Fig. 7 | Nature Communications

Fig. 7

From: Multi-scale magnetic mapping of serpentinite carbonation

Fig. 7

Thin section magnetic anomaly measurements. a NRM and ARM (with the peak alternating field of 260 mT and the DC bias field of 100 μΤ) in 30 µm-thickness thin sections of serpentinite, soapstone and two listvenite samples acquired by SQUID microscopy. The samples are mounted on 1-inch discs. Shown is the total magnetic field at a height of 170 µm above the samples. For comparison, the SQUID images are presented with the color scale of 0–2 µT (Note the grains in the serpentinite and soapstone samples are mostly >2 µT). Listvenite samples show significantly weaker magnetic signal strength compared to serpentinite and particularly soapstone. Relict magnetite grains in the listvenite are mostly present as inclusions in magnesite cores and hence passivated from reaction during listvenite formation. b Schematic of changes in magnetite abundance and predicted magnetic field strength changes versus reaction progress of ultramafic rock serpentinization43 and carbonation. Magnetic susceptibility values are based on Maffione et al.43 and may differ in other alteration settings depending on rock composition and alteration temperature. Diamond symbols show the calculated bulk rock content of magnetite in the different alteration zones assuming bulk rock Fe3+ is exclusively present in magnetite (Supplementary Table 1). Error bars denote the 1σ standard deviation of averaged bulk Fe3+ weight fractions

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