Post conference field trip (FT3) Active and Extinct Epithermal Environments of the North Island

OVERVIEW: The goal of this excursion is to provide an overview of the volcanic-tectonic setting, hydrology, fluid chemistry, alteration and mineralisation of sub-aerial hydrothermal systems and their energy and mineral resources. The itinerary includes visits to geothermal systems in the Taupo Volcanic Zone, volcanoes of Tongariro National Park and White Island, and epithermal Au-Ag deposits in the Coromandel Peninsula.

LEADERS: Tony Christie and Mark Simpson (GNS Science)

Tony is a Senior Minerals Geologist with GNS Science. Following his university education, Tony worked four years in mineral exploration with BP exploring for gold, molybdenum and tungsten deposits in New Zealand. In 1985, Tony joined New Zealand Geological Survey, which is now GNS Science and has carried out research on gold, iron and clay deposits, regional geological mapping, geochemical mapping, and mineral resource assessments.

Mark Simpson is a geothermal and minerals geologist with GNS Science, Wairakei Taupo. His work includes research on epithermal Au-Ag deposits and geothermal systems, and consulting in geothermal exploration. Prior to joining GNS Science in 2012, Mark spent 14 years at The University of Auckland (0.85 FTE) researching epithermal Au-Ag deposits and during this same period he was a consultant geologist to the minerals industry, running own company.

START: Leaves from the Cordis Hotel, Auckland, 7:30 am, Sunday 7 April, 2019 END: Finishes in Auckland, late afternoon - evening, Friday 12 April, 2019 with drop off at Auckland Airport or later at the Cordis Hotel in Auckland city

DURATION: Six days (5 nights)

PROVISIONAL ITINERARY

Coromandel Peninsula / Hauraki Goldfield

Visits will be made to the two largest epithermal gold deposits in the region, Waihi and Karangahake, and other selected sites to view hydrothermal alteration and mineralisation. We will also visit the historic Thames School of Mines to view ore specimens from throughout the goldfield.

Taupo Volcanic Zone

Active geothermal areas: Half-day visits to each of the Waiotapu, Waimangu and Orakeikorako thermal areas to see epithermal processes in action, including the deposition of ore-grade gold precipitates at Champagne Pool at Waiotapu. These areas provide examples of different fluid types, their surface features and hydrothermal alteration.

Volcanoes: We will visit the andesite volcano of Mt Ruapehu at the southern end of the Taupo Volcanic Zone to see andesite volcanic facies that are typical of the host rocks in many epithermal deposits, and we will tour the crater of the active andesite volcano of White Island at the northern end of the zone, offshore in the Bay of Plenty.

Ohakuri epithermal gold prospect: Exposures of stockwork quartz veins in quartz-adularia altered ignimbrite.

INCLUDED:

• Road transport (by bus or coach), during the field trip

• Helicopter flight to White Island

• Meals (breakfast, lunch and dinner) for 6 days and accommodation (twin share) for 5 nights

• Entry fees to thermal areas

NOT INCLUDED:

• Accommodation on the evening of Friday 12 April at completion of the field trip

• Alcohol and daytime snacks

SPECIAL REQUIREMENTS: A moderate level of fitness is required. Sturdy footwear is essential and wet weather gear, sun hat and sunscreen are advised. A flashlight/torch is required for the visit to Karangahake. If you are a visitor to New Zealand, you should arrange for travel and medical insurance before travelling to New Zealand, because many medical services are not free to overseas visitors.

MAXIMUM NUMBER OF PARTICIPANTS: 25

MINIMUM NUMBER OF PARTICIPANTS: 15

COST: NZ $2,700 (Early bird) NZ $3,000 (Standard)

NOTE: This field trip is subject to confirmation and minimum numbers. Some activities may be weather dependent.

FURTHER INFORMATION: Email Tony Christie at t.christie@gns.cri.nz REGISTRATION: Visit http://pacrim.ausimm.com

ROUTE MAP

GALLERY

Martha open pit Au-Ag mine, Waihi (photo: OceanaGold)

Discussion over drill core in OceanaGold’s core logging room, Waihi.

Waitawheta River gorge and Karangahake walkway with Mt Karangahake in distance

Windows walkway at Karangahake

Historic School of Mines museum, Thames

Discussion of Ag-Au-bearing quartz vein stockwork in quartz-adularia altered ignimbrite at the Ohakuri epithermal Au-Ag prospect.

Inspecting the andesite volcanic rocks on Mt Ruapehu

Inspecting the andesite volcanic and intrusive rocks on Mt Ruapehu, with Mt Ngauruhoe in distance.

Overlook of the Wairakei bore field, where steam from geothermal water is used to produce electricity. When commissioned in 1958, Wairakei was the second geothermal power station in the world and the

first to use flash steam.

White Island, an active andesite volcano in the Bay of Plenty

Helicopter in White Island crater

Viewing fumaroles in the crater of White Island

Crater lake, White Island

Orakeikorako sinter sheets. Note the fault scarp in the centre distance. Access to the thermal area is by boat across the Waikato River from the road end entry kiosk. Photo Lloyd Homer.

Champagne Pool at Waiotapu. The pool is a former hydrothermal eruption vent, surrounded by a silica sinter terrace. Photo: Lloyd Homer.

Orange As-Sb precipitates in Champagne Pool that contain up to 80 g/t gold and 175 g/t silver.

View along the Tarawera linear vent zone from Waimangu, across Lake Rotomahana, to Tarawera and Mt Edgecumbe. The pool in the foreground is in the Waimangu themal area. Photo Lloyd Homer.