Simultaneous determination of Sm–Nd isotopes, trace-element compositions and U–Pb ages of titanite using a laser-ablation split-stream technique with the addition of water vapor

Abstract

Titanite is a widespread accessory nesosilicate with high trace-element contents including rare-earth elements, Th, and U, and is thus suitable for in situ isotopic and trace-element analyses and U–Pb dating. Here we describe a laser-ablation split-stream technique for simultaneously determining Sm–Nd isotopes, trace-element compositions and U–Pb ages in titanite. A laser ablation system was connected to multi-collector (MC) and sector field (SF) inductively coupled plasma–mass spectrometry (ICP–MS) systems. The laser-ablated aerosol was split into two gas streams and transported simultaneously to the MC–ICP–MS system for Sm–Nd isotope analysis and to the SF–ICP–MS system for trace-element analysis and U–Pb dating. A small flow of water vapor was introduced to the gas stream after the LA chamber to improve the sensitivity of Nd (by 40%) on MC–ICP–MS and to maintain oxide yields at low levels for SF–ICP–MS trace-element analyses. Three well-constrained reference titanite standards (T3, OLT1, and Ontario) were analysed to evaluate precision and accuracy. Resulting Sm–Nd isotopic and trace-element compositions and U–Pb ages were consistent with recommended values. The method was applied in simultaneously determining Sm–Nd isotopes, trace-element compositions and U–Pb ages for titanite from the Manjinggou marble of the North China Craton.