On May 4, 2016, Minera Alamos Inc. announced the completion of the acquisition, by its subsidiary Minera Alamos de Sonora S.A. de C.V., of 100% of the mineral claims known as the “La Fortuna” gold project.
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Summary:
Deposit Types
Known mineralization within the La Fortuna Project area is spatially associated with calc-alkaline intrusions, with different zones exhibiting a combination of geological characteristics and gold-silver grades of both porphyry and epithermal mineralization styles. Collectively the zones at La Fortuna may be best characterized as intrusion- related ‘transitional’ deposits. They consist mainly of a hydrothermally altered breccia “pipe”, tabular in shape, similar in nature to other quartz-sulphide gold ± copper ± silver epithermal breccia deposits.
Mineralization
The Project area hosts numerous historic adits, and gold-silver showings including the historic La Fortuna Mine (and extensions) and the Ramada, PN, and Cerro Pelon zones to name a few.
Mineralization in the La Fortuna Mine area appears to be spatially associated with a series of parallel fault structures (approximately 1.5–2 km apart) and related to tourmalinized quartz monzonite breccia bodies which are located along the periphery or flanks of a north-northwest striking, west dipping, tabular quartz monzonite intrusive that appears to be approximately 60 m wide and forms a prominent topographic ridge prominent in the mine area. These fault structures and tourmaline breccia bodies have been the source of significant historical mining activity within the Project area.
La Fortuna Mine
The La Fortuna deposit is hosted within a tabular mineralized body that is up to 60 m thick and dips 30° to the west. The lower part of the body rests on a healed breccia base while the upper part consists of quartz stringers and veinlets extending up into the hanging wall.
La Fortuna hosts gold, silver and copper mineralization which occurs as disseminations, stockwork veinlets and fracture fillings. It is noteworthy that the degree of mineralization is directly related to the intensity of brecciation or fracturing and the amount of sulphides (pyrite). Mineralization remains open at depth and along strike. Similar style mineralization exists at surface approximately 400–500 m south of the current resource and can be traced along strike for at least 200 m.
Photomicrograph studies of mineral concentrate indicate gold and silver grains and minerals are present along the grain boundaries of the chalcopyrite and pyrite. Disseminated pyrite within the altered and unaltered wall rocks appears to be associated with some precious metal values. Significant values are found with the quartz-sericite-pyrite-chalcopyrite±tourmaline stockworks and the grades are dependent on the intensity of the fracturing. Thin limonite coatings are common on sulphides exposed by earlier mining. Limonite, hematite and malachite plus azurite occur occasionally within the poorly defined oxide zones.
Ramada Zone
The Ramada Zone lies on a parallel fault structure approximately 2 km northeast of the La Fortuna Mine with a strike length that can be traced at surface for over 600 m. Two groups of showings comprise the Ramada Zone:
• A southern group of showings is mostly covered with overburden. However, a 7 m length of quartz vein is exposed which is 3.3 m wide. Samples taken by Fernando Gold across the vein returned assays of 18 g/t Au and 176 g/t Ag over a width of 3.3 m. Further south the vein is exposed in a creek bed and a sample 3.7 m wide returned results of 4.33 g/t Au and 105 g/t Ag. This site also has a small caved adit and may be the location of two core holes drilled by CRM, which had intercepts of 2.2 m at 5.49 g/t Au, 204.8 g/t Ag and 3.3 m at 2.35 g/t Au and 17.6 g/t Ag.
• The northern group of showings consist of a series of small veins which so far have only returned anomalous gold values.
PN Zone
The PN Zone structure is located approximately 1.5 km northeast of the Ramada Zone and can be traced on surface for approximately 1.5 km. The structure host numerous historic mine workings like La Plomosa, Santa Fe, Guadalupe, Higuerita and Buena Vista. Sampling from this area returned gold grades ranging from 1 to 10 g/t Au and 50 to 400 g/t Ag.
Cerro Pelon Zone
The Cerro Pelon Zone (previously Los Cajones) is located to the south of the La Fortuna Mine. The zone was the subject of historical geochemical sampling by the CRM which outlined a large area of “anomalous” gold approximately 1,500 m long and 200–500 m wide. Gold assays included sample values as high as 10.1 g/t.
Other Zones
There are numerous other zones on the Property which have had various names over the years. These include:
• El Toro Zone – The El Toro prospects are located about 3.5 km west-northwest of the old San Fernando plant site. Some pyrite, chalcopyrite and copper carbonates are present on the dump of the old mine workings and in a caved adit. The limonitic zone is reportedly 150 m wide and 700 m in length. Sampling by CRM showed a 1 m sample assaying 28.4 g/t Au and 283 g/t Ag. Another sample averaged 4.8 g/t Au and 67.2 g/t Ag over a 4 m length. A dump sample assayed 3.6 g/t Au and over 50 g/t Ag.
• La Tocaya Zone – The La Tocaya Zone approximately 200 m east of the La Fortuna Mine’s Level #2 Eastern Portal. Strong sulphides occur adjacent to a major northwest-trending fault which includes trace to 1% pyrite, chalcopyrite, and malachite. The alteration zone is approximately 15–20 m wide and 60–70 m long but steep topography inhibits exact measurement. The La Tocaya Zone appears to be a parallel and separate fault related zone from the main La Fortuna Zone.
• Meloncita East Zone – Meloncita East is located approximately 600 m south-southwest of the La Fortuna Mine. A geological mapping and sampling program outlined an alteration zone with highly anomalous gold values extending from the El Fuego zone of the La Fortuna mine area. The alteration and mineralization found at the Meloncita East zone is very similar to the alteration and mineralization found at the La Fortuna mine main surface showing. It is thought that the two zones are in fact the same zone although the exact surface extension of the Meloncita East Zone, to the north, can only be assumed since extensive overburden cover is present. Faulting is assumed to play a significant role in offsetting the zone. The Meloncita East Zone consists of an alteration zone approximately 20–40 m wide extending approximately 700 m north.
• La Cantarana Zone – La Cantarana lies 1.9 km southwest of the La Fortuna mine and 500 m southwest of the Meloncita West Zone. Historical rock sampling returned anomalous values of up to 6 g/t Au over an area covering approximately 300 m x 50 m.