Numerical unmixing of weakly and strongly magnetic minerals: examples with synthetic mixtures of magnetite and hematite

Application of anisotropy of magnetic susceptibility to construct the palaeocurrent direction using slender fossil orientations

“…Most curves also demonstrate a smaller decline between 585 and 690 C (usually less than 5%-10%), indicating that haematite also is a contributor as well (Dunlop & Ozdemir, 1997;Liu et al, 2019). In addition, a rise in MS in the heating curve between room temperature and 300 C, followed by a decrease between 300 and 500 C, may indicate Ti fraction variation in titanomagnetite (Gilder & Legoff, 2005).…”

“…The χ ‐ T curves show Curie temperature behaviour with a primary decrease of χ between 400 and 585°C during heating (Figure 3), a characteristic of magnetite/maghemite, which is the dominant contributor to χ in all samples (Dunlop & Ozdemir, 1997). Most curves also demonstrate a smaller decline between 585 and 690°C (usually less than 5%–10%), indicating that haematite also is a contributor as well (Dunlop & Ozdemir, 1997; Liu et al, 2019). In addition, a rise in MS in the heating curve between room temperature and 300°C, followed by a decrease between 300 and 500°C, may indicate Ti fraction variation in titanomagnetite (Gilder & Legoff, 2005).…”

Authigenic Ferrimagnetic Iron Sulfide Preservation Due to Nonsteady State Diagenesis: A Perspective From Perseverance Drift, Northwestern Weddell Sea

“…We note that the 206 cmbsf has differences from past examples of pyrrhotite interpreted to be present in diagenetic sediments (e.g., Horng, 2018; Kars & Kodama, 2015; Larrasoaña et al., 2007), which we attribute to the mixture of detrital and authigenic minerals in the sample. While hematite could also explain the high coercivities (Roberts et al., 2006), this would require a high weight percentage of hematite relative to the lower coercivity phases, which is inconsistent with no apparent decrease ∼670°C in the high temperature χ lf curves (Carvallo et al., 2006; Liu et al., 2019).…”

Rock Magnetic Signature of Heterogeneities Across an Intraplate Basal Contact: An Example From the Northern Apennines

“…We applied the cumulative log‐Gaussian function by the online software MAX UnMix (Maxbauer et al., 2016) to discriminate magnetic components based on their mean remanence coercivity (Bh) and the dispersion parameter (DP) (Heslop et al., 2002; Kruiver et al., 2001). In addition, we calculated the remanence ratios (S‐ratios) which are proxies of the relative contribution of high‐versus low‐coercivity minerals (King & Channell, 1991; Liu et al., 2019; Thompson & Oldfield, 1986). Variations in the ratio can be associated with several causes, such as lithological changes, diagenetic processes (Bloemendal et al., 1992) or changes in the magnetic properties of rocks induced by deformation, frictional heating and/or fluid‐rock interaction in slip zones (Chou et al., 2012; Yang et al., 2020).…”