Fig. 4: Frutexites-like microstromatolitic structures and associated compositional maps.
From: Microbial biosignature preservation in carbonated serpentine from the Samail Ophiolite, Oman
A Branching columnar structures display feint lamination under plane-polarized light. B Fluorescence microscopy reveals fine laminations in greater detail. Raman spectroscopic analysis of laminae show the presence of “D” and “G” vibrational bands at ~1350 cm−1 and ~1600 cm−1 respectively (shown at right), indicative of macromolecular carbonaceous material. C SEM secondary electron image shows microscale laminations and marks the locations of EDS spot analyses. EDS measurements show alternation between dark C-rich laminae (e.g., spot 1 & 3), and bright laminae dominantly composed of O, C, Ca, Fe, Si, and Mg (e.g., spot 2). D location of NanoSIMS mapping conducted on microstromatolites cut orthogonal to the growth direction by thin sectioning. Bottom panels of (D) show laminae containing nitrogen and carbon. A yellow arrow marks a surface scratch that appears in the 12C2 ion map introduced during sample preparation. Brighter features in both NanoSIMS images correspond to higher total ion counts per pixel.
