Sagebrush as a sampling medium for gold exploration in the Great Basin — evaluation from a greenhouse study

Abstract

Seedlings of hasin big sagebrush ( Artemisia tridentata subsp. tridentata) germinated from seed collected near Preble, Nevada were grown in soils containing Carlin-type disseminated gold ore from Pinson and Getchell, Nevada. After 4 months growth in a greenhouse, leaves, twigs and stems for each plant were combined and analyzed by instrumental neutron activation analysis (INAA) for the Carlin suite of elements which includes gold, arsenic, antimony and tungsten. Plants grown in soils containing Carlin ore did not accumulate significantly more gold than those growing in control soil ( p < 0.05). Gold measured in experimental plants averaged 0.9–2.6 ng/g (ppb) compared to 1.6 ng/g in controls. On the other hand, sagebrush grown in soils containing Carlin ores accumulated significantly more arsenic and antimony compared to those grown in control soils ( p > 0.95). Mean arsenic in experimental plants varied from 4.4 to 6.4 μg/g (ppm) compared to 0.4 μg/g in control plants. Experimental plants contained 0.2 μg/g (ppm) antimony compared to 0.03 μg/g in control plants. Results suggest that sagebrush would be a good prospecting medium for detecting concealed Carlin-type deposits in the Great Basin if arsenic and antimony are used as the pathfinder elements. Results also suggest that true gold anomalies in sagebrush will be more difficult to separate from aeolian contamination than those for arsenic and antimony in arid environments. Based on this greenhouse study, optimum anomaly-to-background contrast would be obtained from combined arsenic and antimony content of stems or twigs stripped of bark. Leaves would be less likely to show anomalies because surface tissue cannot be adequately cleaned or stripped.