Mineral resources in skarn deposits in the Sierra Madre del Sur

Late Cretaceous-Early Tertiary intrusions, mostly granodioritic porphyries, were emplaced into Mesozoic sedimentary sequences in the Sierra Madre del Sur. The mineralization is associated to both the endoskarns and exoskarns. The Guerrero Gold Belt hosts the largest deposits of Los Filos, Limon-Guajes and Media Luna, while the skarn at Cobre Grande in Oaxaca is associated to a porphyry copper system. Seven of those deposits have resources published that amount to more than 28 M Oz of gold and almost 200 M Oz of silver, with important amounts of copper and some lead, zinc and molybdenum.

In the picture below, Old dumps from the Tlamanca skarn in Puebla, photo by Miguel Heredia.

franja mineralizada1Goldcorp’s Los Filos mine hosts the largest resource for this type of deposit, over 15.5 M Oz of gold and 100 M Oz of silver, while Torex Gold’s Limon-Guajes mine comes second with over 5.4 M Oz Au and more than 9 M Oz Ag, although at a gold grade three times that of Los Filos. Media Luna mine, which also belongs to Torex Gold, hosts almost 4 M Oz gold, 44 M Oz silver and over a billion pounds of copper, is the only significant copper bearing skarn in the Guerrero Gold belt. Timmins Gold’s Ana Paula project hosts almost 2 M Oz of open-pittable gold resource, along with more than 7 M Oz of silver, and Alamos Gold’s Esperanza project (Cerro Jumil) hosts over 1.1 M Oz gold and almost 4 M Oz of silver. In Cobre Grande Linear Metals defined over 20 M Oz of silver, over half a billion pounds of copper, over 40 M Lb of moly and over 200 M Lb of zinc. Taxco is a special case regarding resources, as the only source we could get our hands on was the Grupo Mexico’s annual report, and their IMMSA division only states consolidated figures for the resources of all its mining units. Therefore the total resource was divided by the number of mining units to obtain an estimate of the resource.

Table Skarn deposits, Sierra Madre del Sur1

The numbers we manage are largely from technical reports, company’s websites or yearly filings to the stock exchange.The numbers we manage are largely from technical reports, company’s websites or yearly filings to the stock exchange, most to the end of 2014.

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