George Dan Miron

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Verified

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• PhD.
• Scientist at Paul Scherrer Institute

The chemical composition of fluid inclusions in quartz crystals from Alpine fissure veins was determined by combination of microthermometry, Raman spectroscopy, and LA-ICPMS analysis. The veins are hosted in carbonate-bearing, organic-rich, low-grade metamorphic metapelites of the Bündnerschiefer of the eastern Central Alps (Switzerland). This stro...

GEMSFITS is a new code package for fitting internally consistent input parameters of GEM (Gibbs energy minimization) geochemical-thermodynamic models against various types of experimental or geochemical data, and for performing inverse modeling tasks. It consists of the gemsfit2 (parameter optimizer) and gfshell2 (graphical user interface) programs...

A large amount of critically evaluated experimental data on mineral solubility, covering the entire Na-K-Al-Si-O-H-Cl system over wide ranges in temperature and pressure, was used to simultaneously refine the standard state Gibbs energies of aqueous ions and complexes in the framework of the revised Helgeson-Kirkham-Flowers equation of state. The t...

This study presents an internally consistent thermodynamic dataset for aqueous species in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl, obtained by adding species of calcium, magnesium and carbon to the core system Na-K-Al-Si-O-H-Cl (Miron and others, 2016). Critically evaluated experimental data on mineral solubility (Ca and Mg hydroxides, Ca and Mg silic...

Most of the available thermodynamic data concerning radioactive waste disposal are restricted to values of reaction equilibrium constants (logK298o) at 25 °C and 1 bar. Simple estimation methods such as isocoulombic reactions can be used for extrapolating the properties of reactions involving aqueous species and minerals to elevated temperatures. T...

Thanks to the recent progress in numerical methods and computer technology, the application fields of artificial intelligence (AI) and machine learning methods (ML) are growing at a very fast pace. The field of geochemistry for nuclear waste management has recently started using ML for the acceleration of numerical simulations of reactive transport...

This study presents an advance in predicting long-term stability in waste containment systems. Employing a surrogate model based on the 25 GEMS Python scripts, we simulate geochemical interactions within waste degradation processes over 100 years. The model simplifies complex full-scale geochemical models using a mixing tank approach, primarily exa...

The Si and Al thermodynamic data and Pitzer interaction parameters (IPs) from THEREDA were re-evaluated to extend the applicability of the database for modeling cementitious systems from low to highly saline environments. This study involved reassessing the standard reference thermodynamic data for Si and Al aqueous species and relevant solids (qua...

Rhabdophane is a hydrous phosphate that commonly replaces monazite as a weathering product in critical mineral deposits during the alteration of rare earth elements (REE) bearing carbonatites and alkaline igneous complexes. It is an important host to the light (L)REE (i.e., La to Gd) but the stability and structure of binary solid solutions between...

Innovations in machine learning (ML) provide new opportunities in the safety assessment and design optimization of deep geological repositories (DGRs) and waste containment systems. A study on the Full-scale Emplacement (FE) experiment at the Mont Terri Underground Laboratory demonstrates ML's potential to enhance 3D heat transport models. ML was a...

Modeling geochemical scenarios for the safety analyses of disposal of hazardous radioactive and (chemo)toxic waste requires comprehensive and consistent thermodynamic data as well as sorption data for the surrounding host rocks. Whereas there are several projects running worldwide to develop at the comprehensive and consistent thermodynamic databas...

We introduce a new methodology for inference of fluid composition from measurements of mineralogical or chemical compositions, expanding upon the use of reactive transport models to understand hydrothermal alteration processes. The reactive transport models are used to impute a latent variable explanatory mechanism in the formation of hydrothermal...

The solubility and hydrolysis of Be(II) was investigated from undersaturation conditions in alkaline, dilute to concentrated CaCl 2 solutions (0.05–3.5 M). Experiments were performed with α-Be(OH) 2 (cr) under Ar atmosphere at T = (22 ± 2)°C. Aqueous Be speciation was further investigated by means of molecular dynamics (MD) calculations. For the mo...

The ClaySor model was re-parameterized using the GEMSFITS parameter optimization tool, which refines the equilibrium constants for surface complexation and ion exchange reactions against experimental data. GEMSFITS also offers a range of statistical methods to evaluate parameter correlation and sensitivity to experimental data, as well as a Monte C...

In the context of circular economy and heavy metal (HM) recovery from municipal solid waste incineration (MSWI) fly ash (FA), detailed knowledge of HM binding forms is required for achieving higher extraction rates. The FA mineralogy is still poorly understood due to its low grain size and low metal concentration. To investigate the HM binding form...

Slag is a by-product of the steel industry that can be used as a binder with alkali solutions. In this study, the microstructural development is discussed for two alkali-activated slag mixes with promising properties for structural applications. The reaction products for both mixes were characterized by X-ray diffraction, thermogravimetry, Fourier-...

Steel is used as reinforcement in construction materials and it is also an important component of cement-stabilized waste materials to be disposed of in deep geological repositories for radioactive waste. Steel corrosion releases dissolved Fe(II/III) species that can form corrosion products on the steel surface or interact with cementitious materia...

The effect of Al and of pH on the structure of calcium silicate hydrate (C-S-H), the most important hydration product in Portland and blended cement, was studied at Ca/Si ~1.0. The presence of Al led to higher amounts of secondary phases, larger interlayer distances, longer silicate chains, higher concentrations of dissolved Al and Si, and lower Ca...

The CASH+ sublattice solid solution model of C-S-H aims to predict the composition of C-S-H and its ability to take up alkalis. It was originally developed for dilute systems with high water-solid ratios, and thus in this paper further optimized and benchmarked against measured pore solution compositions of hydrated Portland cement (PC) and PC blen...

Thanks to the recent progress of technology, the fields of artificial intelligence (AI) and machine learning methods (ML) are growing at a very fast pace. The EURAD (European Joint Programme on Radioactive Waste Management) community has recently started using ML for a) accelerating numerical simulations, b) improving the efficiency of multiscale a...

The new CASH+ core sublattice solid solution model of calcium-silicate-hydrate (C-S-H) can describe calcium uptake, solubility, water content, and mean silicate chain length up to 90 °C. In this study, the model has been consistently extended to describe the equilibrium uptake of alkalis (Li, Na, K, Rb, Cs) and alkaline earths (Mg, Sr, Ba, Ra). The...

This paper investigates the effect of KOH and NaOH on C-S-H structure and solubility. Both KOH and NaOH have a similar effect, they increase pH values and silicon concentrations, and decrease calcium concentrations. At higher alkali hydroxide concentrations, more portlandite precipitates, while amorphous silica dissolves. This increases the Ca/SiC-...

A new thermodynamic model, CASH+, is proposed, aimed at accurately describing equilibrium composition, stability, solubility, and density of C-S-H gel-like phases at varying chemical conditions. Taking advantage from recent atomistic and spectroscopic studies, this sublattice solid solution model allows incremental extensions to accommodate alkali,...

Thermodynamic equilibrium calculations for cementitious materials enable predictions of stable phases and solution composition. In the last two decades, thermodynamic modelling has been increasingly used to understand the impact of factors such as cement composition, hydration, leaching, or temperature on the phases and properties of a hydrated cem...

The GEM (Gibbs energy minimization) approach for computing the chemical equilibrium phase assemblages and speciation in complex chemical systems normally uses a single mass balance for the entire system, set up by the total amounts of chemical elements and zero charge. Stoichiometries (formulae) of all chemical substances in the system are thus bui...

https://www.ine.kit.edu/downloads/210713_No-04_ThermAc%20Abschlussbericht_Gesamtdokument%20MIT%20DOI_Altmaier.pdf

Thermodynamic properties of aqueous species are essential for modeling of fluid-rock interaction processes. The Helgeson-Kirkham-Flowers (HKF) model is widely used for calculating standard state thermodynamic properties of ions and complexes over a wide range of temperatures and pressures. To do this, the HKF model requires thermodynamic and electr...

Advanced reactive transport simulations of hydrothermal systems require the modelling of diverse physico-chemical phenomena, many of which have only partially been addressed in previous studies. Utilizing newly implemented capabilities of the CSMP++GEM code, we show the relevance of three phenomena: (1) At the example of alkali feldspars, we inves...

Thermodynamic modelling can reliably predict hydrated cement phase assemblages and chemical compositions, including their interactions with prevailing service environments, provided an accurate and complete thermodynamic database is used. Here, we summarise the Cemdata18 database, which has been developed specifically for hydrated Portland, calcium...

Monazite (CePO4) is a light rare earth element (REE) phosphate occurring as accessory mineral in metamorphic, igneous and sedimentary rocks, and is also a common mineral in REE mineral deposits. Metasomatism of monazite yields important clues about fluid-rock interaction in the crust, in particular, because its compositional variations may enable u...

CePO4 and YPO4 are major components in monazite and xenotime, respectively, which are common hydrothermal phases in REE mineral deposits. Both minerals also occur as secondary minerals in iron-oxide-apatite deposits [1,2], and as accessory phases in high-grade metamorphic rocks where they display varying degrees of metasomatism. Studying the cause...

Thermodynamic database for GEM-Selektor modeling software http://gems.web.psi.ch/ HowToTDB.docx contains the instructions for using the database to create a GEM-Selektor modeling project.

How to create a modeling project in GEMS (http://gems.web.psi.ch/) using the Aq17 thermodynamic database.

The composition of fluid inclusions (FI) hosted in quartz veins from low-grade metamorphic rocks of the Bündnerschiefer (two locations near Thusis and Schiers that represent subgreenschist and lower greenschist facies conditions, respectively), Swiss Alps, was determined by combination of microthermometry and LA-ICPMS microanalysis. Elongate-blocky...

The island-arc volcanics situated in the eastern part of the Căpıîlnaş-Techereu nappe (South Apuseni Mountains, Romania) were studied to evaluate the temperature, fluid properties, and mineral chemistry during low-temperature metamorphism. Detailed observations of metamorphic mineral assemblages were conducted using powder X-ray diffraction and ele...