SAGEBRUSH AS A SAMPLING MEDIUM FOR GOLD EXPLORATION IN THE GREAT-BASIN - EVALUATION FROM A GREENHOUSE STUDY

Seedlings of basin big sagebrush (Artemisia tridentata subsp. tridenta ta) germinated from seed collected near Preble, Nevada were grown in s oils containing Carlin-type disseminated gold ore from Pinson and Getc hell, Nevada. After 4 months growth in a greenhouse, leaves, twigs and stems for each plant were combined and analyzed by instrumental neutr on activation analysis (INAA) for the Carlin suite of elements which i ncludes gold, arsenic, antimony and tungsten. Plants grown in soils co ntaining Carlin ore did not accumulate significantly more gold than th ose 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. O n the other hand, sagebrush grown in soils containing Carlin ores accu mulated significantly more arsenic and antimony compared to those grow n in control soils (p > 0.95). Mean arsenic in experimental plants var ied from 4.4 to 6.4 mu g/g (ppm) compared to 0.4 mu g/g in control pla nts. Experimental plants contained 0.2 mu g/g (ppm) antimony compared to 0.03 mu g/g in control plants. Results suggest that sagebrush would be a good prospecting medium for detecting concealed Carlin-type depo sits in the Great Basin if arsenic and antimony are used as the pathfi nder elements. Results also suggest that true gold anomalies in sagebr ush will be more difficult to separate from aeolian contamination than those for arsenic and antimony in arid environments. Based on this gr eenhouse study, optimum anomaly-to-background contrast would be obtain ed from combined arsenic and antimony content of stems or twigs stripp ed of bark. Leaves would be less likely to show anomalies because surf ace tissue cannot be adequately cleaned or stripped.