*2.3. Mineralogic Method*

The micro-analysis on the selected thin section was performed on a ZEISS SIGMA 300VP SEM equipped with a back-scattered electrons (BSE) detector and two Bruker XFlash 6|30 EDX detectors, with 129 eV energy resolution and with the ZEISS Mineralogic automated quantitative mineralogy software platform located at the Geological Survey of Denmark and Greenland, Copenhagen, Denmark. The description of the Mineralogic method in this section, including screenshots (Figures S1–S7) from the set-up of the Mineralogic recipes can be found in the Supplementary 2. Within each thin section, a region of interest was selected and imaged to provide a high-resolution BSE mosaic of stitched images. Also, on this region of interest, a quantitative mineralogical analysis was carried out using Mineralogic, creating a mineral map with a user defined step size (or pixel size) as well as a list with parameters for grains in the sample. The acceleration voltage of the primary electron beam was set to 15 or 20 kV, to ensure X-ray excitation for all relevant elements (e.g., Fe, Cu, Zn). The 120 μm aperture providing 80 μA beam current used was used to obtain a high input count rate for the EDX detectors. The EDX software is fully integrated with the Mineralogic software, allowing for matrix corrections of each mineral. Therefore, the exact element concentrations can be calculated for each acceleration voltage. A detailed description of the Mineralogic method is given below:


*Minerals* **2020**, *10*,

 47

#### 2.3.1. Zeiss Mineralogic Mining

The ZEISS Mineralogic software platform has a Mining and a Reservoir rock plug-in, though analytical functionalities between both branches largely overlap. The difference between both lies in how obtained data are visualized, e.g., as target and byproduct (Mining), or integrated with porosity measurements (Reservoir). Here, the Mining part of the software was applied. The software offers a recipe-based solution for all steps in the analysis (SEM parameters, holders and stubs used, calibration for the EDX and BSE detectors, image analysis, morphological analysis, mineralogical analysis, lithological analysis, mining output parameters, and criteria that specify how and when the analytical run is performed and terminated). These recipes can be saved, mixed, and changed individually, thus adapting each analysis to the sample at hand. Recipes can also be in- and exported allowing for an exchange between different internal and external users. Routine analyses can be set up allowing a non-geologist/mineralogist can run samples from a batch of similar samples, while the more experienced user gets the freedom to vary many parameters for each analysis [8]. The description here is based on Mineralogic software version 1.6.

## 2.3.2. Image Navigation

The Image Navigation tool of the ZEISS SEM applies digital images of thin sections, the entire sample holder, or overview SEM-images to navigate within the sample (Figure S1). The tool allows the user to define three fiducial points on the navigation image and connect those to stage coordinates, afterwards the movements of the stage can be controlled from the navigation image. The tool is especially ideal to set up analyses on holders with several samples, or on fine grained material in a fast manner.

## 2.3.3. SEM Recipe

In this recipe, the SEM can be operated in a normal mode to set and save the operating conditions for the analysis. The sample can be placed to the correct position, the beam is focused and optimized at the required acceleration voltage (often 15–25 kV) and aperture size (often 60–120 μm). The brightness and contrast of the image are set. The SEM recipe saves the current settings of the SEM (like vacuum settings, beam parameters) and regulates the SEM imaging parameters (dwell time to allow for stage movements, scan speed), see Figure S1.
