Analysis of Trace Elements in Magnetites Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

In-situ microbeam analyses provide unique information about elements and isotopic composition of solid substances, which is extremely helpful in resolving problems in geology, the environment and industry. Trace element geochemistry of magnetite is useful for studying physical and chemical characteristics of ore-forming environments and targeting new deposits. Analysis methods using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) were established in this study and discussed in detail, including the selection of proper calibrating standards, the correct laser beam size and mass interference. For example, the trace element concentrations of magnetite from Ernest Henry IOCG deposit were obtained by LA-ICP-MS with NIST SRM 610 as the external standard and Fe as the internal standard. Under normal operation, beam sizes of 32-60 μm are good for magnetite analysis, however, smaller beam sizes (e.g 24 μm or 16 μm) are better for individual grains fine grains of magnetite. Isotopes of 49Ti, 65Cu and 118Sn were measured for their respective elements Ti, Cu and Sn, respectively, in order to eliminate mass spectrometry interference.