|Land Package:||11,319 hectares|
|Deposit type:||Low sulphidation epithermal|
|Operation:||Underground mine; flotation plant|
For the fourth quarter and year ending December 31, 2014, the Cusi Mine produced the following:
|Cusi||3 Months Ended||12 Months Ended|
|Dec 31, 2014||Dec 31, 2013||Dec 31, 2014||Dec 31, 2013|
|Lead (000 lb)||304||0||1,289||0|
(A detailed summary of production is presented in the Company's Jan 27, 2015 press release.)
On March 27, 2014, the Company released an updated NI 43-101 compliant resource estimate for the Cusi Mine prepared by Gustavson Associates LLC of Lakewood, Colorado.
- The effective date of the mineral resource estimate is Dec 31, 2013.
- Resources are presented at a 90 g/t Ag cut-off grade.
- Details of the estimate are provided in the Company's Mar 27, 2014 press release and within a NI 43-101 compliant technical report filed on SEDAR on May 9, 2014.
- Mineral resources that are not mineral reserves do not have demonstrated economic viability.
(Complete details of the reserve and resource estimate are available in the NI 43-101 technical report - please click here)
The Company's Cusi Mine is an underground silver mine located in Chihuahua State, Mexico some 135 kilometres from Chihuahua City. The Property encompasses 60 concessions covering 11,319 hectares that include 12 inactive mines, each located on a mineralized structure, and which lie within 40 kilometres of the Company's Malpaso Mill. The Promontorio and Santa Eduwiges are currently providing most of the ore to the mill.
Although commercial production was declared in January 2013, the Cusi mine is still considered to be in the development stage as the majority of the production comes from development rock. The Company`s goal to reach 500 tonnes per day of production was achieved in late 2014. A revised 43-101 report along with a Pre-Feasibility Study on the actual operation rate using the Malpaso Plant is planned to be released in 1Q 2015.
The Cusi Project area is located within the municipality of Cusihuiriachic in the central portion of Chihuahua State, Mexico. The Cusi Project area is located 135 kilometers (km) by car from the City of Chihuahua, Mexico. Climate is conducive for year round mining operations. The Project area encompasses 11,657 hectares over a range of elevation of 1,950 to 2,460 masl in the Sierra Madre Occidental Mountain Range. This reference point as defined by the shaft of the Promontorio Mine is located at Northing 3,125,854 meters and Easting 319,019 meters in the 13R UTM grid in WGS84 ellipsoid.
The Cusi property is situated within the municipality of Cusihuiriachic located in the central portion of Chihuahua State, Mexico, approximately 135 kilometers (km) by car west of the City of Chihuahua. Access to the village of Cusihuiriachic from the City of Chihuahua is 105 km along Federal Highway No. 16 to Cuauhtémoc, then south for 22 km along a paved road to the village of Cusihuiriachic, where the Cusi Property is located. An international airport is located in the city of Chihuahua.
Sierra Metals' initially acquired mineral concessions for the Cusi Project area beginning in 2006. Sierra Metals wholly owns rights for exploration and mining for the Cusi Property for 73 mineral concessions covering an area of 11,657 hectares. Production from the Cusi Project area is subject to net smelter royalties ranging from 1.5 to 3%, depending on origin of the mined quantity with respect to the mineral concession area.
Sierra Metals holds surface rights to an area of 1,020 hectares located generally within the area where Sierra Metals holds mineral concessions and including the access points to the Promontorio and Santa Eduwiges underground mines that are in operation.
Gold and silver were first discovered in the Cusi Project within the San Miguel and La Candelaria zones by a Spaniard, Antonio Rodríguez, in 1687, and continued until the Mexican war of independence, which began in 1810. The amounts mined during the Spanish colonial time are not well documented.
The Mexican war of independence occurred from 1810 to 1821. Operators and mined quantities from 1821 to 1881 are not known. From 1881 to 1890, Don Enrique Mining Co. conducted mining operations. From 1896 to 1911, the Helena Mining Company purchased and conducted mining operations: during this period, the Santa Marina and San Bartolo shafts were sunk to the 1,000 foot level. North Mexican Mining Company acquired a portion of the Cusi Project area. In 1911, Cusi Mexicana Mining Co. purchased the property from Helena Mining Company. During the period of the Mexican Revolution from 1910 to 1920, mining at the Cusi Project area occurred intermittently. Total tonnage mined from 1821 – 1920 is not known.
From the 1920s to 1937, concessions of the Cusi Project area were acquired by The Cusi Mining Company of American Capital. Over one million tonnes were mined. From 1924 to 1942, 504,048 tonnes were mined, producing 265,460 kilograms of silver; however, mined areas were not reported. From 1937 to the 1970s, mining from the Cusi property was reportedly dormant. In the 1970s, mining occurred in several mines in the Cusi Project area: an estimated 3,000 tons of ore per month were being produced at an average silver grade of 12 to 18 ounces per ton silver.
As reported in RPA (2006), during the 1980s, Minera Cusi conducted limited mining: no quantities were reported.
Sierra Metals acquired the Malpaso Mill in 2004 and began production in March 2005 with ore from the Bolivar Mine, through 2011. In late 2011, the Piedras Verdes was built at Bolivar Mine, and thus no further ore from the Bolivar Mine was processed at the Malpaso Mill.
GEOLOGY AND MINERALIZATION
Rocks in the Cusi area are mainly volcanic rocks of the Sierra Madre Occidental, predominantly volcanic rocks of Eocene-Oligocene age, continental deposits of the Upper-Middle Tertiary, and in smaller proportion, Quaternary deposits. The geologic column comprises a sequence of volcanic rocks, with a minimum thickness of 750 m in "La Bufa" mountain, but possibly thicker since its base is not exposed nor it has been reached by the deepest mining operations. Volcanic rocks in the area are of the Lower Volcanic Series, the base of which is represented by felsic lavas and tuff dated at 37 Ma. They overlie a sequence of 37 Ma old agglomerates and andesitic lavas with a smaller amount of intercalated volcano-clastic sediments and andesitic tuffs.
The Upper Volcanic Series unconformably overlies the earlier series and is represented by felsic, intermediate and mafic volcanic rocks with an age range of 36-27 Ma. The mafic rocks originated during periods of faulting and are represented by andesitic basalts dated at 28 Ma. The rhyolitic rocks, such as tuffs, breccias and ignimbrites, belong to the Sierra Madre Occidental Superior Volcanic Group. The rocks are intruded and altered by monzonitic intrusions and cut by rhyolitic dykes associated with Ag-Pb-Zn-Cu-Au mineralization.
Epithermal (silver dominant) and base-metal veins occur as hydrothermal fissures filling faults and fractures. The veins are generally narrow, vuggy and chalcedonic and fill major structures. The faults that host veins are undulatory in both strike and dip and fracturing and brecciation increase at inflection points that often correlate with cross structures/veins. Broad zones of disseminated silver mineralization occur at some of these structural intersections, most notably at the Promontorio mine.
The length of the major structures varies between 500 to 2,000 m, with high-grade zones and also barren sections. Second and third-order faults are of much shorter length, on the order of tens to a few hundred meters. Alteration is mainly silicification, oxidation and chloritization.
Construction has begun on a new four-compartment rectangular shaft at the Santa Eduwiges mine The objective is to access the deeper levels and to allow a higher mine output and have a cost efficient method of moving the ore to surface versus the current underground dump trucks utilizing the ramps. The new shaft will be operational in 2016.
Currently, the Company is actively conducting step-out drilling and current targets include Veta del Contacto (Santa Eduwiges) and the Milagro Vein. At Promontorio, the ramp has reached Level 10 and drill stations are being developed to drill the Santa Rosa de Lima and Veta del Contacto (Promontorio) veins at depth.
A pre-feasibility study will be filed in 1Q 2015. This study will evaluate the economic viability of the current operations using the Malpaso plant, will allow moving a portion of the resources to reserves and will also evaluate the economic viability of building a new plant on the Cusi mine site while utilizing all the categories of resources included in the report.
1For the three month period ending September 30, 2014