Silver City's primary targets are high grade silver, base metals and gold deposits. The company's early focus has been on the Proterozoic age Curnamona Province of western NSW and close to the town of Broken Hill. While a SCI remains focussed on, and continues to explore the potential of the Broken Hill district, other opportunities in well-endowed mineral provinces are also assessed.
The district was originally known for its numerous, small but very high grade silver vein deposits known as "Thackaringa type" veins where grades of silver were often reported, not just pennyweights or ounces per ton but in percents.
In 1883 the much larger, world class Broken Hill orebody was found. It was one of the largest natural accumulations of lead, zinc and silver in the world. The pre-mining size of this orebody has been estimated to have been in the order of 280 million tonnes of at least 20% combined lead and zinc with appreciable silver (100-150 g/t). The deposit originally contained 28 million tonnes of lead metal, 24 million tonnes of zinc metal, 1 billion ounces of silver and 1.2 million ounces of gold and has been mined continuously for over 125 years. The wealth created by it underpinned the industrial and mining development of Australia and spawned the world's largest mining company, BHP-Billiton.
The rocks which host the Broken Hill deposit are known collectively as the Willyama Supergroup (Figure 1). These underlie much of the district and host numerous other mineral occurrences. Those occurrences with similarities to the Broken Hill orebody are referred to as "Broken Hill type" deposits or BHT's. To date none of these has been mined or explored to the same extent as the Broken Hill deposit. Within Willyama Supergroup a number of rock sequences are recognised as hosts to BHT mineralisation. One of these in particular, the Broken Hill Group, host to the Broken Hill deposit, occurs extensively throughout the SCI tenements.
It is the opinion of the Directors of SCI that these mineralised rock sequences have been under-explored and offer significant discovery potential. Not only have the existing areas of outcrop have been poorly evaluated, but significant areas of the district which lie under a thin veneer of soil or alluvial cover have never been systematically explored. In the past the district has been the domain of large mining companies which have tended to focus on the discovery of large deposits (plus 40 million tonnes). As a consequence the density of surface geochemical samples (soils and rocks) and of drill holes in exploration prospects has tended to be low. In contrast SCI recognises the potential for discovery of much smaller but profitable orebodies. Exploration for these will require more attention to detailed geological and geochemical exploration than has been undertaken to date.
SCI has sought and acquired extensive exploration tenure in this metallogenic province at a time when a large amount of new information about the geology of the district has become available. In the last ten years comprehensive packages of high quality data including geophysics, geology and geochemistry have become available from government and private sources. Much of this data is the product of new technologies (airborne gravity and portable XRF geochemistry for example) which can be easily be processed, interpreted and integrated with Geographic Information Systems (GIS). This enables rapid prioritization and assessment of mineral targets for future drilling.
The opportunity for new discovery is built around the application of new information, new technologies and new geological concepts to an old, world-class mining camp. It is the intention of SCI to utilise this new information, integrate it with the company's own high quality geological and geochemical surveys and systematically drill targets to assess mineral potential. Whilst the discovery of another Broken Hill-size lead-zinc-silver orebody would be an excellent outcome, SCI considers that a discovery even just a small portion of that size would benefit shareholders considerably.