TRACE-ELEMENT DETERMINATION OF SINGLE FLUID INCLUSIONS IN QUARTZ BY LASER-ABLATION ICP-MS

Single fluid inclusions in quartz from a Pb-Zn-Ag carbonate replacemen t deposit were selected for trace element determination by laser ablat ion ICP-MS. Spikes in element intensities were noted between first bre ached fluids versus subsequent analyses, suggesting that accurate elem ent concentrations may not be determined in smaller fluid inclusions w hen only one analysis is obtained before the fluid is exhausted. Eleme ntal concentrations in the fluid inclusions were determined by externa l standardisation using solutions sealed in microcapillary tubes. Stan dards and single natural inclusion analyses give repeatabilities (%RSD ) of similar to 20% for Rb and Sr. Rubidium and strontium concentratio ns range from 0.56-5.07 mu g ml(-1) and 1.12-27.4 mu g ml(-1), respect ively, whereas Zn and Ag are below detection limits (< 10 ng ml(-1)). The results suggest that nearly all Zn and Ag are removed by the time hydrothermal fluids precipitate gangue minerals.