Exploration of a Combined LIBS and LA-ICP-MS Approach for Apatite Characterisation

Abstract

A combined laser-induced breakdown spectroscopy (LIBS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) method is demonstrated for comprehensive apatite analysis. These measurements provide elemental imaging that can be used as a screening technique for chemical selection of grains for subsequent analysis (e.g., U-Pb geochronology) or can be used to understand elemental distributions within a single grain that would have direct textural-chemical implications (e.g., zoning patterns). Adding LIBS as a simultaneous measurement, to LA-ICP-MS U-Pb geochronology, allowed for the direct determination of F (H and O show promise for future applications) in addition to major and trace elements of interest. The quantitative measurements were validated against a series of apatites with known values and used to characterise a wide range of samples. Fluorine detection limits were determined to be as low as 70 μg g^-1 F (broadband CMOS detector) and 4.2 μg g^-1 F (ICCD detector). U-Pb age dating was simultaneously collected by LA-ICP-MS with the quantitative elemental data from LIBS, providing a comprehensive method for geochronology.