TECHNICAL MEMORANDUM TO: Jamie Joggerst tel: 52-297-7723 Geotechnical Engier, fax: 52-297-7724 Tetra Tech email: Jamie.Joggerst@tetratech.com 331 West Ina Road Tucson, AZ 85741 FROM: Dale Rucker, PhD Sr. Project Manager SUBJECT: Magtic Survey of the Rosemont Mi Facility DATE: November 19, 28 INTRODUCTION A magtic survey was conducted at the proposed Rosemont Mi in southeastern Arizona. The mi is to be constructed on the east side of the Santa Rita range (Figure 1). The purpose of the survey was to deliate the andesite plug that crossed through the facilities location. A Geometrics G-858 with a single sensor acted as the roving magtometer and a Geometrics G- 856 was used as the base station located a few kilometers away. The survey was conducted by walking the G-858 magtometer along 1 parallel lis. The average li length was 1.2 km with a total distance of 12 li kilometers. The lis were spaced approximately 8 m apart. However, surface obstacles and terrain caused some lis to meander within the survey area. Major findings of the survey are as follows: - The andesite does not have a significant susceptibility contrast relative to the background. - Several large ar surface targets (within 2m of the surface) have been identified in the survey area www.hgiworld.com 1 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
Figure 1. Regional Map www.hgiworld.com 2 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
Magtic Survey Acquisition Figure 2 shows the layout of the 1 lis over the proposed mi site. The lis are superimposed over geologic features. The lis were acquired on October 2-21, 28. Table 1 lists the survey parameters. 35235 35234 2 3 4 5 6 7 8 1 1 35233 9 Northing (m) 35232 35231 3523 Geologic Boundaries KM QA QO KTbp Fault 35229 35228 35227 Datum: NAD83 Coordinate System: UTM Unit: Meters 35226 35225 5236 5237 5238 5239 524 5241 5242 5243 5244 5245 Easting (m) Table 1. Rosemont Mi Survey Parameters Length (m) Starting Position (NAD 83 UTM - meters) End Position (NAD 83 UTM - meters) 1 1222 523758.8 352249.4 523515.1 3523387. 2 129 523819.2 3522541.5 523522.1 352341.9 3 122 523948.5 352258.4 523714.2 3523366.2 4 1512 52432.5 35225.6 523723.5 3523385.9 5 1314 524115.6 352253.6 523847.8 3523486.6 6 1445 524172.5 3522534.2 523931.9 3523591.1 www.hgiworld.com 3 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
Length (m) Starting Position (NAD 83 UTM - meters) End Position (NAD 83 UTM - meters) 7 1178 52425.6 3522535.2 52454.9 3523444.7 8 161 52431.8 3522628.6 52497.6 3523427.3 9 937 524425.9 352264.9 524244.6 3523328.1 1 895 52459.4 3522761.6 524332.9 3523439. Magtic Data Processing The magtic data, including the base station and rover, were downloaded using Magmapper2. The software was provided by Geometrics and automatically rectifies the data for diurnal drift of the magtic field and positioning. The data were exported to Excel for additional processing to remove spikes. A heading correction was not applied to the data. A compass rose diagram of magtic data were acquired, which plotted heading direction versus magtic value. The maximum magtic field difference due to heading was 6 nt, which is less than the natural variability of the data along each li. The IGRF, a planar trend along the earth s latitude, was also not removed due to the low influence of the trend on the data. Magtic Results Figures 3-12 shows the magtic field along individual lis. All data are presented from south to north. Figure 12 shows the compiled magtic data as a set of stacked li plots versus the northing position of the reading. The plot was created by shifting the data with the formula (#- 1)*1nT. So, 1 was shifted by -9nT, 2 was shifted by -8nT, etc. The plot also incorporates the best guess for the edge of the andesite dike. www.hgiworld.com 4 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
4 2-2 Magtic Field (nt) -4-6 -8-1 -12-14 -16 1 2 3 4 5 6 7 8 9 1 11 12 13 Figure 3. 1 Distance (m) 6 4 2-2 -4-6 -8-1 1 2 3 4 5 6 7 8 9 1 11 12 13 Figure 4. 2 www.hgiworld.com 5 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
5-5 -1-15 -2 1 2 3 4 5 6 7 8 9 1 11 12 13 Figure 5. 3 2 15 1 5-5 -1 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 Figure 6. 4 www.hgiworld.com 6 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
15 1 5-5 -1-15 1 2 3 4 5 6 7 8 9 1 11 12 13 14 Figure 7. 5 4 35 3 25 2 15 1 5-5 -1-15 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 Figure 8. 6 www.hgiworld.com 7 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
3 25 2 15 1 5-5 -1 1 2 3 4 5 6 7 8 9 1 11 12 Figure 9. 7 2 15 1 5-5 1 2 3 4 5 6 7 8 9 1 11 Figure 1. 8 www.hgiworld.com 8 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
3 25 2 15 1 5-5 1 2 3 4 5 6 7 8 9 1 Figure 11. 9 6 5 4 3 2 1-1 -2-3 1 2 3 4 5 6 7 8 9 1 Figure 12. 1 www.hgiworld.com 9 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
2 Offset Magtic Field (nt) -2-4 -6-8 -1-12 1 2 3 4 5 6 7 8 9 1 Dike 1 35224 35226 35228 3523 35232 35234 35236 35238 Northing (m) Figure 12. Compiled magtic data with offset. Figure 13 shows the compiled magtic data as a contour plot. The color scale is non liar to focus on the majority of the data between -6 and 6nT. Data outside of this range has little color variability because they are typically a result of short wavelength spikes. There are a few exceptions, and these have been identified specifically as magtic targets with arrows drawn to the target. The best guess for the edges of the andesite were also placed on the contour plot. There is low confidence in these picks due to the low contrast between the target rock and background. It was originally assumed that the andesite rock was a dike, that extended relatively deeply into the earth. A revised model includes an isolated buried shallow feature, which may be the cause of the low contrast. It is recommended that a resistivity survey be run over the buried andesite to test if there are electrical differences between the andesite and host rock. www.hgiworld.com 1 November 19, 28 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 tel: 52.647.3315 fax: 52.647.3428
35235 5 Magtic Target 1 Magtic Field (nt) 3 e7 6 8 18 16 14 12 1 8 6 4 2-2 -4-6 -8-1 -12-14 -16-18 -2-22 -24-26 9 4 2 e1 L in 35233 n 35234 Northing (m) 35232 35231 3523 35229 35228 35227 35226 Map Symbols Edge of Andesite Picks Data Acquisition Geologic Boundaries KM QA QO KTbp Fault Datum: NAD83 Coordinate System: UTM Unit: Meters 35225 5236 5237 5238 5239 524 5241 5242 5243 5244 5245 Easting (m) Figure 13. Contoured Magtic data www.hgiworld.com 11 232 NORTH FORBES BLVD. TUCSON, ARIZONA 85745 November 19, 28 tel: 52.647.3315 fax: 52.647.3428