New zircon and monazite geochronology from recent GOMA Drilling

Elizabeth JagodzinskiAnthony Reid

In 2008 Geoscience Australiaas part of its OnshoreEnergy SecurityProgram (OESP)collected deepseismic reflection dataacross the northernGawler Craton into theMusgrave Province. This was the GOMA seismic line

(Gawler-Officer-Musgrave-Amadeus)

The traverse followed the Adelaide to Darwin railway line for ~ 630 km, from Tarcoola in the south to the southern margin of the Amadeus Basin in the Northern Territory.

Due release date December, 2010

89m

4m12m

80m

169m

54m

6m

266m

132m

50m

4m

80m

172m

126m

257m

305m310m

462m

517m

DH1

SouthNorth

DH2 DH3 DH4

basementorthogneiss

basementparagneiss

+ amphibolite dykes

Eromanga Basin(Cretaceous)

Arckaringa Basin(Permian)

1

2

3

4

Tertiary/Quaternary cover

GOMA 1

GOMA 3

GOMA 2

GOMA 4

~1750 Ma~1750 Ma

~1750 Ma

pre-Kimban maximum depositional agesFanning et al., 2007; Payne et al., 2006

~1750 Ma

~1750 Ma

1740±31 Ma 1743±10 Ma

GOMA DH3 155.08-155.91m

R1707903

R1707903 unmetamorphosed well-bedded fine to coarse-grained sandstone GOMA DH3 155.08-155.91m

Provenance:• Gawler Craton• Musgrave Province

R1707903

R1707899

GOMA DH4

R1707899 sillimanite–biotite–quartz–feldspar paragneissGOMA DH2 75.4-75.8 m

R1707899

20 µm

GOMA DH1

285m 310.2 m

256.9 m305.15m

R1707896

R1707895

R1707895 Quartz-feldspar-biotite-magnetite orthogneissGOMA DH1 307.65-307.85 m

• Zoned, resorbed igneous cores• Darker, homogenous

metamorphic rims

R1707896

R1707895

R1707895 OrthogneissGOMA DH1 307.65-307.85 m

R1707895R1707896

GOMA 3

GOMA 2

GOMA 4

1728±10 Ma

1701±9 Ma

Kimban metamorphic agesPayne et al., 2008

1719±8 Ma

GOMA 1

1734±8 Ma

1686±5 Ma

R1707896Fine-grained biotite tonalite GOMA DH1 308.7-308.9 m

• Oscillatory zoned igneous cores • Dark homogenous metamorphic rims

R1707895R1707896

R1707896Fine-grined biotite tonalite GOMA DH1 308.7-308.9 m

R1707895R1707896

1568 ± 6 MaMSWD = 1.3

probability = 0.2n = 18

GOMA DH1

minor resettingat ca 1650 -1570 Ma

metamorphosedat 1690 Ma

emplaced at1920 Ma

emplaced andmetamorphosed

at ca 1570 Ma

R1707895R1707896

GOMA 3

GOMA 2

GOMA 4

1586±8 Ma

‘Kararan’ metamorphic agesFanning et al., 2007; Payne et al., 2006; 2008; Cutts et al., in press

1569±8 Ma

1578±7 Ma

~1560 Ma

~1590 Ma

GOMA 1

1568±6 Ma

GOMA DH4

465.4 m

516.8

494m

502m

R1707908

R1707907

R1707904

R1707908: quartz-feldspar-biotite-hornblende orthogneissGOMA DH4 510 m

• Abundant inheritance as small cores 2680 - 3170 Ma• Homogenous black to zoned cores ca 2520 Ma• Light CL rims ca 1523 Ma

R1707908

• Age pattern of cores consistent with Mulgathing Complex orthogneisses

GOMA 3

GOMA 2

GOMA 4

GOMA 1

• Age pattern of cores consistent with Mulgathing Complex orthogneisses

• No evidence of late Sleaford (2410 - 2450 Ma) or Kimban (1720-1690 Ma)

• Post Kararan (1570-1545) zircon growth at 1521 ± 9 Ma

• Low yield about 15 grains from 30 cm ¼ core

R1707904 quartz monzoniteKspar-quartz-plagioclase GOMA DH4 484 m

R1707904

R1707904quartz monzoniteGOMA DH4 484 m

No sign of zirconovergrowth at

1521 Ma

R1707904

1759 Ma

≤ 1520 Mahigh-level intrusion

1521 Mametamorphism?

magmatism?metasomatism?

DH4

emplaced atca 2520 Ma

ca 2560 Ma metamorphism?

granophyricleucocratic

monzo- to syenogranite

No sign of zirconovergrowth at

1521 Ma

} 1518 Ma

4

• Nearby high level, undeformed intrusions

• Monazites ca 1470 Ma(Swain unpublished)

• No zircon

Acknowledgements

• PIRSA Geological Survey of South Australia responsible for the GOMA Drilling team, in particular Rian Dutch, Marc Davies and Mark Flintoft.

• SHRIMP geochronology is undertaken as part of a National Geoscience Agreement between Geoscience Australa (GA) and PIRSA. The Geochronology group at GA is acknowledged for providing excellent preparation and analytical facilities and for valuable discussions on the methods and specifics of the northern Gawler Craton geochronology.

• Ben Wade at Adelaide Microscopy, the University of Adelaide is acknowledged for his patient and cheerful assistance with the LA-ICPMS work undertaken by AR.

• high resolution drill tray pictures were obtained using HyLoggerTM,a trade mark of CSIRO