ZIRCON AND APATITE SEPARATION USING A SPIRAL PANNING TABLE: EVALUATION OF TIME AND YIELD EFFICIENCY

Mineral separations concentrate the heavy minerals apatite and zircon necessary to accurately date rock samples, but current methods are time-consuming, toxic, expensive, and have unknown yield efficiencies. To evaluate and improve separation methods, I processed five, ~1.4 kg samples (hornblende-biotite tonalite, 65.47 wt % SiO­₂, 137 ppm Zr, 0.138 wt % P₂O₅, collected from the Mt. Stuart Batholith near Leavenworth, WA; expected yields per kg, calculated from CIPW-norm: 30 g zircon; 320 g apatite) with a new procedure using a spiral panning table (panner) to wash and pre-concentrate heavy minerals before magnetic, lithium polytungstate (LST) and methylene iodide (MEI) heavy liquid separations. The control sample (#3) was hand washed, separated magnetically, and processed with LST and MEI, resulting in 34 mg zircon and 155 mg apatite. Panner trial #1 used a fast sample feed rate (58.4 g/min) and slow rotation speed (13.7 rpm), resulting in 3.7 mg zircon and 1.0 mg apatite. Panner trial #2 used a slow sample feed rate (11.5 g/min), the same slow rotation speed as trial #1, and yielded 6.1 mg zircon and 6.0 mg apatite. Surfactant was used in panner trial #4 to cut surface tension along with a slow feed rate of 9.1 g/min and the same slow rotation speed as trial #1, yielding 6.9 mg zircon and 3.4 mg apatite. Last, panner trial #5 used a faster rotation speed (24.7 rpm) and a fast feed rate (36.2 g/min), which produced the highest yields: 13.2 mg zircon, 12.9 mg apatite. Compared with the expected yields (above), the yields from both control (~50% purity separates containing 34 mg zircon, 155 mg apatite) and panner trials (high-purity separates containing 3.7-13.2 mg zircon, 1.0-12.9 mg apatite) were much less, likely due to the loss of small grains and inclusions. The panner technique yielded 10x the concentration of zircon than the control, so toxic MEI would ideally not be needed to separate apatite from zircon in future projects, making this project’s protocol safer than current methods. The experimental process took ~7 hours per sample, compared to ~38 hours for the control. The greater speed, improved zircon concentration, and avoidance of toxic heavy liquids are significant advantages of the methods in this project similar to the larger, more expensive Gemeni table, and further development will improve recovery efficiency.