 |
 |
|
 |
|
 |
|
 |
|
 |
|
|
Uranium exploration in and around the Cabeza de Araya batholith commenced in the mid-1950s with JEN continuing activities until the late 1960s. In this period, the La Zafrilla deposit was located and put into exploitation for a short period during the 1960s. The JEN recommenced exploration in the late 1970s, but ceded these activities to ENUSA in 1974. ENUSA was active until the mid-1980’s, when they also ceased exploration in this area. Subsequently CISA was active between 1989 and 1994. Numerous uranium occurrences associated with this granitic intrusive have been located. The most interesting area appears to be the central part of the batholith which includes the Saguazal deposit. An application for an exploration permit to cover this area was made. The Saguazal prospect within the Caceres III project was the second mineralised area to be tested with confirmatory drilling by Berkeley in its Spanish uranium exploration program.
Geology Three different granite lithologies are delimited in the area of the application:
Deuteric alteration is common in Facies B & C. There is an important series of late Hercynian fractures with direction SW-NE. The Messejana dolerite dyke of Triassic age has intruded following this system of fractures. Uranium Occurrences The occurrences in this area are associated with SW-NE trending fractures particularly in the vicinity de Cuestas de Santo Domingo, but also in the area of Baldios. The mineralisation at El Saguazal consists essentially of secondary minerals, but altered primary mineralisation has been encountered at depth. It is controlled by a series of brecciated granites situated within a thrust zone some 80m wide that strikes WNW-ESE and dips at some 30°NE. The thrust zone continues along strike for up to 4 km and parts of it are well-mineralised. In 1984, ENUSA produced a radiometric grid, carried out a resistivity survey, dug 6 trenches and drilled 6 core holes. Several of these holes intersected strong mineralisation at relatively shallow depth. CISA re-examined this zone between 1991 and 1994. In 1991 they mapped the main area of interest as identified by ENUSA and confirmed the lack of outcrops. In the same period, they completed a radiometric grid some 3.6 km long, ranging in width from 200 to 400 metres. The main anomalies were situated in a central zone some 1.2 km long. In 1993, a VLF–EM survey was carried out which confirmed the principal direction at 130°-135°. During 1994, CISA carried out radon emanation as well as EM and resistivity surveys and excavated a total of 14 trenches for a combined length of 247.1 m. Almost all the drilling carried out was open-hole coupled with gamma-ray borehole logging. A total of 132 such holes were drilled with a combined length of 5,905 metres. Four core-holes were also drilled for a total length of 178 metres, and also were radiometrically logged. Information on two of the core-holes is available:
In early 2007, Berkeley conducted its own initial program of 9 diamond drill holes with the aim of confirming previous high grade intersections and testing potentially mineralised NE-SW sulphide-bearing structures and other geophysical targets defined by an IP survey. This program was preceded by background environmental radiometric and radon surveys and a trial IP survey. The IP survey indicated two fracture sets of a NE-SW set with a sulphide (+/- pitchblende) association and a NW-SE set without sulphides. Domal features in the chargeability profiles appear to coincide with the transition between fresh and weathered rock and the presence of sulphides (from old geological drill logs). However, initial reconciliation with drill results failed to show that either the domal features or IP structures relate to the mineralisation. Integration of the new diamond drill results with radiometric data from historic open hole drilling indicates that high grade uranium mineralisation is associated with a shallow, sub-horizontal zone of pyrite/marcasite +/- pitchblende +/- coffinite mineralization in variably fractured and brecciated granite. Recognition of these structural and mineralogical controls enables a reassessment of all historical data and the opportunity to target new areas for drill testing along the extensive radiometric anomaly at Saguazal. Notable intersections (at a cut-off of 200ppm U3O8) include:
Subsequent to the initial drill campaign, Berkeley has been reinterpreting all historic exploration results, prior to undertaking a further geophysical or drilling program.
|
 |
|||
|
|||
 |
|
|
|
|
|
|
|
