Secondary ion mass spectrometry measurements of silver isotope ratios in gold‐bearing minerals

Abstract

An ion microprobe unit was used to study silver isotope ratios in gold-bearing ores. It was found that for ores formed under high-temperature conditions the light isotope '''Ag is enriched. Low-temperature deposits are enriched in the heavy isotope 'wAg.The Cameca IMS-4f ion microprobe unit has been utilized for the analysis of '09Ag/'07Ag ratios in goldbearing minerals. The samples of ores and rocks studied represent various genetic types of Precambrian and Phanerozoic deposits that have recently been discovered in the Ukraine. Studies of silver isotopic ratios have yielded an interesting result: for the deposits formed under high-temperature conditions, enrichment of the light silver isotope was observed in gold specimens whereas low-temperature deposits were mainly characterized by heavy isotope enrichment. The differences in the values of light silver-isotope content in the surface layer and the main body allowed us to visualize the oxidation degree of gold grains in gold-bearing deposits and sources of their formation. The present paper is devoted to the investigation of gold-bearing minerals using the secondary ion mass spectrometry (SIMS) technique and the investigation of the possibility of using SIMS mass spectra for measurement of ion energy distributions, for isotopic analysis and to obtain images of element distribution over the surface in a single experiment. These are of importance for closer studies of the processes in question and for better understanding of the secondary ion formation mechanism.Demand for gold in recent years has led to a sharp rise in geological prospecting. At the same time, prospecting remains ineffective, owing to the use of procedures that do not allow unequivocal inferences about the prospects of a given geological area to be drawn. The reason is that the formation of deposits is extremely complicated. Processes that result in the localization of ore material are, as a rule, extended in space and time , and have a multistage character determined by the interaction of endogenic and exogenic factors. Geochemical investigation techniques, particularly studies of the ratios of isotopes of elements that are components of the ore bodies, hold much promise for understanding this complex pattern.' To this end, extensive use is now made of the isotopy of oxygen, sulphur, carbon, hydrogen, strontium, lead, neodymium and other elements. The SIMS technique provides a way of extending significantly the range of elements under investigation and improving the quality of prospecting,' by providing the unique capability of in situ isotopic measurements with lateral resolutions of <1 pm and minimal sample consumption. The method is of particular efficiency for constructing genetic geochemical models that serve as a theoretical basis for development of new prospecting criteria. Samples of ores and rocks from deposits and ore manifestations in the Ukraine (the Middle Near-Dnieper region, the Carpathians, the Donets Basin) were selected for investigation. These samples represent various genetic...

The Isotopic Composition of Silver in Ore Minerals

“…The first published measurements of Ag isotopic ratios on samples from ore deposits (four deposits in Russia) were by Didenko (1995) using secondary ion mass spectrometry (SIMS). With a precision of ~1–2‰, SIMS results are imprecise compared to those measured with current multicollector inductively coupled plasma mass spectrometric (MC‐ICP‐MS) techniques, and are not discussed further.…”

Ion Microprobe Silver Isotopic Analysis in Native Silver

“…Positive secondary ions of Ag were analyzed. Ag isotopic compositions were measured with a precision of 1ø, depending on the number of 109 Ag þ / 107 Ag þ ratio [8][9][10][11] measurements made. Chemically pure silver was used as a standard.…”

“…Palladin, 03142, Kyiv, Ukraine; E-mail: center@radgeo.freenet.kiev.ua. [8][9][10][11] The hydrothermal process is one of the most important processes of concentrating silver in nature. The isotopes of light elements such as O, C, N, S, and H are widely used for this purpose.…”