Lower crustal resistivity signature of an orogenic gold system

Abstract 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-pe...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Graham Heinson, Jingming Duan, Alison Kirkby, Kate Robertson, Stephan Thiel, Sasha Aivazpourporgou, Wolfgang Soyer
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/6dae44965b304b16aeed5318418fd832
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:6dae44965b304b16aeed5318418fd832
record_format	dspace
spelling	oai:doaj.org-article:6dae44965b304b16aeed5318418fd8322021-12-02T18:49:29ZLower crustal resistivity signature of an orogenic gold system10.1038/s41598-021-94531-82045-2322https://doaj.org/article/6dae44965b304b16aeed5318418fd8322021-08-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-94531-8https://doaj.org/toc/2045-2322Abstract 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 (FeS2) 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 CO2. 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 CO2 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.Graham HeinsonJingming DuanAlison KirkbyKate RobertsonStephan ThielSasha AivazpourporgouWolfgang SoyerNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-7 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Graham Heinson Jingming Duan Alison Kirkby Kate Robertson Stephan Thiel Sasha Aivazpourporgou Wolfgang Soyer Lower crustal resistivity signature of an orogenic gold system
description	Abstract 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 (FeS2) 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 CO2. 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 CO2 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	article
author	Graham Heinson Jingming Duan Alison Kirkby Kate Robertson Stephan Thiel Sasha Aivazpourporgou Wolfgang Soyer
author_facet	Graham Heinson Jingming Duan Alison Kirkby Kate Robertson Stephan Thiel Sasha Aivazpourporgou Wolfgang Soyer
author_sort	Graham Heinson
title	Lower crustal resistivity signature of an orogenic gold system
title_short	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_sort	lower crustal resistivity signature of an orogenic gold system
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/6dae44965b304b16aeed5318418fd832
work_keys_str_mv	AT grahamheinson lowercrustalresistivitysignatureofanorogenicgoldsystem AT jingmingduan lowercrustalresistivitysignatureofanorogenicgoldsystem AT alisonkirkby lowercrustalresistivitysignatureofanorogenicgoldsystem AT katerobertson lowercrustalresistivitysignatureofanorogenicgoldsystem AT stephanthiel lowercrustalresistivitysignatureofanorogenicgoldsystem AT sashaaivazpourporgou lowercrustalresistivitysignatureofanorogenicgoldsystem AT wolfgangsoyer lowercrustalresistivitysignatureofanorogenicgoldsystem
_version_	1718377566161600512

Lower crustal resistivity signature of an orogenic gold system

Ejemplares similares