SEM-EDS microanalysis

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Method synopsis

Quantitative XRD analysis of powdered rock samples using Rietveld refinement to determine mineral concentrations and spatial distribution. Samples analyzed under multiple conditions including ethylene glycol saturation and heating to identify clay minerals.

Synthesized from method descriptions across 5 papers using this protocol.

Procedure from a recent peer-reviewed implementation

Steps below were extracted from the most recent peer-reviewed implementation of this protocol in the corpus — Aerobic respiration controls on shale weathering (2023), Geochimica et Cosmochimica Acta. Implementations in other papers (listed below) may differ.

1. Collect solid phase samples
   Multi-depth solid sampling and analyses were performed to assess the mineralogy and spatial distribution of carbon in the subsurface. Mineral concentrations in PLM1 and PLM2 were determined from X-ray diffraction (XRD) measurements performed on samples collected during installation. Additional XRD measurements were performed on sub-core samples collected in PLM3 at approximately 0.3 m intervals between surface part of the core and 10 m below ground surface.
   Quantities: Samples collected at 0.3 m intervals from surface to 10 m depth in PLM3, plus samples from PLM1 and PLM2 during installationDuration: Sampling during well installation in 2016Conditions: Samples powdered in agate mortar and stored in glovebox under N2 conditions to avoid thermal oxidation between sample preparation and analysis
   Equipment: agate mortar, glovebox, XRD analyzer, Rigaku SmartLab high-resolution XRD diffractometer, Bragg-Brentano geometry, Cu radiation
2. XRD analysis and mineral quantification
   The XRD analyses were performed using a Rigaku SmartLab high-resolution XRD diffractometer with a Bragg-Brentano geometry. The diffractometer was equipped with a theta-theta goniometer and a rotating sample holder using Cu (λKα1 = 1.5405 Å and λKα2 = 1.5444 Å) radiation. Bulk rock samples were measured on oriented and day samples, whereas the bulk ground rock samples were placed in an aluminum holder to ensure random particle orientations. Bulk rock samples were measured at 10 to 90 °2θ with a 0.02 °2θ step-size and count times of 2 s per step. Oriented clay samples were measured from 2 to 25 and 3 to 75 °2θ with 0.02 °2θ step-size and 10 and 2 s per step.
   Quantities: Measurements at 10-90°2θ for bulk samples, 2-25°2θ and 3-75°2θ for clay samples, 0.02°2θ step size, 2s and 10s count times

Typical Equipment

• Rigaku SmartLab XRD
• theta-theta goniometer
• rotating sample holder
• Cu radiation source
• agate mortar
• glovebox

Output Measurements

• mineral mass fractions
• mineral volume fractions
• bulk surface areas

Papers Using This Protocol (5)

Species Studied With This Protocol

Places Where Used