Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/42247
Title: Tellurium, magmatic fluids and orogenic gold: An early magmatic fluid pulse at Cononish gold deposit, Scotland?
Authors: Spence-Jones, Carl
Jenkin, Gawen R. T.
Boyce, Adrian J.
Hill, Nyree J.
Sangster, Christopher J. S.
First Published: 25-May-2018
Publisher: Elsevier
Citation: Ore Geology Reviews, 2018
Abstract: Significant tellurium enrichment occurs in many orogenic gold deposits but the factors causing this are little understood; some authors suggest this demands a magmatic input whereas others suggest it need not. Fractionation of Te from Se and S could offer insight into source/pathway processes of auriferous fluids. The metasedimentary–hosted Cononish vein gold deposit, Scotland, is unusually Te–rich compared to many orogenic gold deposits with Te/Au ≈ 2.4 whereas most orogenic deposits have Te/Au <1. Here, Ag in Au–Ag alloy increases from ~10 to 90 wt.% through the paragenesis, correlating with decreasing hessite (Ag2Te) abundance. This suggests the Au–Ag alloy composition was controlled by the fluid Te activity, and that this decreased through time. This is coupled to an increase in pyrite δ34S from 2.0‰ to +11.4‰ through the paragenesis. Thus, the deposit formed from a primary fluid with a low–δ34S and high Te+Au+Ag that evolved to a high δ34S–low Te, Pb+Cu bearing fluid. The high δ34S of the later fluid suggests it can only be sourced from specific nearby metamorphosed SEDEX horizons. The early fluid that deposited most of the gold could be sourced from other metasedimentary units in the stratigraphy or be magmatic in origin. We argue that two observations taken together suggest it is most likely that this fluid was magmatic; the age of the mineralisation is identical to the last stage of crystallization of nearby granite batholiths, and the fluid has a S–isotope signature consistent with a magmatic source. Gold deposits in orogenic belts are almost certainly polygenetic and this study demonstrates evidence for Te-rich “orogenic” deposits having a significant magmatic component.
DOI Link: 10.1016/j.oregeorev.2018.05.014
ISSN: 0169-1368
eISSN: 1872-7360
Links: https://www.sciencedirect.com/science/article/pii/S0169136818300192
http://hdl.handle.net/2381/42247
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © the authors, 2018. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Appears in Collections:Published Articles, Dept. of Geology

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