Precise U–Pb baddeleyite dating of the Derim Derim Dolerite: evidence for episodic mafic magmatism in the greater McArthur Basin  


Authors / CoAuthors

Bodorkos, S. | Yang, B. | Collins, A.S. | Crowley, J. | Denyszyn, S.W. | Claoue-Long, J.C. | Anderson, J.R. | Magee, C.

Abstract

<p>The Mesoproterozoic Roper Group of the McArthur Basin has excellent petroleum potential, but its poorly constrained post-depositional history has hampered resource exploration and management. The Derim Derim Dolerite occupies an important position in the regional event chronology, having intruded the Roper Group prior to deformation associated with the ‘Post-Roper Inversion’ event. It was assigned a magmatic crystallisation age of 1324 ± 4 Ma (uncertainties are 95% confidence unless otherwise indicated) in 1997, based on unpublished Sensitive High Resolution Ion Micro Probe (SHRIMP) U-Pb analyses of dolerite-hosted baddeleyite from sample 97106010, collected from the Derim Derim Dolerite type locality in outcrop within the northwestern McArthur Basin. Herein, we refine these data via Isotope Dilution-Thermal Ionisation Mass Spectrometry (ID-TIMS) analysis of baddeleyites plucked from the SHRIMP grain-mounts, which yielded a precise mean 207Pb/206Pb date of 1327.5 ± 0.6 Ma. This date is significantly older than a baddeleyite U-Pb ID-TIMS date of 1313.8 ± 1.3 Ma recently obtained from dolerite ALT-05, sampled in Pacific Oil and Gas Ltd drillhole Altree 2, near the northern margin of the Beetaloo Sub-basin, and 200 km south of 97106010. This pair of results indicates that Derim Derim Dolerite magmatism spanned at least 10-15 Ma. Previously documented geochemical variation in Mesoproterozoic mafic rocks across the Northern Territory (such as the 1325 ± 36 Ma (2σ) Galiwinku Dolerite in the northern McArthur Basin, 1316 ± 40 Ma phonolites intruding the eastern Pine Creek Orogen, and 1295 ± 14 Ma gabbro in the Tomkinson Province) may reflect episodic pulses of magmatism hitherto obscured by the low precision of the available isotopic dates. <p><b>Citation:</b> Bodorkos, S., Yang, B., Collins, A.S., Crowley, J., Denyszyn, S.W., Claoue-Long, J.C., Anderson, J.R. and Magee, C., 2020 Precise U–Pb baddeleyite dating of the Derim Derim Dolerite: evidence for episodic mafic magmatism in the greater McArthur Basin. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

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document

eCat Id

133863

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Commonwealth of Australia (Geoscience Australia)  
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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http://dx.doi.org/10.11636/133863

Keywords

theme.ANZRC Fields of Research.rdf
  • GeochronologyIgneous and Metamorphic PetrologyEARTH SCIENCES
( Project )
  • EFTF
( Project )
  • Exploring for the Future
( Stratum )
  • Derim Derim Dolerite
( Stratum )
  • McArthur Basin
( Discipline )
  • U-Pb dating
( Feature type )
  • baddeleyite
( Instrument )
  • SHRIMP
( Discipline )
  • ID-TIMS
( Theme )
  • Crust
  • Published_External

Publication Date

2020-05-08T02:16:26

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Australian Government Security ClassificationSystem    

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completed

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asNeeded

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geoscientificInformation

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The original Sensitive High Resolution Ion Micro Probe (SHRIMP) data collected in 1997 was lodged in Geoscience Australia's now-obsolete OZCHRON database, and access to the analytical data was lost when OZCHRON was decommissioned in 2008. The current publication (and Bodorkos et al., 2020, Australian Journal of Earth Sciences, https://doi.org/10.1080/08120099.2020.1749929) include re-publication of the 1997 SHRIMP data alongside more newly acquired (2019) SHRIMP data in Geoscience Australia's Geochron Delivery system (http://www.ga.gov.au/geochron-sapub-web/). The underlying ID-TIMS analytical data are published by Bodorkos et al. (2020; https://doi.org/10.1080/08120099.2020.1749929 for sample 97106010) and Yang et al. (2020; https://doi.org/10.1111/bre.12450 for sample ALT-05).

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[-16, -13, 133, 135.5]

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Extended Abstract for download (pdf) [1.6MB]  

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