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GeoWorld February 2013

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center developed as early as 650 AD that was active at the time of Cort��s��� arrival in Mexico in 1519. It���s commonly known that silver and gold were the principle interests of Cort��s and his band of conquistadors when they entered Mexico. They first saw these metals in some abundance at the Aztec city of Tenochtitlan (now known as Mexico City) in 1521. Shortly afterward, the town of Zacualpan was incorporated in 1527, and mining leases bearing Cort��s��� name and the names of other conquistadors first appeared in the neighboring towns of Sultepec and Amatepec in 1531, and one year later in Taxco. Currently residing at the Zacualpan mine site are roughly six rooms of old mining maps, some of which date back to the early 1800s. With this amount of historical information, plus the large modern datasets currently being generated by IMPACT���s exploration team, it became obvious that a GIS data-handling system was necessary. The digitizing of such information has been taken on by a team of three GIS professionals along with a Mexican support staff of five, who now are trained in using ArcGIS. Exploration fieldwork in the form of geological mapping, rock sampling, soil sampling, prospecting and core drilling by a combined staff of 30 (including seven geologists), most of whom have now been trained in ArcGIS, also has been ongoing. Through this team���s efforts, the ArcGIS database has evolved to become the ���engine��� for locating and prioritizing the exploration targets for drilling, of which El Chivo and Nochebuena have become operating mines, with 11 others undergoing various forms of feasibility studies. ���Figure 1. A map shows the ancient migration of R.C. WEST GIS Needed and Used Inca metallurgy techniques. Past Is Prologue Given the densely populated nature of central Mexico and the 500 years of mining history, IMPACT Silver���s exploration team quickly realized that most of the silver veins of the Zacualpan District had likely been previously discovered, and most are known to the local people. Consequently, the most-effective means of finding new silver mines became as much an exercise in archeology in locating the old mines of the Spanish times (see Figure 2) as applying modern exploration techniques in the search for previously undiscovered silver-bearing veins. The finding and documentation of old mine workings has become the cornerstone of IMPACT Silver���s exploration methodology, with interviewing local inhabitants being the easiest and most-direct approach. Shown on the accompanying maps of the La Cadena Area are the locations for 682 old mine workings (Figure 3), having an average density of 34 per square kilometer. a b c ���Figure 2. Examples of different types of mine workings include a) a mine entrance in the form of an adit, b) a prospect pit or mine shaft, and c) the inside of an old underground mine, showing a vein that���s partially mined out. F E B R U A R Y 2 O 1 3 / W W W . G E O P L A C E . C O M 15

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