Understanding Zealandia – Thermal processes Project 1

188980 Kyle Bland GNS Science

This project addresses the major research question of how heat, magma and metals are transferred within the crust in the New Zealand region.

Overview

We’re focusing on the active volcanic regions of the Taupō Volcanic Zone (TVZ), the Kermadec arc and the Havre Trough backarc. We may research inactive volcanic arcs and backarc basins where appropriate and if resources permit.

This project will have strong linkages and dependencies with the underpinning science of other Understanding Zealandia projects including Continental Tectonic Processes and Surface Processes. We expect the results to be of interest to other Social Science Investment Fund programmes, such as Hazards and Risk Management, and also to district councils and GNS Science stakeholders.

Our partners include Land Information New Zealand (LINZ) geodesy group, NIWA marine geology group and vessel management company, Ministry of Business, Innovation and Employment, regional councils, iwi and Māori trusts (including Te Arawa Lakes Trust, Tuhourangi Tribal Authority, Onuku, Rotoiti-15, Ngati Rangithi, Ruawahi 2B, Maori Investments Limited, Tuwharetoa and Rotokawa North No. 2), geothermal electricity generators (such as Contact Energy, Mercury, NTGA, Tuaropaki and Top Energy) and NZP&M.

This project has three workstreams worth about $1.8 m per year. Funding has come from New Zealand and overseas agencies. 

This project aims to

  • Explore the processes at depth that create and localise past and present molten and hot rocks
  • Examines their relationship to deformation, with consequences and implications for volcanic eruptions, geothermal systems and mineralisation
  • Improve stewardship of Te Riu-a-Māui Zealandia's on-land and offshore resource endowments

To achieve these aims, our objectives are to

  • Create more accurate appraisal of New Zealand’s geothermal energy and mineral resources
  • Track and model transfer of heat and mass in the TVZ, which controls geothermal systems
  • Improve understanding of driving forces that transfer heat, metals and fluids in the Earth’s crust
  • Make a more accurate characterisation of New Zealand’s granites as hosts of rare-earth elements and other metals
  • Generate up-to-date geoscientific frameworks for natural hazard analysis
  • Improve definition of long-term space-time controls and episodicity within the wider TVZ-Kermadec arc
  • Identify location and composition of magma under TVZ i
  • Determine localisation and rates of deformation processes in the active TVZ-Havre Rift
  • Develop new models of New Zealand subduction systems, fluids and their evolution with time
  • Map how deformation is, has been and will be accommodated across Zealandia
  • Ensure databases and information are accessible and managed for maximum benefit of New Zealand

 

The project

Understanding molten and hot rock in the Earth’s crust

The presence of molten and hot rock in the Earth’s crust results in a variety of special features including igneous activity, such as plutonism, volcanism, geothermal activity and the transport of metals.

These features occur in the TVZ and continue offshore into the Kermadec arc. In the TVZ, enhanced heat flow is related to extreme rates of tectonic stretching. Knowledge of the interplay between magma and deformation is important to understanding processes of plutonism, volcanic eruption, geothermal systems and seismicity. 

Volcanism in the offshore is manifest by submarine arc volcanoes that are point sources for heat and metal transfer through the crust. Similar processes will have occurred associated with pre-Quaternary volcanism represented by the Colville and Kermadec Ridges. Much of the western onshore Zealandia continent is comprised of plutons which remain as one of the most under-characterised aspects of our basement geology. Understanding the age, composition and distribution of our plutonic igneous rocks is crucial to understanding the geological processes related to mineral deposit formation of critical metals.

What’s driving this research?

In a word, our research is driven by uncertainty.

  • There is uncertainty in the future potential of our geothermal energy because of incomplete exploration for high-enthalpy geothermal systems. We don’t know enough about what controls the location, variability and evolution of geothermal systems in onshore and offshore Zealandia
  • We are uncertain about how heat and metals are transferred between deep and shallow (production zone) geothermal systems and how the boundaries of geothermal fields change with depth. A such, our geothermal development and sustainable management practices are sub-optimal. 
  • We rely on imports for supply of key elements and other resources essential for our transition to a carbon-neutral economy. Why? We don’t understand enough about their formation, distribution and concentration within Zealandia.
  • There is uncertainty in the hazard potential of our volcanic and geothermal systems because we don’t know enough about the links between tectonism, volcanism and geothermal systems .
  • There is also uncertainty in potential earthquake and volcanic hazards due to limited knowledge of how deformation is occurring within the TVZ.

 

The three workstreams

1.  Kermadec and TVZ volcanic and hydrothermal systems

This workstream focuses on the offshore subduction-related volcanoes of the Kermadec active arc front, and their relationship to on-land TVZ volcanoes. The Brothers volcano, drilled by the Integrated Ocean Drilling Program (IODP) in 2018, will be a particular focus with planned MeBo drilling, high-resolution seismics, and CSEM surveys planned with German and British collaborators. If priorities and time permit, this project may also include volcanic lakes and the sublacustrine hydrothermal systems of the Okataina Volcanic Centre as well as the evolution of older, offshore arc systems of the Kermadec Ridge and Colville Ridge and their on-land equivalents.

  • Task 1: Investigate the volcanic and hydrothermal systems of the Kermadec arc / Havre Trough to determine their mineral potential and the effect of hydrothermal discharge on ocean acidity and to improve hazard assessment for risk models.
  • Task 2: Investigate the volcanic and structural controls of submarine and sublacustrine hydrothermal systems in the offshore and onshore TVZ. This will help determine their extent and propensity to focus metals and geothermal potential to enhance supply of “green energy". It will also help improve resource management.

2.  TVZ and Havre Trough structure and rift dynamics

This will produce integrated models of on-land and offshore surface and deep rift structure, fluid flow, kinematics and dynamics using geological, geodetic, magnetotelluric, passive seismology and other geophysical data. Research outputs will include a new surface geological map and an updated gravity map of the TVZ. This project will also support development of an International Continental Scientific Drilling Program (ICDP) proposal for drilling in the Okataina Volcano Centre. 

  • Task 1: Geological and numerical modelling research of geothermal systems and the wider TVZ to improve hazard assessment for earthquake and volcanic risk models and to enhance geothermal resource management and development.
  • Task 2: Geophysical exploration of the TVZ to feed into models in Task 1.

3.  Pre-Quaternary magmatism

We need to know more about the distribution and composition of granites and associated plutonic rocks under New Zealand. Filling this gap will provide a modern framework for industry to help reduce exploration risk for the critical elements essential for transition to a carbon-neutral economy. One of the main outputs from this project will be a national pluton map and digital database (PMAP). 

  • Task 1: Map the extent and mineral assemblage of plutonic rocks – critical mineral hotspots – to enhance resource potential and improve resource management.

 

Bertrand Ted 2396

Ted Bertrand Magnetotelluric (MT) Team Leader

Ted is a Senior Magnetotelluric (MT) Scientist and leads the Thermal Processes Project in the Te Riu-a-Māui Zealandia Programme, researching how heat, magma and metals are transferred within the crust. His primary interests are using MT to investigate geothermal, volcanic and tectonic processes in the Taupo Volcanic Zone. Over the past decade, this research has imaged connections between geothermal fields and their underlying magmatic roots, revealing pathways of heat transfer through the crust. Ted’s work has contributed to both exploration of geothermal resources in NZ and to their sustainable management. He also contributes MT expertise to commercial geothermal projects in NZ and overseas. Ted enjoys fieldwork and has undertaken MT measurements in Canada, USA, Taiwan, New Zealand, Japan, and Antarctica.

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