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Lower crustal resistivity signature of an orogenic gold system
Orogenic gold deposits provide a significant source of the world’s gold and form along faults over a wide range of crustal depths spanning sub-greenschist to granulite grade faces, but the source depths of the gold remains poorly understood. In this paper we compiled thirty years of long-period magn...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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Nature Publishing Group UK
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8338967/ https://www.ncbi.nlm.nih.gov/pubmed/34349155 http://dx.doi.org/10.1038/s41598-021-94531-8 |
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author | Heinson, Graham Duan, Jingming Kirkby, Alison Robertson, Kate Thiel, Stephan Aivazpourporgou, Sasha Soyer, Wolfgang |
author_facet | Heinson, Graham Duan, Jingming Kirkby, Alison Robertson, Kate Thiel, Stephan Aivazpourporgou, Sasha Soyer, Wolfgang |
author_sort | Heinson, Graham |
collection | PubMed |
description | Orogenic gold deposits provide a significant source of the world’s gold and form along faults over a wide range of crustal depths spanning sub-greenschist to granulite grade faces, but the source depths of the gold remains poorly understood. In this paper we compiled thirty years of long-period magnetotelluric (MT) and geomagnetic depth sounding (GDS) data across western Victoria and south-eastern South Australia that have sensitivity to the electrical resistivity of the crust and mantle, which in turn depend on past thermal and fluid processes. This region contains one of the world’s foremost and largest Phanerozoic (440 Ma) orogenic gold provinces that has produced 2% of historic worldwide gold production. Three-dimensional inversion of the long-period MT and GDS data shows a remarkable correlation between orogenic gold deposits with > 1 t production and a < 20 Ω m low-resistivity region at crustal depths > 20 km. This low-resistivity region is consistent with seismically-imaged tectonically thickened marine sediments in the Lachlan Orogen that contain organic carbon (C), sulphides such as pyrite (FeS(2)) and colloidal gold (Au). Additional heat sources at 440 Ma due to slab break-off after subduction have been suggested to rapidly increase the temperature of the marine sediments at mid to lower crustal depth, releasing HS(−) ligands for Au, and CO(2). We argue that the low electrical resistivity signature of the lower crust we see today is from a combination of flake graphite produced in situ from the amphibolite grade metamorphism of organic-carbon in the marine sediments, and precipitated graphite through retrograde hydration reactions of CO(2) released during the rapid heating of the sediments. Thus, these geophysical data image a fossil source and pathway zone for one of the world’s richest orogenic gold provinces. |
format | Online Article Text |
id | pubmed-8338967 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | Nature Publishing Group UK |
record_format | MEDLINE/PubMed |
spelling | pubmed-83389672021-08-05 Lower crustal resistivity signature of an orogenic gold system Heinson, Graham Duan, Jingming Kirkby, Alison Robertson, Kate Thiel, Stephan Aivazpourporgou, Sasha Soyer, Wolfgang Sci Rep Article Orogenic gold deposits provide a significant source of the world’s gold and form along faults over a wide range of crustal depths spanning sub-greenschist to granulite grade faces, but the source depths of the gold remains poorly understood. In this paper we compiled thirty years of long-period magnetotelluric (MT) and geomagnetic depth sounding (GDS) data across western Victoria and south-eastern South Australia that have sensitivity to the electrical resistivity of the crust and mantle, which in turn depend on past thermal and fluid processes. This region contains one of the world’s foremost and largest Phanerozoic (440 Ma) orogenic gold provinces that has produced 2% of historic worldwide gold production. Three-dimensional inversion of the long-period MT and GDS data shows a remarkable correlation between orogenic gold deposits with > 1 t production and a < 20 Ω m low-resistivity region at crustal depths > 20 km. This low-resistivity region is consistent with seismically-imaged tectonically thickened marine sediments in the Lachlan Orogen that contain organic carbon (C), sulphides such as pyrite (FeS(2)) and colloidal gold (Au). Additional heat sources at 440 Ma due to slab break-off after subduction have been suggested to rapidly increase the temperature of the marine sediments at mid to lower crustal depth, releasing HS(−) ligands for Au, and CO(2). We argue that the low electrical resistivity signature of the lower crust we see today is from a combination of flake graphite produced in situ from the amphibolite grade metamorphism of organic-carbon in the marine sediments, and precipitated graphite through retrograde hydration reactions of CO(2) released during the rapid heating of the sediments. Thus, these geophysical data image a fossil source and pathway zone for one of the world’s richest orogenic gold provinces. Nature Publishing Group UK 2021-08-04 /pmc/articles/PMC8338967/ /pubmed/34349155 http://dx.doi.org/10.1038/s41598-021-94531-8 Text en © The Author(s) 2021 https://creativecommons.org/licenses/by/4.0/Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) . |
spellingShingle | Article Heinson, Graham Duan, Jingming Kirkby, Alison Robertson, Kate Thiel, Stephan Aivazpourporgou, Sasha Soyer, Wolfgang Lower crustal resistivity signature of an orogenic gold system |
title | Lower crustal resistivity signature of an orogenic gold system |
title_full | Lower crustal resistivity signature of an orogenic gold system |
title_fullStr | Lower crustal resistivity signature of an orogenic gold system |
title_full_unstemmed | Lower crustal resistivity signature of an orogenic gold system |
title_short | Lower crustal resistivity signature of an orogenic gold system |
title_sort | lower crustal resistivity signature of an orogenic gold system |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8338967/ https://www.ncbi.nlm.nih.gov/pubmed/34349155 http://dx.doi.org/10.1038/s41598-021-94531-8 |
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