As there are no interesting geological mine water sites that can be reached on a day trip from Christchurch, IMWA 2020 will offer a variety of Post Conference Field Trips instead of Mid Conference Excursions. These Field Trips will run from Friday, 13th November to Saturday or Sunday, depending on the distance.
Transport as well as accommodation are included within the fees.
Post Conference Field Trip 1
Prof Dave Craw, University of Otago
After the IMWA 2020 Congress the Otago Schist Gold Province Field Trip will be run over three days (two nights). Participants will travel via bus, leaving central Christchurch at 7 am on Friday, 13 November and returning late evening on Sunday, 15 November. The bus will travel south on the fluvial Canterbury Plains, to the east of the Southern Alps. It will climb through Mesozoic greywacke foothills of the Southern Alps to the inland Mackenzie Basin, and then over Lindis Pass to the upper Clutha River catchment in the Mesoxoic Otago Schist belt. Gold has been mined in this region since a large alluvial gold rush began in 1861.
The field trip will visit a range of historic alluvial and hard-rock gold mining sites, to view mine residues and the environmental issues that accompanied past mining activity. On the last day, we will visit the large active Macraes hard-rock mine (opened 1990; 12 Moz resource) where extensive open-cuts and underground excavations and processing activity have associated water quality issues that require careful management.
Localities to be visited (subject to change in detail).
All localities involve some walking, mostly on well-graded tracks
Travel from Christchurch as above
Bendigo historic hard-rock workings
Bannockburn historic alluvial sluicing sites and tailings
Night in Alexandra
High-salinity sites developed on historic alluvial gold workings
Historic gold dredge tailings
Pit lake in St Bathans (ghost town) historic alluvial gold mine elevator excavation
Naseby alluvial sluicing area and associated tailings
Night in Naseby (regenerated ghost town)
Macraes active hard-rock gold mine. Exact areas to be visited depends on permitted access at the time, but water issues of significance are:
- water management in a dry climate
- processing water compositions (flotation; pressure-oxidation acidification; cyanidation)
- tailings storage and waste rock piles
- dissolved arsenic; sulphate; nitrogen
Depart Macraes site late afternoon for Christchurch, arriving 10-11 pm
Post Conference Field Trip 2
Dr Paul Weber
Following the IMWA 2020 Conference in Christchurch the West Coast Geochemistry Fieldtrip will depart Christchurch on Friday 13th November at 8am, returning Saturday 14th November at 9pm. The fieldtrip will traverse the spectacular southern Alps to reach several destinations on the West Coast to explore both acid and metalliferous drainage geochemistry associated with coal mining of the Brunner Coal Measures and orogenic Au mining within the Greenland Group metasediments. Accommodation will be in Westport on the Friday night.
Your field trip guide, Dr Paul Weber will provide commentary on the geological evolution of New Zealand on the drive over, background notes for each field visit, and then with the help of operational staff at each site discuss best practicable, leading edge management of acid and metalliferous drainage. Highlights will include:
- Presentations by operational and technical staff on AMD management
- Best practicable mine closure – Globe Progress Mine Reefton
- Passive treatment of As-enriched drainage using downflow reactors
- Sulfate-reducing bioreactors for the treatment of acid coal mine drainage using waste mussel shells.
- Operational alkaline cover systems for the management of AMD – Geochemical Control
- Engineered landforms to prevent sulfide mineral oxidation and AMD – Geotechnical Control
- Active treatment (CaO) of 6,000 tpa acidity loads and sludge management
Although it’s a busy couple of days we plan to sneak in some time out for short walks at Cape Foulwind and Punakaiki:
Post Conference Field Trip 3
Dr James Pope
Following the IMWA 2020 Conference in Christchurch the Huntly Coal Basin and Coromandel Gold Geochemistry Fieldtrip will depart Christchurch on Friday 13th November at 7am, returning Saturday 14th November at 9pm. The fieldtrip will fly to Auckland, and travel by bus to the Huntly coal basin, one of New Zealands largest coal producing areas. The Huntly area supplies reactive sub-bituminous coal reduction kiln steel making, thermal power production and process heat for local industry. Here we will visit Rotowaro mine where stream rehabilitation and waste rock management have been combined to deliver a successful surface water management system. The field trip will then travel to the Coromandel Gold province. This gold and silver mining area is an uplifted and eroded volcanic arc that contains andesite hosted low sulphidation epithermal systems. The field trip will visit abandoned legacy mine sites and ore processing facilities including the Tui Mine and then spend the night at spectacular Waihi Beach. The following day we will visit the closed and rehabilitated Golden Cross mine site which includes examples of successful surface rehabilitation of PAF and NAF mine wastes, a rehabilitated tailings storage facility and on-going water treatment. Finally, we will visit the operational Waihi Mine with world leading surface water management, and monitoring systems related to tailings storage and surface waters.
Your field trip guide, Dr James Pope will provide commentary on the geology and mining history during driving and background notes for each field visit. Site staff will assist at operational sites and Iwi representative will give a cultural perspective and abandoned sites.
- Presentations by operational and technical staff on mine drainage management
- Legacy sites and long-term water quality impacts
- Stream rehabilitation and habitat creation
- Passive treatment of tailings leachate using steel slag and limestone
- Surface revegetation to deliver runoff water that is directly discharged to the environment
- Waste rock placement and handling to deliver geochemically stable tailings storage facilities
- Engineered landforms to prevent sulfide mineral oxidation and AMD
- Active water treatment