Property Size: 51,172.5 hectares
Location: 150 kilometers northeast of Hermosillo, Sonora, Mexico.
Status: Commercial Underground Production
Earliest records of work on the property are from the late 19th to early 20th century when an English company by the name of Consolidated Fields operated a mining operation at Santa Elena until the onset of the Mexican Revolution in 1910.
During the 1960’s, Industrias Peñoles S.A de C.V. drilled two or three holes on the property. During the early 1980’s, Tungsteno de Baviacora (Tungsteno) mined 45,000 tonnes grading 3.5 g/t gold and 60 g/t silver from an open cut at Santa Elena. Since 2003, Tungsteno has periodically surface mined high silica/low fluorine material from Santa Elena and shipped it to the Grupo Mexico smelter in El Tajo near Nacozari, approximately 60 km to the northeast.
In early 2004, Fronteer Development Group of Vancouver, B.C., completed an extensive surface and underground mapping and sampling program. A total of 145 channel samples (89 underground and 56 surfaces) were collected and analyzed. The property remained under control of Tungsteno. On December 8, 2005, SilverCrest, using its 100% owned subsidiary Nusantara, entered into an option agreement with Tungsteno to acquire a 100% interest in the Santa Elena property through staged option payments over 5 years. SilverCrest completed payments as per the terms of the agreement in August of 2009. SilverCrest has been extensively evaluating the property since 2005.
Santa Elena is located in the Basin and Range Province, which is part of the Sonora Desert subprovince. The region is near the Proterozoic rifted continental margin of the North American plate, which was the site of deposition of a thick sequence of shallow marine shelf carbonate and siliclastic rocks. Subduction of the Farallon Plate beneath the North American Plate during Jurassic time resulted in continental volcanism. In late Jurassic time, a northwest-trending rift basin formed which was the site of sedimentation and felsic and intermediate volcanism.
Locally, the primary rock types are early Tertiary andesite and rhyolite flows which exhibit propylitic to silicic alteration. The main mineralized zone is a cross-cutting structure trending approximately east-west and dipping about 45° to the south. Alteration is widespread and pervasive with significant silicification, kaolinization and chloritization. Gangue minerals consist of quartz, calcite, chlorite and fluorite.
The Santa Elena deposit is considered to be high calcium, low-sulfidation type with replacements, stockworks and hydrothermal breccias similar to other high level low-sulfidation deposits found in Mexico, Chile and Nevada and Arizona in the United States.
Initial results of the accelerated underground exploration of the El Cholugo Zone ("El Cholugo" or the "Zone") located immediately adjacent to the Main Mineralized Zone ("MMZ") currently in production at the Santa Elena Mine, Sonora, Mexico. SilverCrest's recently released technical report titled, "Update to Santa Elena Pre-Feasibility Study, Sonora, Mexico" ("PFS"), contemplated the exploration and development of El Cholugo in 2016. However, the high gold and silver grades over significant widths and lateral dimensions encountered underground has led the Company to accelerate exploration and development of the Zone with the view to its inclusion in this year's (2015) mine plan. Please refer to attached figures and news release dated March 31, 2015
The El Cholugo Zone is a drill-identified epithermal vein system that intersects the MMZ at an oblique angle (see attached figures). Previous drilling has shown at least two mineralized veins in the Zone, Alejandra and El Cholugo Dos, to range from 1 to 15 metres wide over a strike length of approximately 200 metres and a height of an estimated 150 metres. From previous drilling, the average width of the Alejandra vein is estimated to be 3.2 metres and for El Cholugo Dos vein, 1 to 5 metres. The Company is currently drifting on three levels (625m, 600m, and 575m elevations) from underground at Alejandra. Geometry of the mineralization is favorable for mining by long hole stoping method. Underground drifting on the Alejandra vein to date totals approximately 100 metres on three levels. The Company will also be exploring underground on the 655m level in Q2, 2015. Once the Alejandra vein is sufficiently defined, it may be partially incorporated into the 2015 mine plan. For reference, current PFS estimates for El Cholugo Reserves (cut and diluted) are 251,800 tonnes grading 2.58 gpt Au and 147.1 gpt Ag.
N. Eric Fier, CPG, P.Eng., and COO stated; "The accelerated exploration of El Cholugo is showing very encouraging results to date. The high grade silver and gold values that we are currently seeing from underground drift exploration are exceeding our expectations with respect to currently stated PFS Reserves. This makes El Cholugo a priority target which could potentially add to future underground production when practical. Additional drifting and underground drilling at El Cholugo will be completed over the next several months to confirm and potentially expand current reserves and resources."
A total of 132 composited assay results (see table below and attached figures) from mine face channel sampling of Alejandra underground drifting show an average vein width of 3.3 metres grading 8.80 gpt Au and 419.4 gpt Ag.
Note: All numbers rounded. Grades are uncapped and undiluted. Development metres are estimated. Widths are considered near-true thickness.
All sample analyses were completed onsite at Santa Elena's production laboratory. Internal QA/QC protocols are comparable to industry standards.
For comparison purposes, current MMZ ore grades being mined from underground in April, 2015 are approximately 1.9 gpt Au and 127 gpt Ag. The highest grade individual sample collected to date from the Alejandra vein is on the 575m level over a width of 0.6 metres grading 108.8 gpt Au and 2,705 gpt Ag (uncut and undiluted).
ADDITIONAL OPERATIONS UPDATE
The Company continues to review underground reserve reconciliations with mined stopes (2 and 3, see attached figures) versus PFS reserve model. Indications from reconciliations on Stopes 2 and 3 appear to be higher grade than PFS reserves. Also, the Company continues to optimize gold and silver recoveries based on a higher cyanide levels in the mill and introduction of aeration (pressurized air) into the leach tanks. Currently gold recoveries are above 92% and silver recoveries are averaging 75%. Silver recoveries are 23% higher than previously reported in the first quarter, 2015. Additional metallurgical testwork is underway to further optimize sustainable silver recoveries at or above 70% as forecasted.
SANTA ELENA RESERVES (DECEMBER 31, 2014)
|CLASSIFICATION||TONNES||AU GPT||AG GPT||CONTAINED
SANTA ELENA UNDERGROUND DILUTED AND RECOVERABLE RESERVES*
SANTA ELENA OPEN PIT RESERVES**
SANTA ELENA LEACH PAD RESERVES (PAD ORE)***
TOTAL SANTA ELENA RESERVES
SANTA ELENA RESOURCES (DECEMBER 31, 2014) ****
Note: All numbers are rounded. Underground and Leach Pad Reserves and Resources are based on LOMP metal price trends of $19.50/oz silver, $1,300/oz gold and metallurgical recoveries of 92% Au and 67.5% Ag. All Mineral Resources and Reserves conform to NI 43-101 and Canadian Institute of Mining, Metallurgy and Petroleum definitions for Resources and Reserves. Inferred Resources have been estimated from geological evidence and limited sampling and must be treated with a lower level of confidence than Indicated Resources.
* Underground Probable Reserve is based on a cutoff grade of 2.49 gpt AuEq with an estimated average 10% dilution and 90% mine recovery. Average true thickness of the designed stopes is 10 metres.
** Open Pit Reserve is based on a cutoff grade of 0.20 gpt AuEq in a constrained pit shell with applied capping of 8 gpt Au and 300 gpt Ag.
*** Leach Pad Reserve is based on production and drill hole data for volumetrics and grade model using a cutoff grade of 0.5 gpt AuEq. No capping was applied.
****Mineral Resources exclude Mineral Reserves and are based on a 1.5 gpt AuEq cut off grade using assumptions for prices and recoveries as stated in note above. Capping was applied at 12 gpt Au and 700 gpt Ag.
The operating cost estimates stated below were compiled using Santa Elena mine site operating experience, SilverCrest financial and operational reports, recent contractor quotes, other local producing mines and industry estimations in Mexico to a Pre-Feasibility level.
|Mining Method||Open Pit||Underground
Cut & Fill
|Process Method||CCD Mill||CCD Mill||CCD Mill||CCD Mill|
|Mining Cost/T ore1||$ 9.90||$ 28.71||$ 50.00||$ 0.002|
|Processing Cost/T3||$ 24.49||$ 24.49||$ 24.49||$ 24.49|
|General & Administration/T4||$ 5.29||$ 5.29||$ 5.29||$ 5.29|
1 Long hole stopes are 89% of designed stopes by volume and cut & fill stopes are 11% of designed stopes by reserve volume. Includes adjustment for exchange ratio impact in the mining costs and excludes ore development costs.
2 Mining cost of spent ore on leach pad is covered under processing costs.
3 Processing cost includes crushing, milling, site refining and dry stack tailings disposal.
4 Estimated based on current operations and may vary on an annual basis. A 4% annual inflation rate has been applied to general and administrative costs.
Ore development costs are estimated at $36/T ore and represent approximately 6% of total underground ore planned to be mined during LOMP.
The sustaining capital cost estimates stated below are based on internal estimates for remaining capital expenses over life of mine.
Sustaining Capital Cost Table Including Exploration Drilling Expense
|Mill sustaining capital||$1,785,000|
|Underground waste development expenses||$16,086,600|
|Underground equipment and infrastructure||$6,236,300|
|Underground and 2015 surface drilling||$4,783,300|
|Total capital costs||$30,957,400|
Note: All numbers rounded.