LA-ICP-MS analyses of Fe-rich alloys: quantification of matrix effects for 193 nm excimer laser systems

The use of silicate calibrants for ns LA-ICP-MS analyses of Fe-based samples results in significant matrix effects. The magnitude of these effects, defined by the fractionation index or Fi, is a function of elemental volatility. Using the dependency of the Fi with elemental volatility a predictive model was developed to correct for these effects.

Composition of zircons from the Cornubian Batholith of SW England and comparison with zircons from other European Variscan rare-metal granites

Zircon from 14 representative granite samples of the late-Variscan Cornubian Batholith in SW England was analysed for W, P, As, Nb, Ta, Si, Ti, Zr, Hf, Th, U, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Al, Sc, Bi, Mn, Fe, Ca, Pb, Cu, S and F using electron probe microanalyses. Zircons from the biotite and tourmaline granites are poor in minor and trace elements, usually containing 1.0–1.5 wt.% HfO2, <0.5 wt.% UO2 and P2O5, <0.25 wt.% Y2O3, <0.2 wt.% Sc2O3 and Bi2O3 and <0.1 wt.% ThO2. Zircon from topaz granites from the St. Austell Pluton, Meldon Aplite and Megiliggar Rocks are slightly enriched in Hf (up to 4 wt.% HfO2), U (1– 3.5 wt.% UO2) and Sc (0.5–1 wt.% Sc2O3). Scarce metamictized zircon grains are somewhat enriched in Al, Ca, Fe and Mn. The decrease of the zircon Zr/Hf ratio, a reliable magma fractionation index, from 110–60 in the biotite granites to 30–10 in the most evolved topaz granites (Meldon Aplite and Megiliggar Rocks), supports a comagmatic origin of the biotite and topaz granites via long-lasting fractionation of common peraluminous crustal magma. In comparison with other European rare-metal provinces, the overall contents of trace elements in Cornubian zircons are low and the Zr/Hf and U/Th ratios show lower degrees of fractionation of the parental melt.