District Copper Corp., owns a 100% interest in the Eaglehead porphyry Cu-Mo-Au-Ag Project, located approximately 40 km east of the small community of Dease Lake in northern British Columbia.
The Eaglehead project, centered at 495804 m E and 6481505 m N (UTM NAD83, Zone 9), is comprised of one mineral claim that covers 13,439.61 hectares (134.4 km2) in the Liard Mining Division. The mineral claim is in good standing until January 31, 2021. The property is subject to two Net Smelter Return (NSR) royalties: a 2.5% NSR on the entire mineral tenure and a 2% NSR on a portion (981 hectares) of the mineral tenure on future production.
First discovered in 1963, the project has since been the focus of several exploration programs completed by various companies.
In 2012, Roscoe Postle Associates (RPA) completed a technical report on the Eaglehead project that included an independent resource estimate on the Bornite and East zones. The work was based on the use of 56 diamond drill holes (19,814.50 m) out of a total of 74 holes drilled on the zones. The NI 43-101 technical report is dated June 29, 2012, and was prepared by Messrs. McDonough, P.Geo and Rennie, P.Eng as Qualified Persons. The effective date of the technical report is May 14, 2012.
The results of the RPA resource estimate are outlined below:
Notes: 1. CIM definitions were followed for Mineral Resources. 2. Mineral Resources were estimated using long-term metal prices of US$4.00/lb Cu, US$1,400/oz Au, and US$17.00/lb Mo, and a US$/CS$ exchange rate of 1.00. 3. The copper equivalence (CuEQ) calculation includes a provision for different metallurgical recoveries and a 2.5% Net Smelter Return royalty. 4. Minimum mining width was five metres. 5. Bulk density was 2.70 t/m3. 6. Numbers in the table may not add up exactly due to rounding.
Readers are cautioned that a considerable amount of work has been completed on the Bornite and East zones since the date of the RPA Technical Report, including: additional drilling, sampling, re-analysis of drill core and pulp samples, preliminary metallurgical test work, ground and airborne geophysical surveys, and re-logging historical drill cores. The results of these activities have considerably increased the understanding on the controls of mineralization that could, in turn, significantly affect the results of the RPA 2012 Technical Report. In addition, the information and assumptions used in the 2012 Technical Report have changed since the date of the Technical Report. There is no assurance that the resources and conclusions set out in the 2012 Technical Report will be realized.
The resource estimate was carried out using a block model constrained by 3D wireframes of the principal mineralized domains. The external boundary of these wireframe models was 50 m from the outermost drill holes. Grades for copper, molybdenum, and gold were interpolated into the blocks using Inverse Distance to the Third Power (ID3) weighting. The estimate was further constrained by a Whittle pit shell generated to demonstrate that the mineralized bodies have a reasonable probability of economic extraction, as stipulated in NI 43-101 and the CIM Definition Standards and Guidelines. On the basis of a statistical analysis of the sample data, top cuts applied to the Eaglehead sample data were 7.5% Cu, 0.250% Mo, 50 g/t Ag, and 2.5 g/t Au. These top cuts were applied to the sample assays prior to compositing. The block model used an array of 10 m x 10 m x 5 m blocks, oriented parallel to the property grid. A bulk density of 2.7t/m3 was applied.
Alteration and Mineralization
The geological setting, alteration, and mineralization at the Eaglehead Project are consistent with a calc-alkalic porphyry copper-molybdenum system. Six zones of moderate to intense alteration and mineralization occur within a northwest trending corridor, primarily within biotite granodiorite. From southeast to northwest the zones are: Far East, East, Bornite, Pass, Camp, and West. Collectively, the zones cover a strike length of approximately 8 km and have been the subject of exploration since the discovery of the Camp zone in 1963. Because the area of interest lies in an elongate valley bottom, bedrock exposures of altered and mineralized rock are uncommon.
In the various mineralized zones, hydrothermal alteration is typical of porphyry copper environments and ranges from potassic to phyllic to propylitic. Essentially similar alteration accompanies the mineralization in the Pass, Bornite and East zones. The alteration styles that characterize the mineralized zones on the Eaglehead project are:
Potassic alteration (quartz + K-feldspar + secondary biotite, magnetite+/-hematite, calcite) occurs as envelopes around fractures and veins (which often contain chalcopyrite and/or bornite). Intense potassic alteration is typically accompanied by bornite and chalcopyrite in stringers, fractures, and veinlets but can also occur in more intensely fractured or brecciated zones.
Phyllic alteration (sericite-chlorite alteration) is characterized by a pale green silicified texture with prominent muscovite grains (altered biotite). Fractures within the phyllic alteration zone can contain chalcopyrite-bornite mineralization along with a combination of calcite, hematite, sericite, chlorite, and/or epidote and commonly at depth gypsum/anhydrite.
Propylitic alteration (pervasive epidote, epidote veinlets or epidote in veinlets with chlorite, hematite and pyrite) typically occurs over narrow intervals within zones of potassic and phyllic alteration. Weak to moderate concentrations of copper and molybdenum (from analytical results) do occur in propylitic-altered intervals in the Pass zone.
The main copper-bearing minerals are chalcopyrite and bornite, which occur primarily in sheet-like fractures, breccia, and fault zones, with lesser amounts occurring as disseminated grains and blebs in quartz stockworks. The gold and silver concentrations are associated with the copper minerals. Copper grade is typically a function of fracture density. Late-mineral fault and breccia zones that exhibit intense potassic alteration typically contain higher concentrations of bornite and molybdenite. Molybdenite is primarily concentrated along shear planes, breccia zones, and quartz veinlets and in gypsum veinlets. Malachite (and occasionally azurite and chrysocolla) is common near surface, and often occurs on fractures along with limonite and goethite.
Three phases of mineralization have been observed at the Eaglehead project:
Early phase: copper-silver (pervasive)
Second phase: copper-gold-molybdenum-silver
Third phase: copper-gold-molybdenum-silver (restricted to late fracture/breccia zones that exhibit intense potassic alteration).
Crudely defined sulphide species domains have been recognized in several of the mineralized zones. From the core of a mineralized zone to the periphery, the following general zonations are:
Based on the work completed to the end of 2016, it appears that, in general, molybdenum concentrations increase to the southeast (i.e. the East zone contains more molybdenum, whereas the Bornite zone is characterized by a higher gold content).
A description of the host rocks, dyke activity, alteration, and mineral assemblages in the known zones of mineralization within the Eaglehead project are shown in the table below.
QFP = Quartz Feldspar Porphyry; HBP = Hornblende Porphyry;
HQD = Hornblende Quartz Diorite
Trace element geochemistry indicates that multiple intrusive events may have occurred within the Project with several intrusive events exhibiting moderate to very strong “Adakite” type affinities.
No interpretation of the strike and dip of the mineralization can be provided due to the inconsistencies in data collection, lack of systematic sampling, and short, shallow drill holes.