Sulfur and phosphorus SR-µXANES and µXRF analyses, bulk mineralogical, laboratory XRF and SEM-EDXS data from carbonate microbialites in Lake Alchichica

This dataset contains the sulfur and phosphorus SR-µXANES and µXRF, bulk chemical, laboratory XRF, SEM-EDXS and bulk major dissolved chemical species and physico-chemical in situ parameters of Lake Alchichica microbialites and water column acquired in May 2019 and October 2022. The data are supplementary to:

Caumartin, J., Benzerara, K., Havas, R., Thomazo, C., Mehta, N., Betancourt, V., Colocho Hurtarte, L. C., Cotte, M., Estève, I., Jézéquel, D., Sans-Jofre, P., Tavera, R., Kotopoulou, E. & Lόpez-Garcίa P. (2026). Depth-dependent sulfur speciation in modern carbonate microbialites from a monomictic lake. Advances in Geochemistry and Cosmochemistry, 2(1), 988. https://doi.org/10.33063/agc.v2i1.988

The list of data, including filenames, sample names, data type, IGSN numbers and sampling year are summarized in the excel table “Data_content_Alchichica_microbialites_sulfur_speciation”.

The nomenclature used for the sample names is as follows: Lake abbreviation (AL for Alchichica), Year of sampling_(Type of sample (mb for microbialite))_Depth (in meters)_(number of the data)_Technique (XANES, XRF, chemistry, SEM-EDXS).

1. SR-µXANES and SR-µXRF: These files are in .hdf5 format, which can be opened in the free PyMca software. The hyperspectral map can also be processed using the free quasar (Orange) software. These data were obtained from thick section of the 10-, 30- and 40-m-deep microbialites samples at the ID21 beamline of the European Synchrotron Radiation Facility (ESRF) in Grenoble. µ-XRF maps were acquired using an incident beam at ~2.5 keV. SR-S-µXANES spectra were obtained between 2.46 and 2.53 keV, and SR-P-µXANES spectra between 2.14 and 2.19 keV.

2. Bulk chemistry of microbialites: These data, provided in an excel sheet, were obtained from fine powder samples. The elemental compositions were measured by the Service d'Analyse des Roches et Minéraux (SARM, Centre de Recherches Pétrographiques et Géochimiques, Nancy, France). Total carbon and sulfur analyses were performed on a second fraction of the sample, using the same analyzer, but without the decarbonation phase.

3. Laboratory XRF: The available data comprises elemental maps and global spectra in a .TIF format, which can be processed in the free ImageJ software, for example. These data were obtained from sample thin sections. Elemental maps of major and trace elements were acquired with an X-ray excitation energy of 50 keV and a current of 600 µA, under a 20-mbar vacuum, using a Bruker M4 Tornado XRF spectrometer. Scans were performed with a 20 µm spot size over a ~4 x 3 cm2 area. Each scan (2000 x 1500 pixels) took over 4 hours per sample with a 5 ms dwell time per pixel.

4. SEM-EDXS: The available data comprises elemental maps, AsB images and EDXS spectra in a .TIF format, which can be processed in the free ImageJ software, or using the Bruker software. These data were obtained from non-resin embedded and carbon-coated thick sections of microbialite samples, using a Zeiss Ultra 55 field emission gun SEM. Backscattered electron (BSE) images were acquired at a working distance of ~7.5 mm, an accelerating voltage of 15 keV, and an aperture 60 µm. The high current mode and an angle selective backscattered detector were used. The elemental maps were obtained using a Bruker EDS QUANTAX detector by energy-dispersive X-ray spectrometry, and analyzed using the ESPRIT software (Bruker).

5. Dominant taxonomic groups, along with in situ and bulk chemistry data for the microbialite and water samples from Lake Alchichica are compiled in the excel files named “Bulk_major_dissolved_chemical_species_and_physico-chemical_in_situ_parameters” and “Dominant_taxonomic_groups_and_metabolisms_in_Alchichica microbialites”. These data, in addition to the XRD and FTIR data, are sourced from previous studies using these samples:

Caumartin, J., Benzerara, K., Havas, R., Thomazo, C., Fogret, L., Betancourt, V., Tavera, R., Doisneau, B., Jézéquel, B. & López-García, P. (2025). Huntite [CaMg3 (CO3) 4], a Rare Carbonate Phase Formed during Early Diagenesis in Modern Microbialites. ACS Earth and Space Chemistry, 9(6), 1544-1565, https://doi.org/10.1021/acsearthspacechem.5c00022.

Iniesto, M., Moreira, D., Reboul, G., Deschamps, P., Benzerara, K., Bertolino, P., Saghaï, A., Tavera, R. & López‐García, P. (2021). Core microbial communities of lacustrine microbialites sampled along an alkalinity gradient. Environmental Microbiology, 23(1), 51-68. https://doi.org/10.1111/1462-2920.15252

Saghaï, A., Zivanovic, Y., Zeyen, N., Moreira, D., Benzerara, K., Deschamps, P., bertolino, p., ragon, m., tavera, r., lópez-archilla, a.i. & López-García, P. (2015). Metagenome-based diversity analyses suggest a significant contribution of non-cyanobacterial lineages to carbonate precipitation in modern microbialites. Frontiers in Microbiology, 6, 797. https://doi.org/10.3389/fmicb.2015.00797

Saghaï, A., Zivanovic, Y., Moreira, D., Benzerara, K., Bertolino, P., Ragon, M., Tavera, R., lópez‐archilla, a.i. & López‐García, P. (2016). Comparative metagenomics unveils functions and genome features of microbialite‐associated communities along a depth gradient. Environmental microbiology, 18(12), 4990-5004. https://doi.org/10.1111/1462-2920.13456

Couradeau, E., Benzerara, K., Moreira, D., Gerard, E., Kaźmierczak, J., Tavera, R., & López-García, P. (2011). Prokaryotic and eukaryotic community structure in field and cultured microbialites from the alkaline Lake Alchichica (Mexico). PloS one, 6(12), e28767. https://doi.org/10.1371/journal.pone.0028767

Muller, E., Rapin, W., Caumartin, J., Jézéquel, D., De Wever, A., Thomazo, C., Havas, R., López-García, P., Moreira, D., Tavera, R. & Benzerara, K. (2023). Diagenetic formation of stevensite by replacement of diatom frustules in the sediments of the alkaline Lake Alchichica (Mexico). Sedimentology, 70(4), 1013-1038. https://doi.org/10.1111/sed.13069