Issue link: https://read.dmtmag.com/i/109821
squared��� method using the computer program Geosoft Target (an extension to ArcGIS that���s commonly used by exploration geologists). Again, a pronounced northnorthwesterly alignment is evident, which in turn corresponds to many of the principle veins. Integrating data from the distribution of the old mine workings (Figure 3) provides a focus and starting point for observations concerning vein orientations in rock outcrops (Figure 4) with anomalous patterns for the soil geochemistry (Figure 5), which, in turn, provides the basis for the Vein Interpretation Map (Figure 6). On this map, linear structures (veins and faults) having the same azimuth (direction) and dip (inclination) are connected into an overall interpretation. Lastly, observations concerning the relative timing of various veins and faulting events are incorporated into this final interpretation. When constructing the Vein Interpretation Map, each vein is digitized into what are called ���vein segments,��� which represent those portions on which rock samples have been collected for chemical analysis, and precise structural information concerning the vein���s orientation have been measured by geologists in the field. Figure 7 shows the rock sample assay information, in which various-sized triangles represent differing silver contents. These data reside in an Excel database, which then is converted into Shapefiles based on UTM coordinates. Combining the Vein Interpretation Map for the vein segments with the silver geochemical data from the Rock Sample Database (Figure 7) and the width of the veins produces the Silver Vein Segment Map shown in Figure 8. On this map, the silver value (grams/tonne) from the rock sample assays are multiplied by the width of vein and projected on the Vein Interpretation Map. In this manner, the silver content and tonnage potential for the ���vein segments��� as well as their ���Figure 7. A map plots silver values for rock samples of the quartz-sulphide veins of the La Cadena Area. ���Figure 8. A Silver Vein Segment Map for the La Cadena Area is the product of silver values for rock samples (Figure 7) multiplied by the width of the vein (in meters) and projected onto the Vein Interpretation Map (Figure 6). The resulting highlighted vein segments outline priority targets for drilling. shape and spatial distribution can easily be portrayed. This results in a comprehensive map of the veins that shows which have the most exploration potential. This map then will be used to prioritize the next generation of drilling targets, which could lead to future mines. Using ArcGIS as a data-viewing platform in the same manner as a ���light table,��� the success rate in encountering ���economic drill intersections��� has doubled from 31 percent to 61 percent. Using the approach shown in Figure 8, an additional increase in the ���drilling success rate��� has been realized as well as finding higher silver grades. ���This method of data analysis and viewing that now guides our exploration efforts has saved the company millions of dollars in terms of increased effectiveness for our drilling,��� notes Frederick Davidson, president of IMPACT Silver Corp. ���There have also been savings in terms of time, and it has led to better corporate decisions being made. Coming from an accounting background, the costs of the GIS have more than paid for themselves, many times over.��� Brian Hall is chief geologist and George Gorzynski is vice president for the exploration department of IMPACT Silver Corp.; email: bvhbowen@intergate.ca and ggorzynski@impactsilver.com, respectively. 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 17