Automated and simultaneous in-situ determination of trace element concentrations, Lu–Hf isotopes and U–Pb ages in zircon at high spatial resolution by laser ablation split-stream technology

Abstract

Zircon, a ubiquitous accessory silicate enriched in trace elements (e.g., rare-earth elements, Th, U, and Hf), is widely utilized for in situ U–Pb geochronology and trace-element and isotopic analyses. Here, we present a novel laser-ablation split-stream (LASS) technique enabling simultaneous, automated determination of zircon U–Pb ages, trace-element concentrations, and Hf isotopic compositions at a spatial resolution of 29 µm. This method integrates a laser ablation system with both multi-collector (MC) and quadrupole (Q) inductively coupled plasma mass spectrometers (ICP-MS). Key innovations include optimized gas transfer lines (4 mm and 2.5 mm inner diameters) that ensure stable aerosol splitting without additional mass flow controllers (MFCs) and the introduction of trace water vapor to enhance uranium sensitivity (∼70% increase) while suppressing oxide formation (<1%) during Q-ICP-MS analysis. Data were automatically processed using the built-in “3D Trace Elements DRS”, “U–Pb Geochronology DRS”, and a custom-designed “Hf isotope_LCG DRS” in IOLITE software. Validation against well-characterized reference zircons (91500, Qinghu, Plešovice, Penglai, Tanz, and MUNZirc) and glass standards (NIST SRM 610, USGS BHVO-2G, and BCR-2G) demonstrated high accuracy: trace-element concentrations, U–Pb ages, and Hf isotopic ratios deviated by <20%, <1%, and <2ε units from recommended values, respectively. The method's precision, operational efficiency, and applicability to high-spatial-resolution analyses (spot sizes down to 29 µm) underscore its potential for advancing integrated geochronological and petrogenetic studies.