Contango Ore, through its wholly owned US subsidiary J T Mining, Inc. (J T Mining), holds a Lease Agreement with CIRI with an effective date of May 17, 2019.
The Lease Agreement is for an initial 10-year term (Initial Term), followed by a five-year term (Development Term) to achieve a mine construction decision, and a production term that will continue for so long as operations and commercial production are maintained.
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Summary:
The Johnson Tract Deposit (the Deposit) mineralization is hosted within southeast dipping volcanic and volcaniclastic rocks of the early Jurassic Talkeetna Formation, overlain by middle to late Jurassic sedimentary rocks of the Tuxedni, Chinitna and Naknek formations. To the west of the Deposit, the regional west-dipping Bruin Bay Fault juxtaposes diorite to quartz monzonite intrusive rocks against Talkeetna formation host rocks.
Mineralization at the Johnson Tract Deposit forms a steeply southeast dipping, tabular silicified body that contains a stockwork of quartz-sulfide veinlets and brecciation, cutting through and surrounded by a widespread zone of anhydrite alteration (Proffett, 1993). Drilling has defined silicification and mineralization from surface to a vertical depth of approximately 350 m (1,150 ft.), over a total strike length in excess of 600 m (1,970 ft.), and to a maximum true width of 55 m (180 ft.). The main body of mineralization is bound on the east by the southeast dipping Dacite fault.
The Deposit consists of a complex stockwork system of high-angle, 1-10 cm wide veins and breccia zones containing quartz, sphalerite, chalcopyrite, galena, anyhydrite, barite, Fe chlorite and native gold (Steefel, 1987). In addition to veins and diffuse breccias, mineralization is also characterized by massive structureless intergrowths of quartz and sulfides, commonly with very coarse-grained sulfide mineralogy. Veins show characteristics associated with epithermal styles of mineralization. Open-space fill texture is common and breccias consist of subrounded fragments hosted within a sulfide-silica matrix.
Early and relatively minor base metal mineralization (sphalerite) formed with the pervasive anhydritechlorite-sericite alteration. Later base (sphalerite-galena-chalcopyrite) and precious metal mineralization formed over several mineralizing events within the silicified stockwork vein zone. The genetic and temporal relationship between base metal deposition and precious metal deposition is not well understood (Rockingham, 1993). Re-Os dating of a bulk-sulfide separate, containing both chalcopyrite and pyrite from the footwall zone produced an age of 186 ± 6Ma for mineralization. This suggests that mineralization was contemporaneous with Talkeetna Arc volcanism and the Deposition of Talkeetna Formation host rocks (earliest Jurassic, Detterman et al. 1996), and is consistent with the shallow subseafloor setting for mineralization proposed by Steefel (1987).
Deposit Model
Previous operators have suggested a range of potential deposit models for the Johnson Tract Deposit, from feeder zone beneath a sea-floor Volcanogenic Massive Sulfide deposit (VMS), to Epithermal within coeval volcanic stratigraphy, to the possibility of mineralization being significantly younger than the host volcanic rocks and instead related to regional intrusive activity and/or structures (Proffett, 1993).
VMS-like aspects include submarine volcanic host rocks, widespread and crudely stratabound anhydrite alteration similar to some Kuroko-type VMS, and strong base metal grades coincident with gold mineralization, whereas deposit morphology at the Deposit, consisting of a quartz-sulfide stockwork and breccia body, and vein textures are more consistent with those found in epithermal-type deposits.
Summary:
Flowsheet development has focused primarily on the production of separate flotation concentrates for copper, zinc, and lead, and pyrite with the potential cyanidation of flotation concentrates and flotation tailings, to achieve additional gold recovery.
The operating costs for milling were benchmarked off processing plants with a similar throughout and flowsheet, with a toll milling surcharge added.
Recoveries & Grades:
| Commodity | Parameter | Avg. LOM |
|
Gold
|
Head Grade, g/t
| 5.82 * |
|
Silver
|
Head Grade, g/t
| 5.44 * |
|
Copper
|
Recovery Rate, %
| 84.5 * |
|
Copper
|
Head Grade, %
| 0.54 * |
|
Lead
|
Recovery Rate, %
| 72.4 * |
|
Lead
|
Head Grade, %
| 0.71 * |
|
Zinc
|
Recovery Rate, %
| 92.3 * |
|
Zinc
|
Head Grade, %
| 4.72 * |
* According to 2025 study.