Fig. 4From: FTIR microspectroscopy of carbonaceous matter in ~ 3.5 Ga seafloor hydrothermal deposits in the North Pole area, Western AustraliaThe transmission IR absorbance spectra (1024 scans) of the carbonaceous clots. a Examples of the IR spectra of the carbonaceous clots with aliphatic CH2 and CH3 bonds (blue line: spot #6 in Table 1), only aliphatic CH2 bond (green line: spot #12 in Table 1), and no CH2 bond (red line: spot #13 in Table 1) together with quartz matrix (black line). IR transmission-reflection spectrum of the carbon-based dissolvable adhesive used in this study on an aluminum foil is shown by the brown line (modified from Igisu et al. 2006). One scale unit on the vertical axis corresponds to an absorbance of 0.2. (b) An enlarged view of the IR spectra within 3000–2800 cm−1. The range for b1 is indicated by the dotted rectangle in a. Spot numbers (#1, #2, etc.) are shown in the upper right in each figure. One scale unit on the vertical axis corresponds to an absorbance of 0.02 in b1 and b4–b12, and 0.1 in b2 and b3. c The IR spectra after linear baseline correction of the spectra in b within 3000–2800 cm−1. Spot numbers (#1, #2, etc.) are shown in the upper right in each figure. One scale unit on the vertical axis corresponds to an absorbance of 0.002 in c1 and c12, and 0.001 in c2–c11. The spectra of the adhesive are re-scaled to a quarter in a, one-tenth in b1, and one-hundredth in c1 for clarityBack to article page