Open Access

Appendix C

Analytical tools to study a rock H2 potential with their characteristics.

Analyses Objectives Limitations Spatial resolution Limit of detection Sample type Duration of preparation/analysis/processing
Bulk characterization
 Rock-Eval Characterization of the Total Organic Content (TOC) Powder (~10 mg) min/min/min
Access to mineral and organic contents but also thermal analysis of C and S
 X-ray fluorescence Major elements concentrations (Fe, S, U, Th, K) Does not detect trace elements Depends on the element Soli, powder, liquid –/min/min
 Inductively Coupled Plasma – Mass Spectrometry/Optical Emission Spectroscopy (ICP-MS/OES) Majors, minors, traces, and ultra-traces concentrations (Fe, S, U, Th, K) ppb Powder (~100 mg) hours/hours/days
57Fe Mössbauer spectroscopy Identification and quantification of iron-bearing phases and iron specification in each phase Powder (~400 mg) hours/days/days
 X-Ray Diffraction Phase identification, quantitative composition Do not differentiate polymorphs or minor phase Powder (~500 mg) hours/hours/hours
Observation tool
 Optical microscopy Paragenesis, texture, alteration features Low resolution μm Thin section
 Electro Probe Micro-Analyzer (EPMA) Quantitative measurements of concentration of the element heavier than Li (Fe, S, U, Th, K) punctual or map μm ppm Thin section hours/day(s)/days
 Scanning Electron Microscopy (SEM) High-resolution imaging demi-quantitatve measurements of concentration of the element heavier than Li (Fe, S, U, Th, K) punctual or map Semi-quantitative nm Thin section hours/hours/hours
 Raman Microspectroscopy Phase identification μm Thin section hours/days/days
 X-Rays Microtomography (XCT) Volume and propagation of elements of interest-bearing phase in the whole rock No chemical information, can be hard to distinguish chemically close phases, post-processing can be challenging, time consuming μm cm3–m3 core hours/hours/days

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