 112 tpd average of 6 g/t by the first semester of 2021.
PROJECT: EL BAGRE COMPLEX
La Ye and Los Mangos are Operadora’s two producing mines, and Cordero are a nearby extension of the same type of operation. The first two are 1.4 km apart and share the same plant. Cordero is 2.6 km from Los Mangos and is, in effect, an extension of the existing two operations, and shares many of the characteristics of Los Mangos.
La Ye has been in production since 2010 and Los Mangos since 2013, and both have established infrastructure, mining methods, geotechnical aspects, and a history of production.
La Ye and Los Mangos currently produce 156,000 tpa of ore. Cordero will replace production from the existing operations as they wind down in 2020.
La Ye Mine
La Ye produced ~23,000 tonnes of ore in 2018. It uses a non-mechanized, hand held cut & fill method for near vertical veins, with 30 m to 60 m level spacing. Raises are developed on either side of a stope from which mining progresses. Fill is placed using the same raises as the stope progresses. Development is hand held with pneumatic rocker shovels. Tracked ore drives are used to transport ore to a series of declines along the orebody, from where the ore is hoisted out.
La Ye is currently producing at Level 5 (450m depth) and its development goes down to Level 8 (650m).
La Ye has a fully-equipped mine camp with capacity for 52 employees with water supplied by the company. The processing capacity is 450tns per day, with plans to upgrade this to 660tpd
Los Mangos produced 128,000 tonnes in 2018. It has a similar development configuration to La Ye, however, the levels are spaced at 25m and the orebody dip is 30o to 40o. Mining is carried out by a non-mechanised, hand held room & pillar method, with some pillar robbing where possible.
Los Mangos-Icacales is starting development and production at Level 4 (370m depth) and its development goes down to Level 6 (500m).
An aerial view of the El Bagre plant can be seen below.
The processing facilities consist of:
Crushing, concentration, floatation, leaching and smelting
Merrill Crowe plant with a metallurgical recovery of 85% on average
Average production in the period 2010-2017 was 20,490 ozs Au by year. The estimated production in 2020 is 15,000 ozs Au. In total there has been around 800,000 tonnes of ore production since 2010 with an average gold grade ore or 4,2 g/t with some 150,000 ozs Au produced since 2010.
The actual production cost is US$991 per oz Au Eq, including direct mining costs and SG&A.
The 2019 unit operating costs were:
Underground Mining: US$62 per underground tonne mined
Processing: US$24 per tonne processed
G&A: US$23 per tonne processed
Total: US$109 per tonne processed
The mine operates continuously on a three work-shift roster and employs 650 workers on three work shifts, 440 in the mine, 60 processing facilities, 60 planning, 80 maintenance, 10 administration.
Resources & Reserves
The projects have had a strong resource replacement trend since 2013 when the resources/reserves made a substantial leap.
Paulo J. Andrade, B.Sc. Senior Geologist, VP Exploration for Soma is the Qualified Person, who is responsible for the technical information contained on this website.