The Tierra Blanca Project represents a drill ready polymetallic project located close to infrastructure in the prolific mining district around the City of Chihuahua in Chihuahua State, Mexico. Sampling in an exploration drive has revealed high-grade zinc mineralisation outcropping to surface, with structural interpretation suggesting potential for high-grade silver at deeper levels.
Location and Infrastructure
Tierra Blanca lies 40km from the metropolitan centre of Chihuahua in a district that has yielded prolific silver zinc and lead orebodies and seen a resurgence of interest with Canadian companies acquiring projects that are believed to form extensions of the famous Santa Eulalia mine which produced 500 million ounces of silver in addition to substantial volumes of zinc and lead.
The district surrounding Chihuahua is a significant silver producing region with several substantial mines operated by majors and mid-tier companies, District Historical Production of 50Mt at 310 g/t Ag, 8.2% Pb and 7.1% Zn.
Concentrates produced from mines in the region are either exported from west coast ports where large metals traders operate blending and stockpiling facilities, or transported by paved highways to the large Metalúrgica Met-Mex Peñoles, located in Torreón, Coahuila, which is one of the largest non-ferrous metallurgical complexes in the world.
Tierra Blanca is located in a metallogenic province that has yielded several substantial orebodies predominantly containing silver, zinc and lead. Several significant mines operate in the region, with prolific artisanal workings pointing to multiple exploration opportunities.
Tierra Blanca is interpreted to be what is termed a Carbonate Replacement Deposit (CRD) which are common in the region.
40% of the 10 billion ounces of Silver produced in Mexico have been produced from CRDs The key features of Mexican CRDs are that:
- Deposits occur along a ~2,000 km long belt of carbonate rocks from SE Arizona to south-central Mexico, where fold and thrust architecture controls high temperature Zn-Pb-Ag+/-Cu+/- Au mineralization
- Deposits occur as chimneys (deeply plunging ore from surface), and then at depth, flatter lying mantos (lenses) in Carbonate rocks. Skarn orebodies are frequently associated with this style of deposit.
- Typically, CRD orebodies are Polymetallic, with metal contents ranging from 1- 18% Zn, 1-12% Pb, 60-600g/t Ag, up to 2% Cu and 6g/t Au.
Tonnage and grade data for skarn, chimney and manto ores in seventeen districts of Mexico show a wide range of values (with an average of 11.4 million tonnes (Mt) at 11% Pb, 8.5 %Zn, 0.7% Cu, 243 ppm Ag and 1.8 ppm Au. Santa Eulalia (the district close to which Tierra Blanca lies) is the largest district with 50 Mt of ore grading 5%Pb, 6-7% Zn, 0.1% Cu and 242 ppm Ag.
The Silver grades are high in the majority of deposits with an average of 243 g/t Ag and a range from 14 to 600 g/t Ag with most deposits (14 out of 17) having grades >100 g/t Ag. A trend of silver grades increasing at depth is frequently observed.