Fe isotope data of Xuancheng reticulated red clay

Description

The Fe/Al ratios of the red matrix range from 0.54 to 1.49 (mean = 0.85), substantially higher than those of the white reticular veins, which ranges from 0.13 to 0.53 (mean = 0.27). With decreasing reticulation intensity, Fe/Al decreases in the red matrix but increases in the white reticular veins, resulting in a progressively smaller contrast between the two domains. At 0.5 m depth, their Fe/Al ratios become nearly indistinguishable. The δ56Fe values of the red matrix range from -0.05‰ to 0.21‰ (mean = 0.00‰), whereas those of the white reticular veins range from 0.08‰ to 0.48‰ (mean = 0.33‰). With decreasing reticulation intensity, δ56Fe of the red matrix increases slightly, whereas that of the white r reticular veins decreases markedly. Consequently, the isotopic contrast between the two domains progressively diminishes upward, with their δ56Fe values approaching the average upper continental crust value of 0.09‰ at 0.5 m depth . TOC ranges from 0.07% to 0.19% in the red matrix (mean = 0.10%) and from 0.04% to 0.23% in the white reticular veins (mean = 0.10%). TOC becomes increasingly heterogeneous with the development of reticulation. However, strongly reticulated horizons are characterized by relatively low TOC contents in the white reticular veins, whereas weakly reticulated horizons show relatively lower TOC contents in the red matrix. The δ13Corg values of the red matrix range from -26.0‰ to -19.6‰ (mean = -24.2‰), whereas those of the white reticular veins range from -26.0‰ to -19.1‰ (mean = -24.6‰). With increasing reticulation intensity, δ13Corg values of both domains generally decrease. In weakly reticulated horizons, the red matrix and white reticular veins show comparable δ13Corg values, whereas in strongly reticulated horizons, the white reticular vein is characterized by δ13Corg values approximately 0.8‰ lower than those of the red matrix.

Institutions

• Northwest University

  Shaanxi, Xi'an

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