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New 3D model to help reassess Broken Hill mineral resources.

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    Warren Entsch, MP       Parliamentary Secretary to the

Minister for Industry, Science and Resources    

30 May 2000            00/180 

New 3D model to help reassess Broken Hill mineral resources   A new 3D structural geology model will provide a clearer understanding of the patterns of distribution and dispersion of mineralisation in the Broken Hill-Olary region.  

The 3D model revealed today at the Broken Hill Exploration Initiative (BHEI) conference combines surface, structural-geology mapping with deep seismic reflection imaging and detailed cross-sections to provide a multidimensional picture of the area.  

The Parliamentary Secretary to the Minister for Industry, Science and Resources, Warren Entsch said this would give mineral explorers a new way of looking at previously explored areas in the Broken Hill region. 

"By combining the results from various techniques it is possible to determine the configuration, attitude and trend of rocks, including any mineralised layers occurring beneath the surface," Mr Entsch said. 

The 3D crustal model reassesses long-held notions of Broken Hill's regional structure and offers new interpretations of aeromagnetic data in complex and highly deformed mineralised terranes. 

Mr Entsch said this may help mineral exploration companies to identify new areas to focus their search for base-metals, both in the Broken Hill region and in other areas. 

The model has been developed by the Broken Hill Exploration Initiative - a Commonwealth-State venture involving the Australian Geological Survey Organisation (AGSO), NSW Department of Minerals Resources (NSW DMR) and the Department of Primary Industry and Resources of South Australia (PIRSA). 

Mr Entsch compared the geological character of the area studied to a piece of origami.  

"Imagine the rock terrain beneath any surface is at first flat like a piece of new paper," he said. 

"An activity occurring some 1700 million years ago folded the 'paper' horizontally. This

was a geological deformation impacting on the area. Most mapping techniques identify this pattern and exploration needs to be targeted at specific mineralised sites within these complexly folded rocks. 

"The 3D crustal model shows the impact of other geological deformation occurring after that time where the rocks have been folded for a second time and forced to crack and break along vertical zones, known as shear zones. These shear zones which in turn become fluid pathways and potential traps for mineralisation. 

"The Line of Lode, which contains the Broken Hill ore body, may be present in one such shear zone - the result of fluid flow through deeply rooted fractures," Mr Entsch said. 

The model suggests many shear zones in the Broken Hill-Olary region do not have the orientation previously thought. Rather, the combination of structural data and seismic imaging provides strong evidence that these shear zones and associated fluid conduits are inclined in the opposite direction. This provides a new insight to the region and may help explorers untangle the complex geological history. 

"Should this interpretation prove correct in the case of the Broken Hill-Olary region, then the same approach and methodology to 3D imaging of the crust could be adapted to suit any mineralised province in Australia," Mr Entsch said. 

Broken Hill-Olary was an ideal location for studies as it met a number of significant criteria:   It was already known as a region of silver, zinc and lead mineralisation; ● There are many geological parallels between Broken Hill-Olary and other major

mineral provinces in Australia (eg Mt Isa); ●

The stratigraphy of the region is well known  ●

The new 3D model was revealed today at the BHEI conference in Broken Hill. The conference brings together the major participants in the joint initiative to present their results to the mineral exploration industry and runs from the 29 to 31 May.  

For more information contact:

Greg Doolan, Mr Entsch's office: (02) 6277 4656 or 0418 213 243

Heather Wallace, AGSO: (02) 6249 9511 or 0417 689 757 


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