Seven samples of hydrothermal quartz displaying textures suggestive of vein formation in an epithermal environment were collected from quartz veins at two sites on north-eastern Eyre Peninsula. A combined fluid inclusion and oxygen-isotope study was initiated to determine the characteristics of the fluid sources involved in vein formation. Five samples were collected from a quarry excavation on the 23-Mile quartz deposit, which is situated on the Pankalla Fault, and two samples were collected from vein material from the Parkinson Dam Au-Ag prospect. 100 micron thickness thin-sections were prepared on four quartz samples, to use for fluid inclusion observational analyses to determine the temperature at which the veins formed; this work was necessary to do prior to proceeding to oxygen isotope analysis. The data obtained from laboratory step heating of the fluid inclusions showed that their trapped fluid homogenisation temperatures have ranges in excess of 100 °C (collective Th = 148 to 308 °C). The wide range of these measured temperatures indicates that the chemical compositions of the fluid inclusions have been modified since entrapment. As a result, making further freezing measurements on these samples was not recommended by the analytical contractor. The inability to accurately determine the temperature of vein formation means that the appropriate related fractionation factor, a value necessary to know to correct for the effect of mass dependent fractionation of the oxygen-isotopic system, could not be determined, and so any derived O-isotope measurements if made would be equally unreliable. As a result, the anticipated oxygen isotope analyses did not proceed.