In situ raman spectral mapping study on the microscale fibers in blue coral (Heliopora coerulea) skeletons.

The presence and localization of organic matrix associated with the aragonite phase in the fibers of blue coral Heliopora coerulea skeletons were studied by in situ microRaman mapping spectra, with a spatial resolution of ∼0.3 μm. Spatial variations in the amounts and chemical compositions of the fibers were imaged. The results showed that the amide I and the α-helix of amide III were perpendicular to the c-axis of fibers’ growth, whereas the β-turns/sheet of amide III was in the parallel conformation. Visible S–S and C–S bonds were consistent with the XANES results, which indicated the existence of organic sulfur in coral skeletons. Regular cyclic changes between aragonite and organic matrix refined a stepping growth mode of the fibers’ biomineralization. An inorganic PO4 bond was detected and exhibited the same concentration variation trends as the v4 aragonite bands. Instead of providing an ocean P proxy on the subseasonal to centennial scale by LA-ICPMS, the possibility was raised of producing high re...