Projects

La Bufa Property

 

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La Bufa Facts
Location:
Guadalupe y Calvo mining district,
Chihuahua, Mexico
Commodities:
Gold, silver, copper, lead, zinc
Land:
2,311.3 hectares (5,711.4 acres)
Ownership:
100% interest
Target:
Epithermal vein system
Status:
Early-stage exploration
Drilling:
37 core holes for 10,569.30 meters
NI 43-101 Technical Report:
Filed June 17, 2011
Plan:
Market and sell the La Bufa property with net proceeds to be split equally between Elgin Mining and Lincoln.
 

Summary
The La Bufa Property is a group of concessions which cover most of the Guadalupe y Calvo mining district within the Sierra Madre mineral belt in southwestern Chihuahua State, Mexico. Lincoln, through its Mexican subsidiary, purchased a 100% interest in the property from Almaden Minerals Ltd. in February 2010. The district has historic production of 2 million oz gold and 28 million oz silver from the El Rosario mine which is now controlled by Endeavour Silver Corp. Lincoln's land position covers over 9 km of the NW-trending epithermal vein system. Drilling in the southern concession and in the northern concession has produced encouraging results. Core drilling of 20 holes in 2011 in the northern concession confirmed the presence of major structures and anomalous gold and silver with some significant intercepts (see details in '2011 Drill Program' below).

The Company believes that the district, like others in the trend, has significant gold-silver exploration potential with the opportunity for a high-grade underground mine. As significant silver-gold intercepts have been made in multiple holes, deeper offset drilling of anomalous zones in the northern targets is warranted.

On June 4, 2013, Lincoln announced a settlement with Elgin Mining, (see news release June 4, 2013).


Panorama view of La Bufa Property


 


La Bufa location map.




La Bufa Property concession map

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Sierra Madre Occidental Map

 

 

Location
The La Bufa Property lies within the Sierra Madre Occidental in the southwestern portion of the State of Chihuahua. The property occupies most of the Guadalupe y Calvo mining district which falls within the northwest-trending Sierra Madre mineral belt. This belt consists of gold and silver mines including: Dolores, Moris, Ocampo, Pinos Altos, Palmarejo, Piedras Verdes, Bolivar and El Sauzal, along with numerous deposits. Access is excellent via paved Highway 24 from Hidalgo del Parral, a mining-based city with a population of 100,000. The property concessions are adjacent to the small town of Guadalupe y Calvo, which has an estimated population of 4,400. The town has electrical power from the national grid and a local airstrip is available for small charter and private aircraft. Logistics are excellent for mining.

Land
La Bufa is a large property that covers four concessions (La Bufa, La Bufa 1, La Bufa 2 and El Chapito) encompassing 2,311.1 hectares. Lincoln Mining originally entered into a binding letter agreement with Almaden Minerals Inc. (“Almaden”) on the La Bufa Property in 2005 and completed a joint venture agreement with Almaden in 2007. On November 25, 2009, Lincoln Mining announced that it has reached an agreement with Almaden Minerals Inc. ("Almaden") to purchase 100% of the La Bufa Property, subject to TSX Venture Exchange approval. The new agreement supercedes the previous joint venture agreement that allowed Lincoln to earn a 60% interest in the La Bufa. Under the new agreement, Lincoln purchased 100% interest by issuing 6 million Lincoln Mining shares to Almaden and granting a 2% NSR on production from La Bufa. Lincoln has the option to buy down the NSR by 1% within one year following a decision to place the property into production. Fair market price for the NSR buy down will be determined by an independent consultant. In February 2010, Lincoln finalized the La Bufa purchase agreement.

The La Bufa property completely surrounds the old Rosario mine property which was purchased in April 2012 by Endeavor Silver Corp. from Aurico Gold Inc. (see La Bufa concession map).

History
Historical production in the district extended largely from 1834 to 1939 and came mostly from high-grade epithermal quartz breccia veins at the underground Rosario Mine. Past production is estimated at 2 million ozs gold and 28 million ozs silver with ore averaging 37 gpt (1.08 opt) Au plus 870 gpt (27 opt) Ag with excellent metallurgy. The ores were so rich that the Mexican government established a mint in Guadalupe y Calvo. This mint is still present as a museum.

Multiple small, underground workings occur along the Santo Niño vein in the southern portion of the La Bufa property. Historic workings include the Monte Cristo shaft, El Chapito mine, and Santo Niño adit. All workings are collapsed.

Geology & Mineralization
The geology of the Guadalupe y Calvo district consists of two main groups of volcanic rocks typical of the Sierra Madre Occidental. The "Lower Volcanics" (38 to 65 million years) are dominated by stocks, flows, and tuffs of mafic to intermediate composition. The "Upper Volcanics" (25 to 38 million years) are dominated by extrusive flows and tuffs of intermediate to silicic composition and may occur as dikes and small intrusive bodies. The "Upper Volcanics" are the dominant rock type on the La Bufa Property with erosional windows of "Lower Volcanics" locally exposed on the property. Lower Volcanic Group rocks are the host to nearly all the major gold-silver deposits found in the Sierra Madre Occidental.

Mineralization on the La Bufa is classified as typical low-sulfidation, quartz-adularia epithermal gold-silver veins and is similar to numerous other deposits in the Sierra Madre Occidental. The mineralized trend strikes northwest in varying intensity. The veins contain pyrite, arsenopyrite, galena, sphalerite and copper minerals. The ore minerals are thought to be electrum and argentite. The southern portion of La Bufa covers at least 1,700 meters of vein system strike. Multiple quartz veins crop out intermittently and range in thickness from 1 meter to 3+ meters within a complex fault zone up to 70+ meters wide. Multiple vein sets occur in the northern concession with strike lengths from 1000 to 2000 meters. Significant quartz stockwork zones are also present. Various surface samples have returned ore-grade gold and silver values. Results from the 2011 core drilling program are encouraging and confirm numerous quartz zones and some significant silver-gold intercepts.

Previous Work
Minor core drilling at La Bufa was conducted in the 1970s. In 2004, Grid Capital drilled five shallow core holes (666.15 m) on the southern concession. Drilling encountered encouraging intercepts on the order of 6 to 9 grams per tonne gold plus 363 to 503 grams per tonne silver. Multiple ore-grade intercepts were encountered in one hole.

In 2005, Lincoln conducted aerial photography over the entire district and produced a high-quality topographic base map. The base map was used for a soil sample survey and detailed geologic mapping over the southern portion of the district vein system. Numerous targets were identified and marked for drill testing. Previous sampling of the northern portion of the property returned encouraging assays ranging from 1.07 to 4.28 grams per tonne gold and 186 to 838 grams per tonne gold.

In 2008, Lincoln drilled 12 angle core holes for a total of 4,811.85 meters. Drilling was focused on the southern portion of the property. Hole depth averaged 400 meters. The drill holes were widely spaced angle holes focused on the El Rosario gold-silver vein system which extends southward from the historic Rosario mine onto the La Bufa concessions. Encouraging results were received from over 300 meters of vein system strike length, which remains open to the northwest towards the adjacent Rosario mine (held by Endeavour Silver Corp.) approximately 400 meters away. Gold-silver mineralization occurs in steeply dipping quartz-breccia veins and stockworks. Drill results suggest that gold-silver mineralization occurs primarily in the shallower portions of the vein system.


La Bufa Drilling
August 2011

During December 2009, January and February 2010, Lincoln Mining conducted a large geophysical survey totaling 20,000 line-meters. This work was carried out on the northern part of the La Bufa Concession. The geophysical program consisted of both resistivity and chargeability surveys which were followed up by rock-chip sampling. Sampling focused on three target areas which were highlighted by the geophysical survey. Geological mapping was also conducted. Two hundred and thirty-four (234) samples were collected from available outcrops. Each sample was typically comprised of various rock-chips from a 2 meter x 2 meter area. Sample spacing was variable, usually tens of meters and based on availability of outcrops and physical access. Samples were sent for assay to Eco Tech Laboratory Ltd. and ALS Chemex Labs Ltd., both certified assayers located in Canada. Quality control was carried out by way of random duplicate assaying and standards that were provided by the labs. Surface assays produced results up to 20+ grams per tonne gold and over 900 grams per tonne silver.

Target areas were identified by coincident geophysical and geochemical anomalies. Target Areas 1 and 2 are long brecciated quartz structures which may extend to considerable depth as suggested by their geophysical signatures. Target Area 1 extends for over 1,000 meters as intermittently exposed zones that exhibit locally high silver and gold values. Target Area 2 extends for over 650 meters and exhibits elevated silver values with attending anomalous gold. Additional targets are also present (click here to view detailed rock-chip assay table)  and go to the map gallery to view a detailed 2011 targets and drill hole map.



La Bufa 2011
Core Drill Target Areas & Drill Holes
(Click to enlarge image)

2011 Drill Program
Past production in the district came mainly from quartz breccia veins hosted in "Lower Volcanics". The main mineralized structural zone trends in a northwesterly direction and carries onto Lincoln Mining's ground.

In July 2011, Lincoln received permission from the Ministry of Environmental and Natural Resources, Semarnat (Secretaria de Medio Ambiente y Recuersos Naturales) to carry out its planned 5,000-meter drill program in the northern portion of the La Bufa Property. The Company contracted Perforaciones Corebeil SA de CV of Mazatlan to conduct the core drilling program which commenced on July 14, 2011 and was completed early December 2011.

Eighteen (18) of the 20 holes encountered multiple quartz-breccia veins, quartz stockwork, or quartz veinlet zones. Eighty-seven (87) quartz zones were intercepted in the drill holes. Eighty-six percent (86%) of the quartz zones contained detectable gold and silver (>0.005 ppm Au; >0.2. ppm Ag). Anomalous gold (>0.1 gpt) and silver (>1.0 gpt) are present in 15 holes. Stockwork zones are prevalent and commonly 5 to 12+ m in apparent thickness. Thicker zones of stockwork and quartz veinlets range from 21 to 54 meters. The best gold intercept is in hole LB-22 which hit 4.38 gpt gold with 11.6 gpt silver from 179.5 to 181.0 m (1.5 m) hosted in Tertiary andesite with quartz veinlets. The best silver intercept is in hole LB-23 which hit 249 gpt silver with 0.481 gpt gold from 116.5 to 118.0 m (1.5 m) hosted in Tertiary andesite with quartz veinlets. Significant base metals are largely absent. Note:  See News Release April 26, 2012. Drill hole intercepts reported for the 2011 drill program are apparent and do not represent true thicknesses. 



La Bufa (2011 Targets
& Drill Holes Close Up)

2011 Core Drill Holes Locations                          
The drilling program confirmed the presence of major structures and anomalous gold and silver with some significant intercepts. The abundance of quartz breccia veins, quartz stockwork, and quartz veinlets attended by consistent intercepts of detectable and anomalous gold-silver with low base metals suggest that drilling to date is high in the mineralized system. Deeper offset drilling of anomalous zones in both targets appears warranted.

Target 1 - Nine (9) holes (LB-13 to LB-21) were drilled in Target 1 which consists of at least three prominent high-angle structures with anomalous gold/silver mineralization. Intercepts of quartz breccia veins were encountered up to 17.6 m in thickness and quartz stockwork up to 26.0 m in thickness. Anomalous gold and silver intercepts are narrow and range from 1.0 to 4.5 m. High values are 1.66 gpt gold with 10.2 gpt silver (hole LB-21) and 1.28 gpt gold and 4.4 gpt silver (hole LB-13) - see table below.

Target 2 – Seven (7) holes (LB-22 to LB-27, LB-29) were drilled in Target 2, approximately 1,000 m northeast of Target 1. Stockwork zones are present at the surface and the drill road exposed shattered quartz veins and quartz stockwork. Each drill hole had 3 to 10 zones of quartz breccia vein, quartz stockwork, or quartz veinlets. Hole LB-27 intercepted 54 m of quartz stockwork. Anomalous gold and silver intercepts are narrow ranging from 0.7 to 2.7 m with high assays of 4.38 gpt gold (hole LB-22) and 249 gpt silver (hole LB-23) – see table below.  This mineralization is hosted in andesite with quartz veinlets.

Deep Target – One deep hole, LB 32, was drilled near the northern perimeter of the El Rosario mine property (held by Endeavour Silver Corp.) The hole was drilled to 787.5 m and failed to intercept the favourable "Lower Volcanics" host rock.

Other Drill Holes – Three (3) widely spaced drill holes (LB-28, LB-30, LB-31) were drilled on scattered targets. Holes LB-28 and LB-29 encountered multiple intercepts ranging up to 1.355 gpt gold and 21.6 gpt silver (see following table).


SUMMARY OF ANOMALOUS GOLD AND SILVER IN LA BUFA CORE HOLES   (NA=Not Applicable)

Hole No.
Area
TD
(m)
Angle
No. Quartz
Zones
Best
Gold
(gpt)
Best
Silver
(gpt)
From
(m)
To
(m)
Intercept
(not true thickness)
(m)
LB-13
1
232.00
-65
4
1.28
4.4
23.73
25.33
1.60
LB-14
1
226.50
-45
2
0.355
3.0
3.0
7.50
4.50
LB-15
1
151.50
-65
0
NA
NA
NA
NA
NA
LB-16
1
181.00
-60
1
NA
NA
NA
NA
NA
LB-17
1
231.50
-45
5
0.216
0.8
184.50
187.50
3.00
 
 
 
 
 
0.652
1.8
214.40
215.40
1.00
LB-18
1
220.50
-45
2
0.064
1.5
170.55
171.80
1.25
LB-19
1
247.50
-45
5
NA
NA
NA
NA
NA
LB-20
1
255.00
-65
2
0.239
1.5
24.00
26.00
2.00
LB-21
1
258.00
-70
5
1.66
10.2
57.60
58.50
0.90
LB-22
1
247.50
-75
4
0.293
6.4
162.00
163.50
1.50
 
 
 
 
 
4.38
11.6
179.50
181.00
1.50
 
 
 
 
 
0.538
1.6
184.00
185.50
1.50
 
 
 
 
 
1.16
6.6
220.70
222.00
1.30
 
 
 
 
 
0.144
2.4
223.50
225.10
1.60
LB-23
2
169.20
-75
4
0.341
8.5
49.50
50.20
0.70
 
 
 
 
 
0.481
249
116.50
118.00
1.50
LB-24
2
231.00
-60
6
0.038
19.5
6.00
7.50
1.00
 
 
 
 
 
0.016
28.7
194.50
200.50
6.00
LB-25
2
225.00
-60
5
0.122
5.4
198.50
199.50
1.00
LB-26
2
256.00
-45
9
0.110
4.1
18.00
19.50
1.50
 
 
 
 
 
0.712
3.1
73.50
75.00
1.50
LB-27
2
248.40
-80
6
0.106
4.1
124.50
126.00
1.50
 
 
 
 
 
0.151
1.3
187.50
189.00
1.50
 
 
 
 
 
0.388
11.8
244.50
245.70
1.20

Base Metals
The drilling program revealed low base metal values associated with the anomalous gold-silver intercepts in the quartz zones. Copper and lead are each typically less than 100 ppm with spikes greater than 300 ppm. Zinc is typically in the range of 65 to 95 ppm with spikes greater than 100 ppm. A single base metal intercept was made in hole LB-24 (Target 2) where 6.0 m of silicified volcanic breccia was encountered containing 0.60% copper, 28.7 gpt silver, elevated lead (232 ppm), trace zinc (69 ppm), and trace gold (0.016 ppm).

Project Scope & Plans
Lincoln management believes that the La Bufa project has multi-million ounces gold-silver potential. The prolific Lower Volcanics offer exceptional potential to host multiple economic silver-gold deposits on the La Bufa property. Lincoln geologists have been focusing on defining drill targets in the northwest part of the property and the 2011 20-hole drill program has confirmed the presence of major structures and anomalous gold and silver with some significant intercepts. The abundance of quartz breccia veins, quartz stockwork, and quartz veinlets attended by consistent intercepts of detectable and anomalous gold-silver with low base metals suggest that drilling to date is possibly high in the mineralized system or and possibly an extension of similar NW-SE structures that occur about 8 km south on Lincoln's property.  Deeper offset drilling of anomalous zones in both targets is warranted. 

In March 2011, Lincoln and Elgin Mining Inc. ("Elgin Mining" or "Elgin") entered into an exploration financing agreement, granting Elgin the exclusive right and option to acquire up to a 60% undivided interest in the La Bufa property by funding exploration expenditures of $1MM on La Bufa over a two year period, prior to earning any interest in the project. In September 2012, Lincoln announced that it has terminated the Letter Agreement as certain obligations under the agreement have not been fulfilled by Elgin Mining. Elgin has disputed the validity of Lincoln's termination of the Agreement and the parties are now proceeding to arbitration under the terms of the agreement to address and resolve the dispute.

On June 4, 2013, Lincoln announced that further to the Company’s news release of September 14, 2012 reporting the arbitration of the Letter Agreement of March 31, 2011(the “Agreement”) with Elgin Mining Inc. (“Elgin”), Elgin and Lincoln (together, the ”Parties) have signed a full and final Settlement Agreement (the “Settlement”).   Under the Settlement, the Parties have decided to terminate the Agreement in relation to the La Bufa property for the following consideration:

  • Lincoln shall take all commercially reasonable steps to market and sell the La Bufa property; the net proceeds of such sale (after allowable expenses) to be split equally between the Parties.

Currently, a sale of the La Bufa property is not imminent.