Microanalysis of Fluid Inclusions in Crustal Hydrothermal Systems using Laser Ablation Methods

Wagner, Thomas; Fußwinkel, Tobias; Wälle, Marküs; Heinrich, Christoph A.

doi:10.2113/gselements.12.5.323

Cited by 44 publications

(16 citation statements)

References 28 publications

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“…Based on the elevated molar Br/Cl ratios (for example LV10 assemblages in sample PH238 approximate endmember fluid C; marked in Figures 12 and 13), halite dissolution can be excluded as the source of salinity of fluid C, but a component of magmatic salinity is possible besides contributions from sedimentary rocks or bittern brines. The Pb/Cl ratios of fluid C are similar to ratios in metal-rich basin brines (Stoffell et al, 2008;Wilkinson, 2013;Fusswinkel et al, 2013;Wagner et al, 2016). The ranges in Ca/K and K/Na mass ratios support this interpretation, because FIA similar to fluid C closely overlap with data from red bed brines, interpreted as modified ore fluids of Kupferschiefer type Cu mineralization (Fusswinkel et al, 2014).…”

Section: 2supporting

confidence: 55%

Hematite Breccia-Hosted Iron Oxide Copper-Gold Deposits Require Magmatic Fluid Components Exposed to Atmospheric Oxidation: Evidence from Prominent Hill, Gawler Craton, South Australia

et al. 2018

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The Prominent Hill deposit is a large iron oxide Cu-Au (IOCG) resource located in the Olympic IOCG province of South Australia. The deposit is hosted by brecciated sedimentary rocks and structurally underlying lavas of the ca. 1.6 Ga old Gawler Range Volcanics. Both rock units are altered and mineralized, forming characteristic hematite breccias. They are located in the footwall of the Southern Overthrust separating the host rock package in the footwall from Paleoproterozoic metasedimentary rocks in the hanging wall. The metasedimentary rocks were intruded by the Hiltaba Suite granites, which are co-magmatic with the Gawler Range Volcanics and show widespread magnetite-rich alteration. Economic mineralization was formed through a two-stage process. Early pyrite and minor chalcopyrite were deposited from moderately reduced fluids during sulfide stage I and are hosted in subeconomic magnetite skarns and in the brecciated sedimentary host rocks. This pre-ore stage was overprinted by the economically important stage II sulfides, deposited from hypogene, oxidized fluids ultimately sourced from the paleo-surface. The high-grade Cu ores contain dominantly chalcocite, bornite, chalcopyrite and gangue minerals including fluorite, barite and minor quartz, hosting mineralization-related fluid inclusion assemblages. Petrography, microthermometry and LA-ICP-MS microanalysis were used to characterize pre-, syn-and post-mineralization fluid inclusion assemblages. The results permit discrimination of four fluid end-members (A, B, C and D). Fluid A is the main ore fluid and hosted in fluorite and barite intergrown with Cu-sulfides in the breccia matrix. It is weakly saline (≤ 10 wt.% eqv. NaCl) and contains low concentrations of K, Pb, Cs, and Fe (600 ppm), but is rich in Cu (1000 ppm) and U (0.5-40 ppm). A magmatic origin of the salinity is supported by the low molar Br/Cl ratio of 0.003. We suggest that the solute inventory was derived from shallow fluid exsolution and degassing of late Gawler Range Volcanics, and subsequent complete oxidation of the fluid via contact with atmospheric oxygen. Fluid A migrated through oxidized aquifers to the site of the Prominent Hill deposit, where it became the main driver of stage II copper mineralization. Fluid B occurs in fluid inclusions in siderite + quartz-bearing veins crosscutting the hematite breccia. It is the most saline fluid with a total NaCl + CaCl2 concentration of 36 to 45 wt.% and a low Ca/Na mass ratio of 0.3. Fluid B is rich in K, Fe, Pb, and Cs, and contains modest Cu (~70 ppm). Its composition is typical of a moderately reduced magmatic-hydrothermal brine, modified by fluid-rock interaction. Fluid C is hosted by fluid inclusions in fluorite and barite within bornite + chalcocite bearing ores. It is a calcic-sodic brine with 16-28 wt.% NaCl + CaCl2 and has an elevated Ca/Na (0.6) and high Br/Cl ratios characteristic of basin brines of residual bittern origin. It is quite rich in Cu (~200 ppm), and likely contributed metals to economic mineralization. Fluid D is hosted by i...

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Section: 2supporting

confidence: 55%

Hematite Breccia-Hosted Iron Oxide Copper-Gold Deposits Require Magmatic Fluid Components Exposed to Atmospheric Oxidation: Evidence from Prominent Hill, Gawler Craton, South Australia

et al. 2018

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“…Coupled with automated mineralogy (see below), LA-ICP-MS allows for reliable deportment models to be generated for elements of interest. Moreover, LA-ICP-MS also offers a platform for in-situ geochronology [11], and in-situ chemical characterization of fluid inclusions [12]. Cook et al (2016) [13] provide an overview of current applications of LA-ICP-MS to the trace element analysis of minerals in hydrothermal ore deposits, also noting research gaps, some of the outstanding issues, and future opportunities.…”

Section: Laser-ablation Inductively-coupled Plasma Mass Spectrometry mentioning

confidence: 99%

Advances and Opportunities in Ore Mineralogy

et al. 2017

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Abstract:The study of ore minerals is rapidly transforming due to an explosion of new microand nano-analytical technologies. These advanced microbeam techniques can expose the physical and chemical character of ore minerals at ever-better spatial resolution and analytical precision. The insights that can be obtained from ten of today's most important, or emerging, techniques and methodologies are reviewed: laser-ablation inductively-coupled plasma mass spectrometry; focussed ion beam-scanning electron microscopy; high-angle annular dark field scanning transmission electron microscopy; electron back-scatter diffraction; synchrotron X-ray fluorescence mapping; automated mineral analysis (Quantitative Evaluation of Mineralogy via Scanning Electron Microscopy and Mineral Liberation Analysis); nanoscale secondary ion mass spectrometry; atom probe tomography; radioisotope geochronology using ore minerals; and, non-traditional stable isotopes. Many of these technical advances cut across conceptual boundaries between mineralogy and geochemistry and require an in-depth knowledge of the material that is being analysed. These technological advances are accompanied by changing approaches to ore mineralogy: the increased focus on trace element distributions; the challenges offered by nanoscale characterisation; and the recognition of the critical petrogenetic information in gangue minerals, and, thus the need to for a holistic approach to the characterization of mineral assemblages. Using original examples, with an emphasis on iron oxide-copper-gold deposits, we show how increased analytical capabilities, particularly imaging and chemical mapping at the nanoscale, offer the potential to resolve outstanding questions in ore mineralogy. Broad regional or deposit-scale genetic models can be validated or refuted by careful analysis at the smallest scales of observation. As the volume of information at different scales of observation expands, the level of complexity that is revealed will increase, in turn generating additional research questions. Topics that are likely to be a focus of breakthrough research over the coming decades include, understanding atomic-scale distributions of metals and the role of nanoparticles, as well how minerals adapt, at the lattice-scale, to changing physicochemical conditions. Most importantly, the complementary use of advanced microbeam techniques allows for information of different types and levels of quantification on the same materials to be correlated.

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“…10,11 It is now the preferred method for studying microscopic fluid and melt inclusions -droplets of paleo-fluids and melts preserved in various minerals. [12][13][14] Such inclusions are trapped as originally homogeneous micro-samples of fluid or melt, but may separate into several phases during cooling and exhumation to the Earth's surface. 15 UV lasers, such as the 193-nm ArF-Excimer, allow controlled ablation of a single inclusion, thereby re-integrating the bulk composition of the original inclusion.…”

Section: Introductionmentioning

confidence: 99%

“…15 UV lasers, such as the 193-nm ArF-Excimer, allow controlled ablation of a single inclusion, thereby re-integrating the bulk composition of the original inclusion. 14,[16][17][18] Modern ICP-MS systems, notably single-collector sector-field (SF-ICP-MS) instruments, have greatly enhanced sensitivities for a wide range of elements. 19,20 In our attempts to make full use of this increased sensitivity and to reach correspondingly lower limits of detection (LOD), new challenges of instrument and sample contamination have become apparent.…”

Section: Introductionmentioning

confidence: 99%

LA-ICP-MS analysis of fluid inclusions: contamination effects challenging micro-analysis of elements close to their detection limit

Schlöglova

Wälle

Heinrich

2017

J. Anal. At. Spectrom.

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Microanalysis of Fluid Inclusions in Crustal Hydrothermal Systems using Laser Ablation Methods

Cited by 44 publications

References 28 publications

Hematite Breccia-Hosted Iron Oxide Copper-Gold Deposits Require Magmatic Fluid Components Exposed to Atmospheric Oxidation: Evidence from Prominent Hill, Gawler Craton, South Australia

Hematite Breccia-Hosted Iron Oxide Copper-Gold Deposits Require Magmatic Fluid Components Exposed to Atmospheric Oxidation: Evidence from Prominent Hill, Gawler Craton, South Australia

Advances and Opportunities in Ore Mineralogy

LA-ICP-MS analysis of fluid inclusions: contamination effects challenging micro-analysis of elements close to their detection limit

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