Copalquin mining district

La Soledad-El Cometa is a pre resource advanced exploration target, one of at least six target areas within the Copalquin concessions.  The La Soledad-El Cometa target is permitted and drill ready for a 2019 programme to allow an initial resource estimate within this first target area.

Sun Minerals Pty Ltd (through its wholly owned Drummond Gold S.A. de C.V. subsidiary) has an option to purchase the Copalquin concessions from Compañia Minera Copalquin S.A. de C.V. at anytime over a 6 year period while funding and conducting exploration within the concessions.

Figure 1. Location of the Copalquin Mining District and some current and past mines.

The Copalquin Mining District (Copalquin) is located in Sierra Madre Occidental, Durango State, Mexico, about 80km NNE of the city of Culiacán.  The group of contiguous concessions covers an area of 7,005 hectares.  The district hosts at least 32 high grade gold/silver mines within a major epithermal centre, with widespread argillic alteration, and evidence of multiple events, frequently associated with large deposits.

Two past drilling programmes were completed between 1998 and 2007 by others plus geochemical, rock channel sampling and alteration studies.  There are at least 6 drill target areas with one area an advanced pre resource target which was the focus of the previous drilling. Bell Coast Capital Corp. drill intersections at El Cometa mine in 1998 of particular technical interest are given below.

EC-2 from 33.6m to 46.85m, 13.25m @, 74.89g/t gold and 706g/t silver

EC-9 from 28.8m to 47m, 18.2m @, 8.55g/t gold and 144g/t silver

EC-10 from 32.45m to 45.9m, 13.45m @, 10.39g/t gold and 232g/t silver

EC-12 from 18m to 26m, 8.0m @, 9.34g/t gold and 190g/t silver

EC-13 from 13.15m to 22.5m, 9.35m @, 25.32g/t gold and 247g/t silver


The Copalquin District’s oldest rocks are the Cretaceous-Tertiary andesites of the Lower Volcanic Series. These rocks were intruded by a large granodiorite stock that is part of the Sinaloa Batholith. At the time of the intrusion low-angle breccia zones sub-parallel to the intrusive contact formed within the andesite. These breccia zones and the surrounding andesite show potassic alteration. The low-angle, contact parallel breccias and the potassic alteration are characteristic of IOCG type mineralization. However, the target mineralization at Copalquin is likely to be later, associated with the late Oligocene-Miocene Upper Volcanic Series ignimbrite flareup. The ignimbrites overlay the andesite and granodiorite at Copalquin and are likely to have associated rhyolite intrusives that were the heat sources for the epithermal mineralization. Multiple events are frequently associated with large deposits.

The current structural model is that the extensive approximately E-W low-angle structure will potentially host several million tonnes (15M – 20M or more) of epithermal mineralization. This structure is cut by later, steeply north-dipping structures that strike WNW (La Soledad, Veta Leon, La Lina, Deidad, etc). These structures host bonanza grades which probably bleed out locally into the low-angle structure significantly increasing the contained ounces in the deposit. The N-S steeply east-dipping veins at San Manuel, further south, host similar high-grade mineralization and their relative age is uncertain as there are no cross-cutting features or intersections with the other structural systems. Further to the east at Constancia, there is another moderately dipping structure that may possibly be related to the low-angle structure at Cometa- Los Reyes (2km west), but mapping has not yet been completed to demonstrate a correlation between these areas. Again, indications of high-grade structures are evident in this area too.

Figure 2. Best rock chip channel sample assay and past drill results. 1,600Ha area within the 7,005Ha Copalquin concessions area where the initial exploration activity is focussed.

Argillic alteration at Copalquin is widespread. The alteration from Refugio to Los Reyes is over 2,000 meters long and from 100 to 400 meters wide. It is expected that the widest zones are related to shallow-dipping portions of the Cometa-Los Reyes structures where the structure is nearer the outcrop surface. Similar alteration is present well to the west at El Platanal and well to the east at Constancia. It cannot be stressed enough that this strong, widespread argillic alteration forming a large-volume halo well out from the veins is the observable geologic characteristic that identifies Copalquin as a major epithermal centre.

Figure 3. La Soledad mine long section showing exploration potential in this one area of the district.

Copalquin Mining District History

  • Discovered in the 1848, production ceased during the Mexican Revolution.

  • El Refugio first mined in 1849. By 1897 there were 10 head stamp batteries installed with cyanidation plants.

  • 1935 the company Minera CIBOLA milled ore from the San Manuel and El Cometa mines.

  • Detailed sampling of some workings by Industrial Mineral Mexico S.A. de C.V. (IMMSA) in 1983.

  • 1995 Alta and Kennecott outline a potential target of a million ounces of gold and 50 million ounces of silver.

  • 1997, Bell Coast Capital Corp (BCCC) conducted a helicopter supported, 31-hole, 2,500 m diamond drill program from 6 to 8 drill pads. This first-pass drilling program returned excellent results, but BCCC withdrew from the project due to difficulty in acquiring financing during a period of very low gold and silver prices.

  • BCCC completed an extensive program of geochemical sampling and mapping, resulting in the discovery of three large anomalies.

  • UC Resources explored at Copalquin from 2003 - 2007, drilling 39 diamond core holes for 4,200m. UC also completed geochemical sampling and an ASTER study. UC experienced funding difficulties and ceased activities late 2007.