Linex Pty Ltd
The last great lineament analysis and the discovery of the Carrapateena IOCGU deposit, South Australia?>
“Lineament” is a junk-basket term that is applied widely but respected very little. There is no definition consensus. Some use the term to describe small features on the ground, such as joints. Others use the term to describe structures encircling the globe. Most authors attempt to convince the reader they are profoundly significant, albeit enigmatic, structures. Attempts to prove their existence typically relate “lineaments” to minerals or petroleum accumulations - hoping that correlation does imply causation. This is rarely the case.?>
Tim O’Driscoll is a rare, if not unique, lineament analyst who successfully targeted a giant ore body. He delineated the position of the giant Olympic Dam IOGCU deposit under several hundreds of metres of cover beneath the Stuart Shelf in South Australia. There continues to be differing and contradicting versions of the discovery process, however, Woodall (1994) is the most authorative.
Tim’s ore-targeting method using lineaments was unique. He used 1”:1 mile (1:63,360) scale air photo mosaics to map 2 mile linear trends (“chicken tracks”) that were sampling linear zones that were visible transecting the mosaic. These were then traced and combined with geological, geophysical and morphological data to delineate lineaments. These lineaments and their intersections were ranked and favourable sites selected for drilling.
In 1996, I was working for the Petroleum Division of Primary Industries and Resources South Australia (PIRSA). Tim had retired from WMC. I was concerned that Tim’s unique lineament analysis and ore targeting technique was not taught to the next generation of geologists. Tim had only taught a few geologists the process and these people had either retired or moved into other areas. I suggested to the Director of the Petroleum Division, Bob Laws, that PIRSA engage Tim to pass on his skills.
On 6/2/96 Bob Laws wrote to the Director of the Minerals Division, Ric Horn, to organise a joint project whereby I was released 50-60% of my time to work with Tim on a pilot project. Tim was initially engaged on a 40 day contract to the end of the financial year as the first part of a 2 year project that would map the entire state. The July 1996 MESA Journal announced the commencement and aims of the project.
The first task was digitising the published 1:250,000 “chicken tracks” and lineaments over the Andamooka and Torrens 1:250,000 map sheets. These were the same data that were used by Tim to generate the targets that led to the discovery of Olympic Dam. The sheets adjacent to these were mapped next as we worked our way towards the Cooper Basin to the north. Initially Tim and I took turns at the mapping process, with him demonstrating or observing my progress. It was arguably the most difficult thing I have learnt to do. Without Tim’s guidance and attention to detail, there is no way I would have reproduced a similar result. By 1996, most data were available digitally and once our mapped “chicken tracks” were digitised by the diligent PIRSA drafting staff, we were quickly able to generate the raw data plots needed for the interpretation process.
On 23/2/96 General Gold Resources(GGR) wrote to the ASX announcing they’d entered into a JV with Rudy Gomez on the tenement which covered Carrapateena. The Adelaide Advertiser contained an article on 10/10/96 detailing their aims to find the next Olympic Dam. After I suggested to Bob and Ric that we alert them of our project, Ric wrote to both GGR and Rudy Gomez on 18/10/96 inviting them to PIRSA to discuss lineaments. Rudy rang me on 23/10/96 to discuss what our project involved and organised a time for himself and the directors to visit Tim and I. Upton (2010) quotes Rudy’s major motivation to persist to drill the Carrapateena target from Tim’s advice when he was working with the PIRSA petroleum division in 1996.
Tim and I mapped eastwards from the Stuart Shelf, across the Adelaide Fold Belt and up into the Cooper Basin. Two reports were produced. The first in 1997 discuss the outline of the project and presented the data compiled to the stage. The second in 1998 discussed hypothesis on lineament controls on hydrocarbon distribution in the Cooper Basin. Both reports are available for download from PIRSA’s web site. The latter report was concluded after I moved back to Victoria for family reasons. At this time I established my consulting company, Linex (initially under a parent company, Whitehorse Geoscience), to provide services in lineament exploration. One of the first jobs I took was to conduct a lineament analysis for Rudy Gomez on his tenements to the east of Carrapateena at Lake Gairdner. Unfortunately, following 1997 gold prices and exploration fell into a prolonged slump. I consulted in more traditional areas of structural geology, developed my own niche and have never had or sought the opportunity to use the lineament analysis skills learnt from Tim. Unfortunately, the original plans to map all of SA were never fulfilled, however, a significant part of the state was covered then and subsequent to that project.
Tim O'Driscoll passed asway in 2004.
On 8/3/05 I received a package from Rudy Gomez with a CD of data from the Carrapateena target. Rudy requested that I review the lineament data at Carrapateena and advise on the hole positions he had. He had some urgency for this review as he had receieved a PIRSA PACE grant for half of the drilling costs and was keen to get underway. I retrieved the data generated at PIRSA and emailed Rudy on 14/3/05 with these data overlain on his proposed hole positions.
The discovery hole was the first hole started at Carrapateena, but due to drilling difficulties was the second completed and hence named hole CAR002. This hole intersected 70m @ 3% copper and 0.4g/t gold. The hole was drilled on the gravity target and the chicken track trend in Tim's 1970's data. This is a truly remarkable exploration achievement given the deposit lies over 470 m below barren cover.
Rudy entered into a joint venture with Teck Cominco to develop the project. It was sold to Oz Minerals in early 2011 for $US250m with further payments of $US50m on the first commercial production.
This tale accounts only for the role of lineaments in the discovery of Carrapateena. It should in no way detract from the vast amount of important exploration work conducted by others in the discovery or the bold exploration attempts by Rudy himself who had the belief in the project and investing his own money into the exploration.
Page created 30/10/07