Mesoarchaean Gold Mineralisation in the Barberton Greenstone Belt: A Review

Details

Serval ID
serval:BIB_1089D35CA018
Type
A part of a book
Collection
Publications
Title
Mesoarchaean Gold Mineralisation in the Barberton Greenstone Belt: A Review
Title of the book
Regional Geology Reviews
Author(s)
Agangi Andrea, Hofmann Axel, Eickmann Benjamin, Marin-Carbonne Johanna
Publisher
Springer International Publishing
Address of publication
Cham
ISBN
9783319786513
9783319786520
ISSN
2364-6438
2364-6446
Publication state
Published
Issued date
2019
Editor
Kröner Alfred, Hofmann Axel
Pages
171-184
Language
english
Abstract
The Barberton Greenstone Belt hosts abundant structurally controlled gold mineralisation of Mesoarchaean age. More than 300 gold occurrences have been reported, although most of the gold production so far (>350 tonnes Au) has come from a handful of deposits located along the northern margin of the greenstone belt. Most deposits are hosted by greenschist-facies metasedimentary and metamafic rocks, with the notable exception of the amphibolite-facies rocks at New Consort mine. Mineralisation is associated with quartz--carbonate veins that truncate major compressional structures at the greenstone belt scale. The age of mineralisation is loosely constrained at circa 3080--3030 Ma, based on U--Pb dating of hydrothermal rutile and titanite. In greenschist-facies deposits, the ore assemblage is dominated by pyrite and arsenopyrite, which contain up to thousands of ppm of `invisible' gold, Ni--As--Sb sulphides and native gold. At New Consort mine, mineralisation includes massive replacement-style ore and vein-hosted or disseminated types. Both structural studies in the field and microstructural observation point to a multistage ore deposition process, which is reflected in the re-activation of brittle to ductile structures and the overprinting of sulphide assemblages. The presence of mass-independently fractionated S isotopes ($\Delta$33S{\thinspace}={\thinspace}--0.6 to +1.0{\texttenthousand}) in pyrite from Sheba and Fairview mines suggests that hydrothermal fluids mobilised S from volcanic and sedimentary rocks of the greenstone belt and places constraints on the origin of the Au itself.
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27/01/2020 15:13
Last modification date
27/01/2020 15:14
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