Consistency between apatite and zircon petrochronology supports the robustness in fingerprinting igneous processes in porphyry systems. In this paper, we systematically investigate geochronology and mineral chemistry of apatite and zircon hosted in syenogranite and monzogranite intrusive rocks in the large Hutouya skarn-type Cu–Pb–Zn–Fe deposit, in order to corroborate their potential chronological monitoring capabilities in fingerprinting igneous processes in porphyry systems. Zircon grains of magmatic origin provide crystallization ages of 224.70 ± 0.61 Ma in the syenogranite and 225.75 ± 0.66 Ma / 226.31 ± 0.78 Ma in the monzogranite, respectively. Apatite yield ages of 229.0 ± 6.6 Ma in syenogranite and 224.3 ± 4.5 Ma / 223.7 ± 3.9 Ma in monzogranite and are within analytical uncertainty of ages displayed by zircon. Geochronology results suggest that the associated hydrothermal mineralization events at Hutouya probably have similar short durations of just a few million years or less. Trace element compositions in the two intrusives indicate the apatite and zircon crystallized under volatile-undersaturated conditions and have primary a magmatic origin. However, in the later volatile-oversaturated stage, the early crystallizing zircon is altered by the fluid phase, and shows distinctive amorphous textures with pores filled with numerous hydrothermal minerals. Accordingly, U–Pb dates of apatite and zircon, as well as corresponding in-situ trace element compositions, can provide constraints on rock formation ages, temperature, oxygen fugacity, magma source, and tectonic background.

The Auckland Volcanic Field (AVF) consists of ~53 volcanoes, distributed over an area of ~ 360 km2. Located within the AVF is Auckland City, New Zealand’s largest population centre (~1.7M people), highlighting the need to adequately model future pre-eruption scenarios for enhanced preparedness. Geological evidence shows that past eruptions were variably explosive and formed maars, lava shields, and tuff rings, largely controlled by the extent of magma-water interaction. Any future eruption from a new vent location within the AVF would cause significant socio-economic impacts, extensive evacuations, and national-scale impacts. Our work aims to constrain the next probable vent location using novel physics-based approaches. Current approaches to identifying the next AVF vent location use statistical analysis to define probability maps. Here we use a novel approach based on physical understanding of dyke propagation and newly developed 3D numerical codes that consider crustal stresses as the main controls on the orientation of dyke pathways. We estimate regional stresses based on GNSS data and consider surface mass redistributions at the Hauraki Rift and other volcano-tectonic structures in the wider area to constrain the overall elastic stress field. We backtrack magma pathways from known vent locations downward through the crust. Pathways are oblique and reach below the Hauraki Gulf or Firth of Thames (~30 km E of Auckland City) at the inferred depth of magma dyke release (35-50 km). We infer a common magma source is physically plausible in that location. Further work will improve the robustness of the model, constrain the spatial spread of vents over time, dyke propagation velocity, and implications for early identification of future volcanic unrest.

Volcanic hazards are dependent on eruption size and explosivity, thus, the forecasts of these is crucial for emergency management decisions. Monitoring a volcano potentially offers valuable insights to assess when, where, and how explosive a future eruption might be. Data are collected from various monitoring equipment, such as seismometers, tiltmeters, and thermometers, that are installed at different locations and distances, from near-vent to satellite. However, establishing direct links between monitoring signals and even eruption onset remains challenging, especially for volcanoes lacking recent eruptions or without monitoring equipment installed prior to eruption. This challenge extends to eruption explosivity, where establishing links becomes even more difficult. The Global Volcanism Program (GVP) has compiled monitoring data in bulletin reports recorded by observatories and research institutions. These reports start from 1968 and summarise volcanic activity that occurs before, during and after an eruption. Importantly, these reports include descriptions about activity and/or raw data (number of earthquakes, frequencies, plots of the seismic signals or displacements on tiltmeters) from various monitoring equipment, providing a general understanding of precursor activities preceding an eruption. This is potentially key information for forecasting eruption explosivity. This study aims to establish a quantitative link between monitoring signals and eruption explosivity across multiple volcanoes. Data are compiled from 23 volcanoes worldwide, utilising information from the Global Volcanism Program (GVP) database and local volcano observatory reports where accessible. The different descriptions obtained by each class of monitoring equipment—whether seismic, thermal, deformation, SO2 fluxes, or crater alterations—will be statistically categorized and calibrated into predictor variables to be used in machine learning algorithms. We hope to develop a procedure for estimating the explosivity of the next eruption, as a step towards statistically forecasting future eruption styles.

Apatite low-temperature thermochronology can be double or even triple dated allowing for a reconstruction of the thermal history of rock from ~ 550 oC to near-surface temperatures. Even though it has disadvantageous U–Th–Pb contents (high Pb contents and low U and Th contents) and an unstable nature, apatite is still regarded to have the same robustness in fingerprinting igneous processes in porphyry systems as zircon, so far as to be replace zircon. Hence, we systematically studied characteristics of morphology, geochronology and geochemistry of apatite hosted in syenogranite and monzogranite intrusive rocks in the large Hutouya skarn deposit, in order to corroborate its potential thermochronological monitoring capabilities like zircon in fingerprinting igneous processes in porphyry systems. In this study, apatite grains can be subdivided into two types, FI-free Apatite I formed in the early less fractionated magma and FI-rich Apatite II crystallized in the late highly fractionated magma stage. We obtained ages of 229.0 ± 6.6 Ma in syenogranite and 224.3 ± 4.5 Ma / 223.7 ± 3.9 Ma in monzogranite from Apatite I of magmatic origins. Zircon grains in the two granites can be classified into three types. Zircon I is characterized by transparent and bright zones, Zircon II by dark and metamict features, and Zircon III by mineral inclusions. Zircon I grains with a magmatic texture of well-developed bright oscillatory zones, are most likely primary magmatic zircon that crystallized early in the evolution of granitic magma, dating results of which are 224.70 ± 0.61 Ma in syenogranite intrusions and 225.75 ± 0.66 Ma / 226.31 ± 0.78 Ma in monzogranite, respectively. The apatite–zircon timing is coincident. Furthermore, apatite trace rare earth element contents in the syenogranite and monzogranite intrusions display a negative-slope chondrite-normalized distribution from La to Lu with strong negative Eu anomalies and weak positive Ce anomalies, with major element contents that are statistically identical with enriched F but poor Cl. Zircon trace element compositions in the two intrusions show consistent and steeply increasing chondrite-normalized REE diagrams from La to Lu with negative Eu anomalies and strong positive Ce anomalies. Accordingly, apatite U–Pb dates and the corresponding in-situ trace element compositions and isotopes can test precise constraints on rock formation ages, temperature, oxygen fugacity, material source, and tectonic background, which can be relatively more robust when used as proxies for magma oxidation state.

The El Zorro gold district is the most recent gold discovery in the Coastal Cordillera of northern Chile. Ternera is the largest deposit in the district with total resources currently estimated at 1.282 Moz. New geology, geochemistry and geochronology data indicate that hydrothermal mineralization is mostly hosted within felsic to intermediate, ilmenite-bearing calc-alkaline dikes and stocks of the Upper Triassic to Lower Jurassic Relincho Pluton, and some of the adjacent Devonian to Carboniferous metasediments of the Chañaral Epimetamorphic Complex. Sheeted veins, veinlets, and fault zones with quartz, low amounts of pyrite, pyrrhotite and arsenopyrite, and local calcite are surrounded by narrow haloes of albite-biotite-quartz ± sulfides-K-feldspar-sericite-chlorite. Gold (mostly in the veins) is associated with elevated W-Bi and also As-Te-Sn, and not with iron enrichment or base metals, even though this system is proximal ( 20 km) to IOCG and IOA deposits of the Coastal Cordillera. The main phase of gold mineralization occurred soon after emplacement of tonalitic dikes and granodiorite from the Relincho and Cuevitas plutons (U–Pb zircon between 205 and 190 Ma), about 80 m.y. later than the development of orogenic fabrics. An absolute upper age limit is provided by compositionally distinct ore-cutting mafic dikes dated at 175–170 Ma (U–Pb apatite). The deposit falls into the intrusion-related gold category, as indicated by the cutting of earlier orogenic fabrics, the metal and alteration associations, and the spatial and temporal connection to reduced ilmenite-series intrusions, which are also very similar geochemically to the ‘type-locality’ IRG intrusions of the Tintina Belt in Yukon/Alaska. The El Zorro gold district represents the oldest and geologically western-most mineralizing event in the Central Andes of northern Chile, consistent with its time–space placement within the tectonic framework of easterly-younging mineralization and igneous activity in the Chilean Cordillera.

• Holistic overview of the Okataina Volcanic Centre (OVC) of New Zealand. • Crustal imaging and melt distribution. • Tectonic-volcanic interactions. • Heat and hydrothermal activity. • Modelling the hydrosphere.

Seasonal underground hydrogen storage (UHS) in porous media provides an as yet untested method for storing surplus renewable energy and balancing our energy demands. This study investigates the technical suitability for UHS in depleted hydrocarbon fields and one deep aquifer site in Taranaki Basin, Aotearoa New Zealand. Prospective sites are assessed using a decision tree approach, providing a “fast-track” method for identifying potential sites, and a decision matrix approach for ranking optimal sites. Based on expert elicitation, the most important factors to consider are storage capacity, reservoir depth, and parameters that affect hydrogen injectivity/withdrawal and containment. Results from both approaches suggest that Paleogene reservoirs from gas (or gas cap) fields provide the best option for demonstrating UHS in Aotearoa New Zealand, and that the country’s projected 2050 hydrogen storage demand could be exceeded by developing one or two high ranking sites. Lower priority is assigned to heterolithic and typically finer grained, labile and, clay-rich Miocene oil reservoirs, and to deep aquifers that have no proven hydrocarbon containment.

In the last decade the international push for the development of various renewable energy and the increase of the carbon tax for emitters, has put high enthalpy geothermal on a hot seat. Anthropic geothermal emissions in volcanic areas are not negligible due to the inherent nature of their volcanic setting but are counted regardless, similarly to a gas or coal power plant, despite their non-fossil carbon origin. Natural volcanic emissions are however poorly constrained due to the lack of field scale soil CO2 flux assessments. In this study, we analyse the temporal and spatial variations of soil CO2 flux and soil temperature in the Taupō region, Taupō Volcanic Zone, New Zealand, in the light of seasonal variation, field utilisation, and seismicity. Fortnightly monitoring between 2019 and 2023 at 8 sites across the Tauhara and Wairakei geothermal fields provides insight into changes of seasonal variations and geothermal activities. To understand the broader distribution of natural degassing and to compare the CO2 flux over decades, we repeated the CO2 flux survey between 2019 and 2023 and compared to previous results at Karapiti, Wairakei geothermal field (2004, 2018), Ring of Fire, Tauhara geothermal field (2006), and Rotokawa geothermal field (2003, 2011). Similar emissions but a change in the spatial distribution at Tauhara geothermal field suggests that human surface development has affected permeability in the shallow subsurface. In contrast, a similar spatial distribution of flux, but higher emissions, at Karapiti, Wairakei indicates the recovery or modification of reservoir pressure. Finally, a decrease of total emission flux of the natural geothermal features at Rotokawa coincides with the decrease of CO2eq emissions at the power stations. This study showcases the complexity and uncertainties of natural CO2 emission calculations and provides recommendations for future monitoring studies.

Novel biosignatures of laminated, microbial, digitate sedimentary structures - stromatolites - from modern geothermal fields of the Taupo Volcanic Zone, New Zealand, and from El Tatio, Chile, provide an opportunity to investigate evidence of extremophile life preserved in siliceous hot spring deposits, or sinters, interpreted as analogs for early life on Earth and possibly Mars. Synchrotron-mu XRF, electron microprobe analysis, Raman spectroscopy, and optical microscopy are used in a coordinated approach to identify corroborating textural and chemical (organic, inorganic) evidence of life in these modern, opaline (amorphous) siliceous materials. Fluid mobile elements, such as As and Sr, track the growth history of the digitate structures. Trace element enrichments of Ca, Al, Ga, +/- Fe, Mn, As, Rb, Cs, and Sr, are identified in silicified sheaths of microbial filaments embedded within the sinter. In contrast, silicified diatoms in some sinter samples show no trace element enrichment. Gallium enrichments have also been observed in other 16 ka and Jurassic (150 Ma) microbial palisade sinter textures, suggesting the potential for preservation through geologic time, even after recrystallization to quartz. Raman analysis reveals spectra of organics, consistent with pigments for UV protection in cyanobacteria, in silicified sheaths around microbial filaments and are co -located with trace metal enrichments in digitate structures. Due to spectral bands, the location of these molecules (i.e., in the sheaths), and the sampling locations, we ascribe the spectra to scytonemin and carotenoid class molecules. The combined analytical approach outlined here provides a robust means to assess the validity of novel biosignatures, with application to the exploration of Mars, where preservation of opaline silica in >3.6 Ga deposits has the potential to preserve a range of microbial biosignatures.

Hydrothermal silica deposits on the surface of Mars with textures analogous to terrestrial hot spring deposits are, arguably, one of the best potential targets in the search for evidence of life beyond Earth. Here we investigate terrestrial hot spring digitate silica structures (modern: El Tatio, Chile; Mars Pool at Rotokawa geothermal area, and Te Kopia thermal stream, New Zealand; 1.6–1.8 ka: Opal Mound, Utah, U.S.A.), which are texturally and mineralogically analogous to martian deposits in the Columbia Hills of Gusev crater, in order to elucidate how their physical properties vary with depositional environment, and to help guide future remote sampling endeavors. Micro-computed tomography allows visualization of the internal texture of geological materials through variations in porosity and relative density, and is demonstrated here as a key, non-invasive technique for investigating future returned planetary samples. Bulk porosity, associated with pore sizes greater than >1–2 μm, varies from 4.7 to 21.3% in the four studied terrestrial digitate sinter samples, representing a range of fluid pHs of formation. Moreover, density variations between laminae largely reflect a nano-scale porosity (<1–2 μm) controlled by silicification of microbial material and/or recrystallization due to incipient diagenesis. Nano-indentation measurements of the digitate structures reveal variations in hardness and the reduced Young's modulus. The hardness of opal-A in modern digitate sinter varies, on average, from 2 to 4 GPa (El Tatio, Mars Pool, Te Kopia), but hardens with incipient diagenesis to >6 GPa (Opal Mound). Regions of nano-porous silica in all samples reduces the hardness in these areas to <1 GPa. No significant variation in material properties can be correlated to different fluid chemistries of the modern samples. Collectively, these results imply that the preservation of silicified microbes in digitate sinter structures should lead to a decrease in material hardness and elastic modulus owing to higher porosity in microbial laminae, whereas recrystallization of opal-A or secondary fluid precipitation will lead to hardening. For future remote sampling on Mars, the range of material properties of siliceous materials must be considered when designing appropriate sampling devices, as martian materials both harder and softer than accounted for in the design process may create sampling challenges.

Volcanic lakes in large silicic caldera volcanoes are an important source of CO2 emissions. However, quantifying CO2 output is challenging due to the lack of observed historical CO2 flux records and the large size of the volcanic and hydrothermal systems. Twenty percent of the surface area of Okataina Caldera, Taupo Volcanic Zone, New Zealand is covered with lakes. Geothermal expressions, predominantly on the Okataina caldera margin, occur in at least six different locations, with surface expressions both on land and under water. Lake Rotoiti is located at the northwest edge of the Okataina Caldera, spans across the Tikitere and Taheke geothermal fields, and has inputs from on-land thermal springs, lake floor hydrothermal vents, and from Lake Rotorua. CO2 flux from Lake Rotoiti was assessed using the accumulation chamber method and three techniques are used to process the data for total CO2 emission of the lake: (1) sequential Gaussian simulation (sGs) method allows quantification of CO2 emission with spatial control, (2) graphical statistical approach (GSA) allows the quantification of CO2 emission from different degassing regimes, and (3) a method based on water chemistry of the lake. We find CO2 is mostly emitting at Tumoana Bay and Central Basin, and the emission rate is 271 +/- 38 t d-1 of CO2 (based on sGs). We then added this estimated emission data to the existing CO2 data for individual geothermal systems distributed around the active Okataina volcanic centre and calculate that the entire caldera is emitting at least 1856 t d-1 of CO2. The total emission is dominated by the lakes, where the topography is lower. We discuss the implications of this study in terms of preferential degassing locations and the amount of degassing, in particular for CO2, in an active caldera setting.

Hydrothermal sealing is one of the mechanisms thought to aid pressure build-up within a volcano. Whakaari (White Island), New Zealand’s most active volcano, has a long history of phreatic and phreatomagmatic eruptions, and is ideally suited for an investigation into seal development from conduit-filling lithologies, where little prior experimental evidence exists. Here we provide an insight into Whakaari’s conduit by studying variably altered rocks ejected as ballistics. We find that hydrothermal alteration, particularly acid sulphate alteration, affects conduit-filling lithologies, lavas and tuffs, differently. In inherently low porosity lithologies like lavas, alteration increases fluid pathways by net dissolution of primary minerals and reduces rock stiffness. Counterintuitively, in tuffs that are inherently porous and permeable, alteration decreases fluid pathways by net precipitation of secondary minerals and increases rock stiffness. Such alteration-related pore filling of tuffs together with pore compaction under subsurface pressures can develop zones of low porosity and permeability within the volcano's conduit. When fluid injection rates are high, these zones could aid pressure build-up and predispose the volcano to eruptions. We discuss these results with observed seismicity at Whakaari and provide implications for ground deformation.

Hydrothermal alteration is generally associated with the weakening of volcanic rocks. Here we evaluate the possible role of hydrothermal alteration in lava dome collapses at Mt. Taranaki by evaluating the petrophysical (mineralogy, fluid pathways, crystallinity) and elastic properties (stiffness) of variably altered lavas from its summit dome area and block and ash flow deposits. Our results show that acid-sulfate alteration changes the mineralogy of the lavas by dissolving primary feldspars, pyroxenes, amphiboles, Fe-Ti oxides, and volcanic glass and precipitating secondary alunite and silica. These changes alter the fluid pathways and crystallinity of the lavas. However, despite these alteration-related petrophysical changes, we find that altered lavas are stiffer, and inferentially stronger, than fresh lavas of similar porosity. We attribute this at least partially to the precipitation of relatively strong secondary minerals like alunite and silica instead of weaker minerals like clays. We discuss the implications of these findings for dome stability at Mt. Taranaki. We suggest that the role of hydrothermal alteration in weakening volcanic rocks is not merely dependent on the alteration intensity but also on the type of alteration. Altered lavas, without extensive dissolution and with precipitation of strong secondary minerals, are unlikely to weaken the dome.

Gisborne (North Island, NZ) is affected by rainfall-induced landslides, earthquakes and tsunami, as well as mud volcanoes (MVs). The latter form via upward mobilization of Eocene–age sediments, and have not been studied from an engineering geological standpoint, so the 15 December 2018 Waimata Valley MV eruption provided a unique opportunity. The event erupted c. 16 900 m 3 of mud, forming an elevated vent area, and three mudflows propagating north, east and south. Scanning electron microscopy (SEM) identified smectite as the dominant clay in the Sr-rich mud, and Atterberg limits indicate high plasticity. In-situ testing using dynamic cone penetrometer and shear vane (3–168 kPa) revealed wide variability in strength properties with depth, while ring shear values are 11.3–13.5°. A fault extends NW beneath the Waimata Valley MV, coinciding with the pre-existing Arakihi Road MV. The Waimata Valley MV area was subject to uplift and cracking during the September 2016 Te Araroa earthquake ( M w 7.1), which caused increased activity at pre-existing mud volcanoes at that time. Geodetic data for the Gisborne district shows an uplift phase culminating around the December 15 2018 MV eruption, followed by the commencement of a Hikurangi subduction zone ‘slow slip event’. Nevertheless, relationships between tectonics and MV eruptions remain equivocal.

Regional to micron-scale controls on preservation of biosignatures in Phanerozoic hot spring microbial sinter KATHLEEN A CAMPBELL1, DIEGO GUIDO2, AYRTON HAMILTON1, MICHAEL ROWE1, BARBARA LYON1, DR. BONNIE TEECE3, FREDERIC FOUCHER4, FRANCES WESTALL5, STEVE RUFF6 AND MARTIN J. VAN KRANENDONK7 1The University of Auckland 2Universidad Nacional de La Plata 3University of New South Wales 4Centre National de la Recherche Scientifique 5Centre de Biophysique Moléculaire, CNRS 6Arizona State University 7Australian Centre for Astrobiology, University of New South Wales Presenting Author: ka.campbell@auckland.ac.nz

Our understanding of habitable early Earth environments is limited by the preservation potential of Archean rock deposits. Sedimentary intervals within the relatively homogeneous volcanic sequences of the Barberton Greenstone Belt (BGB), South Africa and Swaziland, and the eastern Pilbara Craton (PC) in Western Australia provide the best windows into interpreting variability in early Earth environments due to their low strain and low metamorphic grade. These deposits host Earth's oldest, most convincing, evidence of life (~3.3-3.5 Ga), and contribute to a better understanding of both the setting and the origin of life (OoL) and the search for life on other planets, such as Mars. The 3481 ± 2 Ma Dresser Formation, PC contains one of these preservation windows. Previous outcrop studies indicate changes in dominant volcanism composition (mafic to felsic), transitions from subaqueous to subaerial sedimentary facies, and large regional tectonic events that promoted circulation of hydrothermal fluids and secondary alteration. Here we present detailed lithologic and mineralogic details of this early Earth surface deposit, obtained from a recent drilling campaign. Three fresh drillcores obtained through the lower chert member of the Dresser Formation (~15 m thickness) were drilled at ~75 m below the weathered surface via HQ diamond drilling. Core sites were selected to provide a 3D perspective of geologic variability. Results show a high degree of complex lithology consisting of repeating bedded black carbonaceous cherts (TOC of up to 0.16 wt %), jaspilitic cherts, bedded carbonates, volcanogenic sandstones, beds of sulfidized stromatolites, edgewise conglomerates, laminated siliceous deposits that are texturally similar to hot spring sinter and directly overlie putative feeder veins, and thin spherulitic beds with petrographic similarities (spherical shapes, quenched features, radial crystal splays, and off-centered vesicles) to younger impact spherule beds. In addition, veins of carbonate, chert, barite and sulfides were identified throughout much of the lower chert member. Lithologic variability occurs on scales of millimetres-decimetres vertically, and from metres to decametres laterally, while mapping of regional scale (kms) stratigraphic sections indicate repetition of specific lithologic successions identified in the cores. The marked heterogeneity and variability both across stratigraphy and along strike contrasts sharply with marine settings, which are relatively homogeneous and consistent over 10’s-100’s of kilometres laterally, and across tens of metres vertically. Younger geologic systems that show similar depositional associations and sharp lateral facies changes include geothermal environments. The presence of sulfidized stromatolites, bedded black cherts, and hot spring deposit indicate that there were a diverse range of habitats (both marine and terrestrial) that hosted life. If spherulitic beds are impactor in origin, they would represent the oldest evidence of a bolide impact in the geologic record. The Dresser Formation provides insights into complex, dynamic, early Earth environments that host apparently already diverse microbial communities adapted to a range of habitats.