Figure 1: Plan view of drill holes. Source: Marimaca Copper
Marimaca Copper (TSX:MARI) has reported the latest findings of its recent five-hole diamond drilling exploration program at the eastern edge of the Marimaca Oxide Deposit (MOD). The program was initially carried out to follow up on the sulphide-bearing intersection of the formerly disclosed hole MAD-22, renowned for its higher concentration of primary copper mineralization located down-dip of the Marimaca oxides.
Sergio Rivera, VP Exploration at Marimaca Copper, commented in a press release: “Despite challenging drilling conditions we continue to improve our understanding of Marimaca’s genesis and target generation for the potential sulphide feeder zones. We are very encouraged to see the continuation of the alteration assemblages and rock types observed in MAD-22 in the follow-up program, which is the first time that consistent sulphide-associated alteration has been observed below the MOD. MAD-25, in particular, which stepped out 500m to the south of MAD-22, intersected the expected alteration mineral assemblages with strong mineralization at the targeted horizon, but was terminated before the expected higher-grade zone due to the intersection of a fault zone, which deviated the hole.
Planning for the next phase of sulphide exploration will incorporate learnings from this first phase campaign, including adjusting the approach to drilling from east to west to allow for easier orientation of the drilling to the deeper target horizons. Approaching from the west will take time to plan new drilling infrastructure rather than using existing eastern drill pads at the MOD, however we believe the sulphide potential warrants this. We continue to believe that the sulphide potential is high, particularly considering the scale of the oxidized mineralized body at the MOD and the indications, such as Hole MAD-22, that higher grade remnant feeder structures, remain intact in the shallower down-dip zones of the MOD.”
Figure 2: Idealized 3D view of MOD (looking North) with interpreted sulphide feeder horizon and 2023 MRE pit. Source: Marimaca Copper
Drilling operations faced considerable difficulties, largely due to the direction of drilling from existing pads along the MOD’s primary known structures. The data generated from this effort, along with insights regarding future deeper drilling tactics, especially their origin and orientation, will inform the layout of ensuing exploration activities.
Expanding on individual drill hole observations, hole MAD-25 was a 500m step out to the south of MAD-22. It discovered strong mixed and primary sulphide mineralization from nearly the projected target horizon, which was roughly 136m downhole. However, operations were halted at 218m due to an encountered fault.
Holes MAD-25, 26, and 27 intersected extensions of alteration-mineralization assemblages similar to those found in MAD-22. These included sections displaying massive to stringer filling chalcopyrite and pyrite and pervasive hydrothermal magnetite replacement. The latter was partially linked to coarse actinolite veinlets associated with the porphyritic quartz-diorite intrusion host rock.
Figure 3: Idealized long and cross 3D view of MOD with MAD-22 interpreted Chalcopyrite-dominated zones identified. Source: Marimaca Copper
The drill holes were found immediately adjacent to the eastern wall of the whittle pit limits, in accordance with the Mineral Resource Estimate (MRE) from October 2022. This positioning indicates the possibility of high-grade, open-pit-able mineralization.
The sulphide copper mineralization observed in the deeper mineralized intercepts appeared less consistent than in MAD-22, which was attributed to variability in the pyrite/chalcopyrite ratio in the primary zones. Such variation is typical in Iron Oxide Copper Gold (IOCG) systems and requires further analysis to vector to the zones bearing a higher amount of chalcopyrite. This particular observation was corroborated in MAD-26, which intersected strong magnetite alteration from 186m. Nonetheless, it presented a higher pyrite/chalcopyrite ratio compared to MAD-22, which corresponds to lower grade copper intersections.
Highlights from the results are as follows:
Four drill holes recovered to a maximum depth of 349m from surface, with three holes completed successfully to target depth
The fourth hole, although recovered, MAD-25 was terminated above target depth due to poor rock quality caused by localized faulting
Holes MAD-24, 25, 26 and 27 intersected the extension of the upper oxide and mixed/enriched copper mineralization
This zone is interpreted as the near-surface, oxidized expressions of high-grade mineralized structures encountered in MAD-22
MAD-25 intersected 56m at 0.40% CuT from 136m including 24m at 0.63% CuT of secondary and primary sulphides in-line with the projected horizon from MAD-22, however, could not progress further into the horizon due to rock quality in a fault zone and was terminated at 218m
Hole MAD-24 intersected 74m of 0.52% CuT from 24m including 18m at 0.68% CuT from 24m and 28m at 0.79% CuT from 64m above the projected sulphide horizon
Hole MAD-24 intersected a barren post-mineral dyke from 224.3m which occupied the projected extension of the sulphide horizon from MAD-22
Hole MAD-27 intersected 40m at 0.50% CuT from 68m including 18m at 0.90% CuT of mixed and enriched mineralization from 74m, and a deeper intersection of 12m at 1.0% CuT of chalcopyrite mineralization from 162m
Hole MAD-26 intersected strong magnetite alteration from 186m, however with a higher pyrite/chalcopyrite ratio relative to MAD-22 corresponding to lower grade copper intersections
MAD-23 was terminated as a result of contractor operational performance leading to contractor replacement for subsequent holes (MAD-24, 25, 26, 27)
The above references an opinion and is for information purposes only. It is not intended to be investment advice. Seek a licensed professional for investment advice. The author is not an insider or shareholder of any of the companies mentioned above.