DOI: 10.6084/m9.figshare.24785643.v1
title: Sulfur isotopes from the Paleoproterozoic Francevillian Basin record multigenerational pyrite formation, not depositional conditions

description: The dataset contains in situ and bulk geochemical analyses results for the LST12 and Doumé drill cores from the ca. 2.1 Ga Francevillian Basin (Gabon). The table files contain bulk stable isotope results (incl. chromium reducible sulfide, acid extractable sulfate, organic sulfur compounds S isotope and organic matter and carbonate C isotope data), SIMS sulfur isotope data from pyrite, normalized XANES and linear combination fit (LCF) results of natural samples, and select bulk mineralogy and geochemistry. All necessary software to retriew the data is either standard or openly accessible, such as Athena for XANES.<b>Supplementary Data 1</b>. Bulk stable isotope results. The bulk chromium reducible sulfide (δ<sup>34</sup>S<sub>CRS</sub>), acid extractable sulfate (δ<sup>34</sup>S<sub>AES</sub>), organic sulfur compounds (δ<sup>34</sup>S<sub>OSC</sub>) S isotope and organic matter (δ<sup>13</sup>C<sub>org</sub>), and carbonate (δ<sup>13</sup>C<sub>carb</sub>) C isotope data from the Doumé and LST12 cores from the Francevillian Basin of Gabon.<b>Supplementary Data 2</b>. Bulk mineralogy and geochemistry. Pyrite, dolomite, and calcite content using XRD analysis and Mn content determined by ICP-MS measurements from the Doumé core.<b>Supplementary Data 3.</b> XANES results. Normalized XANES spectra of natural samples.<b>Supplementary Data 4.</b> The linear combination fit (LCF) results. LCF was performed on the normalized XANES spectra.<b>Supplementary Data 5</b><b>.</b> SIMS findings. Sulfur isotope data for SIMS spot and scanning ion imaging of unknowns and in-house pyrite standard from four samples. The raw isotope ratios for unknowns were calculated across the listed region of interest (ROI) by integrating the <sup>34</sup>S/<sup>32</sup>S ion count ratio over all analyzed cycles. Both a dead‐time and QSA correction were applied to the raw isotope ratios, and the δ<sup>34</sup>S values are reported relative to Vienna Canyon Diablo Troilite (VCDT). The reported crystal habit, texture, and size for individual pyrite crystals were determined after SIMS analysis by SEM microscopy and compared to SIMS ion images to confirm imaging areas and identify potential imaging artifacts related to ion beam interactions with the sample (surface topography and matrix effects).<b>Supplementary Data 6</b>. Summarized Rayleigh model results.<b>Fig. S1.</b><b> </b>XANES spectra and LCF results. XANES standard spectra of (A) organic and (B) inorganic sulfur compounds used in LCF and measured natural samples (C – L) with LCF results beside. The dashed gray lines represent the energies of primary features identified in the natural samples XANES spectra. On the figures, DM stands for Doumé core. Color maps from<sup>1</sup>.<b>Fig. S2.</b><b> </b>Dissolution textures. (A) Backscatter scanning electron microscopy (SEM BSE) image of sample LST12-35.5. The pore space between pyrite (brightest backscatter) contains pyrobitumen, mica, and quartz. (B) SEM BSE image of sample LST12-31.3. The brightness and contrast have been adjusted to show that the dissolution textures cut across the primary growth zonation of pyrite.<b>Fig. S3.</b><b> </b>The type 2 stratiform pyrite and type 3 massive pyrite nodule’s trace element and δ<sup>34</sup>S<sub>PY</sub> differ. Backscatter scanning electron microscopy (SEM BSE) image of sample LST12-53.8 (1-inch round) with locations of trace element maps (A) and (B). The Cu/As maps traverse stratiform bands and nodule pyrite. (B) In panel 2, the SIMS measurements reveal noticeable differences in the δ<sup>34</sup>S values between the massive type 3 pyrite and the octahedral type 2 pyrite in stratiform bands and its remnants within the massive nodule. For other trace elements, see Fig. S4. Color maps from<sup>1</sup>.<b>Fig. S4.</b> Trace element maps from LST12-53.8. The mapped areas (A) and (B) in sample LST12-53.8 are shown in Fig. S3. Color maps from<sup>1</sup>.<b>Fig. S5.</b> Trace element maps from LST12-61.18. Pyrite trace element concentration maps generated from a bed-parallel stratiform band in sample LST12-61.18 (1-inch round). The distance between the two map areas (<b>A</b>) and (<b>B</b>) is ca. 2 mm. (<b>A</b>) In panel 2, the SEM BSE image reveals micro-scale zonation of the pyrite and that smaller octahedral crystals are encased by massive cubic pyrite. Color maps from<sup>1</sup>.<b>Fig. S6.</b> Trace element maps from LST12-31.3. (A) Pyrite trace element concentration maps from sample LST12-31.3 generated for a matrix-dominated nodule outlined in Fig. 5 B3. (B) The SEM BSE image of zoned pyrite is from a more cemented part of the nodule. Color maps from<sup>1</sup>.1. Crameri, Fabio. Scientific colour maps. (2021) doi:10.5281/ZENODO.5501399.<br>