VANCOUVER (miningweekly.com) – TSX-listed uranium explorer U3O8 Corp continues to build on the recent discovery of higher-grade uranium/vanadium mineralisation at La Rosada, part of the Laguna Salada project in Argentina, announcing on Tuesday that it has delineated similar channels in, and beneath, the bottom gravel layer of the existing resource.

The explorer said these levels are over and above the layer of mineralisation on which the May 2011 resource estimate is based, and may represent significant resource growth potential.

"By applying what we have learned from the discovery of higher-grade uranium/vanadium in the La Rosada area, our exploration team has identified similar higher-grade layers at the base of and beneath the gravel at Laguna Salada," said CEO Dr Richard Spencer.

U3O8 had recently announced assays from a second type of uranium/vanadium mineralisation that occurs in addition to the typical mineralised gravel at La Rosada. Trenching over the last couple of months has shown that uranium/vanadium in the volcanic rock constitutes a target in its own right, adding to the potential of the La Rosada target.

Since becoming involved at Laguna Salada, U3O8 has expanded the mineralised footprint by about 200 ha, but expects that figure to grow quickly as the company extends exploration efforts in the new area.

Spencer noted that identifying the higher-grade potential provides an opportunity to further reduce the already comparatively low estimated production costs for the Laguna Salada deposit. It also opens new targets for shallow uranium/vanadium mineralisation in soft gravel, sand and silt that can be inexpensively explored through trenching, he added.

U3O8 reported that higher-grade uranium/vanadium at the base of the gravel occurs in an elongated zone that extends from north-west to south-east over at least 6 km. The mineralised gravel averages 0.7 m thick with an average grade of 0.04% (421 ppm) uranium oxide (U₃O₈) and 0.08% (807 ppm) vanadium pentoxide (V₂O₅), over an area of 4 km², about half of which is included in the current resource estimate.

According to a press release issued on Tuesday, testwork on Laguna Salada gravel has shown that removal of the pebbles and coarse sand by sieving results in an 11-times increase in uranium grade and a four-times increase in vanadium grade in the fine material that would be fed to a processing plant. Screening of gravel with these grades would, therefore, generate a fine-grained feed with an estimated grade of about 0.46% U₃O₈ and 0.32% V₂O₅.

Underlying the gravel in some parts of the north-western margin of the Laguna Salada deposit is an unconsolidated sand layer very similar to that observed at La Rosada. The mineralised part of the sand layer averages 0.5 m thick and has an average grade of 353 ppm U₃O₈ and 0.11% (1 144 ppm) V₂O₅ over an area of about 4 km². The beneficiation characteristics – the extent to which grades can be increased in the fine-grained fraction by sieving – are currently being investigated, the company said.

Further, underlying either unconsolidated gravel or sand is a fine-grained silty unit, the mineralised component of which has an average grade of 408 ppm U₃O₈ and 0.15% (1 531 ppm) V₂O₅ over a true thickness of 0.7 m. The beneficiation characteristics of the silty layer, which may be weathered volcanic rock like that observed at La Rosada, are unknown at this time and will be tested in due course.

U3O8 noted that there is a possibility that each of these three layers represents a zone of mineralisation in its own right that is separate and distinct from the true "caliche" mineralisation located in the upper part of the gravel on which the resource estimate is based. 

The company has identified several target areas for exploration for more higher-grade resource potential.