Crossland has been able to secure a totally owned contiguous holding of prime prospectivity for URD that has fewer access issues than those that commonly burden explorers on ground of similar prospectivity for URD in the Northern Territory. Crossland will explore the tenements systematically and thoroughly utilising the latest methods.
Source of uranium
In the case of the Chilling project, the district is located in a zone of high uranium background, in both granites and metasediments and volcanics. The ultimate source of these high uranium background values is the Achaean granite basement, which is exposed in the Rum Jungle and Waterhouse granites, 20+ km to the NNE of the project area. These rocks probably exist at depth through the project area, and in gneiss belts around the western side of the project area.
Transport mechanism
Basin- forming structures, the Giants Reef and Adelaide River Faults, traverse the project area. It seems likely that the latter may have been active at the appropriate time for related structures to provide channelways for uranium-bearing fluids, and Crossland's holdings give priority to securing this. Generally, mineralisation will be in subsidiary structures rather than major faults.
Site for deposition
The classic site for deposition of URD is the unconformity surface between (older) metasediments and overlying (younger) sandstones. The project area contains about 130km of strike length of this unconformity, over the structures most likely in Crossland's view to provide suitable channelways for uraniferous fluids. These could also control the structures that host mineralisation. Almost all of the important Australian examples of these deposits lie below the unconformity surface, while those in the similar Athabasca Basin setting in Canada occur both above and below the unconformity surface, and some of the largest and richest deposits occur in fault structures within the upper sandstone.
The more spectacular Canadian discoveries have been made in the last few decades, and are probably a function of the much longer period of active exploration through the cover rocks that has been enjoyed by the uranium exploration industry in the Athabasca Basin relative to the equally prospective districts of the Northern Territory. By definition, deposits in and below the cover rocks will be more difficult to locate quickly than those exposed where the cover is removed, as is the case in most discoveries in the ARUF, with the exception of the largest discovery, Jabiluka II, and the most recent to be announced, Ranger 68.
The Depot Creek Sandstone of the Tolmer Group is equivalent in age to the Kombolgie Sandstone in the ARUF. Both these sandstone units are older than most of the mineralisation in ARUF and Rum Jungle, and structures that control the deposition of ore cut the sandstones. There are many potential sites for uranium deposition throughout the Depot Creek Sandstone, and probably below it, within the Chilling Project Area, and it is Crossland's intention to locate and test them.
The Uranium Expert's Report for the prospectus points out that alteration similar to that associated with URD in ARUF has already been identified in the project area, and that there are several known uranium occurrences, including secondary uranium mineralisation with values up to 0.395% U3O8 . Crossland expects that thorough exploration will find more.