Cáceres VI Uranium Project

Click to Enlarge Images
Figure 1 – Cáceres VI Geology
Figure 1 – Cáceres VI Geology 
Figure 2 - Cáceres VI, Berkeley Drilling at Gambuta
Figure 2 - Cáceres VI, Berkeley Drilling at Gambuta 
Figure 3 - Cáceres VI, Gambuta Cross Section
Figure 3 - Cáceres VI, Gambuta Cross Section 
Figure 4 - Cáceres VI, Gambuta Schematic Long Section
Figure 4 - Cáceres VI, Gambuta Schematic Long Section 
Figure 5 - Cáceres VI, Airborne Radiometrics
Figure 5 - Cáceres VI, Airborne Radiometrics 
Figure 6 - Cáceres VI, Gambuta Airborne Radiometrics
Figure 6 - Cáceres VI, Gambuta Airborne Radiometrics 
Figure 7 - Cáceres VI, Ojaranzo Radiometrics
Figure 7 - Cáceres VI, Ojaranzo Radiometrics 

The Cáceres VI Uranium Project is located approximately 165 km west-southwest of Madrid in the Cáceres Province of Spain. Within the Cáceres VI Uranium Project, the Gambuta and Ojaranzo deposits have been partially evaluated. The Gambuta deposit is located 6kms to the west of Bohonal de Ibor in the extreme west of Berkeley's Cáceres VI project area while Ojaranzo is in the eastern part of the tenement. This Project contains a number of perigranitic uranium mineral occurrences of which Gambuta and Ojaranzo are typical examples. Other prospects include El Zarzal and Cancho del Queso, located in the central and eastern part of the tenement respectively.

In August 2008, Berkeley announced an initial inferred resource estimate of 9.23 million pounds of U3O8 at an average grade of 371ppm U3O8 (at a 200ppm cutoff) for the Gambuta deposit.

Gambuta Deposit

The Gambuta deposit is associated with an area of anomalous radiometrics defined by the Junta de Energia Nuclear ("JEN") in the 1960's and briefly explored by CISA (a joint venture between COGEMA (now AREVA) and ENUSA) in the early 1990's. Roto percussion drilling by CISA (24 holes) identified a mineralised, north-westerly trending, structural zone with dimensions of approximately 900m x 400m, including a central untested area of Tertiary cover.

A 36 hole program by Berkeley has confirmed the CISA results and defined a continuous, structurally controlled, zone of mineralisation which is 250 - 350m wide, up to 94m below surface (see Figure 3) and is continuous for 1,500m in a west-northwesterly direction. This zone appears to extend beneath Tertiary and Quaternary cover to the north-west and about 1,300m of untested strike potential remains within the license.

Uranium mineralisation occurs within a sequence of strongly deformed Proterozoic spotted and banded grey to black phyllites which have been contact metamorphosed by Hercynian granites. The contacts between the phyllites and the granite to the east and northeast are tectonic. The sequence of host phyllites at Gambuta is similar to that hosting the Retortillo deposit in the Salamanca I license.

As at Retortillo, the Gambuta uranium mineralisation is generally sub-horizontal and associated with the weathering profile; a similar model of formation is envisaged. Most mineralisation occurs in the zone of partial oxidation. Deeper mineralisation is associated with oxidation along steeply dipping shears and fractures, dominantly sub-parallel to the mineralised trends. Uranium mineralisation occurs within the schistosity, particularly in zones of shearing and fracturing. The only visible uranium minerals are secondary autunite and torbernite.

The main mineralised horizon averages 9.4m in thickness and occurs at an average depth of 18.0m, beneath Tertiary cover and shales. A lower mineralised horizon averages 2.1m in thickness and is separated from the main horizon by 16.3m of shales. A central, higher grade (+0.1% U3O8,) zone, about 100m wide, is evident in the north-western half of the deposit and is open along strike.

Drilling results have been previously reported in Announcements to the ASX on 10th April and 6th of June, 2008. A resource estimate was reported to the ASX on the 8th August, 2008.

Initial inferred uranium resources for the Gambuta deposit have been calculated as follows:

  • At a 200ppm U3O8 cut-off, 11.29Mt of ore at a grade of 371ppm U3O8 containing 9.23Mlbs U3O8
  • At a 150ppm U3O8 cut-off, 15.49Mt of ore at a grade of 318ppm U3O8 containing 10.85Mlbs U3O8
  • At a 100ppm U3O8 cut-off, 19.46Mt of ore at a grade of 278ppm U3O8 containing 11.95Mlbs U3O8

In late 2007 Berkeley completed a helicopter-borne radiometric and magnetic survey over the Cáceres VI Project to better define the extent of the known uranium occurrences and to identify potential extensions and possible new occurrences.

The survey comprised 1,468 line kilometres on 100m spaced north - south lines using a towed magnetic sensor at a nominal height of 35m and a spectrometer inside the aircraft.

The results show the Gambuta uranium mineralisation to occur adjacent to thorium-rich, differentiated granite with potential for significant extensions to the South East along the granite margin.

The Gambuta radiometric anomaly appears to be blanketed by Tertiary cover which extends to the north and west into areas where the magnetics suggest east- north-east orientated structures in the underlying granitic body. The northern portion of the Gambuta anomaly increases in strength towards the northern most contact with the Tertiary.

A magnetic anomaly also occurs under the cover and magnetic features are associated with uranium mineralisation in most areas.

Ojaranzo

The initial discovery of uranium mineralisation at Ojaranzo was made by JEN during the 1960's. Follow up by CISA during the early 1990's included a program of geological mapping, detailed ground radiometrics, approximately 1,000 wagon drill holes and 21 trenches, which helped target a program of 23 roto-percussion drillholes.

Anomalous radiometrics occur in a 1,200 by 600m area of spotted and fine-banded dark phyllites striking about 1400 with sub-vertical bedding and cleavage. In places the phyllites shows strongly oxidation. Some uranium mineralisation is related to a bedding parallel fracture system containing quartz, sulphides and iron oxides.

A two hole diamond drilling program by Berkeley intersected:

  • OJA-001:
    • 4 m @ 0.079% U3O8 from 47 m
  • OJA-002:
    • 6,5 m @ 0.0635% U3O8 from 15,5 m
    • Including: 4 m @ 0.0935% U3O8 from 18 m
    • 0,85 m @ 0.0881% U3O8 from 23 m

Mineralisation appears related to weathering of dark shale bands containing increased quartz - pyrite veins. Secondary mineralisation occurs on oxidised fractures and zones with chloritic, kaolinitic and hematitic alteration.