scholarly journals Isotope geochemistry of gallium in hydrothermal systems

2021 ◽  
Author(s):  
◽  
Constance E. Payne
Keyword(s):  
New Zealand ◽  
Ion Exchange ◽  
Column Chromatography ◽  
Hot Spring ◽  
Isotope Geochemistry ◽  
Isotopic Ratio ◽  
Hydrothermal Systems ◽  
Phase Changes ◽  
Hydrothermal Fluids ◽  
Taupo Volcanic Zone

<p>Little is known about the isotope geochemistry of gallium in natural systems (Groot, 2009), with most information being limited to very early studies of gallium isotopes in extra-terrestrial samples (Aston, 1935; De Laeter, 1972; Inghram et al., 1948; Machlan et al., 1986). This study is designed as a reconnaissance for gallium isotope geochemistry in hydrothermal systems of New Zealand. Gallium has two stable isotopes, ⁶⁹Ga and ⁷¹Ga, and only one oxidation state, Ga³⁺, in aqueous media (Kloo et al., 2002). This means that fractionation of gallium isotopes should not be effected by redox reactions. Therefore the physical processes that occur during phase changes of hydrothermal fluids (i.e. flashing of fluids to vapour phase and residual liquid phase) and mineralisation of hydrothermal precipitates (i.e. precipitation and ligand exchange) can be followed by studying the isotopes of gallium. A gallium anomaly is known to be associated with some hydrothermal processes as shown by the unusual, elevated concentrations (e.g. 290 ppm in sulfide samples of Waiotapu; this study) in several of the active geothermal systems in New Zealand.  The gallium isotope system has not yet been investigated since the revolution of high precision isotopic ratio measurements by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and so a new analytical methodology needed to be established. Any isotopic analysis of multi-isotope elements must satisfy a number of requirements in order for results to be both reliable and meaningful. Most importantly, the analysis must represent the true isotopic composition of the sample. Ion-exchange chromatography is generally utilised to purify samples for analysis by MC-ICPMS and exclude potential mass interfering elements but care must also be taken to recover as close to 100% of the element of interest as possible, as column chromatography can often result in fractionation of isotopes (Albarède and Beard, 2004).  An ion exchange column chromatography methodology for the separation of gallium based on earlier work by Strelow and associates (Strelow, 1980a, b; Strelow and van der Walt, 1987; Strelow et al., 1974; van der Walt and Strelow, 1983) has been developed to ensure a quantitative and clean separation from the majority of elements commonly associated with hydrothermal precipitates and waters (i.e. As, Sb, Mo, Hg, W, Tl, Fe and other transition metals). A protocol to measure the isotopes of Ga was developed by the adaptation of methods used for other stable isotope systems using the Nu Plasma MC-ICPMS at the School of Geography, Environment and Earth Sciences, Victoria University of Wellington, NZ.  Gallium isotopic ratios have been collected for a suite of samples representing the migration of hydrothermal fluids from deep fluids in geothermal reservoirs to the surface expression of hot spring waters and associated precipitates in hydrothermal systems. A range in δ⁷¹GaSRM994 values is observed in samples from Taupo Volcanic Zone geothermal fields from -5.49‰ to +2.65‰ in silica sinter, sulfide, mud and brine samples. Mineral samples from Tsumeb and Kipushi mines range from -11.92‰ to +2.58‰ δ⁷¹GaSRM994. Two rock standards, BHVO-2 and JR-2 were also analysed for gallium isotopes with δ⁷¹GaSRM994 values of -0.92‰ ±0.12‰ and -1.91‰ ±0.23‰ respectively.</p>

scholarly journals Isotope geochemistry of gallium in hydrothermal systems

2021 ◽  
Author(s):  
◽  
Constance E. Payne
Keyword(s):  
New Zealand ◽  
Ion Exchange ◽  
Column Chromatography ◽  
Hot Spring ◽  
Isotope Geochemistry ◽  
Isotopic Ratio ◽  
Hydrothermal Systems ◽  
Phase Changes ◽  
Hydrothermal Fluids ◽  
Taupo Volcanic Zone

<p>Little is known about the isotope geochemistry of gallium in natural systems (Groot, 2009), with most information being limited to very early studies of gallium isotopes in extra-terrestrial samples (Aston, 1935; De Laeter, 1972; Inghram et al., 1948; Machlan et al., 1986). This study is designed as a reconnaissance for gallium isotope geochemistry in hydrothermal systems of New Zealand. Gallium has two stable isotopes, ⁶⁹Ga and ⁷¹Ga, and only one oxidation state, Ga³⁺, in aqueous media (Kloo et al., 2002). This means that fractionation of gallium isotopes should not be effected by redox reactions. Therefore the physical processes that occur during phase changes of hydrothermal fluids (i.e. flashing of fluids to vapour phase and residual liquid phase) and mineralisation of hydrothermal precipitates (i.e. precipitation and ligand exchange) can be followed by studying the isotopes of gallium. A gallium anomaly is known to be associated with some hydrothermal processes as shown by the unusual, elevated concentrations (e.g. 290 ppm in sulfide samples of Waiotapu; this study) in several of the active geothermal systems in New Zealand.  The gallium isotope system has not yet been investigated since the revolution of high precision isotopic ratio measurements by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) and so a new analytical methodology needed to be established. Any isotopic analysis of multi-isotope elements must satisfy a number of requirements in order for results to be both reliable and meaningful. Most importantly, the analysis must represent the true isotopic composition of the sample. Ion-exchange chromatography is generally utilised to purify samples for analysis by MC-ICPMS and exclude potential mass interfering elements but care must also be taken to recover as close to 100% of the element of interest as possible, as column chromatography can often result in fractionation of isotopes (Albarède and Beard, 2004).  An ion exchange column chromatography methodology for the separation of gallium based on earlier work by Strelow and associates (Strelow, 1980a, b; Strelow and van der Walt, 1987; Strelow et al., 1974; van der Walt and Strelow, 1983) has been developed to ensure a quantitative and clean separation from the majority of elements commonly associated with hydrothermal precipitates and waters (i.e. As, Sb, Mo, Hg, W, Tl, Fe and other transition metals). A protocol to measure the isotopes of Ga was developed by the adaptation of methods used for other stable isotope systems using the Nu Plasma MC-ICPMS at the School of Geography, Environment and Earth Sciences, Victoria University of Wellington, NZ.  Gallium isotopic ratios have been collected for a suite of samples representing the migration of hydrothermal fluids from deep fluids in geothermal reservoirs to the surface expression of hot spring waters and associated precipitates in hydrothermal systems. A range in δ⁷¹GaSRM994 values is observed in samples from Taupo Volcanic Zone geothermal fields from -5.49‰ to +2.65‰ in silica sinter, sulfide, mud and brine samples. Mineral samples from Tsumeb and Kipushi mines range from -11.92‰ to +2.58‰ δ⁷¹GaSRM994. Two rock standards, BHVO-2 and JR-2 were also analysed for gallium isotopes with δ⁷¹GaSRM994 values of -0.92‰ ±0.12‰ and -1.91‰ ±0.23‰ respectively.</p>

Influence of thermophilic bacteria on calcite and silica precipitation in hot springs with water temperatures above 90 °C: evidence from Kenya and New Zealand

1996 ◽  
Vol 33 (1) ◽  
pp. 72-83 ◽  
Author(s):  
Brian Jones ◽  
Robin W. Renaut
Keyword(s):  
New Zealand ◽  
Hot Springs ◽  
Hot Spring ◽  
Thermophilic Bacteria ◽  
Active Role ◽  
Crystal Nucleation ◽  
Taupo Volcanic Zone ◽  
Filamentous Bacteria ◽  
Silica Precipitation ◽  
Up Elements

Hot and boiling springs in Kenya and New Zealand that are emitting water with temperatures more than 90 °C are commonly characterized by a complex array of CaCO3and SiO2precipitates that have been formed through abiogenic and biogenic processes. Thermophilic bacteria are the only microbes that can survive in the boiling water that is discharged into pools around the spring orifice. Analysis of modern substrates from various springs in the Kenya Rift Valley and the Taupo Volcanic Zone in New Zealand shows that they are inhabited by a diverse array of coccoid and filamentous bacteria. In some areas these bacteria produce copious amounts of mucus that coat the substrates. Although the coccoid and filamentous bacteria provide substrates for CaCO3and SiO2precipitation, the microbes do not seem to have any direct influence on the morphology of the precipitates that are produced. Conversely, the mucus found in these hot spring pools selectively takes up elements such as Si, Mg, Al, and Fe, but is not calcified. In many cases the elements that are selectively fixed by the mucus are only present in very low concentrations in the spring water. In one of the Waikite springs in New Zealand, the mucus plays an active role in the formation of the calcite deposits by providing a template for crystal nucleation and binding the small calcite crystals to the substrate. The latter process is especially important because the flowing waters of the spring could easily transport the grains if they were not bound to the substrate.

scholarly journals Field-Based Tests of Geochemical Modeling Codes: New Zealand Hydrothermal Systems

1993 ◽  
Vol 333 ◽  
Author(s):  
Carol J. Bruton ◽  
William E. Glassley ◽  
William L. Bourcier
Keyword(s):  
New Zealand ◽  
Nuclear Waste ◽  
Kinetic Data ◽  
Geochemical Modeling ◽  
Geothermal Field ◽  
Hydrothermal Systems ◽  
Taupo Volcanic Zone ◽  
Volcanic Zone ◽  
Mineral Assemblages ◽  
Modeling Code

ABSTRACTHydrothermal systems in the Taupo Volcanic Zone, North Island, New Zealand are being used as field-based modeling exercises for the EQ3/6 geochemical modeling code package. Comparisons of the observed state and evolution of the hydrothermal systems with predictions of fluid-solid equilibria made using geochemical modeling codes will determine how the codes can be used to predict the chemical and mineralogical response of the environment to nuclear waste emplacement. Field-based exercises allow us to test the models on time scales unattainable in the laboratory.Preliminary predictions of mineral assemblages in equilibrium with fluids sampled from wells in the Wairakei and Kawerau geothermal field suggest that affinity-temperature diagrams must be used in conjunction with EQ6 to minimize the effect of uncertainties in thermodynamic and kinetic data on code predictions.

Taxonomic fidelity of silicified filamentous microbes from hot-spring systems in the Taupo Volcanic Zone, North Island, New Zealand

2003 ◽  
Vol 94 (4) ◽  
pp. 475-483 ◽  
Author(s):  
Brian Jones ◽  
Robin W. Renaut ◽  
Michael R. Rosen
Keyword(s):  
New Zealand ◽  
Hot Springs ◽  
Hot Spring ◽  
Morphological Characteristics ◽  
Colony Morphology ◽  
Taupo Volcanic Zone ◽  
Volcanic Zone ◽  
The North ◽  
Preservation Potential ◽  
Physical Changes

ABSTRACTModern, silica-precipitating hot springs, like those found in the Taupo Volcanic Zone (TVZ) on the North Island of New Zealand, are natural laboratories for assessing microbial silicification. Many of the silicified microbes found in the siliceous sinters of these spring systems seem to be life-like replicas of the original microbes. Such preservation reflects the fact that many of the microbes are replaced and encrusted by opal-A before they are destroyed by desiccation and decay. The taxonomic fidelity of these silicified microbes depends on the preservation potential of those features which are needed to identify them. For example, identification of extant cyanobacteria, relies on as many as 37 different features, most of which are not preserved by silicification.In the hot-spring systems of the TVZ, characterisation of cyanobacteria which have been replaced and encrusted by opal-A is typically restricted to colony morphology, the length, diameter and morphology of the filament, and the presence/absence of septa, branching or a sheath. In many cases, description is limited to a subset of these parameters. Such a limited set of morphological characteristics severely impedes identifications in terms of extant taxa. The physical changes which accompany the stepwise diagenetic progression from opal-A to opal-CT ± opal-C to microcrystalline quartz may lead to further degradation of the silicified microbes and the loss of more taxonomically important features. Clearly, considerable care must be taken when trying to name silicified microorganisms and make palaeoenvironmental inferences.

Diagenetic transformations (opal-A to quartz) of low- and mid-temperature microbial textures in siliceous hot-spring deposits, Taupo Volcanic Zone, New Zealand

2003 ◽  
Vol 40 (11) ◽  
pp. 1679-1696 ◽  
Author(s):  
Bridget Y Lynne ◽  
Kathleen A Campbell
Keyword(s):  
New Zealand ◽  
Low Temperature ◽  
Hot Spring ◽  
Morphological Changes ◽  
Taupo Volcanic Zone ◽  
Volcanic Zone ◽  
Alkali Chloride ◽  
Silica Phase ◽  
Outflow Channels ◽  
Geologic Record

Silica sinter is a subaerial hot-spring deposit formed upon cooling (<100 °C) of discharging alkali-chloride waters. Silica deposition traps and fossilizes living microbes in low-temperature (<35 °C) to mid-temperature (~35–59 °C) apron–terrace outflow channels and pools, which record distinctive macrotextures and microtextures along a thermal gradient. Sinters from four geothermal fields, Orakei Korako, northern Waiotapu, Te Kopia, and Umukuri, within the Taupo Volcanic Zone, New Zealand, were sampled from two common microbe-rich microfacies (low-temperature palisade, mid-temperature bubble mat) through a range of ages (modern to ~40 000 years BP). We observed morphologic changes in microbial silicification and stepwise transitions in silica phase mineralogy throughout diagenesis (opal-A to quartz). X-ray powder diffractometry analysis of Taupo Volcanic Zone sinter samples revealed that mode of microbial fossilization is controlled by silica phase mineralogy, which also determines the preservation potential of environmentally significant and measurable filament parameters. Typical low-temperature palisade microfacies display thick sheaths (>3 µm diameter) and coarse tubular filament moulds >5 µm in diameter, whereas mid-temperature bubble mat microfacies characteristically consist of thin sheaths (~1 µm diameter) with fine moulds < 3 µm in diameter. Upon diagenesis and silica phase transformation to opal-CT, the two subenvironments cannot be distinguished based on filament diameter alone. This study of recurring microfacies in sinters of different ages allowed us to systematically track the transformation of mineralogical and morphological changes in biotic–abiotic depositional elements during diagenesis of silica sinter, and therefore enhance the paleoenvironmental, paleobiological, and paleohydrologic utility of hydrothermal deposits in the geologic record.

Natural Occurrence and Stability of Pyrochlore in Carbonatites, Related Hydrothermal Systems, and Weathering Environments

1995 ◽  
Vol 412 ◽  
Author(s):  
Gregory R. Lumpkin ◽  
Anthony N. Mariano
Keyword(s):  
Exchange Rate ◽  
Ion Exchange ◽  
Cation Exchange ◽  
Low Temperatures ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Natural Environments ◽  
Natural Occurrence ◽  
The Stability ◽  
A Site

AbstractStoichiometric and non-stoichiometric (defect) pyrochlores crystallize during the magmatic and late magmatic-hydrothermal phases of carbonatite emplacement (T > 450–550 °C, P < 2 kb). Defect pyrochlores can also form at low temperatures in laterite horizons during weathering. After crystallization, pyrochlore is subject to alteration by hydrothermal fluids (T ∼ 550-200°C) and ground water. Alteration occurs primarily by ion exchange of low valence A-site cations together with O, F, and OH ions. The high valence cations Th and U are generally immobile; however, we have documented one example of hydrothermal alteration involving loss of U together with cation exchange at the B-site in samples from Mountain Pass, California. During laterite accumulation, the cation exchange rate of pyrochlore greatly exceeds the rate of matrix dissolution. The exceptional durability of pyrochlore in natural environments is related to the stability of the B-site framework cations. In carbonatites, defect pyrochlores may contain significant amounts of Si (up to 7.6 wt% SiO2) which is negatively correlated with Nb.

3D Anatomy of a 60-year-old siliceous hot spring deposit at Hipaua-Waihi-Tokaanu geothermal field, Taupo Volcanic Zone, New Zealand

2020 ◽  
Vol 402 ◽  
pp. 105652 ◽  
Author(s):  
Kathleen A. Campbell ◽  
Kirsty Nicholson ◽  
Bridget Y. Lynne ◽  
Patrick R.L. Browne
Keyword(s):  
New Zealand ◽  
Hot Spring ◽  
Geothermal Field ◽  
Taupo Volcanic Zone ◽  
Volcanic Zone ◽  
3D Anatomy

scholarly journals Complex crater fields formed by steam-driven eruptions: Lake Okaro, New Zealand

2020 ◽  
Vol 132 (9-10) ◽  
pp. 1914-1930 ◽  
Author(s):  
Cristian Montanaro ◽  
Shane Cronin ◽  
Bettina Scheu ◽  
Ben Kennedy ◽  
Bradley Scott
Keyword(s):  
New Zealand ◽  
Phase I ◽  
Phase Ii ◽  
Hydrothermal System ◽  
Host Rock ◽  
Hydrothermal Systems ◽  
Phase Iii ◽  
Taupo Volcanic Zone ◽  
Fracture Development ◽  
Lake Okaro

Abstract Steam-driven eruptions are caused by explosive vaporization of water within the pores and cracks of a host rock, mainly within geothermal or volcanic terrains. Ground or surface water can be heated and pressurized rapidly from below (phreatic explosions), or already hot and pressurized fluids in hydrothermal systems may decompress when host rocks or seals fail (hydrothermal eruptions). Deposit characteristics and crater morphology can be used in combination with knowledge of host-rock lithology to reconstruct the locus, dynamics, and possible triggers of these events. We investigated a complex field of &gt;30 craters formed over three separate episodes of steam-driven eruptions at Lake Okaro within the Taupo volcanic zone, New Zealand. Fresh unaltered rock excavated from initially &gt;70 m depths in the base of phase I breccia deposits showed that eruptions were deep, “bottom-up” explosions formed in the absence of a preexisting hydrothermal system. These phreatic explosions were likely triggered by sudden rise of magmatic fluids/gas to heat groundwater within an ignimbrite 70 m below the surface. Excavation of a linear set of craters and associated fracture development, along with continued heat input, caused posteruptive establishment of a large hydrothermal system within shallow, weakly compacted, and unconsolidated deposits, including the phase I breccia. After enough time for extensive hydrothermal alteration, erosion, and external sediment influx into the area, phase II occurred, possibly triggered by an earthquake or hydrological disruption to a geothermal system. Phase II produced a second network of craters into weakly compacted, altered, and pumice-rich tuff, as well as within deposits from phase I. Phase II breccias display vertical variation in lithology that reflects top-down excavation from shallow levels (10–20 m) to &gt;70 m. After another hiatus, lake levels rose. Phase III hydrothermal explosions were later triggered by a sudden lake-level drop, excavating into deposits from previous eruptions. This case shows that once a hydrothermal system is established, repeated highly hazardous hydrothermal eruptions may follow that are as large as initial phreatic events.

Hot spring and geyser sinters: the integrated product of precipitation, replacement, and deposition

2003 ◽  
Vol 40 (11) ◽  
pp. 1549-1569 ◽  
Author(s):  
Brian Jones ◽  
R W Renaut
Keyword(s):  
New Zealand ◽  
Hot Spring ◽  
Pollen Grains ◽  
Taupo Volcanic Zone ◽  
Critical Importance ◽  
Volcanic Zone ◽  
The North ◽  
The World ◽  
Siliceous Sinter ◽  
Flow Through

Complex ornate sinter deposits are found in many hot spring and geysers systems throughout the world, including those located in the Taupo Volcanic Zone on the North Island of New Zealand. Those sinters are formed of opal-A that replaced microbes, opal-A precipitated as cement, accessory minerals (e.g., kaolinite, jarosite, calcite), biological detritus (e.g., leaves, wood, pollen grains), and lithic detritus. The opal-A is compositionally variable because of the amount of water (OH and H2O) and, in some cases, accessory elements (e.g., Au, Ag) bound into its structure. The composition and fabric of the siliceous sinter found at any locality reflect the relative balance among the processes of replacement, precipitation, and deposition. The microbes that inhabit these systems are of critical importance because they are commonly replaced by and (or) encrusted with opal-A. In many settings, copious amounts of opal-A are precipitated as cement around the frameworks of silicified filaments. The cementation process, which continues for as long as waters supersaturated with respect to opal-A flow through the sinter, commonly reduces the porosity of the sinters by as much as 50%. This process is probably of far greater significance than has been previously recognized. The textural and compositional complexity of siliceous sinters found in hot spring and geyser systems reflects the myriad of interrelated processes that control their formation.

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