Drilling at the Angostura gold-silver project in northeastern Colombia has returned impressive results for
The Vancouver-based company drilled three infill holes from the same station; two were directed northward, the other, southwards. One of the north-bearing holes passed through old workings and was abandoned at 68.1 metres, but not before intersecting 6.5 metres (from 59 to 65.5 metres) grading 3.11 grams gold and 8.64 grams silver per tonne.
Hole 2A, which was inclined 10 steeper than the abandoned hole, returned nine intervals averaging 0.79-2.03 grams gold and 2-7 grams silver. The hole thickness of the intervals varied from 2.5 to 13 metres, with the highest gold values coming from a 6.5-metre zone that began at a down-hole depth of 28.5 metres. The lowest gold grade came from a 4-metre zone that began at 187 metres down-hole.
Results from hole 3 were even more impressive, with 302 metres (from 3 to 305 metres) — just 16.9 metres shy of the hole’s entire length — averaging 1.08 grams gold and 4.5 grams silver. However, this interval includes 141 metres (from 124 to 265 metres) averaging 1.83 grams gold and 5.8 grams silver, which accounts for 79% of the entire interval’s weighted average for gold and 60% of its weighted average for silver.
Silver assays have also been received from infill hole 1, which was collared 80 metres to the northeast and for which gold values have already been released. Like hole 2, this one returned several separate intervals, the longest of which was 80 metres long (starting from surface) and averaged 2.53 grams gold and 7.1 grams silver. That interval included 10.6 metres of 14.07 grams gold and 14.2 grams silver.
All three holes mainly passed through pyritic porphyry characterized by ubiquitous hydrothermal breccia and alunite, plus silicified, sericitic and argillic zones. Gold-silver mineralization is associated with sulphide minerals occurring as stockworks of pyrite stringers, shear zones with sulphide veinlets and pyrite dissemination.
Stepout drilling is also going well, with the first hole intersecting two high-grade and two low-grade intervals. Proceeding down-hole, 3.5 metres (from 5.5 to 9 metres) graded 0.89 gram gold and 2.17 grams silver; 4 metres (52-56 metres) graded 1.88 grams gold and 7 grams silver; 2.5 metres (115-117.5 metres) graded 30.29 grams gold and 74.32 grams silver; and 5.5 metres (136.5-142 metres) graded 30.94 grams gold and 13.8 grams silver.
The high-grade zones occurred in a 60-metre-long (115-to-175-metre) envelop of lower-grade mineralization that averaged 5.19 grams gold and 10.1 grams silver. Greystar believes the zone correlates with a 30-metre interval (69-99 metres) cut by hole AL97-1, which averaged 19.26 grams gold, including 54.08 grams in the final 3 metres.
The stepout hole was collared 700 metres northeast of, and 400 metres higher in elevation than, the zone being infilled. The mineralization encountered is hosted by silicified and pyritic porphyry, with irregular patches of brecciated chert.
Mine Development Associates of Reno, Nev., has pegged Angostura’s La Alta, Veta de Barro and Los Laches zones at a combined 53.5 million tonnes averaging 2.37 grams gold and 7.96 grams silver. The calculation is based on a cutoff grade of 0.7 gram and incorporates results from 36,785 metres drilled previously, as well as those from surface and underground sampling. At last report, the consulting firm had not yet confirmed these data.
Greystar has two drill rigs on site and intends to drill 20,000 metres in the current campaign. Roughly 15 holes will infill the southeastern area of La Alta, while another 45 will target the El Silencio, Quebrada Pozo, Los Laches, and Armenia areas.
Elsewhere in Colombia,
Combined resources for the Zona Alta and Zona Baja deposits are pegged at 36 million tonnes grading 1.98 grams gold and 6.32 grams silver. The figure, which was estimated by Mineral Resource Development Inc. (MRDI), falls into the inferred category and is the most conservative of several reported, being based on the highest cutoff grade of 1.25 grams gold. (All calculations consider dilution of between 15% and 20%.)
Resources at Marmato are divided between two deposits, dubbed Zona Alta and Zona Baja. The former descends into the other from a peak in the rugged terrain (the two are separated for reasons of property-ownership), and each consists of multiple subparallel and/or converging zones that collectively cover a strike length of 1 km, extend to a vertical depth of 800 metres and are spread across a width of 1.5 km.
Structurally, mineralization is controlled by two sets of northwesterly-trending fracture systems. One dips steeply to the northeast; the other, to the southwest. Where crossed, these systems form high-grade shoots characterized by abundant illite, elevated sulphide concentrations and generally greater widths of gold-bearing mineralization.
One such shoot, Zone 5, has received the most attention to date, as it has returned the most favourable results. For example, one hole drilled in early 1998 returned 60 metres (true width) averaging 1.23 grams gold, including 17.7 metres (true width) grading 2.24 grams.
Since 1996, Conquistador and its Colombian partners have drilled 14,676 metres, as well as extensively sampled and mapped numerous surface and underground exposures. MRDI considered all the results in its calculation and suggests that another 408 holes need to be sunk to boost the resource to the measured category.
Conquistador currently owns a 13.2% equity interest in Mineros Nacionales, which owns the 991-ha Zona Baja property, and can boost this to 50.1% provided certain conditions are met. Conquistador and a separate Colombian partner (which actually owns the remaining shares in Mineros) are applying for the mineral rights to the 47-ha Zona Alta property.
Currently, the company has $500,000 left over from a recently closed private placement that saw 3 million units sold at 35 cents each. As funds are tight, exploration has been scaled back to mapping and sampling. Meanwhile, confidentiality agreements have been signed with several majors in hopes of bringing one on-board.
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