A drill program carried out by Geomaque Explorations (GEO-T) at the Vueltas del Rio gold deposit in northwestern Honduras has boosted the resource estimate to 922,000 oz. gold.
The new figure represents an increase of 84% over the previous estimate of 500,000 oz.
Geomaque, which snapped up the open-pit project in 1996 by absorbing previous owner Milagro Minerals, expects to bring it into production in 1999. The company already operates the San Francisco open-pit mine in Mexico’s Sonora state, which yields 70,000 oz. gold per year.
To date, Geomaque has drilled 294 holes at Vueltas del Rio. The total resource, most of which is classified as measured and indicated, now stands at 12.6 million tonnes grading 2.27 grams gold per tonne uncut, or 1.61 grams cut. High grades are cut to 20 grams gold in the San Juan zone and 25 grams in the Main zone.
Of the 744,000 oz. gold classified as measured and indicated, about half is contained in oxide mineralization and half in primary mineralization. All of it is heap-leachable, with recoveries projected at greater than 70%.
Drilling is currently focused on defining near-surface mineralization to estimate minable reserves for an upcoming feasibility study. Most of the interim resource lies within 100 metres of surface, with most of the measured and indicated material within 50 metres of surface.
The deposit remains open at depth and to the east and west along strike. A new phase of exploration drilling, to begin this month, will attempt to define mineralization in previously undrilled areas between the Main and San Juan zones, and west of the San Roberto zone.
“Using a tightly spaced drill pattern [an average of 20 metres] has resulted in most of the resource being classed as measured and indicated, and this will enable us to quickly upgrade resource ounces to reserves,” states Phillip Watford, vice-president of exploration. “The resource confirms that Vueltas del Rio is a robust deposit with significant upside potential.” Geomaque’s president, John Paterson, says the first-phase drill results far exceeded the company’s expectations. “When we acquired Vueltas del Rio, we were anticipating a 40,000-oz.-per-year production rate; this interim resource justifies a production rate of 70,000 oz. per year.” Although gold mining on the property dates back to colonial times, only modest production has ever been recorded. The adits that dot the property serve as a reminder of those early efforts. Past operators left behind about 500 metres of underground development in tunnels roughly 40 to 50 metres deep as they drifted along veins to recover the highest-grade oxide material.
Vueltas del Rio lies just south of the Caribbean-North American plate boundary, where the Paleozoic metamorphic rocks that comprise the core of Central America meet intensely folded Cretaceous sediments. The Vueltas del Rio formation itself comprises Jurassic volcanics and sediments, including welded tuffs, tuff breccias, vent intrusives and volcanic wackes and shales.
Tuffs, flows and sediments of Miocene age disconformably overlie all other units, though gold mineralization has yet to be found in those younger rocks.
The Vueltas del Rio shear zone, which strikes in an east-west direction, has a known length of 1.5 km and an average width of 300 metres. The structure hosts numerous old workings and is the site of the historic San Martin mine, which, in the 1940s, produced 15,000 oz. gold from ore grading roughly 13 grams per tonne.
Gold mineralization is structurally controlled, occurs primarily in native form and is hosted by a residual saprolitic soil horizon resulting from the weathering of quartz-sulphide veinlets and host rocks.
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