Dia Bras Exploration Inc.

Dia Bras Exploration Inc.

November 15, 2011 07:30 ET

Dia Bras Confirms Discovery of a Large Disseminated Silver Zone at Its Cusi Property

TORONTO, ONTARIO--(Marketwire - Nov. 15, 2011) - Dia Bras Exploration Inc. (TSX VENTURE:DIB) ("Dia Bras" or the "Company") is pleased to report that exploration drilling from the surface at Promontorio mine (Figure 1: http://diabras.com/files/media/a20ec_figure1.pdf) combined with underground channel and bulk samples from drifting in the Promontorio mine continue to identify wide zones of disseminated silver mineralization, confirming the discovery of a new zone with large tonnage potential. The underground channel sampling has returned bonanza grades of silver (Table 2) and underground bulk sampling from drifting in the disseminated zone has also returned significant grades of silver. Milling of the bulk sample yielded good silver recovery.

"The Promontorio disseminated zone is one of Dia Bras' most important discoveries in recent years, due to the combination of wide mineralized zones and high silver grades for a disseminated-type mineralization", stated Daniel Tellechea, President and CEO. "This new discovery is emerging as an important deposit because it is located close to the Promontorio mine shaft and several levels of old mine workings that provide access to sub-horizontal silver-mineralized bodies up to 25 m thick. We expect the wide zones to allow low mining costs. Our bulk sampling of the zone has already shown good silver grades and excellent silver recoveries. We are currently developing this zone, which will allow us to increase our silver production at Cusi significantly in 2012. This discovery is very timely because our Malpaso mill, located only 35 km from Cusi, has idle processing capacity after the start-up of our new Piedras Verde mill at our Bolivar copper-zinc-silver mine."

The Promontorio mine is part of the important, historic high-grade Cusi silver district, but flooding of mine kept Dia Bras from accessing it until late last year. The discovery of the disseminated mineralized deposit opens a new geologic concept for the entire Cusi mining district, which Dia Bras has consolidated in recent years. Dia Bras is currently producing silver from pilot mining at Cusi and also from its Yauricocha mine in Peru. The Company also produces silver as a by-product from its recently expanded Bolivar copper-zinc-silver mine in northern Mexico. In addition, Dia Bras owns 100% of the Melchor Ocampo silver-lead-zinc project in Zacatecas State, Mexico and the Bacerac silver-lead-zinc project in Sonora State, Mexico.

Promontorio Disseminated Zone:

This zone of disseminated mineralization occurs near the Promontorio shaft and several levels of workings (Figure 2: http://diabras.com/files/media/36413_figure2.pdf). Although the limits of the zone are not fully defined, the Company's geologists have interpreted that it occurs over an area of at least 200 x 200 m in the Promontorio mine (Figure 3: http://diabras.com/files/media/83477_figure3.pdf) bounded by the Cusi and Renovacion faults. Its extent to the SE and NW has yet to be defined. Drilling continues to follow the zone to the northwest and drill core from 2007 has potentially-economic silver grades within it.

The higher grade portion of the disseminated zone is hosted by rhyodacite characterized by strong silicification, disseminated silver-sulphide minerals such as argentite, and narrow, infrequent quartz-galena-argentite stringers and veinlets. The higher grade portion is surrounded by a lower-grade halo, or envelope, of rhyodacite that is silicified, but to a lesser degree, and contains chlorite and finely-disseminated pyrite (<1%). Both zones are cut by veins and veinlets.

Alteration and mineralization occurred in four phases:

  1. Pervasive silicification of rhyodacite accompanied by minor amounts of very-fine-grained and inter-grown pyrite, chalcopyrite and sphalerite;

  2. Injection of micro-veinlets (~1 mm thick) with fine-grained black sulphides (argentite 1-2 mm in size) that cut feldspar and quartz phenocrysts (5-15 mm in size) and argentite crystals that are disseminated in un-veined rock. The rhyodacite appears pale brown due to very-fine-grained hematite in the matrix;

  3. Injection of veins and veinlets of quartz-galena-sphalerite-argentite (0.1- 5 m thick) that cross-cut the micro-veinlets;

  4. A final phase of vein brecciation and intense silicification.

Drilling: The Company has drilled 36 diamond holes totaling about 9,100 m on the disseminated zone; assays have been returned for 11 holes. Cross-section A (Figure 2 : http://diabras.com/files/media/36413_figure2.pdf & Figure 3: http://diabras.com/files/media/83477_figure3.pdf) shows 2007 and 2011 drill holes that penetrated the disseminated zone and zones of higher-grade silver within it. This section has the most holes with assay data returned, so it is used to illustrate the zone's potential. The Company's geologists are calculating the resources for this section, which will be published soon after this release. Table 1 below shows silver results for holes on Section A (Pb, Zn and Cu values are minimal).

Table 1: Drill Assay Results along Section A of the Promontorio Disseminated Zone
Hole Number Interval (m) Core Length (m) Ag, g/t
DC07B132 144.0-158.0 9.0 79.5
162.5-174.5 12.0 333.4
271.0-278.0 7.0 132.7
278.0-282.8 5.6 30.8
DC07B151 113.0-115.5 2.5 1028.5
115.5-159.0 37.5 50.4
Incl. 153.0-159.0 6.0 693.0
159.0-181.5 22.5 18.0
181.5-196.5 15.0 527.7
196.5-222.0 25.5 68.9
241.7-232.1 9.6 51.3
241.7-249.0 7.3 521.4
DC07B154 361.3-373.2 11.9 19.4
DC07B161 393.0-397.0 4.0 343.0
DC11B363A 107.2-133.6 26.4 266.0
DC11B380A 100.45-131.8 31.35 79.0
Incl. 100.45-105.10 4.65 176.3
Incl. 107.60-111.50 3.9 115.9
Incl. 113.75-116.50 2.75 107.9
Incl. 118.30-119.95 1.65 95.9
Incl. 123.30-126.15 2.85 159.9
139.4-141.2 1.8 107.1
152.6-157.3 4.7 146.2
170.35-191.85 21.5 62.0
Incl. 183.50-191.85 8.35 90.5
DC11B395 333.85-350.45 16.6 138.5
A: results from these and other intervals published September 14, 2011

Drifting: A drift on Level 9 of the Promontorio mine adjacent to the old drift is being developed and rock from the development work was shipped to the Company's Malpaso mill for processing, which makes a good bulk sample. The drift is in the outer halo of the disseminated zone where quartz-galena veinlets and stringers (1-10 cm wide) occur about every 0.5-1.0 m. The 160 t processed from the drift averaged 250 g/t Ag. Another 205 t of "waste" from previous mining (pre-1950) of the old drift also averaged 250 g/t. These results illustrate the good bulk grades in the disseminated zone. These are good silver values given the fact that this rock is not in the higher grade core of the zone but from the lower-grade outer halo. As with other rock from Cusi, the Malpaso mill achieved 80-85% recovery of silver from this bulk sample by a combination of flotation and cyanide vat-leach methods.

Channel Sampling: In addition to drilling and drifting, channel sampling has been done within the zone on Promontorio Levels 8 & 9. These samples were taken on veinlets and veins within the disseminated zone to determine their grades, which often returned bonanza grades of silver. The results are shown in Table 2 below.

Table 2: Assay Results from Selected Channel Samples, Levels 8 & 9, Promontorio Disseminated Zone
Sample # Location Width (m) Ag g/t Pb % Zn %
4414 Promontorio Level 8 0.25 393.3 0.40 1.22
4417 " 0.70 799.2 0.85 1.50
4419 " 0.25 2918.9 1.00 0.85
4421 " 0.45 192.8 0.05 0.27
4422 " 0.55 4479.2 2.43 7.04
4423 " 0.60 3465.2 3.05 5.35
4424 " 0.50 113.5 0.03 0.18
4217 Promontorio Level 9 0.75 671.8 0.29 0.28
4220 " 0.75 409.7 0.21 0.24
4221 " 0.80 307.5 0.48 0.35
4252 " 0.30 2383.2 7.90 8.51
4253 " 1.00 357.1 0.18 0.17

Update on Santa Eduwiges Mine and Positive Development of the San Bartolo Vein:

Dia Bras is also pleased to report that it is delineating and developing the San Bartolo high-grade silver vein, which is one of several veins in the vein system within the Santa Eduwiges mine. Santa Eduwiges is located only 700 m southeast of the Promontorio mine ( see map : http://diabras.com/files/media/a20ec_figure1.pdf) and is where the Company is currently mining rock for its pilot mining operations.

Drifting: Dia Bras has completed a drift along the San Bartolo vein on Level 8 that crossed the Cusi fault. Sampling has confirmed good silver mineralization along the vein, but also proved that mineralization does not extend past the NE side of the fault. There are other veins with good mineralization splaying off the main vein on Level 8. Altogether, there are about 300 meters of drift along the Level 8 strike length of the San Bartolo vein and its splays. Level 10, 25 m under Level 8, is partially developed along the vein and the drift has also encountered good mineralization, as shown in Table 3 below. The Level 10 drift will be extended to the Cusi fault as part of mine development, and then the area between Levels 8 and 10 will be mined.

Table 3: Sampling along Development Drifts, San Bartolo Vein
Level Location Length along
drift (m)
Number of
Avg. Sample
Width (m)
Silver g/t
8 Fte. N8-423 NE 35 Channel 22 1.2 150
8 Fte. N8-428 NE 38 Channel 18 1.2 200
8 " 39 Muck 8 2.2 277
8 " 54 Channel 13 1.1 280
8 " 14 Channel 13 1.0 430
8 Fte. N8-676 SW 37 Channel 12 1.0 500
8 " 11 Channel 18 1.0 200
10 Fte. N10-9402 SW 19 Channel 14 2.2 180
10 Fte. N10-9408 NE 22 Channel 6 2.2 307

In addition, sampling of the veinlets and veins in the mine, without including low-grade wall rock, has returned bonanza grades of silver as shown in Table 4 below.

Table 4: Sampling of Veinlets and Veins, San Bartolo and San Antonio Veins
Level Location Vein Sample Width (m) Ag g/t
8 Cross-cut B S San Bartolo 0.60 494.6
8 " " 1.40 255.4
10 Cross-cut No. 1 S San Antonio 0.15 1177.6
10 " " 1.00 328.0
10 " " 0.50 789.5

During September, 3,014 t of rock from the 2.2 x 2.5 m drift were shipped to Malpaso that averaged 185 g/t silver. Given that on Level 8 the vein is about half the width of the drift and therefore the mill feed was diluted with low-grade wall rock, the mining production grade is expected to average 300-350 g/t Ag.

Milling: During the month of October, 2011 the Malpaso mill processed the 3,014 tonnes of rock from the San Bartolo drift that averaged 185 g/t silver, 0.57% lead and 0.94% zinc, which illustrates the silver-rich nature of the Cusi mineralization. Recovery of silver for the month was 83.88% from a combination of flotation and cyanide vat-leach methods. During October, the Company produced 46.63 kilograms of silver in doré.

Pilot Mining:

As part of its pilot-mining program, the Company has been sending mineralized rock from Santa Eduwiges to its 100% owned Malpaso mill, which is located only 35 km by road from the mine. Pilot mining provides important information on metallurgy, recovery rates, mining and milling costs, etc., that are essential in determining the economic viability of a project. The Company produces silver-rich lead concentrate and silver doré from the Cusi rock.

Method of Analysis

Samples were prepared at the Company's lab facility at its Malpaso lab and analyzed by atomic absorption for Cu, Zn, Pb, Bi, Co, Mn, Sb, Cd and Fe. Gold and silver are analyzed by fire assay method. Diamond drill samples sent for analysis consisted of half NQ-size and BQ-size diamond core split on site. Duplicate samples are sent to the ALS Chemex lab facility in Chihuahua, Mexico, where they are prepped and analyzed by ICP and AA methods at their facilities in Vancouver, Canada, and assayed for Au by 50 g fire assay with AA finish, and for Ag by AA on 50 g split sample at the ALS Chemex North Vancouver Laboratory. Assays for Pb, Zn and Cu are analyzed by Induction Coupled Plasma (ICP) at ALS Chemex.

The Malpaso laboratory follows the quality control methodology recommended by CANMET of Canada, such as assaying of blanks, duplicate samples, and check assays by commercial laboratories such as Chemex.

Quality Control

The quality assurance-quality control (QA-QC) of Dia Bras has been described in detail in both RPA's NI 43-101 reports of December 2006 at Cusi and October 2005 for Bolivar.

The technical content of this news release has been approved by Thomas L. Robyn, Ph.D., CPG, RPG, a Qualified Person as defined in NI 43-101.

About Dia Bras

Dia Bras Exploration Inc. is a Canadian listed mining company focused on precious and base metals in Peru and Mexico. The Company owns and operates the Yauricocha Mine (Ag-Cu-Zn-Pb) in central Peru and the Bolivar Mine (Cu-Zn-Ag) in Chihuahua State, Mexico. Dia Bras is also pursuing the development and exploration of the Cusi Property (Ag) and exploring several base and precious metals targets In Peru and Mexico.

The Company's shares trade on the TSX Venture Exchange under the symbol "DIB".

Forward-looking Statements

Except for statements of historical fact, all statements in this news release without limitation regarding new projects, acquisitions, future plans and objectives are forward-looking statements which involve risks and uncertainties. There can be no assurance that such statements will prove to be accurate; actual results and future events could differ materially from those anticipated in such statements.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this news release.

Contact Information

  • Daniel Tellechea
    President & CEO
    Dia Bras Exploration Inc.
    1 (866) 493-9646