Cr Valence States (IMAGE)

Science China Press

Cr Valence States

Caption

The curves show the normalized XANES spectra of the Cr(VI) standard K2CrO4, the Cr(III) standard Cr(OH)3, the Cr(III) standard CuCr2O4, Ediacaran carbonate WJ705.6 (~0.63 Ga) and 12JLW44 (~0.56 Ga), Triassic carbonate XK127 (~0.25 Ga), Carboniferous carbonate BCS-CRM513 (~0.35 Ga), Quaternary carbonate 1460A26F1W110/116 (~0.83 Ma), and Mid-Proterozoic carbonate J1-52.6 (~1.44 Ga). There is no prominent peak at pre-edge region of the spectra of all the carbonate samples, suggesting that Cr(III) dominates in the natural carbonates.

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