Modelling of hydrothermal fluid compositions in the crust and upper mantle

At a Glance

Metadata	Details
Publication Date	2017-06-01
Journal	ResearchOnline at James Cook University (James Cook University)
Authors	Adrian G. Parker, Jan Marten Huizenga
Analysis	Full AI Review Included

Technical Analysis and Documentation for High P/T Geochemistry Research

Executive Summary

The research analyzed—“Modelling of hydrothermal fluid compositions in the crust and upper mantle”—focuses on the extreme conditions necessary for natural diamond formation, providing critical insights for high-pressure/high-temperature (HPHT) synthesis and instrument design.

The study successfully models the compositions of Carbon-Oxygen-Hydrogen (COH) fluids (including H₂O, CO₂, CH₄, O₂) integral to the formation of natural diamond and other ore deposits.
The model operates under extreme conditions, specifically targeting pressure > 0.5 kbar and a vast temperature range of 300°C to 1500°C.
Core methodology relies on the Zhang and Duan (2009) equation of state combined with the NIST reference dataset to calculate thermodynamic variables and fugacity coefficients.
The findings highlight the hostile environments encountered in diamond genesis, emphasizing the need for robust, ultra-high-performance materials, such as MPCVD Single Crystal Diamond (SCD), in laboratory replication experiments.
6CCVD specializes in custom CVD diamond materials (SCD, PCD) ideal for high P/T instrumentation, including DAC anvils, optical windows, and robust thermal spreaders required for high-energy density systems operating up to 1500°C.
The development of this validated fluid model provides a reference baseline for optimizing parameters in industrial synthetic diamond growth recipes.

Technical Specifications

The following table summarizes the operational parameters derived from the COH fluid modeling research:

Parameter	Value	Unit	Context
Modeled Temperature Range	300 - 1500	°C	Relevant to crustal and upper mantle fluids
Modeled Pressure Range (Minimum)	> 0.5	kbar	Equivalent to 50 MPa
Primary Fluid Constituents	H₂O, CO₂, CH₄, H₂, CO, C₂H₆, O₂	N/A	Components of COH fluid integral to diamond formation
Equation of State Utilized	Zhang and Duan (2009)	N/A	Used for calculating fugacity coefficients
Data Validation Methods	VBA, Python, SQL scripting	N/A	Used to ensure model accuracy in Excel platform

Key Methodologies

The researchers employed a detailed modeling approach combining thermodynamic theory and computational validation to predict fluid compositions under deep Earth conditions:

Constraint Definition: Establishing a pressure range (> 0.5 kbar) and temperature range (300-1500°C) based on crustal and upper mantle requirements.
Equation of State Application: Utilizing the reliable Zhang and Duan (2009) equation of state, necessary for calculating fugacity coefficients of complex fluid mixtures under high P/T.
Thermodynamic Data Integration: Incorporating critical thermodynamic variables (enthalpy, entropy, isobaric heat capacity) sourced from the high-fidelity NIST reference dataset.
Modeling Tool Creation: Developing a user-friendly Excel spreadsheet to perform real-time calculation of fluid compositions based on input P-T parameters.
Computational Validation: Ensuring the accuracy and reliability of the spreadsheet model through data manipulation and validation checks executed via VBA, Python, and SQL scripting.

6CCVD Solutions & Capabilities

6CCVD is positioned as the ideal partner for scientists and engineers replicating or advancing this research, particularly those requiring materials that maintain structural and optical integrity in extreme 1500°C, high-pressure environments (e.g., in DACs or hydrothermal flow reactors).

Applicable Materials

To study or replicate the fluid conditions modeled in this paper, materials with exceptional thermal, mechanical, and optical properties are mandatory.

6CCVD Material	Specific Relevance to High P/T Research	Key Advantages
Optical Grade Single Crystal Diamond (SCD)	Critical for Diamond Anvil Cell (DAC) windows, allowing in situ observation and spectroscopy of fluids up to 1500°C.	Superior transparency, extreme hardness, and chemical inertness in COH environments.
Thermal Grade SCD (Type IIa)	Use as ultra-efficient heat spreaders for focusing energy or dissipating heat from surrounding electronics in the reactor.	Thermal conductivity > 2000 W/m·K.
Polycrystalline Diamond (PCD)	High-strength support structures or large-area substrates for high-temperature flow systems.	Available in large formats (up to 125mm wafers) with exceptional mechanical stability.
Custom Boron-Doped Diamond (BDD)	Potential use as robust, stable electrochemical electrodes for redox sensing within high-pressure aqueous fluids.	Highly conductive, robust electrode surface resistant to fouling.

Customization Potential

6CCVD’s advanced fabrication capabilities enable the precise specifications needed for demanding geological research:

Precision Dimensions: We provide custom SCD layers from 0.1 µm up to 500 µm, and robust SCD/PCD substrates up to 10mm thick, ensuring optimal mechanical stability for high-pressure fixtures.
Ultra-Smooth Polishing: For optical windows used in fluid spectroscopy and imaging, 6CCVD guarantees surface roughness of Ra < 1nm (SCD), minimizing scattering loss at high pressures.
Custom Metalization: If high P/T sensors or resistive heaters are integrated onto the diamond component, 6CCVD offers internal metalization services (e.g., Ti/Pt/Au, W/Cu stacks) tailored to withstand high operating temperatures without delamination.
Global Supply Chain: We ensure reliable delivery of custom diamond solutions worldwide, with flexible shipping options (DDU default, DDP available).

Engineering Support

This study provides valuable constraints for synthetic diamond growth and material longevity. 6CCVD’s in-house team of PhD material scientists can assist researchers and engineers in selecting the optimal SCD or PCD material grade, crystal orientation, and finishing parameters necessary to survive the extreme temperatures (up to 1500°C) and pressures encountered in high-pressure geochemistry and synthetic diamond growth applications.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Carbon-oxygen-hydrogen (COH) fluids are integral to the formation of many hydrothermal ore deposits (including orogenic gold, graphite), and diamond. Typically, a crustal/upper mantle COH fluid comprises H2O, CO2, CH4, H2, CO, C2H6, and O2. Crustal and upper mantle fluid compositions are constrained by pressure, temperature and redox state, and can be calculated if: (1) A reliable equation of state for fluid mixtures is available for the relevant pressure-temperature conditions is available for the calculation of fugacity coefficients; (2) Reliable thermodynamic variables including enthalpy, entropy and isobaric heat capacity can be obtained. Here, we used the equation of state by Zhang and Duan (2009) in conjunction with the NIST reference dataset to develop a user-friendly Excel spread sheet that allows the calculation of fluid compositions for a pressure-temperature range of > 0.5 kbar and 300-1500°C, respectively. Data manipulation and modelling was achieved with a combination of VBA, Python and SQL scripting and allowed us to validate the model calculations in the Excel spread sheet. Here, we used the equation of state by Zhang and Duan (2009) in conjunction with the NIST reference dataset to develop a user-friendly Excel spread sheet that allows the calculation of fluid compositions for a pressure-temperature range of > 0.5 kbar and 300-1500°C, respectively. Data manipulation and modelling was achieved with a combination of VBA, Python and SQL scripting and allowed us to validate the model calculations in the Excel spread sheet.

Tech Support

Original Source

DOI: None