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Hyperspectral imaging, mineralogy, and outgassing, exploring the volcanic hydrothermal system of Red Crater, Tongariro, Aotearoa / New Zealand

Daniel Sturgess1 , Gabor Kereszturi1, Agnes Mazot2, Nitin Bhatia3, Stuart Mead1

  • Affiliations: 1Volcanic Risk Solutions, Massey University, New Zealand; 2GNS Science Te Pū Ao, Wairakei, New Zealand; 3School of Food and Advanced Technology, Massey University, New Zealand

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 39

  • Programme No: 3.8.23

  • Theme 3 > Session 8

Abstract

Volcanic flank collapse and phreatic (steam driven) eruptions pose considerable proximal and distal hazards, while being notoriously difficult to forecast. Such phenomena are associated with hydrothermal activity, where hot, acidic subsurface fluids circulate through and alter the rock beneath the surface. This process of hydrothermal alteration may reduce rock strength and cause landslides (Tongariro, 2012), as well as seal degassing pathways, which may generate overpressure in the system and cause a phreatic eruption (Whakaari/White Island, 2019). Hyperspectral remote sensing presents a unique opportunity to explore both the outgassing and alteration associated with these hydrothermal systems, whereby diagnostic spectral signatures in the VNIR (400--1000 nm) and SWIR (930--2500 nm) regions of the electromagnetic spectrum are used for mapping common alteration minerals and carbon dioxide detection. We combine remote sensing (lab/airborne hyperspectral, thermal infrared), field (soil gas surveys), and laboratory (XRD, SEM-EDS) based techniques to assess the spatial extent, physical structure, and mineralogy of surface hydrothermal alteration at Red Crater, Tongariro, Aotearoa/New Zealand. Surface weathering, and silicic and argillic alteration styles at Red Crater precipitate distinct assemblages including native sulphur, silica polymorphs, Fe- oxides (goethite, hematite), phyllosilicates (kaolinite, smectite), and sulphates (alunite). The active geothermal areas here are characterised by heated ground (~90°C), fumaroles (~100°C) and soil CO2 fluxes of ~5.7 t/day. Our study aims to provide data to inform new models and forecasting methods for volcanoes with active hydrothermal systems.