Santa Teresa is located four kilometers southwest of IMPACT's producing Guadalupe processing plant and immediately south of the former producing mines at Noche Buena (silver) and Carlos Pacheco (gold) in the Valle de Oro subdistrict of the Royal Mines of Zacualpan Silver District.
Situated in the Valle de Oro sub-district of dominantly gold veins located four kilometers southwest of IMPACT's producing Guadalupe mill and immediately to the south of IMPACT's past producing Nochebuena (silver) and Carlos Pacheco (gold) mines. To the northeast is the large Coronas mine, one of the oldest and better known past producers of the Zacualpan district.
Numerous north-south striking veins similar to the Nochebuena or Carlos Pacheco veins transect the Santa Teresa area. Elsewhere in the Zacualpan district veins of this orientation have the greatest degree of structural and grade continuity, producing many of the district's better mines historically. In addition, there are number of northeast trending, northwest dipping veins that resemble the historic Coronas mine in structural style. Rock sampling by IMPACT has produced gold grades ranging up to 114.5 g/t, with 15 samples having more than 10.0 g/t, and 214 greater than 1.0 g/t gold. In proximity to the historic Coronas Mine some sizable old underground workings exist. However elsewhere in the Santa Teresa area there is little evidence of historical exploration or mine development, which the low sulphide content of these auriferous veins may have caused these veins to be overlooked by the historical prospecting.
Roughly half of the veins hosting the better gold grades contain very little sulphide minerals and as such would fall into a class of gold occurrences known as "Epithermal Low Sulphidation". Native gold or electrum would be the most likely host minerals, which would be readily amenable to gravity concentration methods. These veins are most abundant in the southwestern portion of the Santa Teresa area where the density of these north-south striking veins is the highest of the entire Zacualpan district. In addition, this portion of the Santa Teresa area contains the only known outcrops of an Eocene Feldspar Porphyry within the Zacualpan district which are the only know magmatic intrusive rocks on the property. Fifty-two porphyry outcrops have been mapped over a one kilometer area with the southern and western boundaries currently undefined. Previously this rock type had only been observed as clasts within the gold-bearing portions of the Nochebuena type hydrothermal breccias of the Nochebuena and Carlos Pacheco mines, located immediately to the north. These Eocene Feldspar Porphyries are thought to be similar to the Tilzapotla Rhyolite, an enigmatic intrusive stock located midway between the Taxco and Zacualpan Districts that is considered to be the heat source responsible for the formation of the Zacualpan Southeast and Taxco veins. It has been dated at 32 million years, the same age as a vein in the Taxco District, and by inference a similar age has been assigned to the Zacualpan veins. Associated with this Feldspar Porphyry are the highest gold/silver ratios of all the Zacualpan veins, again suggesting an environment of localized, very high heat flow suggesting the Feldspar Porphyry is probably the heat engine for the formation of these gold veins and beyond that, the silver veins in the Zacualpan district.
Brecciation and silicification of the older host rocks immediately surrounding this Feldspar Porphyry is a common feature, suggesting the formation of a cupula similar to a number of the Nevada type epithermal low sulphidation gold occurrences. Rock samples from this Feldspar Porphyry itself return very low values for precious and base metals, however silicified and brecciated portions of the host rock adjacent to and above this Feldspar Porphyry have numerous high gold values (up to 17.95 g/t) presenting a potentially very intriguing bulk tonnage exploration target.
Santa Teresa Location Map
Santa Teresa Area Map