Detrital zircon geochronology of the Glyde and Favenc packages: implications for the geological framework of the greater McArthur Basin, Northern Territory

Tim Munson1 1NTGS

greater McArthur Basin

• Informal NTGS term for a vast predominantly sedimentary terrane stretching across the northern part of the NT.

• Includes Palaeo- to Mesoproterozoic successions of McArthur Basin, Birrindudu Basin and the Tomkinson Province, interpreted to be linked in the subsurface (from geophysical and drilling evidence).

• New results provide information on maximum depositional ages and provenance.

• Very useful tool for testing and refining inter- and intrabasinal correlations, in combination with other data.

Detrital zircon geochronology

NTGS stratigraphic projects

Completed(Munson 2016)

underway

Sedimentary packages of greater McArthur Basin

• Five broad stratigraphic subdivisions of McArthur Basin, defined by Rawlings (1999).

• Definitions extended by NTGS to include correlative successions across greater McArthur Basin.

Correlation chart incorporating new interpretations from completed and current NTGS stratigraphic projects

Unit names in red = this presentation

1

5

3

4

2

• Mix of siliciclastic, carbonate and heterolithic rocks.

• ca 1660–1610 Ma.

• Dominantly shallow-marine to emergent palaeoenvironments.

• Hosts world-class McArthur River and other base metals deposits.

• Prospective for petroleum.

Glyde package, as defined here

• Siliciclastic and carbonate rocks, and minor mafic volcanics.

• 1600–1580 Ma or possibly younger.

• Shallow-marine to fluvial.

Favenc package, as defined here

Distribution of Glyde and Favenc package exposures

Simplified correlation chart, as here interpreted, showing units sampled for geochronology

McArthur Basin: Age and correlation of Glyde package units

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McArthur Basin: Age and correlation of Glyde package units

• Correlation between Nagi Fm (Vizard Gp), Yarrawirrie Fm (Balma Gp) and Batten Subgroup is supported.

• Correlation between upper Balma and upper Habgood groups is not supported.

• upper Habgood Group is appreciably older (35–80 my) than upper Balma Group and probably correlates with units lower in McArthur and Balma groups.

McArthur Basin: Age and correlation of Favenc package units

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McArthur Basin: Age and correlation of Favenc package units

• Spectra of upper Balma Group more closely resemble those of Favenc package than Glyde package.

• No evidence of a regional unconformity either above Bath Range Fm or under Baiguridji Fm.

• Nathan Gp age is favoured.

• Absolute ages of tuffs: Nathan Gp 1589 ± 3 Ma Bath Range Formation 1599 Ma ± 11 Ma upper McArthur Group 1609 ± 3 Ma.

Birrindudu Basin: Age and correlation of Glyde package units

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Birrindudu Basin: Age and correlation of Glyde package units

• Correlation between Farquharson Sandstone and Tatoola Sandstone is supported.

• Correlation between basal units, Stirling Sandstone and Masterton Sandstone, is not supported.

Stirling Sandstone spectrum from Carson (2013).

Birrindudu Basin: Age and correlation of Glyde package units

• Formation-level correlation between Limbunya Group and lower McArthur Group as suggested by Dunster (1998) is supported.

• Stirling Sst might correlate with older Palaeoproterozoic units overlying NAC basement, such as Depot Creek Sandstone, Westmoreland Conglomerate, or Mamadawerre Sandstone, as suggested by Carson (2010, 2013).

• New absolute age from Fraynes Formation confirms correlation with Barney Creek Formation.

Birrindudu Basin and Tomkinson Province: Age and correlation of Glyde package units

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1592 ± 46 Ma (n=3) for Jeromah Fm 1595 ± 10 Ma (n=14) for Shillinglaw Fm 1582 ± 17 Ma (n=4) for Willieray Fm Youngest two zircons 1526 ± 26 Ma!

Birrindudu Basin and Tomkinson Province: Age and correlation of Glyde package units

• Namerinni Gp previously correlated with McArthur Gp, supported by 1639 ± 27 Ma age for ‘tuff’ sample (Nunn 1997).

• Detrital zircon maximum depositional ages for Namerinni Gp:

• Namerinni Gp must be much younger than McArthur Gp and is better correlated with Nathan and Wattie groups in Favenc package.

Wattie Group spectra from Carson (2013, Kositcin and Carson 2017).

ConclusionsCompleted and ongoing NTGS projects are substantially revising the fundamental architecture of the greater McArthur Basin:

1. Vizard Group correlates with units of medial Balma Group and upper McArthur Group.

2. upper Habgood Group is possibly equivalent to units much lower in Balma and McArthur groups than previously interpreted.

3. Limbunya Group can be correlated with lower McArthur Group at formation level.

4. upper McArthur Group is more restricted in geographic extent than previously interpreted.

3. Favenc package is far more extensive than previously recognised. It includes Wattie, Namerinni and probably uppermost Balma groups.

4. Glyde package is absent in Tomkinson Province, unless poorly dated rocks at top of underlying Tomkinson Creek Group are younger than previously interpreted.

Revised greater McArthur Basin correlation chart

Revised Wattie Group interpretation based on Carson (2013) and Kositcin and Carson (2017). Revised Wilton package correlations from Munson (2016).

(Ahmad and Scrimgeour 2013) 2019

ReferencesAhmad M and Scrimgeour IR, 2013. Geological framework: in Ahmad M and Munson TJ (compilers) ‘Geology and mineral resources of the Northern

Territory.’ Northern Territory Geological Survey, Special Publication 5. Carson CJ, 2010. The Victoria and Birrindudu basins: A U-Pb SHRIMP study and review of resource potential: in 'Annual Geoscience Exploration

Seminar (AGES) 2010. Record of abstracts'. Northern Territory Geological Survey, Record 2010-002.Carson CJ, 2013. The Victoria and Birrindudu Basins, Victoria River region, Northern Territory, Australia: a SHRIMP U-Pb detrital zircon and Sm-Nd

study. Australian Journal of Earth Sciences 60, 175–196.Dunster JN, 1998. Reconnaissance of the Proterozoic Rocks of the Victoria River Region. North Ltd. Northern Territory Geological Survey, Open File

Company Report CR1998-0082.Kositcin N and Carson CJ, 2017. New SHRIMP U–Pb zircon ages from the Birrindudu and Victoria Basins, Northern Territory: July 2016–June 2017.

Geoscience Australia, Record 2017/16. Munson TJ, 2016. Sedimentary characterisation of the Wilton package, greater McArthur Basin, Northern Territory. Northern Territory Geological

Survey, Record 2016-003. Nunn T, 1997. Second annual report for the period 2 June 1996 to 1 June 1997 for Els 9022-9025, 9325-9327, 9570 Helen Springs project. BHP

Minerals Pty Ltd. Northern Territory Geological Survey, Open File Company Report CR1997-0444.Rawlings DJ, 1999. Stratigraphic resolution of a multiphase intracratonic basin system: the McArthur Basin, northern Australia. Australian Journal of

Earth Sciences 46, 703 –723.

Darwarunga Fm, Habgood Gp Vaughton Siltstone, Balma Gp Campbell Springs Dlst, Birrindudu Gp