The Sierra Madre del Sur is the ugly duckling of the mining regions in Mexico. This is not because it lacks geological potential (which is good, to say the less), or the low infrastructure level (which it suffers), but by socioeconomic woes accentuated by weak government practices that have long roots in the past. In Guerrero and Michoacan the federal and states governments have been recently tightening its grip on the security issues that hindered development of any type in the region, and we can only hope that this effort continues with the attention and strength it deserves. The case for Oaxaca and Chiapas is even deeper rooted on the lack of integration and development of indigenous communities, and will take a lot more time, resources and , more importantly, political will to make the socio economic changes needed to the advancement of its society. On the other hand, in spite of all the troubles encountered, mining companies have been able to delineate resources in 19 properties, 9 of which are in production, and 4 more in feasibility or development.
The figure below shows the mines (in red) and projects (in blue) with published resources in the Sierra Madre del Sur Region (outlined in orange).
To date, resources have been delineated in only 5 types of ore deposits; skarns, LS epithermal veins, IS epithermal veins, VMS and porphyry coppers. Skarns take the lion’s share of the gold endowment of the region, with 84% of the 33.5 M Oz Au so far defined, plus 200 M Oz of silver, 1.7 B Lb of copper, as well as some molybdenum, lead and zinc. To note is the size of the Nukay-Los Filos resource, with 15.5 M Oz Au, Limon-Guajes with 5.3 M Oz Au and Media Luna hosting almost 4 M Oz Au. Away from the Guerrero Gold Belt, the three low sulfidation epithermal vein systems host 810 K Oz of gold and 121 M Oz of silver, whereas the intermediate sulfidation epithermal veins contain 192 K Oz of gold, over 29 M Oz of silver and some copper, lead and zinc resources. Porphyry copper deposits contain 75 % of the copper endowment for the region, with 7.3 M Lb Cu, although most of these resources are in just one deposit, La Verde in Michoacan. They are also host to over 2.6 M Oz of gold and 63.7 M Oz of silver. Volcanogenic massive sulfide (VMS) deposits are truly polymetallic beasts, with the three deposits with resources hosting over 1.9 M Oz of gold, more than 201 M Oz of silver, 716 M Lb of copper, 902 M Lb of lead and 3.9 B Lb of zinc.
Among the deposit types present in the region without published resources, but deserving attention, are orogenic gold, high sulfidation epithermal, Mississippi Valley Type (MVT), stratiform copper and even placer gold deposits.