HEAVY MINERAL SEPARATION VIA SPIRAL PANNER: AN INEXPENSIVE, BUT EFFECTIVE ALTERNATIVE TO A TRADITIONAL SHAKE TABLE

Zircon is one of the more useful trace minerals for analysis of geologic settings and can provide insights into depositional and metamorphic ages, the magmatic evolution of silicic magmas, and the tectonic setting of zircon-bearing rocks. However, because zircon is an accessory mineral, most rock compositions contain at most a small fraction of zircon (<1% volume). Extraction of zircon from those rocks in which it is present is time consuming, expensive, and labor intensive. Since robust isotopic analyses often require 50-100 grains per sample analyzed, the facilities required for processing is generally limited to research institutions able to acquire the requisite equipment and personnel trained in these separation techniques. For this project, artificial and real samples have been hydraulically sorted for zircon using both an inexpensive (~$300) spiral panning machine and a more expensive (~$5,000) traditional water shake table in order to optimize zircon recovery, and to quantify and compare the effectiveness of each techniques. Artificial samples consisting of quartz and heavy mineral sands were processed via spiral panner and shake table under independent conditions in order to maximize recovery of zircon. Subsequently, utilizing optimal processing conditions for each, artificial samples were hydraulically sorted in both the spiral panner and shake table and compared against one another. For both the spiral panner and shake table, 80-95% of the heavy mineral fraction consisted of zircon, with the spiral panner recovering more zircon than the shake table over the same processing period. The spiral panner, additionally, was able to recover ~99% of the zircon in the artificial sample vs. ~67% zircon recovery for the shake table. Finally, developing lab techniques to optimize recovery of zircon using a shake table required more effort and training than those required to maximize recovery using the spiral panner. This work suggests an inexpensive spiral panner can be used to effectively concentrate zircon as an alternative to a more expensive shake table. Incorporation of spiral panner separation techniques in rock processing labs should result in both time and cost-savings when processing real rocks for heavy mineral separation.