Figure S2. Magnetic mineralogy tests for representing samples. (A) and (B) Vibrating Sample Magnetometer (VSM) hysteresis loops. The raw data (red curves in the small boxes) indicates the dominancy of paramagnetic minerals (positive slope) and negligible contribution of ferromagnetic minerals (linear slop). The slope-corrected data (blue curves) indicates the presence of low-coercivity ferromagnetic minerals. (C) and (D) Alternating Field demagnetization curves (AF curves). The samples were first magnetized by AC field of 100 mT and DC field of 500 T and then demagnetized in 5 mT steps. The curves indicate that most of the magnetic remanence (up to 90%) is lost by a demagnetization field of 60 mT, suggesting that mostly low-coercivity minerals carry the remanent magnetization. (E) and (F) Temperature‐dependent susceptibility curves (k(T)). The susceptibility changes during heating (red curves) indicate slight variations, suggesting negligible contribution of ferromagnetic minerals. The cooling curves (blue) indicate substantial susceptibility increase at ~580 °C, suggesting the formation of magnetite.