Synchrotron micro-probe X-ray diffraction data from seafloor sulfide deposits collected during cruise AT42-09 on the East Pacific Rise (EPR) in April 2019

Synchrotron micro-probe X-ray diffraction data were collected for seafloor sulfide deposits. Seafloor sulfide mineral samples were collected from hydrothermally active chimneys and inactive off-axis massive sulfide deposits at East Pacific Rise (EPR) 9.50°N in 2019-2021 on cruise AT42-09. Samples were collected using the HOV Alvin. Samples were placed in a positive-pressure glove bag flushed with N2 (g), sparged with N2, heat-sealed into mylar bags containing Anaeropaks, and stored at -20°C.

Epoxy embedded petrographic thin sections were created using these samples. Subsamples were dried for 24 hours under N2 (g), vacuum embedded in epoxy resin (Struers EpoFix Resin, 1L kit: Part #40200030) following manufacturer’s guidelines, and cured under N2 (g) for 24 hours. Each epoxy-embedded sample was pre-cut using a wafering saw then sent to Spectrum Petrographics, Inc. (Washington, USA) for preparation as 30 micron thick, double-polished thin sections mounted on quartz slides using methods to limit sample exposure to water and ambient air. When not in use, thin-sections were stored under N2 (g) to limit oxidation. Thin sections were analyzed for X-ray diffraction at the X-ray Fluorescence Microprobe beamline "XFM", National Synchrotron Light Source II (NSLS II), Brookhaven National Laboratory, NY.