EXPLORATION 1997 — Ambrex intensifies work on Brazilian targets

Ambrex Mining (AMBX-C) continues to explore in the garimpeiro gold fields of Brazil’s Mato Grosso state, where it is earning an interest from Ourominas Minerals (OMI-T) on a number of properties.

Since June 1996, Ambrex has been drilling the Aripuana project, in northwestern Mato Grosso. Though Aripuana was first explored as a gold prospect, where garimpeiro miners had excavated a large open pit, it has become apparent that the gold is held in a body of massive base metal sulphide mineralization. The property to the west and south was held by Unigeo, the Brazilian arm of Anglo American, which was busy drilling on a grid pattern that suggested the company was delineating a mineral reserve.

On Ambrex’s property, drill holes north and west of the pit were the first to intersect significant base metal mineralization (T.N.M., Oct. 14/96) and soil geochemistry and induced-polarization surveys produced coincident anomalies along a 3.1-km strike length centred on the old open pit.

Four of the next seven holes intersected massive sulphide mineralization, and a picture started to emerge of a massive sulphide zone with zinc and lead mineralization, as well as one or more zones of gold-copper mineralization believed to be in the footwall of the massive sulphide. Grades in the zinc-lead zone ranged from 2.5% to 7.6% zinc and from 1.2 to 1.6% lead over core lengths of 4-10 metres, plus higher-grade sections over shorter intervals. In the gold-copper zones, gold concentrations were in the 1.5-to-2-gram-per-tonne range, and copper typically came to about 1% (though it was as high as 5% in one interval).

Geophysical evidence implied that the massive sulphide body dipped almost vertically and extended to at least 400 metres vertical depth.

Results have now been released from another four holes at Aripuana, and widths and grades are improving. Hole 16 cut three intersections of massive sulphide mineralization, 20.8, 10, and 2.5 metres long, including one zone 5.9 metres long grading 16.07% zinc, 1.64% lead, 132 grams silver and 0.4 gram gold per tonne.

Hole 17, a stepout west of one of the earliest holes, cut two zones, one of 5.6 metres grading 11.51% zinc, 2.27% lead and 220 grams silver, and another of 3 metres grading 8% zinc, 3.56% lead, and 157 grams silver.

Hole 18 encountered a single intersection of 6.3 metres grading 3.55% zinc, 0.67% lead and 27 grams silver.

The deepest hole drilled so far, hole 19, cut four separate mineralized zones, three over core lengths in the 3-to-4-metre range with grades ranging from 6.83% to 10.02% zinc and 1.34% to 2.56% lead. Another intersection, 29.4 metres long, graded 4.37% zinc and 1.38% lead. All four intersections had silver values in the range 25-50 grams per tonne.

Ambrex is earning a 49% interest, and St. Genevieve Resources (SGV-T) 21%, in Aripuana and four other properties. Ourominas will keep 30%, with the garimpeiro miners retaining net smelter returns.

Ourominas is active in its own right on the Jaruana property, about 150 km northeast of Aripuana. The company is drilling 8,000 metres at Jaruana which features several previously worked pits in overburden and weathered rock.

After drilling several holes with narrow zones of gold mineralization, with grades ranging from a fraction of a gram to 2 grams per tonne, Ourominas has released assays from five holes with substantial gold grades.

The gold appears to be in near-vertical fracture systems, oriented north-northeast, north-northwest and west-northwest, with stockworks at their intersections.

Hole J-6 intersected 1.9 metres grading 5.6 grams gold, whereas hole J-7, drilled under another pit, cut multiple-gram intersections averaging 17.1 grams gold over 21.8 metres and 43.5 grams over 5.8 metres.

Hole J-8 intersected a 4-metre interval grading 6.8 grams gold, hole J-9 a 12-metre interval grading 4.2 grams, and hole J-10 two intervals — one of 3 metres grading 4.3 grams and one of 1.2 metres grading 11.6 grams.