Cobrecon Target
The Cobrecon, Cobrecon Sur, and Cobrecon Este porphyry Cu-Au targets are the most recent focus of drilling, with the program starting at the northern Cobrecon anomaly. The targets bear many similarities in geology to the porphyry deposits in the Mirador District to the north (Mirador, Panantza, and San Carlos porphyry deposits). These deposits are classic calc-alkaline porphyries related to the emplacement of late-stage subvolcanic intrusive phases of the Zamora batholith.Cobrecon and Cobrecon Sur are parallel anomalies, located one kilometre apart, and each measure one by three kilometres and are supported by initial rock sampling along limited exposures within creeks. They were located based on coincident geophysical-geochemical data that indicated the presence of twin porphyry copper mineralized systems. Their northwest trend is regionally the most significant mineralized trend in the belt: an important characteristic of the large porphyry and epithermal gold deposits across the border in Ecuador.
Subsequent to the definition of these targets, a third area of strong copper-molybdenum anomalous soil samples and airborne EM data was defined to the east of Cobrecon Sur, approximately 2-3 kilometres southeast of the current drill holes. Preliminary rock samples from the area have returned altered intrusive rocks (quartz-sericite-pyrite and quartz vein stockwork) with disseminated chalcopyrite and chalcocite indicative of a porphyry system. Perhaps most encouraging is that the molybdenum anomaly is coincident with a zinc low anomaly, which suggests a strong system. This mineral zoning is very important in the Cu-Au-Mo porphyry deposits across the border in Ecuador, in the Mirador District.
Drill core assay results from the first four holes at Cobrecon confirm the subsurface extent of the porphyry mineralization, with wide intervals of low-grade copper intersected to depth. The upper portion of hole CBC-01 intersected 0.16% Cu, 0.03g/t Au, and 0.002% Mo over 100 metres, and a second, deeper intercept returned 0.12% Cu, 0.02g/t Au, and 0.002% Mo over 165 metres. Hole CBC-02 intersected 228 metres of 0.16% Cu, 0.04g/t Au, 0.002% Mo, from 6 to 234 metres, including 126 metres of 0.19% Cu, 0.04g/t Au, 0.002% Mo.
Average grades in all holes are consistent with rock samples collected at surface along creek outcrops, which ranged from 0.1% to 0.2% copper. Assay highlights are shown below:
Table 1: Cobrecon Significant Drill Intersections.
| Hole | From (m) | To (m) | Interval | Cu% | Mo (ppm) | Au g/t | Ag g/t | CuEq* |
|---|---|---|---|---|---|---|---|---|
| CBC-01 | 0 |
20.5 |
20.5 |
0.1018 |
10.9 |
0.033 |
2.8 |
0.1228 |
20.5 |
121 |
100.5 |
0.1626 |
16.5 |
0.027 |
0.6 |
0.1798 |
|
163.11 |
183.7 |
20.59 |
0.1819 |
4.7 |
0.037 |
0.5 |
0.2054 |
|
240 |
405.47 |
165.47 |
0.1181 |
20.5 |
0.017 |
0.4 |
0.1289 |
|
| CBC-02 | 5.74 |
234 |
228.26 |
0.1607 |
15.7 |
0.041 |
0.7 |
0.1867 |
5.74 |
108.25 |
102.51 |
0.1212 |
13.5 |
0.039 |
0.9 |
0.1459 |
|
| incl. | 108.25 |
234 |
125.75 |
0.1930 |
17.5 |
0.043 |
0.7 |
0.2200 |
234 |
264 |
30 |
0.1425 |
12.3 |
0.017 |
0.4 |
0.1534 |
|
346 |
430 |
84 |
0.1196 |
15.6 |
0.032 |
0.4 |
0.1397 |
|
| CBC-03 | 10.3 |
94 |
83.7 |
0.1558 |
27.0 |
0.039 |
0.6 |
0.1799 |
| CBC-04 | 0 |
61.65 |
61.65 |
0.1236 |
12.7 |
0.062 |
0.8 |
0.1625 |
| CBC-05 | 85.5 |
270.5 |
185 |
0.1154 |
16.3 |
0.023 |
0.5 |
0.1299 |
| incl. | 85.5 |
219 |
133.5 |
0.1247 |
17.4 |
0.026 |
0.6 |
0.1407 |
344 |
380.15 |
36.15 |
0.1259 |
25.6 |
0.078 |
0.5 |
0.1751 |
|
| CBC-06 | 8.92 |
122 |
113.08 |
0.1786 |
12.0 |
0.135 |
1.0 |
0.2630 |
| incl. | 21.7 |
85.5 |
63.8 |
0.2454 |
16.9 |
0.196 |
1.2 |
0.3679 |
| CBC-08 | 23 |
126 |
103 |
0.1418 |
10.3 |
0.081 |
1.1 |
0.1926 |
| CBC-09 | 3 |
42 |
39 |
0.1079 |
9.6 |
0.036 |
0.6 |
0.1305 |
| CBC-10 | 10 |
180 |
170 |
0.1028 |
388.5 |
0.002 |
41.7 |
0.1043 |
| incl. | 10 |
27.26 |
17.26 |
0.1688 |
20.0 |
0.037 |
1.1 |
0.1920 |
The better mineralization is related to, but not confined by, northwest-trending, subvertical phreatic breccia dikes. Mineralization occurs as fine disseminated chalcopyrite as well as coarser blebs in the breccia matrix. Diorite, hornfels arenite, and diabase also host disseminated chalcopyrite. Quartz-sericite-pyrite and argillic alteration predominates, with common late-stage calcite veining within the breccia. Only one significant post-mineral dike was intersected, in hole CBC-02, near the outer margin of the mineralization. Copper grades decrease within more common early dacite porphyry dikes, which are closely associated with the mineralization. These dacite dikes precede the breccia.
REGIONAL PORPHYRY SYSTEMS
Porphyry copper-gold-molybdenum systems, and related skarn and epithermal gold systems, occur in Early to Late Jurassic intrusive and volcano-sedimentary rocks along the length of the Cordillera del Condor. Intrusive rocks of the Zamora Batholith host the porphyry deposits, skarn deposits occur in the older, intruded sedimentary rocks as well the overlying volcano-sedimentary rocks, and epithermal deposits are hosted by the volcano-sedimentary rocks. All these are overlain by Early Cretaceous sedimentary rocks. (Read More...)