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projects > cueva del chacho uranium

The Cueva del Chacho property of is a tenement running 9,250 m N-S by 3,243 m E-W located approximately 70 km south-southwest of the provincial capital city of La Rioja adjacent to a major paved road. The 3,000 hectare (11.5 sq mi) claim is immediately adjacent to a major highway in low-lying desert terrain accessible year round. The Cueva del Chacho property lies on-trend, 8 kms north of the Los Colorados Mine, on a regional sedimentary reduction-oxidation boundary where approximately 55,000 kg of uranium concentrates were produced from classic sedimentary roll-fronts between 1992 and 1996 by a local Argentine company under contract to the Argentine National Atomic Energy Commission (CNEA).

In February 2010, Pacific Bay reported soil and rock samples strongly anomalous in Rare Earth Elements, with values up to 832 ppm Cerium and 338 ppm Lanthanum. A follow up program of sampling and mapping is planned for March 2010. The strongly anomalous samples were taken in 2006 over zones of elevated radioactivity in an area of poor outcrop exposure during a uranium exploration reconnaissance program. Most of the radioactivity was determined to be caused by Thorium, but the two REE results included in the multi-element analysis package, Lanthanum and Cerium, were not reviewed at the time.

Significant REE assays:

Claim Location

Detailed Claim Location

Property Geology

Idealized Stratigraphic
Column with Radiometrics

Based on geological field work done in the 1970's by the CNEA, the Los Colorados uranium mine and the surface radiometric anomalies on the Cueva del Chacho claim are hosted in a series of gently dipping continental sediments of the Carboniferous age Saladillo Fm. which, together with redbeds of the Permian Patquía Fm., overlie Paleozoic granite that is the likely source of the uranium. The Saladillo Fm. outcrops consist of a succession of mostly siltstones and arkosic sandstones with lesser carbonaceous shales and thin conglomerates. These Saladillo Fm. sediments host radiometric anomalies in multiple stratigraphic horizons throughout the approximately 420 m of section exposed on the Cueva del Chacho property and can be seen in purplish-gray colors on the Landsat photo. The overlying redbeds of the Permian age Patquía Fm. are thoroughly oxidized and show up as a striking orange color on the photo. To the north and east of the Cueva del Chacho property the underlying, strongly fractured Paleozoic age granites of the Paimán Fm. can be seen forming the extreme southern tip of the prominent Sierra de Velazco Massif.

The regional oxidation- reduction front within the Carboniferous age clastic sediments of the Saladillo Fm. which was responsible for ore deposition at the Los Colorados Mine very clearly extends to the north into the Cueva del Chacho property. PacBay geologists believe that the discovery potential for additional roll front uranium deposits similar to the roll front exploited in the 1980' and 1990's at the Los Colorados Mine is potentially much greater on the Cueva del Chacho property due to the greater thickness of exposed favorable stratigraphy hosting reported radiometric anomalies and uranium minerals at multiple stratigraphic horizons at Cueva del Chacho.