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An isotopic characterisation of rocks from the Stavely region, western Victoria:a zircon perspective
The Stavely region has been described as a continental-margin arc system that developed on the eastern margin of Australia in the mid-Cambrian (c. 510490 Ma). The joint Geoscience AustraliaGeological Survey of Victoria Stavely Project, investigating the regional geology and mineral systems of the Stavely region, resulted in 14 stratigraphic holes being drilled testing regional geological models and recovering material from potentially prospective basement rocks under cover to characterise the subsurface geology. Drill core and field site samples were taken for mineral separation to extract zircon for U-Pb, Lu-Hf, O isotope and trace element geochemical analyses. The analysed samples reported here include rocks from the Mount Stavely Volcanic Complex (MSVC), including mineralised dactic porphyries, and the Bushy Creek Igneous Complex (BCIC).
The U-Pb data provide age constraints on the rocks; the Lu-Hf data indicates the relative `maturity of the rocks; the O isotopes indicated the degrees of continental crustal input/recycling into the parent melt; the trace element data provides an indication of the crystallisation environment, including providing evidence of mixing of magmas and subsequent compositional changes.
U-Pb data indicate that the ages of many of the igneous rocks in the Stavely region are c. 510500 Ma. Available data indicate that the MSVC was emplaced both during and after deposition of the turbiditic Nargoon Group sediments. Mineralised dacitic porphyries were syn-eruptive with the MSVC, and rocks of the BCIC were emplaced at the same time and after both the MSVC and porphyries. New U-Pb dating of zircon from rocks of the BCIC also suggests they may be syn- to post-deformation, rather than purely post-deformation.
O isotope data yield d18O values less than that of the `normal mantle through to values similar to and greater then `normal mantle (values), indicating possible evolution of the arc and increase of crustal material that assimilated into later stage magmas. The samples that yield lower than `normal mantle d18O values are interpreted to have been derived from hydrothermally altered, subducted rocks that were remelted and did not significantly interact with the overlying continental crust at the time of emplacement.
The mineralised porphyries display eHf values indicative of depleted mantle suggesting the melt is juvenile (i.e. do not display significant amounts of crustal reworking), while the eHf values of the MSVC rocks are more evolved. This suggests that there were multiple, distinct source magmas that had a different history (i.e. porphyries little to no crustal input, while MSVC rocks had a source with some crustal input). The plutonic rocks of the BCIC are interpreted to have had a greater degree of crustal input again.
The combination of isotopic and trace element geochemical data from zircon allows for discrimination of the differences of rock units based on timing, maturity and degree of crustal reworking of their parent melts. This provides a powerful tool in assisting in unravelling the tectonic environment of the continental margin arc setting of the Stavely region.
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Identification info
- Date (Publication)
- 2016-01-01T00:00:00
- Citation identifier
- Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/89877
- Cited responsible party
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Role Organisation / Individual Name Details Author Lewis, C.J.
External Contact Author Bodorkos, S.
MEG Internal Contact Author Schofield, A.
MEG Internal Contact Author Crowley, J.
External Contact Author Armstrong, R.A.
External Contact Author Fu, B.
External Contact
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Role Organisation / Individual Name Details Custodian RD
Owner Commonwealth of Australia (Geoscience Australia)
Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact Lewis, C.
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- Geoscientific information
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Product data repository: Various Formats
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- Australian and New Zealand Standard Research Classification (ANZSRC)
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Earth Sciences
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Published_Internal
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Creative Commons Attribution 4.0 International Licence
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CC-BY
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4.0
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Australian Government Security ClassificationSystem
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- 2018-11-01T00:00:00
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- English
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Role Organisation / Individual Name Details Distributor Commonwealth of Australia (Geoscience Australia)
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Download the poster (pdf) [2.3 MB]
Download the poster (pdf) [2.3 MB]
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pdf
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- OnLine resource
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Download the abstract (pdf) [5.9 MB]
Download the abstract (pdf) [5.9 MB]
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pdf
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Unknown
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- Non geographic dataset
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External Publication
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Source data not available.
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Australian Government Security ClassificationSystem
- Edition date
- 2018-11-01T00:00:00
- Classification
- Unclassified
Metadata
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urn:uuid/2996ade2-57bf-41d4-e053-10a3070a5e7b
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GeoNetwork UUID
- Language
- English
- Character encoding
- UTF8
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Role Organisation / Individual Name Details Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact Lewis, C.
Corporate Division Internal Contact
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- Document
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Abstract & Poster
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Geoscience Australia - short identifier for metadata record with
uuid
- Citation identifier
- eCatId/89877
- Date info (Revision)
- 2018-04-10T23:13:16
- Date info (Creation)
- 2016-01-18T00:00:00
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
- https://pid.geoscience.gov.au/dataset/ga/122551