Fig. 9.
Images of a spearhead-like particle prepared by focused ion beam milling. False-color NanoSIMS images of the 16O− (A), 18O− (B), and FeO− (C) composition of one of the spearhead-like magnetite particles milled in half by the FIB. Bright colors (white or yellow) indicate higher amounts of the measured oxygen isotopes or iron oxide. The SEM image (D) shows the copper grid with two spearhead-like particles mounted with tungsten to the grid. The analyses were performed on the particle outlined by the circle.