2.5 km²
Prioritized Target Area
Target area narrowed down from the 680 km² preliminary prospective zone based on Stage Two results
17–19 tons
Estimated Gold Reserves
Projected gold reserves within the study area, equivalent to approximately 600,000–670,000 troy ounces
95%
Probability of Gold Presence
Predicted probability of gold presence at the maximum-intensity points recommended for drilling
STAGE TWO — AERIAL SURVEY
680 km² Screened by Helicopter
This report reflects results of DDT gold deposits surveys in the Humboldt County, State of Nevada. After completion of the three Star and the Stage I surveys, OGD conducted the Stage II DDT™ survey on the previously identified primary anomalies of the intrinsic radiation of gold-bearing formations ranked in accordance with the DDT™ method. The identified prospective areas are shown in Fig.1 on a satellite image and a topographic map.
The total preliminary area of the selected prospective areas is approximately 680 sq.km.
The two-day Stage II express aerial survey involves movement along a zigzag track designed to explore territories over 200 sq.km. and isolate the most attractive areas for commercial extraction for further investigation.
The planned fly-over track is shown in blue in Fig. 2. The track also passes through the nearest known commercial deposit – "Turquoise Ridge" – owned and operated by Barrick and Newmont, which will be used as a reference for assessing the studied areas. The length of the planned track is approximately 800 km. The actual flight track for the first two days of flights is shown in red in Fig. 3.
Fig. 1. Identified prospective areas on a satellite image and a topographic map
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Fig. 2-3. The planned and actual flight track for the first two days of flights
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Fig. 4-5. The level of the intrinsic radiation is indicated at each measurement point
The collected data were processed and analyzed in accordance with DDT™ method. The analysis results – ranked anomalies of the intrinsic radiation of gold- bearing formations – are depicted on a satellite image and a topographic map
The actual survey flight path along the northern site (No. 2) was much different from the track originally planned. The flight was made along the foot of the mountains because the mountains themselves were considerably steep and inaccessible. Working in such mountains would significantly increase the cost of the project. At the same time, the signal level of the intrinsic emission of gold-bearing formations along the track was below estimated commercial scale. Therefore, prospective area No. 2 was excluded from further consideration in view of its probably low commercial attractiveness.
Target Selection
During the flights, high level intrinsic radiation readings were recorded within the red range of the intensity scale. One place, located in the foothills, is the known commercial "Turquoise Ridge" deposit. The second place is located at the north of site No. 1. It was this place that was selected for additional research via the Stage II enhanced aerial survey on the third day. The ideal planned flight track is shown in Fig. 6. It is based on three previously identified points with high intrinsic radiation intensity. The actual track is shown in Fig. 7.
Given the strong wind and the complexity of the planned spiral trajectory, it was impossible to follow the initial flight plan. Fig. 9 shows some incompleteness of the area with indices of intrinsic radiation of gold-bearing anomalies. However, the studies carried out were quite enough to calculate the extremum points recommended for setting up the drilling operations and to evaluate the location of the expected gold reserves.
The recorded field data were processed and analyzed in accordance with DDT™ technology. The analysis results – ranked anomalies of the intrinsic radiation of gold-bearing formations – are depicted on a satellite image and a topographic map (WGS84) in Fig. 8 and Fig. 9, respectively.
The figures, in accordance with the intensity scale, show the change in the main registered factor of the intrinsic radiation of gold, conventionally called the "intensity of intrinsic radiation". The maximum intensity indicator at the site reached I = 2.2. This is an integral factor characterizing the general energy state of gold-bearing formations at a given point on the surface. It is an integral factor because, as established experimentally, its readings are influenced by such characteristics as the thickness of the productive layer, the percentage of gold itself, and several other indicators.
Target Selection
As an area of interest, section 8T35H was chosen, the corner coordinates of which are shown in Table 1. The identified anomalies of intrinsic radiation within the boundaries of section 8T35H are presented on a satellite image, a topographic map, and a coordinate grid (WGS84) in Fig. 10, 11 and 12, respectively.
The studies carried out made it possible to identify the points of maximum extremum located within the red contour of the identified anomalies. The locations of the extremum points that will be recommended for drilling the first three wells are shown in Fig.13.
The indicated coordinates of the extremum points, as presented in Table 2, represent the center of a circle with a radius of 30-50 meters. Inside this circle, the precise borehole setting point should be located. This degree of precision is associated with a certain amount of calculated error in data collection and GPS positioning. Final identification of the exact location for vertical drilling needs to be done on the ground by an OGD crew during a one-day field expedition (Stage III Survey).
Quantitative Forecasting
For quantitative forecasting in the study area, data from the report on the neighboring mining operation, "Turquoise Ridge," were used as a reference. Fig. 15 shows the measured intrinsic radiation intensity data for gold bearings from a single flight over the "Turquoise Ridge" production area. The intensity indicator varied in the range I = 1.2 to 2.1 (from green to red on the intensity scale). Corresponding information was taken from the company's public record, an excerpt of which is shown in Fig. 14.
Table 2 shows the depth ranges, up to 500 meters, within which we predict the location of the productive horizons. It should be noted that the indicated depth ranges do not represent the actual thickness of a single productive horizon, but rather this is a range in which only one or several productive horizons with a much lower thickness are located. The depth measurement is carried out from the surface at the given coordinate point. In addition, the distribution of peak signals was ranked, and each predicted range was highlighted in different colors in accordance with the adopted intensity scale. This is a conditional ranking of the predicted efficiency of the productive layer. Each color corresponds to certain characteristics described above. For the locations of maximum intensity (red), a forecast is given for the percentage of gold in the rock. This is also a range. The average gold grade in each relevant horizon should be within the associated predicted range. For the remaining horizons, the percentage varies in accordance with the intensity parameter and the associated scale characteristics as described above.
As our experience shows, at this stage, when predicting the range of depths of occurrence of productive layers, the error does not exceed 5-7%. We believe that at this stage of research, it is quite enough to determine the very existence of the productive layer and, with some small discrepancy, predict the depth and percentage of gold.
As mentioned earlier, the "intensity of intrinsic radiation" indicator is an integral indicator, i.e., it incorporates the influence and the corresponding contribution of all productive horizons located vertically up to a depth of 500 meters. However, this contribution is nonhomogeneous and, as we believe, is proportional to the value of the intrinsic radiation intensity index.
Adopting the data on the "Turquoise Ridge" deposit, as shown in Fig. 14, as a standard, a remote assessment of potential reserves was carried out according to our own methodology. The considered volume of the earth's crust was represented in the form of a tetrahedral prism, the upper horizontal face of which is the selected prospective area (in this case, the entire earth's surface bounded by the 8T35H sector), and the lateral, vertical edges reflect the depth of exploration – 500 meters. Reserves of the sought-after substance – gold – were remotely estimated according to its intrinsic radiation within the given volume of the earth's crust. (This method has nothing to do with the classical method for estimating reserves based on geometric constructions, inter- and extrapolations. Using the classical interpretation, our assessment would probably be more in line with the Indicated-Measured categories, although the methods of determination are completely different.) This type of assessment indicates that the potential gold reserves in the study area may be 17-19 tons of gold.
RESERVE ESTIMATE & RECOMMENDATION
Conclusions and Recommendations
1. Stage II Survey results supported our preliminary conclusions regarding the selected prospective areas.
2. Survey field studies and subsequent analysis identified anomalies of maximum intensity (red and blue on the scale) and points of maximum extremum of intrinsic radiation of gold-bearing formations.
3. At the extremum points, we predicted the depth ranges within which the productive horizons of gold-bearing formations are located. These ranges are ranked by importance and shown in different colors in accordance with the intensity scale of intrinsic radiation.
4. It is at these extremum points that drilling operations must be performed. We predict that there will be a 95% probability that gold will be present at these locations with the predicted grade. Drilling in the specified ranges of depths (Table 2) must be done for core sampling.
5. The intensity of intrinsic radiation of gold in the selected study area is very close to the nearest known commercial deposit – “Turquoise Ridge.” However, it is more compact and localized (with approximately 2.5 km2 or 640 acres of land. We estimate the projected gold reserves to be 17-19 tons or 600,000 - 670,000 troy ounces.