Femtosecond laser ablation-ICP-mass spectrometry and CHNS elemental analyzer reveal trace element characteristics of Danburite from Mexico, Tanzania, and Vietnam

Danburite is a calcium borosilicate that forms within the transition zones of metacarbonates and pegmatites as a late magmatic accessory mineral. We present here trace element contents obtained by femtosecond laser ablation-inductively coupled plasma (ICP)-mass spectrometry for danburite from Mexico, Tanzania, and Vietnam. The Tanzanian and Vietnamese samples show high concentrations of rare earth elements (∑REEs 1900 µg∙g⁻¹ and 1100 µg∙g⁻¹, respectively), whereas Mexican samples are depleted in REEs (<1.1 µg∙g⁻¹). Other traces include Al, Sr, and Be, with Al and Sr dominating in Mexican samples (325 and 1611 µg∙g⁻¹, respectively). Volatile elements, analyzed using a CHNS elemental analyzer, reach <3000 µg∙g⁻¹. Sr and Al are incorporated following Ca²⁺ = Sr²⁺ and 2 B³⁺ + 3 O²⁻ = Al³⁺ + 3 OH⁻ + □ (vacancy). REEs replace Ca2+ with a coupled substitution of B3+ by Be2+. Cerium is assumed to be present as Ce4+ in Tanzanian samples based on the observed Be/REE molar ratio of 1.5:1 following 2 Ca2+ + 3 B³⁺ = Ce⁴⁺ + REE³⁺ + 3 Be²⁺. In Vietnamese samples, Ce is present as Ce³⁺ seen in a Be/REE molar ratio of 1:1, indicating a substitution of Ca²⁺ + B³⁺ = REE³⁺ + Be²⁺. Our results imply that the trace elements of danburite reflect different involvement of metacarbonates and pegmatites among the different locations.