Determination of hematite contributions to sedimentary magnetizations is an important but difficult task in quantitative environmental studies. The poorly crystalline and fine-grained nature of hematite nanoparticles makes quantification of their concentrations in natural environments challenging using mineralogical and spectroscopic methods, while the weak magnetization of hematite and often significant superparamagnetic nanoparticle concentrations make quantification difficult using magnetic remanence measurements. We demonstrate here that much-used magnetic parameters, such as the S-ratio and ‘hard’ isothermal remanent magnetization (HIRM), tend to significantly underestimate relative and absolute hematite contents, respectively. Unmixing of isothermal remanent magnetization (IRM) acquisition curves is among the more suitable approaches for defining magnetic mineral contributions, although it has under-appreciated uncertainties that limit hematite quantification. Diffuse reflectance spectroscopy and other methods can enable relative hematite and goethite content quantification under some conditions. Combined use of magnetic, mineralogical, and spectroscopic approaches provides valuable cross-checks on estimated hematite contents; such an integrated approach is recommended here. Further work is also needed to rise to the challenge of developing improved methods for hematite quantification.

中文翻译：

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沉积磁性中的赤铁矿（α -Fe ₂ O ₃）定量：现有代理的局限性和前进的方向

在定量环境研究中，确定赤铁矿对沉积磁化的贡献是一项重要但艰巨的任务。赤铁矿纳米颗粒的结晶性差且细颗粒性质，使其在自然环境中的浓度定量难以使用矿物学和光谱学方法，而赤铁矿的弱磁化强度和通常显着的超顺磁性纳米颗粒浓度使得使用剩磁测量难以定量。我们在这里证明了常用的磁参数，例如S比率和“硬”等温剩余磁化强度（HIRM），往往会分别大大低估相对和绝对赤铁矿的含量。等温剩余磁化（IRM）采集曲线的不混合是定义磁性矿物成分的更合适方法之一，尽管它具有不确定的不确定性，限制了赤铁矿的定量。在某些条件下，漫反射光谱法和其他方法可以实现相对赤铁矿和针铁矿含量的定量。结合使用磁学，矿物学和光谱学方法可以对估计的赤铁矿含量进行有价值的交叉核对；在这里推荐这种综合方法。还需要进一步的工作来应对开发改进的赤铁矿定量方法的挑战。在某些条件下，漫反射光谱法和其他方法可以实现相对赤铁矿和针铁矿含量的定量。结合使用磁学，矿物学和光谱学方法可以对估计的赤铁矿含量进行有价值的交叉核对；在这里推荐这种综合方法。还需要进一步的工作来应对开发改进的赤铁矿定量方法的挑战。在某些条件下，漫反射光谱法和其他方法可以实现相对赤铁矿和针铁矿含量的定量。结合使用磁学，矿物学和光谱学方法可以对估计的赤铁矿含量进行有价值的交叉核对；在这里推荐这种综合方法。还需要进一步的工作来应对开发改进的赤铁矿定量方法的挑战。