Dia Bras is a Canadian exploration mining company focused on precious and base metals in Chihuahua State and other areas of northern Mexico.
Dia Bras Exploration Inc. reports that a major geophysical survey has been completed on its 100% owned Bolivar Property which is not subject to any royalties, Chihuahua State, Mexico. Field checks have been conducted to examine anomalies detected during a recently completed Titan 24 Induced Polarization (IP)/resistivity survey contracted to Quantec Geoscience of Toronto, Ontario. Two areas were covered during the survey, where eight lines totaling 9,000 metres were measured across the Banda Fault near the Bolivar Mine, and three lines totaling 2,700 metres were measured at the La Cascada high-sulfidation gold deposit. Condor Consulting of Lakewood, Colorado, has been retained by Dia Bras to assist in the planning of the IP/resistivity surveys and with the interpretation of the results.
“The surveys just completed at La Cascada and the Banda Fault areas have shown very promising results that confirm important mineralization can occur in these areas,” stated Daniel Tellechea, President & CEO. “These very positive results focus our drilling on targets that have the potential to host very important mineralization. At La Cascada, our target is a multi-million ounce gold deposit, while at the Banda Fault area our target is a major, stratabound skarn or replacement deposit with copper-zinc grades equivalent to what we have been producing from the Bolivar Mine for the past five years.”
Three survey lines at La Cascada were completed in this area of rugged terrain: a 1,000-m-long N-S line and two E-W lines (800 and 900 m), which resulted in detection of three significant chargeability and resistivity anomalies – all of which are associated with anomalous grades of gold in outcrop, as evidenced by the results of chip-channel sampling over 2-metre widths. The southernmost anomaly on the N-S line starts at 50 m depth. Sampling of outcrops over an area of 50 x 85 m was conducted prior to the survey and the six samples assayed 0.6 – 1.1 g/t gold.
Sampling in the area of the central anomaly (also starting at 50 m depth), completed over a 40 x 50 m area (also prior to the survey) resulted in the eight samples assaying 0.5 – 2.1 g/t gold.
Sampling in the area of the northernmost anomaly, completed over a 10 x 20 m area (also prior to the survey) resulted in the three samples assaying 0.4 – 3.0 g/t gold.
The sampled areas between the anomalies yielded very low grades of gold, generally less than 0.1 g/t.
These survey results are very positive because of the strong correlation between elevated gold in outcrop and strong chargeability anomalies. This correlation indicates that the probability that the three chargeability anomalies are associated with gold mineralization at shallow depths is very high.
The truncation of the chargeability anomalies at an apparent constant 50 m depth is inferred to be the result of oxidation of the high-sulfide zones, remnants of which appear on the surface as 1-2% pyrite and abundant jarosite, hematite and goethite.
Drilling will target the near-surface, coincident strong chargeability (IP) and resistivity zones detected during the survey. Drilling is scheduled to commence during late August, when an access road is completed to the selected drill sites. At least ten holes of 200-300 m depth each are planned for this first phase of drilling.
The area surveyed is only about 10% of the area known to host strong gold anomalies, where sampling has returned values up to 15 g/t Au.
Eight E-W lines 600 m to 1500 m in length at the Banda Fault area were measured across this major, NW-trending fault. The objective of the survey was to locate geophysical anomalies associated with NW-trending and NE-trending faults. Faults of these orientations control the location of high-grade copper-zinc mineralization in the Bolivar Mine. The anomalies can be separated into two general groups: near-surface anomalies and sub-surface anomalies.
Each of the near-surface anomalies occurs in andesite and is associated with elevated sulfide content, usually 1-3%, epidote and minor silicification. The anomalies are generally on low hills, reflecting their being underlain by the resistant silicified rock. The anomalies on lines 3, 5, 6 & 7 indicate a NW-trending structure (herein named the Nathalie Fault) parallel to the Banda Fault that passes near Increíble. There are significant geochemical anomalies associated with this structure, which may be a very important feeder of mineralizing fluids into the metasediments. This structure may be the main feeder of the mineralizing fluids, and not the Banda Fault as has been inferred prior to the survey.
The sub-surface anomalies are generally located west of the Banda Fault and are in a position to be the stratabound, large-tonnage replacement and/or skarn deposits that have been a major target for the Company.
The survey results are very encouraging. It has identified the Nathalie Fault, which is now inferred to be the major feeder for mineralization at the property. Drill hole 287, completed in March 2009, was drilled to a depth of 650 metres as a test of the Banda Fault and was placed between the Banda Fault and the Nathalie Fault. It was collared on what is now known to be the edges of a chargeability anomaly, a magnetic low and a moderate resistivity anomaly. The chargeability anomaly tops out at 100 m depth at the drill site, and at this depth, the hole entered increasingly skarnified andesite with disseminated sulfide mineralization. At 450 m depth, the hole entered the metasediments, which are present as marble and represent the upper portion of the metasedimentary section – above the Upper Skarn target. That is, the hole did not reach the target of the Upper Skarn horizon.
The new interpretation is that the Nathalie Fault, which is west of hole 287, will have on its west side the Upper Skarn target at a shallower depth, possibly 300-400 m. This area will be drilled by placing a NE-SW line of holes about 200 m NW of hole 287 and straddling the Nathalie Fault. This is an important target.