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Sedimentary basin controls on orogenic gold deposits : new constraints from U-Pb detrital zircon and Re-Os sulphide geochronology, Lynn Lake greenstone belt, Canada.

Lawley, C.J.M. and Yang, X.M. and Selby, D. and Davis, W. and Zhang, S. and Petts, D.C. and Jackson, S.E. (2020) 'Sedimentary basin controls on orogenic gold deposits : new constraints from U-Pb detrital zircon and Re-Os sulphide geochronology, Lynn Lake greenstone belt, Canada.', Ore geology reviews., 126 . p. 103790.

Abstract

Sedimentary basins that open and close during the last stages of mountain building represent an important exploration criterion for orogenic gold deposits. However, the genetic and/or preservation controls of these synorogenic, or “Timiskaming-type”, sedimentary basins and their controlling fault systems on orogenic gold deposits remain unclear. Herein we address that knowledge gap and report new U-Pb detrital zircon and Re-Os sulphide (arsenopyrite and pyrite) geochronology and sulphide Pb isotope results for the Paleoproterozoic Lynn Lake greenstone belt (LLGB), Manitoba, Canada. The youngest detrital zircon from all six meta-conglomerate and -psammite samples of the synorogenic Sickle Group, and previously reported U-Pb zircon ages for post-Sickle Group intrusions, are used to constrain its depositional timing from 1836 ± 15 to 1831 ± 4 Ma. Replicate analyses of one highly-radiogenic arsenopyrite sample from an auriferous vein at the MacLellan gold deposit yield a weighted average Re-Os model age of 1824 ± 12 Ma, which is identical to previously published in situ U-Pb xenotime ages at the same deposit (1827 ± 8 Ma). Each of these hydrothermal ages demonstrate that early-stage auriferous veins immediately post-date deposition of the Sickle Group and most likely occurred prior to peak metamorphism (1814–1801 Ma). This sequence of events is very similar to the Abitibi greenstone belt, suggesting that a synorogenic phase of extension and rapid burial of auriferous veins by Timiskaming-type Sickle Group sediments may have played an important genetic and/or preservation control on early-stage gold mineralization in the LLGB. However, unlike the Abitibi greenstone belt, none of the known gold deposits within the LLGB are hosted within the Sickle Group. Younger Re-Os model arsenopyrite ages at 1782 ± 16 Ma from the MacLellan gold deposit also post-date synorogenic sedimentary basins by ca. 50 Myr. These late-stage auriferous veins are unrelated to the synorogenic extensional phase and more likely reflect repeated fluid focusing along reactivated structures during a post-peak metamorphic phase of hydrothermal activity. The multi-stage hydrothermal history of orogenic gold deposits in the LLGB also provides a possible explanation for the mixture of depleted mantle-like and highly radiogenic fluid components that are inferred from age-corrected sulphide Pb isotope compositions (µ1.8 Ga = 8.9–10.6). Reworked cratonic margins and their associated greenstone belts thus represent favourable depositional settings for auriferous fluids at multiple stages throughout the lifespan of an orogen.

Item Type:Article
Full text:(AM) Accepted Manuscript
Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1016/j.oregeorev.2020.103790
Publisher statement:© 2020 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Date accepted:17 September 2020
Date deposited:15 October 2020
Date of first online publication:25 September 2020
Date first made open access:25 September 2021

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