Only summaries of our excursion activities will be posted to the website. You will have to consult the Bulletin for the detailed geological information. At least here we can have a few colour photos! Point cursor on photo for title. Also click on underlined words (links) for more data from relevant websites. This year's activities (2008) will be reported as they occur.
When an ore body is being analysed, the geologists need to know the extent and quality of the ore body at various depths and across the area. By taking samples from drill cores the body can be assessed for its mineral concentration and to establish the best way to process the ore for most effective extraction.
Joe Lorenzin and Ian Pontifex showed how a rock sample is prepared for examination on a microscope. Joe demonstrated rock cutting, polishing and lapping of samples. The aim being to mount a thin sliver of rock on a microscope slide and reduce it to about 30 microns in thickness. This exposes the crystalline structure and makes identification of minerals possible.
Some samples are drill cores or solid pieces of rock. Some are particles of partly processed ore which are encapsulated in clear resin then polished to make them ready for examination. The examination can be through an optical microscope, either top or bottom lit, or for electron microscope examination performed off-site.
Photos and report by Steve Elsby.
The region between Wallaroo, Moonta and Kadina is known as the Copper Triangle, and one of the main aims of this four day excursion was to visit the mines, now defunct, to which it owes this sobriquet. Our geological observations began well before we reached the Triangle with a stop to examine limestone and dolomite at the Hummock Range which marks the western limit of the Adelaide Geosyncline. Westward of these low hills everything is flat and has been more or less undisturbed since Precambrian times.
Our first day at Moonta began with a visit to the town’s Vietnam War Memorial, which includes a memorial to 11 dogs who were used to sniff out land mines and the enemy. We then spent most of the day exploring the Wheal Hughes mine, now developed as a tourist attraction. A small train took us around the above-ground workings and we observed how copper mining operated in the late 19th and early 20th century. The life of a miner was hard in those days! In the underground mine we spotted shiny patches of chalcopyrite and copper minerals gleaming temptingly in the walls. There were even green stalactites formed of copper minerals, hanging from the roof of the mine, and green coppery rivulets on the floor. There is still copper to be mined, but it is no longer economical.
On our second day we visited Wallaroo, whose mine has not been developed for tourists but there is still much to see of the old mine workings, and the heaps of slag which has been used to construct walls and some buildings. One enterprising member managed to obtain permission for us to visit an operation which is cleaning up the groundwater contaminated by the mining operations. We spent a very enjoyable hour in a quarry that is extracting an unusual kind of rock called harlequin stone on account of its colourful appearance : pink, cream, green and black. It is formed by metasomatism (contact metamorphism) of a siliceous limestone. We were allowed to pick up as many fragments as we liked of this attractive rock and returned to the bus laden with heavy bags.
During the late afternoons, after having explored the mines and quarries, we relaxed by walking along the beach by our caravan park at Moonta Bay where, under the tuition of our leader Bob Major, we studied the stratigraphy exposed in the cliffs and on the shore: Precambrian granite, Cambrian sandstone, tertiary Hindmarsh Clay and plenty of calcrete and silcrete which we learned to distinguish from each other and from calcarenite, all abundant along the coasts of South Austraia. In the morning early risers were able to observe the unconformity between the Precambrian Basement (Tickera Granite) and Cambrian Winulta Formation (a quartzitic sandstone) which was exposed low tide.
A final highlight was a visit to Mick Vort-Ronald’s fascinating Money Museum at Kadina, unfortunately due to close at the end of 2008.
Report by Frances Williams and photo by Diana Rogers
