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DETERMINATION OF MODES AND STRUCTURE OF GOLD AND SILVER OCCURRENCE IN HYPERGENE DEPOSITS BY ELECTRON PROBE MICROANALYSIS METHOD (EXEMPLIFIED BY LOOSE SEDIMENTS OF WATER CURRENTS OF THE DUKAT DEPOSIT)

AUTHOR/S: R. KRAVTSOVA, L. PAVLOVA
Sunday 1 August 2010 by Libadmin2010

10th International Multidisciplinary Scientific GeoConference - SGEM2010, www.sgem.org, SGEM2010 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 20-26, 2010, Vol. 1, 1-8 pp

ABSTRACT

This paper reports the results of electron probe x-ray microanalysis (EPMA) aimed at
identification of the modes of gold and silver occurrence in loose sediments of lithochemical
stream sediments (LSS) of the Dukat gold-silver deposit in northeastern
Russia. Modes of occurrence of major ore elements Ag and Au have been investigated
and their chemical composition has been identified.
The EPMA technique has been elaborated to measure the composition of stream
sediments (minerals) containing silver and gold using the microanalyzers JCXA-733
and JXA8200. To minimize the influence of temperature from an electron probe on an
analytical signal the stability of samples (minerals and mineral formations) effected by
an electron beam was studied and the best compromise conditions for excitation and
recording of the analytical signal were selected. The studies indicate that it is possible to
determine the element composition of hypergene silver- and gold-containing sediments
if the beam power density is in the range from 2.00 to 2.65 μW*μm–2. Metrological
characteristics of quantitative determinations of hypergene sediment by EPMA comply
with the “applied geochemistry” category of performance (category 2).
We found, that modes of Ag and Au occurrence in loose alluvial sediments of watercurrents,
draining the Dukat Au-Ag deposit are closely related to features in the
composition of the studied zones. The major elements both in alluvial sediments of LSS
and in Au-Ag ores are native Ag, its intermetallic compounds (electrum, kystelite),
sulfides (akantite, sternbergite) and silver sulfosalts (pyrargyrite). Fine-dispersed native
Au and the so-called invisible Au are mainly associated with Fe hydroxides and
corroded grains of sulfides (pyrite, chalcopyrite and Ag minerals).
In terms of the application the modes of Ag and Au occurrence in LSS are an effective
indicator of ore-formation belonging of the revealed anomalies and, hence, are an
additional criterion of their industrial importance. This indicator can be well applied at
all stages of forecast and prospecting both within and outside of the Northeast of Russia.

Keywords: modes of Au and Ag occurrence, litho-chemical stream sediments, EPMA

PAPER 2010/s01.1: DETERMINATION OF MODES AND STRUCTURE OF GOLD AND SILVER OCCURRENCE IN HYPERGENE DEPOSITS BY ELECTRON PROBE MICROANALYSIS METHOD (EXEMPLIFIED BY LOOSE SEDIMENTS OF WATER CURRENTS OF THE DUKAT DEPOSIT)

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