Product catalogue
Low δ18O volcanism in the Neoarchean Fortescue Group, Pilbara Craton
<div>Archean greenstone belts are a vital window into the tectonostratigraphic processes that operated in the early Earth and the geodynamics that drove them. However, the majority of greenstone belts worldwide are highly-deformed, complicating geodynamic interpretations. The volcano-sedimentary sequence of the 2775-2690 Ma Fortescue Group is different in that it is largely undeformed, offering a unique insight into the architecture of greenstone sequences. In the Fortescue magmatic rocks, geochemical signatures that in deformed belts in the Superior or Yilgarn Cratons might have been interpreted as arc-like, are explained by contamination of rift-related mantle and plume-derived magmas with Pilbara basement crust; understanding the wider geological and structural setting allows a more complete interpretation.</div><div>
However, contamination of Fortescue magmas by an enriched sub-continental mantle lithosphere (SCLM) is an alternative hypothesis to the crustal contamination model. If demonstrated, the addition of sediments and fluids to the SCLM, required to form enriched/metasomaytised SCLM, would suggest active subduction prior to the Neoarchean. To test this hypothesis, we collected Hf-O isotopic data on zircons from felsic volcanic rocks throughout the Fortescue Group; if the contamination had a subducted sedimentary component (δ18O>20‰), then the O-isotopes should record a heavy signature.</div><div>
The results show that the ca. 2775 Ma Mt Roe Formation has εHfi from 0 to -5.6, and δ18OVSMOW of +4.8- +0.3‰, with the majority of values <+3‰. The ca. 2765 Ma Hardey Formation (mostly sediments) has highly unradiogenic εHfi of -5 to -9.4, and δ18O of +7.8- +6.6‰. The ca. 2730 Ma Boongal Formation displays similar values as for Mt Roe, with εHfi +1.9 to -5.5 and δ18O +3.0 to -0.6‰. The ca. 2720 Ma Tumbiana Formation shows the greatest range in εHfi from +4.9 to -4.6, with δ18O +7.1- +0.7‰, with the majority between +4.5 and +2.5‰. Data from the 2715 Ma Maddina Formation are more restricted, with εHfi between +4.0 and -0.1, and δ18O +5.0- +3.8‰. The youngest formation, the 2680 Ma Jeerinah Formation, has εHfi +2.3 to -6.2, and δ18O +5.1 to -2.1‰.</div><div>
Importantly, these data provide little evidence of a cryptic enriched SCLM source in the Fortescue magmas. Furthermore, the dataset contains some of the lightest δ18O data known for Archean zircon, highlighting a ca. 100 Myr period of high-temperature magma-water interaction, with long-term continental emergence implied by the trend to meteoric δ18O compositions. The exception to this is the Hardey Formation, which may have formed via crustal anatexis in a period of reduced heat-flow between the 2775-2665 and 2730-2680 Ma events. Data from the other formations show a broad trend of increasing δ18O and εHf from 2775 to 2680 Ma. We suggest this represents the effects of progressive cratonic rifting, allowing mantle-derived magmas to reach the surface less impeded, and also a decreasing role of meteoric water in the rift zone as the sea invades. As a result, the εHf and δ18O data from the Fortescue Group represent the evolving nature of an Archean rift zone, from an emergent volcanic centre, to a submarine environment.</div><div><br></div>This Abstract was submitted/presented to the 2023 6th International Archean Symposium (6IAS) 25 - 27 July ( https://6ias.org/)
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Identification info
- Date (Creation)
- 2023-02-16T07:00:00
- Date (Publication)
- 2023-09-14T23:40:24
- Citation identifier
- Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/147723
- Cited responsible party
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Role Organisation / Individual Name Details Publisher Commonwealth of Australia (Geoscience Australia)
Voice Author Mole, D.
Internal Contact Author Howard, H.M.
External Contact Author Smithies, R.H.
External Contact Author Kirkland, C.L.
External Contact Author Fiorentini, M.L.
External Contact Author Martin, L.A.J.
External Contact Author Stern, R.A.
External Contact Author Parra-Avila, L.A.
External Contact
- Name
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6th International Archean Symposium 25-27 July 2023 Fremantle Perth WA
- Purpose
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Conference abstract for the 6th International Archean Symposium in Perth, WA 25-27th July 2023.
- Status
- Completed
- Point of contact
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Role Organisation / Individual Name Details Resource provider Minerals, Energy and Groundwater Division
External Contact Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact Mole, D.
Internal Contact
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- Geoscientific information
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))
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- Not planned
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Product data repository: Various Formats
- Website
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Data Store directory containing the digital product files
Data Store directory containing one or more files, possibly in a variety of formats, accessible to Geoscience Australia staff only for internal purposes
- Project
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Isotopic Atlas of Australia
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- Keywords
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Pilbara
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- Keywords
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Western Australia
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- Keywords
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zircon
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- Keywords
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Archean
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- Keywords
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isotopes
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- theme.ANZRC Fields of Research.rdf
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Isotope geochemistry
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- Keywords
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Published_External
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Resource constraints
- Title
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Creative Commons Attribution 4.0 International Licence
- Alternate title
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CC-BY
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4.0
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© Commonwealth of Australia (Geoscience Australia) 2023
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Australian Government Security Classification System
- Edition date
- 2018-11-01T00:00:00
- Classification
- Unclassified
- Classification system
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Australian Government Security Classification System
- Language
- English
- Character encoding
- UTF8
Distribution Information
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Role Organisation / Individual Name Details Distributor Commonwealth of Australia (Geoscience Australia)
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Link to Conference Page
Link to Conference Page
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- OnLine resource
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Link to Abstract Volume
Link to Abstract Volume
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- Statement
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<div>Data collected as part of an on-going collaboration with the Geological Survey of Western Australia (GSWA) and linked to the GA Isotopic Atlas of Australia.</div>
Metadata constraints
- Title
-
Australian Government Security Classification System
- Edition date
- 2018-11-01T00:00:00
- Classification
- Unclassified
Metadata
- Metadata identifier
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urn:uuid/e0ff502c-7240-43b9-b3da-d4ea2524b0d2
- Title
-
GeoNetwork UUID
- Language
- English
- Character encoding
- UTF8
- Contact
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Role Organisation / Individual Name Details Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact Mole, D.
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Type of resource
- Resource scope
- Document
- Name
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Conference Abstract
Alternative metadata reference
- Title
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Geoscience Australia - short identifier for metadata record with
uuid
- Citation identifier
- eCatId/147723
- Date info (Creation)
- 2023-09-14T23:29:14
- Date info (Revision)
- 2023-09-14T23:29:14
Metadata standard
- Title
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AU/NZS ISO 19115-1:2014
Metadata standard
- Title
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ISO 19115-1:2014
Metadata standard
- Title
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ISO 19115-3
- Title
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Geoscience Australia Community Metadata Profile of ISO 19115-1:2014
- Edition
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Version 2.0, September 2018
- Citation identifier
- http://pid.geoscience.gov.au/dataset/ga/122551