
OVERVIEW
The El Chanate Mine is a conventional open-pit, heap-leach operation, located in Sonora State, Mexico. The mine is located 4,618 hectares encompassed within 22 mineral concessions.
Location
El Chanate is located in northern Mexico in the northwest corner of the State of Sonora. The mine site is 37 kilometres ("km") northeast of Caborca, 280km northwest of Hermosillo, 150km southeast of Sonoyta, and 170km southwest of Tucson, Arizona. Caborca is the largest town in the area with a population of approximately 100,000.
History
Historical workings suggest the area has been mined for gold since the early 19th century. The current open pit mine has now been developed below the level of those historical small-scale mine workings. The open pit mine plan covers an area approximately 1,700 metres ("m") long, 845m wide, and 300m deep.
GEOLOGY AND MINERALIZATION
Geology
El Chanate’s main structural feature is the Chanate fault zone, a 7km-long northwest-striking, variably southwest-dipping structure. The area is underlain by deformed sedimentary rocks of the Late Jurassic-Early Cretaceous Bisbee Group and the Late Cretaceous Chanate Group, which locally are overlain by andesites of the Cretaceous El Charro volcanic complex.
The sedimentary strata are locally intruded by andesitic sills and dikes, a microporphyritic latite, and a diorite stock. These strata comprise mudstone, siltstone, sandstone, conglomerate, shale, and limestone.
Sandstone, conglomerate, and lesser mudstone that lie above the Chanate fault are of the Middle Cretaceous Chanate Group. Below the fault, siltstone and sandstone lenses are assigned to the Arroyo Sasabe Formation of the Lower Cretaceous Bisbee Group.
Mineralization
Alteration and mineralization associated with the Chanate fault zone are exposed across a northwest strike length of over 3.5km. The rock units in this zone are altered to varying degrees by sericite, pyrite, ankerite, and quartz veining.
In surface outcrops the mineralized zone is distinguished by its bleached appearance relative to unmineralized rock. Sub-parallel sheeted zones of quartz veinlets form thick, mineralized lenses, within a larger area of sub-economic but anomalous gold concentrations.
MINING AND PROCESSING
Conventional open pit mining methods are employed at El Chanate. Ore is trucked from the open pit to the three stage crushing circuit after which crushed ore and lower grade run of mine ore is placed on the heap leach pad where it is irrigated with an alkaline cyanide bearing solution. This is used to extract, or dissolve the gold and silver contained within the ore. The resulting “pregnant” solution is further processed in an ADR plant, followed by electro-winning and refining. The processing is a closed circuit, zero-discharge operation where solution is continuously re-used.
Technical Information and Cautionary Notes on non-GAAP Measures and Additional GAAP Measures