The Mount Padbury Project covers a relatively unexplored area of the Murchison Mineral Field where uranium mineralisation has been found in calcrete deposits developed within intermittently flowing tributaries of the Murchison and Talga Rivers.
The Mount Padbury Project comprises Exploration Licences E51/1147 and E51/1150 and is located near the town of Meekatharra, WA about 700 km north of Perth. Access to Mount Padbury tenements from Meekatharra is by way of the Meekatharra-Mount Clere Road, which passes from south to north through the centre of the area.
Regional Geology
The regional geological setting of the Mount Padbury Project area comprises the contact zone between the Archaean Yilgarn Craton, with the Paleoproterozoic Bryah Group rock sequence to the north. This contact trends south easterly through the northern part of E51/1150.
The north western part of the Yilgarn Craton, which forms the basement to these Paleoproterozoic rocks, is composed of the Murchison and Narryer Terranes. The Murchison terrain, which mostly underlies the Mount Padbury Project, consists mainly of "hot" (radioactive) granitic intrusives into greenstone remnants.
The Narryer Terrane, to the north, contains extensive remnants of old cratonic granitic gneisses inter-leaved with younger Archaean subcrustal rocks and late Archaean granitoids intrusives.
Project Geology
The geological setting of the Mount Padbury Project is made up of an extensive cover of quaternary-aged alluvium, sheet-wash deposits of clay, silt, sand and colluvium within an extensive south westerly draining system of intermittently flowing drainages.
Within these watercourses there are irregular areas of calcrete. Underlying these surficial deposits is a radioactive biotite monzogranite which is present within most of the northern tenement, E51/1150. This granite is intruded by generally east-west trending Proterozoic-aged dolerite dykes. To the west of E51/1150 there is a 3km thick succession of mafic to ultramafic and felsic volcanic rocks of the Mount Maitland Greenstone Belt.
In the northern part of E51/1147, there are small outcrops of Proterozoic sandy and silty sediments.
Carnotite mineralisation in the area is exposed in two shire quarries; Discovery Pit 1 and Discovery Pit 2. Carnotite mineralisation in Discovery Pit 1 occurs over an area of some 1,200m², while in Discovery Pit 2 it occurs over a 250m X 75m area in a shear developed in granite.
Both pits are within a few kilometres distance and lie to the east and west of the Meekatharra-Mount Clere Road. Mount Padbury carnotite uranium discovery is hosted within surficial sediments and overlying calcrete developed within the fossil drainage profile of the tributary system of Murchison River.
This dendritic fossil drainage system overlies deeply eroded Late Archaean granitic basement rocks. The catchment area includes "hot" radiometric granitic intrusives giving the prospect a geologic setting bearing considerable similarities to the "Yeelirrie-type valley calcrete uranium deposit".
Mount Padbury Exploration 2006-2007
Exploration work for the Project area included: the study of available information, reconnaissance field visits and "garb sampling" from Discovery Pit 1 for uranium analysis, study of airborne radiometric data, acquisition of digital high resolution photography over E51/1147 area for geological mapping, and meetings with Yamatji Land & Sea Council for Heritage Clearance of a selected area (about 4km²) around Discovery Pit 1 in the Exploration Licence E51/1147.
Some uranium grab sample results from the Mount Padbury - Discovery Pit 1 are shown below:
| Uranium (Grade ppm) | |||
|---|---|---|---|
| Sample Number | Element - U (XRF Assay) | Compound - U3O8 (Pure Yellowcake) | Chemical Conversion Factor |
| YC001 | 2410 | 2841.4 | 1.179 |
| YC002 | 472 | 556.5 | 1.179 |
| YC003 | 603 | 710.9 | 1.179 |
| YC004 | 116 | 136.8 | 1.179 |
| YC005 | 258 | 304.2 | 1.179 |
| YC006 | 58 | 68.4 | 1.179 |
| YC007 | 764 | 909.2 | 1.179 |
| YC008 | 352 | 415.0 | 1.179 |
| YC009 | 1876 | 2211.8 | 1.179 |
| YC010 | 283 | 333.7 | 1.179 |
| YC011 | 74 | 87.3 | 1.179 |
| YC012 | 22 | 25.9 | 1.179 |
Field observations suggest the presence of two styles of carnotite mineralisation in the area; the valley-fill as in Discovery Pit 1, and shear zone (in granite) associated as in Discovery Pit 2.
Despite discovery of calcrete hosted carnotite (uranium), within quaternary alluvial and colluvial sediments in tributaries to the Murchison River, due to a lack of economic incentives no follow up exploration for valley-filled uranium has been conducted in the area.
The identification of anomalous uranium values in tributaries of the Murchison and Yalga Rivers, near Moorarie, suggests a possible upstream source. This is by way of the active erosion of Fairstar's identified carnotite mineralisation formed by leaching of uranium from radioactive "hot" late Archaean granites within the catchment area.
Further, the presence of "shear hosted" carnotite mineralisation suggests that there may be other such settings in the Project area; contributing to an increase in the project's potential prospectivity.
Additionally, in E51/1150 the soil covered inferred contact zone between the Paleoproterozoic Narracoota Formation and the granite/greenstone terrain, south of the Murchison River is considered to have potential for gold mineralisation.
Outlook
The style of uranium mineralisation as observed in two shire pits and the presence of Wiluna hardpan covering the known mineralisation makes the normal uranium exploration approach of airborne radiometric survey followed by drilling difficult in the area. Further, rock exposures within the Project area are very poor - less than 1% over much of the area.
Therefore, in the coming months study of airborne magnetic data together with on ground radiometric traverses, and enhanced satellite imagery along with geological and regolith mapping will be initiated.
