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Study of trace element zonation in vent chimneys from the Silurian Yaman-Kasy volcanic-hosted massive sulfide deposit (Southern Urals, Russia) using Laser Ablation-Inductively Coupled PlasmaMass Spectrometry (LA-ICPMS)
Maslennikov, VV and Maslennikova, SP and Large, RR and Danyushevsky, LV (2009) Study of trace element zonation in vent chimneys from the Silurian Yaman-Kasy volcanic-hosted massive sulfide deposit (Southern Urals, Russia) using Laser Ablation-Inductively Coupled PlasmaMass Spectrometry (LA-ICPMS). Economic Geology, 104. pp. 1111-1141. ISSN 0361-0128
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Very well preserved fossil vent chimneys from the Silurian Yaman-Kasy volcanogenic-hosted massive sulfide
deposit in the Southern Urals range in decreasing temperatures from chalcopyrite-pyrite black smoker to sphalerite-
chalcopyrite-marcasite-pyrite gray smoker to sphalerite-quartz-barite white smoker assemblages. Laserablation
ICPMS analyses show systematic trace element distribution patterns across chimneys. Coarse-grained
layers of chalcopyrite in the central conduits are relatively high in Se and Sn but are low in other elements.
Chalcopyrite at the margins of such layers is enriched in Bi, Co, Au, Ag, Pb, Mo, Te, and As, which reside in
microinclusions of tellurides and/or sulfoarsenides. Sphalerite in the conduits and the outer chimney wall contains
elevated Sb, As, Pb, Co, Mn, U, and V. Antimony, As, and Pb reside in microinclusions of a galena-fahlore
assemblage, whereas the Co and Mn likely substitute for Zn2+ in the sphalerite structure. The highest concentrations
of most trace elements are found in colloform pyrite within the outer wall of the chimneys and likely
result from rapid precipitation under high- temperature-gradient conditions. The trace element concentrations
in the outer-wall colloform pyrite decrease in the following order, from the outer wall inward: Tl > Ag > Ni >
Mn > Co > As > Mo > Pb > Ba > V > Te > Sb > U > Au > Se > Sn > Bi, governed by the strong temperature
gradient. In contrast, pyrite in the high- to mid-temperature central conduits exhibit concentration of Se, Sn,
Bi, Te, and Au. The zone between the inner conduit and outer wall is characterized by recrystallization of colloform
pyrite to euhedral pyrite, which becomes depleted in all trace elements except Co, As and Se.
The mineralogical and trace element variations between chimneys are likely due to increasing fO2 and decreasing
temperature caused by mixing of hydrothermal fluids with cold oxygenated seawater. Average values
of Se (a high-temperature element) decrease in the order from black to gray to white smoker chimneys. The
medium-temperature association (Te, Bi, Co, Mo, and Au) is typically present in the gray smoker chimneys.
The white smoker chimneys are depleted in most elements except for Ag, Tl, Te, Sb, and As, probably due to
the dilution of the vent fluid by seawater which penetrates deeper parts of the hydrothermal system. U and V
are concentrated in the outer wall of most chimneys due to their extraction from seawater associated with the
more reduced fluids of black and gray smokers.
|Keywords:||VHMS, VMS, Pyrite, vent chimney, black smoker, gold, Tellurides|
|Journal or Publication Title:||Economic Geology|
|Page Range:||pp. 1111-1141|
© 2009 Society of Economic Geologists, Inc.
|Date Deposited:||12 Jul 2010 02:53|
|Last Modified:||18 Nov 2014 04:10|
|Item Statistics:||View statistics for this item|
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