Adelaide, Dec 5, 2006 AEST (ABN Newswire) - Tasman Resources is pleased to announce that it has been approved for funding to the level of $75,000 to test for base metals (zinc, silver, lead) on the Stuart Shelf in central SA.
Tasman's 100% owned Exploration Licence 3209 covers part of the complex structural zone known as the Torrens Hinge and the Chudys and 50 Mile Prospects, which are located approximately 40km northeast of Olympic Dam within EL3209.
Tasman commenced exploration in the area in 2002, with partial leach geochemical sampling, detailed gravity and induced polarisation geophysical surveys and relatively shallow drilling. The principal target of this exploration was Mississippi Valley-type (MVT) mineralisation within the Andamooka Limestone. MVT deposits are an important class of orebodies that have provided a significant proportion of the world's lead and zinc. Limited success was achieved with base metal sulphides being located within parts of the Andamooka Limestone, particularly at the base. However, focussing the exploration remained a fundamental problem.
The release of Geoscience Australia seismic data from along the borefield road north of Olympic Dam in 2004 delivered a previously unknown picture of the structures and geology of the area. Major faults in the subsurface that would have influenced the pathways of mineralising fluid flow during in the compression and folding of the basin 500 million years ago were clearly visible. Reprocessing of detailed aeromagnetic data revealed the locations of these faults could be traced away from the seismic traverse.
Tasman recognised that the new picture presented by the seismic image enabled the MVT targeting process to be refined. With the concept for the formation of MVT limestone-hosted base metal mineralisation comprising:
- Compression and folding of the older Adelaidian lead to expulsion of mineralised brines from deeper layers;
- Major faults forming the Torrens Hinge Zone channelled mineralised fluid flow into the lower layers of the Andamooka Limestone;
- The carbonates of the Andamooka Limestone were the trap site where MVT style mineralisation may have formed.
The introduction of the Soil Desorption Pyrolysis (SDP) geochemical approach was the final element in undertaking a new MVT exploration programme on the Stuart Shelf in EL3209. SDP is a relatively new geochemical technique that involves "fingerprinting" mineral deposit types with a high degree of confidence.
SDP measures trace amounts of volatile compounds that are adsorbed onto clay-sized particles in soil. Volatiles such as light hydrocarbons, halogens and sulphur compounds migrate readily through thick columns of rock. Most of these compounds reach the surface and are lost to the atmosphere. A tiny proportion of the gases present just below ground level are adsorbed onto the surface of soil particles. This fine soil material is sampled and the gas contents measured by heating the clay particles from the soil and analysing the gases released.
Rocks degas constantly due to burial, metamorphism and interaction with groundwater. However, ore deposits and the fluids that form them are chemically very different from their surroundings, and are frequently also associated with higher temperatures. The net result is that the gases above a buried mineral deposit are quite distinct from the regional background signal.
MVT deposits are particularly well suited to this approach because they are very commonly associated with hydrocarbons that are particularly easy to detect using the SDP approach.
Tasman plans to drill a traverse of drill holes over the two best anomalies at Chudys and 50 Mile. Access issues are already largely resolved with only one group remaining to be addressed. Negotiations for a suitable drill rig have already commenced and Tasman plans to drill these holes by the middle of 2007.
Contact
Kevin Skinner
Senior Consultant
FIELD PUBLIC RELATIONS
231 South Road
MILE END SA 5031
Tel: (08) 8234 9555
Fax: (08) 8234 9566
Mob: 0414 822 631
kevin@fieldpr.com.au
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