EFFECTIVE USE OF A LOW-COST SPIRAL PANNING MACHINE FOR ZIRCON SEPARATION

Much of the geology of the southern Appalachians has been mapped at the regional scale, but geochemical data constraining the age and tectonic setting of igneous rocks within the region has been slow to develop, especially within the southern Appalachians of Georgia and Alabama. This is due in part to the labor intensive and time consuming techniques involved, as well as the expense of materials and equipment (e.g. jaw crusher, pulverizer, magnetic separator) necessary for mineral separation prior to radiometric and trace element analysis, which is typically only available at research institutions. Although partial grain size reduction of rock samples can be achieved with hand tools (i.e. hammer) and powerful, but inexpensive rare earth magnets can be used to separate magnetic mineral fractions from pulverized samples, initial hydraulic separation in water using simple methods (e.g. decanting) is highly inefficient at separating low density mineral phases (e.g. quartz and feldspar) from high density phases (e.g. zircon) prior to final heavy liquid separation. Although utilized primarily in small volume gold panning operations, here we used an inexpensive spiral panner (<$500) as an alternative to a more expensive (>$5K) shake table (e.g. Wilfley) to concentrate high density accessory minerals such as zircon. In a series of tests in which prepared mixtures of zircon, staurolite, and quartz were run through the spiral panner at varying inclinations and rotational speeds, we are able to show that not only is the technique more effective than simple decanting, but were able to optimize the panner to achieve maximum concentration of zircon in our prepared mixture. Over a series of 15 trials, an inclination of ~30⁰ for the bowl at a rotational velocity of ~11 rpm produced the greatest separation of low and high density minerals. Development of an efficient and inexpensive mineral separation technique would vastly improve the ability for researchers at smaller institutions to effectively concentrate mineral phases such as zircon and baddeleyite in preparation for subsequent geochemical analysis, effectively allowing for development of zircon ‘libraries’. As a follow-up to this work, we will also compare the effectiveness of the spiral panner to a traditional water shake table.