The location of Mn and Fe in axinite–(Fe) from Nandan, China determined by anomalous X–ray scattering (AXS)

Abstract

The distribution of Mn and Fe in axinite–(Fe) from Nandan, China, with the structural formula Ca₂(Fe_0.565Mn_0.33Mg_0.08Ca_0.025)(Al_1.94Fe_0.06)Si₄BO₁₅(OH), Z = 2, space group P1, a = 7.1488(4) Å, b = 9.1970(4) Å, c = 8.9688(3) Å, α = 91.708(6)°, β = 98.099(6)°, and γ = 77.201(5)°, was determined by anomalous X–ray scattering measurements at Mn and Fe K–absorption edges. The elemental distribution map of Mn obtained by AXS analysis indicates the residence of Mn at the Y site. Conversely, the elemental map of Fe shows the location of Fe at both the Y and Z 1 sites. XANES analysis clarifies the progressive incorporation of Fe³⁺ with decreasing Al content in axinite–(Fe). These experimental results readily suggest the substitution of Al³⁺ by Fe³⁺ at the Z 1 site.