Bellhaven Copper & Gold Inc. (TSX VENTURE:BHV) has announced that the recently completed ground-based geophysical surveys at La Mina have identified three new exploration targets: El Cafetal, La Virgen, and Filo de Oro.
Three other targets identified in the surveys coincide with the previously known, but undrilled, El Limon prospect as well as the drilled mineralized intrusive centers at La Cantera and the Middle Zone. A total of six geophysical targets have been identified to date within the 1.5 km by 0.6 km corridor located on the eastern portion of the concession.
Geophysical surveys are the primary target-generation tool being used in the Middle Cauca belt of Colombia. Bellhaven announced on December 15th the commencement of ground-based induced polarization (IP), magnetometric, and radiometric surveys at the La Mina porphyry Au-(Cu) project in Colombia. The work program was conducted inside a 1.5-km long by 0.6-km wide grid consisting of approximately 18.5 line-kilometers spaced 50-m apart. The surveys were performed by ARCE Geofisicos SAC, an independent geophysical consulting firm headquartered in Lima, Peru.
Paul Zweng, Bellhaven's Interim CEO and Director, commented as follows:
"The geophysical surveys were successful in achieving their primary goal—providing better definition to the known prospects, namely, La Cantera, Middle Zone, and El Limon. These data will be valuable in the drilling of these targets, particularly the undrilled El Limon prospect. In addition, we are pleased to report that three new exploration targets have emerged as a result of these ground-based geophysical surveys. These additional targets hold the potential to grow the scale of the La Mina project. We look forward to drilling all of these prospects in the months ahead."
Discussion of the Geophysical and Geological Characteristics of the Target Zones
To understand better the significance of each geophysical target, Bellhaven compared the geophysical data of the targets against the geophysical signature of La Cantera, the best characterized prospect in the survey area by virtue of 12 diamond drill holes collared in its vicinity. The gold- and copper-bearing rocks at La Cantera are characterized by K-silicate alteration surrounded by sericite- and clay-bearing alteration assemblages, low amounts of total sulphide, and an abundance of hydrothermal magnetite. The magnetic susceptibility and total field magnetic-reduced to pole anomaly "highs" are inferred to represent rocks with relatively high quantities of hydrothermal magnetite. The magnetic susceptibility survey was particularly useful in revealing the locations of the six principal targets at La Mina.
The anomaly "highs" shown on the potassium radiometric survey map are inferred to represent rocks overprinted by K-silicate (potassic) alteration. High potassium values occur over a distance of 900 m along a ~ north-south trending corridor defined by the La Cantera-El Cafetal-Filo de Oro-Middle Zone targets. High values also occur to the north at El Limon along an approximately east-west belt that is 500-m long.
Zones characterized by high chargeability occur outboard of the drilled gold- and copper-bearing zones at La Cantera and Middle Zone. High chargeability can be attributed to rocks containing high quantities (typically 5-10 volume percent) of pyrite. At La Cantera, high chargeability occurs outboard to the west and east, but only weakly wraps around to the south and north. At the Middle Zone, high chargeability also occurs to the west and east of known mineralization and only weakly wraps around the northern margin (but not the southern margin). High chargeability zones also occur locally along the margins of the three new prospects at El Cafetal, La Virgen, and Filo de Oro.
La Cantera spatially coincides with a strong resistivity "low". The Middle Zone is characterized by a weakly defined "low". It is unclear why these zones yield relatively low resistivity readings as the rocks at La Cantera and the Middle Zone contain an abundance of quartz veinlets and only minor amounts of clay. Another prominent area characterized by a strong resistivity "low" occurs between the El Limon and Middle Zone targets.
Given the increase in the number of new exploration targets, Bellhaven is now actively seeking an additional drill rig to supplement the current exploration drilling program.
This news release has been prepared under the supervision of Mr. Thomas J. Drown, P.Geo., who serves as the qualified person as defined by National Instrument 43-101 responsible for ensuring that the geological information in this release is accurate.
La Mina porphyry Au-(Cu) prospect
La Mina (also known as Venecia) lies within the Middle Cauca belt of Miocene-age volcano-plutonic rocks in central Colombia known to host large porphyry gold deposits such as La Colosa (12.9 Moz Au contained in 468 Mt @ 0.86 g/t Au; AngloGold Ashanti), Titiribi (3.7 Moz Au contained in 230 Mt @ 0.5 g/t Au; Sunward Resources), Quebradona (AngloGold Ashanti – B2Gold), Quinchia (Batero Gold), and Yarumalito (Colombian Mines), as well as large epithermal gold districts such as Marmato (7.5 Moz Au contained in 245 Mt @ 0.95 g/t Au; Medoro Resources).
In mid 2006, AngloGold Ashanti and Bema Gold drilled six holes into the La Mina porphyry (now called the La Cantera prospect), with Holes 2 and 5 yielding 90+ m intercepts of greater than 1 g/t Au and significant copper at shallow depths.
The most important host rocks observed in drill core include the Combia Formation intermediate volcanic rocks as well as early, intra- and post-mineral diorite porphyry. Alteration is typical of gold porphyry deposits as exemplified by a potassic-calcic core encircled by sericitic, intermediate argillic, and propyllitic alteration zones. Specifically, most of the gold and copper discovered so far at La Cantera are spatially associated with quartz-magnetite-chalcopyrite ± bornite veinlets in potassic altered porphyry and breccias containing elevated quantities of hydrothermal magnetite. As a result, the gold-bearing rocks are highly magnetic (ca. 200x10-3 SI) which creates a sharp contrast with the barren and weakly magnetic intermediate argillically altered rocks as well as the non-magnetic sericitically altered rocks that surround the potassic core.
Three other potentially important targets occur due north of the La Cantera target: Middle Zone, El Limon, El Cafetal, La Virgen, Filo de Oro and El Tanque. These prospects occur within a 1.5 km long by 0.5 km wide zone containing elevated values of gold and copper in rock-chip and soil samples.
Source: Bellhaven Copper & Gold Inc.