The analyzes from the current drilling campaign at "Santo Toms" continue to provide encouraging insights into the nature of the copper mineralization there. Like Oroco Resource Corp. (TSX-V: OCO, WKN: A0Q2HB, ISIN: CA6870331007) on Wednesday evening, new results are available from the property in Northwest Mexico. The Company previously announced encouraging results from exploration drilling assays at the North Zone target in January. The newly arrived evaluations of boreholes N009 to N012 also prove that the Canadian copper developer is on a promising path. The results of the investigations at the "Brasiles" target are still pending. Next, Oroco intends to explore an unexplored but already IP-modeled extension of the "North Zone" with permits pending.
In his statement on the new results, Oroco CEO Craig Dalziel stated that Oroco's chances at “Santo Toms” continue to gain strength. We are pleased that mineralization in the North Zone has been intersected to expected depths and that significant intercepts have been returned from all drill holes. Drilling results have demonstrated broad and near-surface intervals of high-grade copper-molybdenum-gold mineralization; this was also the main goal of the drilling campaign. As the structure of the mineralization becomes more precise, the Company will now target a down dip extension of the "North Zone" which has not yet been explored.
The North Zone drilling As part of the 2021/22 drilling campaign, 14,838 meters of diamond drilling have been carried out on "Santo Toms" so far, mostly in HQ core format. (96 mm outer hole and 63.5 mm inner core diameter). Total meters drilled are in twenty holes, sixteen of which are in the "North Zone" testing the present Gradeshell model from 2009 to 300 to 400 meters depth. The program has now extended over 900 meters along the core of the deposit.
With the update, assays for the first dozen drill holes totaling 8,633 meters are now available. Mineralization has been intersected at expected depths; all holes returned intervals of notable grades. The most striking result came from hole N010, south of hole N008. At the time, this had yielded the best section to date (328.3 meters at 0.45 percent copper equivalent). N010 comes close: 311.9 meters at 0.42 percent copper equivalent were returned from drill core interpretation.
The background of the drilling program In the "North Zone" between 1968 and 1994 mainly vertical exploration wells were drilled. However, these were not suitable for defining the deposit in its full width and depth, especially in its southern part, which is hidden under a layer of limestone. The current drilling campaign has been drilling aligned with the orientation of the deposit and drilling angled holes that are perpendicular to the strike and dip of the deposit. This is the first hanging-wall to footwall drilling program with assays including molybdenum, gold and silver in addition to copper. (“Hanging” denotes rock that overlies a reference layer, “lying” underlies the reference layer). Geological and geophysical modeling suggests a westerly orientation that extends significantly further at depth.
The twelve previously interpreted "North Zone" holes were thus designed to test the mineralization at an almost perpendicular angle to its structural orientation. Drilling is within 10 percent of true width with the exception of hole N004.
Hole N004 was drilled to test a geophysical target, not to test the deposit. The resulting core intervals are therefore not representative of the true width of the drill hole. Hole N005 had to be completed early after just 38 meters due to unstable ground. However, hole N006 drilled next door was completed as planned.
the next steps The drilling program is not yet complete: Although holes N013 to N016 at "North Zone" and B001 to B004 at "Brasiles" have been completed (a total of 6,205 meters of drilling), however, no assay results have yet been received. Exploration drilling is currently continuing with hole B005.
3D IP modeling by Dias Geo (a ground geophysical services provider specializing in 3D and 2D surveying solutions) shows broader chargeability responses on the west side of the deposit. Oroco Resource now has the necessary permits to begin drilling this western extension targeting a deeper level of possible mineralization (300 to 400 meters below the Gradeshell model).
Conclusions from the analysis Drilling results available to date provide Oroco Resource with important insights for further exploration of the project. The copper grades determined from boreholes N009 to N012 are comparable with the historical boreholes that are available for the corresponding cross-sections. Furthermore, they confirm the resulting geological conclusions and the mentioned Gradeshell model.
An important finding is that two of the holes drilled to the south of the "North Zone" (holes N008 and N010 mentioned above) had intersected increasing widths of mineralization. Also, in the area of these holes, the copper grades of the alteration zone in the footwall on the east flank are higher than in the area immediately north of holes N001 through N003.
"Santo Toms" from a mineralogical point of view The "Santo Toms" copper-molybdenum-gold deposit is geologically consistent with the Laramid-age porphyry copper deposits found in the southwestern United States and northwestern Mexico. Simultaneously with the formation of the deposit, there were faults, fractures, mylonite zones. Control Laramid intrusive dykes as well as veins and sulphide mineralization. The best mineralization in the center of the "North Zone" is hosted in strongly potash-altered volcanic and intrusive rocks, with an overlay of phyllic (that is, influenced by circulating hydrothermal fluids) alteration.
The geological record suggests that the copper is in the form of chalcopyrite and there is significant intercalation and vein infill of covellite, chalcocite and bornite. In contrast, low levels of pyrite are present in the key drill intersections - this explains the results of the IP survey, where the responses are only in the mid-range of chargeability.
Drilling in the footwall of the "North Zone" consistently intersected propylitic altered andensite. The footwall contains extensive disseminated pyrite, demonstrating high chargeability and low resistivity in IP modelling.
Across the width of the North Zone elevated values of molybdenum, gold and silver are noted along the central axis. Disregarding metallurgical recovery, they contribute about 15 percent to the copper equivalent grade. However, silver is not included in Oroco's copper equivalent calculations.
Both historical pre-feasibility studies, new 3D modeling of historical drilling and multiple recent geophysical survey programs have identified drill targets on the property that confirm historical mineral resource estimates and define additional resource exploration.
About Santo Toms Oroco Resource holds a net interest of 73.2 percent of "Santo Toms"'s 1,172.9 hectares of core claims. This share can be increased to 85.5 percent through project investments of up to CAD 30 million. In addition, there is a 77.5% interest in 7,807.9 hectares of mineral claims circumferentially adjacent to the core claims.
The project site is located in Northwest Mexico, in the Santo Toms district between the city of the same name and the Jinchuan Group-operated Bahuerachi project approximately 14 kilometers to the northeast. The deep sea port of Topolobampo can be reached 160 kilometers away: the project area is accessible via a motorway, a nearby railway line and parallel corridors of electricity and natural gas pipelines. There is also a 32-kilometer access road that was originally built for the "El Sauzal" mine in the state of Chihuahua.
The copper porphyry deposit was defined by historical exploration (more than 100 holes totaling 30,000 meters of drilling) between 1968 and 1994. A historical pre-feasibility study prepared by Bateman Engineering Inc. in 1994 is available.
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