Geochemical applications of the tandem LA-ICP-MS/LIBS analytical technique

Improvements in Laser Ablation for material sampling over the past few decades have led to the emergence of several applications of this in-situ technique to some important geochemical measurements. The technique is commonly used for both elemental [1] and isotopic analyses [2], and has multiple advantages compared to dissolution techniques, notably higher spatial resolution, easier and faster sample preparation, and for many applications a non-destructive method. A significant advantage of this technique in geochemistry is full characterization of a sample (e.g., glass or mineral) using a single spot of limited size (i.e., 20-80 μm) to eliminate or minimize complexities due to potential chemical zonations. Major advancement is being realized in the analysis of volcanic glasses for their elemental and volatile concentrations as well as zircon elemental and U-Pb isotopic compositions using a new approach that combines the capabilities of the two most common laser ablation modalities; LA-ICP-MS/LIBS, which stands for Laser Ablation Inductively Coupled Plasma Mass Spectrometry/Laser Induced Breakdown Spectroscopy. LIBS is based on direct measurement of the optical emission originating from the laser-induced plasma [3] whereas LA-ICP-MS involves transport and excitation of the ablated aerosol to a secondary source (ICP), before entering a mass spectrometer [4]. Analysis by these two techniques can complement each other quite well, as every laser pulse for ablation provides the optical plasma for emission spectroscopy and particles for ICP mass spectrometry. We will present data demonstrating that rare-earth element (REE) concentrations can be determined using LIBS in both zircon and volcanic glasses. In addition, we have promising, provisional hydrogen concentration data measured concurrently with the REE in volcanic glasses, which is not possible using only LA-ICP-MS.