Program > Browse abstracts by speaker > Salazar-Naranjo Andrés Fabián

Mineral-melt partition coefficients (Di), primarily determined through equilibrium experiments, are essential for understanding magma origin and evolution from trace elements (TE). This study presents preliminary TE partitioning data between olivine and alkali melts, derived from crystallization experiments on basanite and tephrite at 1-atm [1]. The experiments were performed using a high-temperature vertical furnace coupled with a CO/CO₂ gas mixing system to control the oxygen fugacity (fO₂). Temperatures varied from 1200 to 1000°C, with a cooling rate of 60°C/h, and fO₂ was maintained at five conditions within two log units above and below the quartz-fayalite-magnetite (QFM) buffer. Results indicate olivine crystallization in all basanite experiments, displaying polyhedral/tabular morphologies. In contrast, olivine crystallized from tephrite only under reduced conditions, exhibiting tabular/skeletal textures. Compositionally, olivine from basanite showed cores with Fo of 89 and tinny rims ranging from Fo 87 to 82. Tephrite-derived olivine displayed non-zoned, evolved compositions, ranging from Fo 73 to 60. TE concentrations were determined via LA-ICP-MS. Based on their Di, elements are categorized as follows: compatible (Di > 1): Ni, Zn, Co, Mn, Cr; slightly incompatible (0.1 ≤ Di ≤ 1): Li, Cu, Sc, Ti; moderately incompatible (0.01 ≤ Di≤ 0.1): Ca, Al, HREE, V, Hf; highly incompatible (Di ≤ 0.001): Na, Sr, Ba, LREE, Zr. Di for trivalent cations (Al, Sc, HREE, excluding Cr) were accurately modeled by the lattice strain model [2]. The parameters, r0 and D0, closely approximated the values obtained for Sc. Contrary to previous works [3], Cr partitioning displayed a dependence on fO₂: Cr was more compatible under reducing conditions (QFM-2) and less compatible under oxidizing conditions (QFM+2). The same behavior is depicted by the V.

References: [1] Salazar-Naranjo & Vlach (2023) J. Petrol. 64 (11), [2] Blundy and Wood (1994) Nature 352, [3] Mallmann & O'Neill (2009) J. Petrol. 50.

Funding: FAPESP Project 2019/22084-8 and Novos Docentes/USP/2023.