AIG QLD Presentations – New England Orogen Field Trip – 6-8 June 2015

The Queensland AIG and GSAco-hosted a 3 day field trip visiting geological and mineralisation locations within the New England Orogen around Stanthorpe, Texas and Tenterfield on the June long weekend. Doug Young co-ordinated and sourced the speakers, trip itinerary, and guide notes with huge support from Davina Halloran, Adrian Day, Martin I’Ons, and Julius Marinelli. The intrepid group of 32 people ranging from young to the young at heart were sourced from industry, academia and government bodies.

The trip started from Brisbane and headed west to the first stop at Mt Sylvia, 40km south of Gatton in the Lockyer Valley. Here we visited a quarry with a diatomite deposit hosted within basalt where both the diatomite and the basalt are being mined. Our visit was kindly hosted by geologists, Martin I’ons and Guy Lewington, and Guy provided an informative and entertaining overview of the quarry products and their uses. The geological focus of the quarry operations has led to the development of a diverse product range, which includes various size and treated fractions of the diatomite, road metal from the unweathered basalt, and palagonite developed during weathering of basaltic glass; the latter is used as a high quality soil conditioner as it provides a natural slow release available silica source for farmers.

After leaving Mt Sylvia the trip continued on to Warwick through the Heifer Creek Gorge with some fantastic inside geological information provided by Edwin Willey, whose knowledge of the ClarenceMorton Basin and Main Range volcanics knows few peers. Exposures of the coarse blocky Heifer Creek sandstone make up the spectacular cliffs leading up the gorge.

On to Crystal Mountain and the Pirates Hoarde! No actually it was a fascinating breccia pipe that is associated with anomalous copper and gold mineralisation, and exhibitsa range of volcanic paragentic relationships that have been mapped many times over the years by the UQ geological students as part of undergraduate studies.

We moved on to Stanthorpe for the first overnight stop and a fabulous dinner at the Ravens Croft winery with our generous host Mark Ravenscroft providing a tasting of all his fabulous whites and reds. The barbeque dinner in amongst all the wine making equipment was both convivial and well lubricated.

Sunday started bright and early, well early anyway, for some of us. We headed west from Stanthorpe, with its dredged tin streams and subtly beautiful granite outcrops, out into the Texas beds with some fabulously informative geological notes from Davina Halloran to guide us. We stopped at various locations to view the Texas Bed sediments and the faulted contact with the Permian conglomerates. On to the historic Waroo open pit gold mine and a chance to wander around looking at the multiples of sulphidic flat lying structures that hosted the gold resource that was developed by Valdora Minerals from 1987 and mined and heap leached in 1990 to 1992, and which produced approximately 11,000 ounces of gold. A supergene copper zone halted the attempts at leaching well short of the planned production life.

Just outside Texas we visited the c. 1888-1894 Hornet copper mine workings for a wander through the paddock trying to work out the contextual relationships and mineralisation style; after viewing Twin Hills silver mine from the gate (unfortunately visits were not allowed due to administrators being appointed) we struggled through the barbed wire fence to view the dumps and the old workings, head frame and battery footings of the Silver Spur Mine, and to debate various ideas about the genesis and style of the mineralisation. The Silver Spur mine produced silver, gold, lead and copper ores over an intermittent period from 1892 to 1996. A total of 68 t of silver, 140 kg of gold, 990t of copper, 1050t of lead and 690t of zinc is recorded. The last stop of the day as the sun was setting was at the beautiful Glenlyon Dam and a viewing of the information centre and placid waters of Lake Glenlyon.

After overnighting in Tenterfield it was on through the stunning and ruggedGirard State Forest east to the Drake Deposits at Mt Carrington and our hosts White Rock Minerals. Liam Fromhyr generously led the group and talked us through the complex geology with intermediate sulphidationepithermal silver, goldand base metal mineralisationvery evident in the pit exposures and in the core laid out for us. The excited exclamations from our ginger ninja Josh Leigh made up for the physical effort required to drag him kicking and screaming back onto the bus.

The bus then turned around and,following brief stops at Stanthorpe for lunch and Undercliffe falls to view the beautiful coarsely porphyritic monzogranite outcrops (and waterfalls), we headed home to Brisbane via Cunningham’s Gap.

The intriguing geology, the unstinting efforts of the organising team, the pleasant company, and the glorious weather, all contributed to making it a thoroughly enjoyable and informative long weekend.