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Gold recycling and enrichment beneath volcanoes: A case study of Tolbachik, Kamchatka

Citation

Zelenski, M and Kamenetsky, VS and Hedenquist, J, Gold recycling and enrichment beneath volcanoes: A case study of Tolbachik, Kamchatka, Earth and Planetary Science Letters, 437 pp. 35-46. ISSN 0012-821X (2016) [Refereed Article]

Copyright Statement

2015 Elsevier B.V. All rights reserved.

DOI: doi:10.1016/j.epsl.2015.12.034

Abstract

Magmas supply metals to hydrothermal ore deposits, although typical arc basalts may be unable to produce a gold-rich ore-forming fluid, as such basalts rarely exceed 5 ppb Au. Consistent with this, the occurrence of native gold of magmatic origin is extremely rare, and only a few finds of micron-sized gold particles in unaltered basalts have been documented. Surprisingly, some lava flows and scoria cones of the historic basaltic eruptions of Tolbachik volcano (Kamchatka) are unusually gold-rich. Tolbachik basalts contain up to 11.6 ppb Au based on whole rock analyses, nuggets of gold (electrum) up to 900 μm in size and native gold droplets up to 200 μm, plus numerous vapor-deposited gold crystals within fumarolic incrustations and directly on surfaces of basaltic lapilli. Our results demonstrate that the gold nuggets in Tolbachik basalt are of hydrothermal origin and were physically scavenged from epithermal veins hosted by country rocks during intrusion of mafic magmas. Depending on the melt temperature and/or time span of the melt-rock interaction, gold was ejected by the erupting volcano either in the form of abraded nuggets or liquid droplets, or was fully assimilated (dissolved) into the shallow long-lived magma chamber to provide a 4-fold increase in gold content over background concentration of 2.7 ppb Au, characteristic of mafic volcanic rocks in Kamchatka. Upon the end of the eruption, the continued discharge of volcanic vapors enriched in gold deposited abundant crystals of gold on cooling lava and scoria. Similar to Tolbachik, recycling of metals from prior accumulations (ore deposits) in the shallow crust may take place in other long-lived magma reservoirs, thus upgrading the gold and other metal contents and contributing to the ore-forming potential of a magma.

Item Details

Item Type:Refereed Article
Keywords:volcano, eruption, native gold, epithermal veins, crustal assimilation, ore recycling
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
ID Code:107935
Year Published:2016
Web of Science® Times Cited:4
Deposited By:Earth Sciences
Deposited On:2016-03-31
Last Modified:2017-11-02
Downloads:0

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