Analytical methods used in geochemical exploration, 1984

Abstract

Geologic materials are decomposed by a mixture of aqua regia and hydrofluoric acid. Arsenic is reduced to the trivalent state with potassium iodide. Interferences are minimized by the addition of SUMMARY Interferences commonly encountered in the determination of bismuth, cadmium, copper, lead, silver, and zinc at crustal abundance levels are effectively eliminated using a rapid, sensitive, organic extraction method. A potassium chloratehydrochloric acid digestion solubilizes the metals not tightly bound in the silicate lattice of rock, soil, and stream-sediment samples. The six metals are selectively extracted into an organic phase of 10 percent tricaprylylmethylammonium chloridemethyl isobutyl ketone in the presence of ascorbic acid and potassium iodide.Metals in the organic extract are determined by flame atomic absorption spectrometry to the 0.05 ppm level for cadmium and silver and to the 1. 0 ppm level for bismuth, copper, lead, and zinc. About 40 samples can be analyzed per day for the six metals. If only selected metals are determined, more samples can be analyzed.

Mineral resources of the Aubrey Peak Wilderness Study Area, Mohave County, Arizona

“…In addition, rock and stream-sediment samples were analyzed for certain elements by more sensitive methods. These elements and methods are as follows: arsenic, antimony, bismuth, cadmium, and zinc by inductively coupled plasma-atomic emission spectrometry (Crock and others, 1987); gold, tellurium, and thallium by electrothermal atomic-absorption spectroscopy (Hubert and Chao, 1985); and uranium by a fluorometric method (O'Leary and Meier, 1984). These analyses were used to identify drainages with anomalous concentrations of minor elements.…”

Mineral resources of the Medicine Lodge, Alkali Creek, and Trapper Creek Wilderness Study Areas, Big Horn County, Wyoming

“…No additional analyses were made on the nonmagnetic heavy-mineral concentrates due to the limited amount of sample material. The stream-sediment samples and rock samples were also analyzed for arsenic, bismuth, cadmium, and zinc using an inductively coupled argon plasma-atomic emission spectrograph (Crock and others, 1987); uranium was analyzed using fluorimetry (O'Leary and Meier, 1984). The mineralogy of the rock samples was determined by X-ray diffraction to determine the presence of any ore-forming minerals and to compare the results with the chemical analyses.…”

Gold in big sagebrush (Artemisia tridentata Nutt) as an exploration tool, Gold Run District, Humboldt County, Nevada

“…About 20 g of the homogenized ground material were then ashed by dry ignition in an electric muffle furnace at about 450 C for 24 h. This amount of dry material yielded the 500 mg of ash needed for the analyses of Au by graphite furnace atomic absorption spectrometry (O'Leary and Meier, 1984), and 250 mg of ash for nine ore-related elements~Ag, As, Bi, Cu, Cd, Mo, Pb, Sb, and Mo by flame atomic absorption (O'Leary and Viets, 1986). Selenium analyses of pulverized samples from only traverse C were done by fluorometry, after acid digestion of 1 g of dry material (Harms and Ward, 1975).…”