NanoSIMS study of the 30 × 30 μm site at the surface of organo-mineral association in combination with SEM-SE/EDX and optical microscopy in reflected light. ROIs – selected regions of interest with different correlations between ions. Optical microscopy initially suggested close links between OM and Fe species. Nitrogen rich OM (higher 12C14N− counts) is more frequently directly colocalized with other mineral compounds, mainly containing aluminum (seen at the NanoSIMS 27Al16O−/12C14N− composite image and ROI 1 ion spectra). Rough and flaky patterns seen in SEM-SE in vicinities of ROIs 1–3 are indicative of clay particles, and these regions are enriched in 12C14N− and 32S−.