EXPLANATORY NOTES GEOLOGY OF THE DIXON 1:100 000 SHEET
by I. M. Tyler
1:100 000 GEOLOGICAL SERIES MONTAGUE DRYSDALE- MEDUSA SD 52 SOUND LONDON- BANKS DERRY 12 5,9 10 CAMDEN SOUND ASHTON CAMBRIDGE PRINCE REGENT- GULF 16 15, 13 14 PENDER o YAMPI CHARNLEY MT LISSADELL 16 ELIZABETH 2 3 4 1 2 BROOME DERBY LENNARD LANSDOWNE DIXON RIVER RANGE 6 SE 51 7 8 5 6 LA GRANGE MT NOONKAN- MT RAMSAY GORDON SE 52 ANDERSON BAH DOWNS 10 11 12 9 10 MANDORA MUNRO McCLARTY CROSSLAND MT BANNER- BILLILUNA HILLS MAN PORT 13 14 15 16 13 HEDLAND- 14 YARRIE ANKETELL o DAMPIER ROEBOURNE BEDOUT JOANNA DUMMER CORNISH LUCAS 20 BARROW SPRING ISLAND ISLAND 2 3 1 2 3 4 1 4 1 2 PYRAMID MARBLE NULLAGINE PATERSON SAHARA PERCIVAL HELENA STANSMORE ONSLOW YARRALOOLA BAR RANGE 8 5 6 7 5 6 7 SF 51 8 5 6 SF 50 BALFOUR ROY HILL RUDALL TABLETOP URAL WILSON WEBB SF 52 NINGALOO YANREY WYLOO MT BRUCE DOWNS 10 11 12 9 10 11 12 9 12 9 10 TUREE NEWMAN ROBERTSON GUNANYA RUNTON MORRIS RYAN MACDONALD SF 49 MINILYA WINNING EDMUND POOL CREEK 15 16 13 14 15 16 13 16 13 14 14 COLLIER BULLEN TRAINOR MADLEY o MT PHILLIPS MT WARRI COBB RAWLINSON 24 QUOBBA KENNEDY EGERTON RANGE 2 3 4 1 2 3 4 1 4 1 2 NABBERU STANLEY HERBERT GLENBURGH ROBINSON PEAK HILL BROWNE BENTLEY SCOTT SHARK WOORAMEL RANGE BAY- 8 5 6 7 5 6 7 SG 51 8 5 6 SG 50 GLENGARRY WILUNA YOWALGA SG 52 SG 49 YARINGA KINGSTON ROBERT TALBOT EDEL BYRO BELELE COOPER 10 11 12 9 10 11 12 9 8,12 9 10 CUE SANDSTONE SIR DUKETON THROSSELL WESTWOOD LENNIS AJANA MURGOO SAMUEL WAIGEN 15 16 13 14 15 13 14 16 13 14 o KIRKALOCKA YOUANMI LEONORA LAVERTON RASON NEALE VERNON 28 GERALDTON- YALGOO WANNA HOUTMAN ABROLHOS 2 3 4 1 2 3 4 1 2 1 MENZIES EDJUDINA PERENJORI NINGHAN BARLEE MINIGWAL PLUMRIDGE JUBILEE MASON
7 8 5 6 7 8 DONGARA- 6 SH 51 5 6 SH 50 JACKSON KAL- SEEMORE LOONGANA HILLRIVER CUNDEELEE SH 52 MOORA BENCUBBIN GOORLIE KURNALPI FORREST 12 9 10 11 5,9 10 11 12 9 10 BOOR- PERTH KELLER- SOUTHERN WIDGIE- ZANTHUS NARETHA MADURA EUCLA BERRIN CROSS ABBIN MOOLTHA 13 14 15 14 15 16 16 13 14 o CORRIGIN HYDEN LAKE NORSEMAN BALLA- CULVER BURN- 32 PINJARRA JOHNSTON DONIA NOONAERA ABBIE 2 3 4 1 2 3 4 1 2 COLLIE DUMBLE- NEWDE- RAVENS- ESPERANCE- MALCOLM- YUNG GATE THORPE MONDRAIN CAPE ARID ISLAND 6 7 8 5 7, 11 BUSSELTON- SI 50 SI 51 BREMER 6, 10 AUGUSTA PEMBERTON- MT BAY 5, 9 IRWIN INLET BARKER- 10, 14 11, 15 12 ALBANY
120 o o 114 o 126
MOUNT TURKEY REMARKABLE CREEK OSMAND 4463 4563 4663
DIXON RANGE SE52–06
McINTOSH DIXON LINACRE 4462 4562 4662
IMT104 25.03.04 GEOLOGICAL SURVEY OF WESTERN AUSTRALIA
GEOLOGY OF THE DIXON 1:100 000 SHEET
by I. M. Tyler
Perth 2004 MINISTER FOR STATE DEVELOPMENT Hon. Clive Brown MLA
DIRECTOR GENERAL, DEPARTMENT OF INDUSTRY AND RESOURCES Jim Limerick
DIRECTOR, GEOLOGICAL SURVEY OF WESTERN AUSTRALIA Tim Griffin
REFERENCE The recommended reference for this publication is: TYLER, I. M., 2004, Geology of the Dixon 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 30p.
National Library of Australia Card Number and ISBN 0 7307 8960 8
ISSN 1321–229X
Grid references in this publication refer to the Australian Geodetic Datum 1984 (AGD84). Locations mentioned in the text are referenced using Australian Map Grid (AMG) coordinates, Zone 52. All locations are quoted to at least the nearest 100 m.
Copy editor: M. Apthorpe Cartography: D. Sutton Desktop Publishing: K. S. Noonan
Published 2004 by Geological Survey of Western Australia
Copies available from: Information Centre Department of Industry and Resources 100 Plain Street EAST PERTH, WESTERN AUSTRALIA 6004 Telephone: (08) 9222 3459 Facsimile: (08) 9222 3444 This and other publications of the Geological Survey of Western Australia may be viewed online at www.doir.wa.gov.au/gswa or purchased through the Department’s bookshop at www.doir.wa.gov.au.
Cover picture: Landsat image of DIXON. Copyright Commonwealth of Australia — ACRES, Geoscience Australia Contents
Abstract ...... 1 Introduction ...... 2 Physiography, vegetation, and climate ...... 2 Regional geological setting ...... 4 Palaeoproterozoic Lamboo Complex ...... 8 Introduction ...... 8 Eastern zone ...... 8 Halls Creek Group ...... 8 Biscay Formation (#Hr, #Hrb) ...... 10 Olympio Formation (#Ho) ...... 10 Maude Headley Member (#Hov) ...... 11 Woodward Dolerite (#dw) ...... 11 Central zone ...... 11 Tickalara Metamorphics (#mTa, #mTan, #mTav, #mToa, #mTpa, #mTps, #mTpn, #mTpc, #mTgd, #mTgm, #mTog, #mTgl, #mTss, #mTgs) ...... 11 Early deformation and metamorphism in the Central zone ...... 13
Deformation (D1/D2) ...... 13 Metamorphism (M1/2) ...... 14 Halls Creek Orogeny ...... 16 Deformation ...... 16
First deformation (D3) ...... 16 Second deformation (D4) ...... 16 Metamorphism (M3 and M4) ...... 17 Palaeoproterozoic Red Rock Basin ...... 18 Red Rock Formation (#k, #kc, #kb) ...... 18 Mesoproterozoic Yampi Orogeny ...... 18 Neoproterozoic Wolfe Creek Basin ...... 19 Ruby Plains Group ...... 19 Mount Kinahan Sandstone (#Pk) ...... 19 Eliot Range Dolomite (#Pi) ...... 19 Illjarra Sandstone (#Pj) ...... 19 Duerdin Group ...... 21 Fargoo Tillite (#Ef ) ...... 21 Moonlight Valley Tillite (#Em) ...... 21 Ranford Formation (#Eo) ...... 21 Jarrad Sandstone Member (#Eoj) ...... 21 Albert Edward Group ...... 21 Mount Forster Sandstone (#Lo) ...... 22 Elvire Formation (#Le) ...... 22 Boonall Dolomite (#Lb) ...... 22 Timperley Shale (#Lj) ...... 22 Nyuless Sandstone (#Ly) ...... 22 Neoproterozoic King Leopold Orogeny ...... 22 Palaeozoic Ord Basin ...... 22 Lower Cambrian Antrim Plateau Volcanics (_a) ...... 22 Bingy Bingy Member (_ab) ...... 23 Blackfella Rockhole Member (_ar) ...... 23 Middle to Upper Cambrian Goose Hole Group ...... 23 Negri Subgroup ...... 23 Headleys Limestone (_Gh) ...... 23 Nelson Shale (_Gn) ...... 23 Linnekar Limestone (_Gl) ...... 23 Panton Formation (_Gp) ...... 23 Elder Subgroup ...... 24 Eagle Hawk Sandstone (_Ge) ...... 24 Overland Sandstone (_Go) ...... 24 Upper Devonian Mahony Group ...... 24 Glass Hill Sandstone (DMg) ...... 24 Palaeozoic Alice Springs Orogeny ...... 24 Quartz veins (q) ...... 25 Cainozoic surficial deposits ...... 25 Economic geology ...... 25 Precious metal ...... 25 Vein and hydrothermal — undivided ...... 25
iii Regolith — alluvial to beach placers ...... 25 Base metal ...... 25 Orthomagmatic mafic and layered mafic–ultramafic ...... 25 Skarn ...... 25 Stratabound volcanic and sedimentary — undivided ...... 26 Stratabound sedimentary — undivided ...... 26 Vein and hydrothermal — undivided ...... 26 References ...... 27
Appendix
Gazetteer of localities on DIXON ...... 30
Figures
1. Physiography and drainage sketch map of DIXON (after Warren, 1997) ...... 3 2. Location of 1:100 000 and 1:250 000 map sheets in the east Kimberley and their relationship to tectonic units ...... 4 3. Simplified geological map of DIXON ...... 5 4. Simplified time-space plot for the three zones of the Lamboo Complex ...... 9 5. Inclusion of amphibolite, veined by metamorphosed tonalite and trondhjemite, within the Dougalls Tonalite ...... 12 6. Inclusion of amphibolite, veined by metamorphosed tonalite and trondhjemite, within the Fletcher Creek Monzogranite ...... 12
7. Small-scale, isoclinal D2 fold closures in pelitic schist, Tickalara Metamorphics ...... 14 8. Garnet porphyroblasts (a) wrapped by the S2 and S4 crenulation cleavages; (b) preserve earlier straight to sigmoidal inclusion trails of fine-grained quartz or iron oxide (GSWA 108376) ...... 14 9. Stretched amygdales in amphibolite derived from basalt lava in the Tickalara Metamorphics ...... 15 10. Garnet (Grt) surrounded by sillimanite (Sil) and irregular to subhedral crystals of staurolite (St) intergrown with biotite (Bt) (GSWA 108361) ...... 15 11. Irregular to rounded orthopyroxene in Dougalls Tonalite (GSWA 113593) ...... 16 12. Asymmetric ‘mica-fish’ in mylonitic pelite (GSWA 108355). Arrows indicate sense of shear ...... 17
13. Transposed, isoclinal, small-scale D2 fold hinges wrapped by a strong schistosity in mylonitic pelite (GSWA 108358) ...... 17 14. Lozenge-shaped porphyroclasts of quartz and plagioclase in metatonalitic rocks wrapped by an asymmetric, finely schistose to laminated mylonitic fabric (GSWA 108353) ...... 18
15. S4 schistosity wrapping ovoid patches of sericite intergrown with iron oxide and relict garnet (GSWA 108407) ...... 18
Tables
1. Summary of the geological history of DIXON ...... 6 2. Summary of SHRIMP U–Pb zircon and monazite dating of samples relevant to units on DIXON ...... 7 3. Stratigraphy of the Palaeoproterozoic to Palaeozoic sedimentary rocks on DIXON ...... 20
iv GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
Geology of the Dixon 1:100 000 sheet
by I. M. Tyler
Abstract
The DIXON 1:100 000 map sheet (SE 52-6, 4562) lies entirely within the Halls Creek Orogen, a major northeasterly trending orogenic belt developed in the Palaeoproterozoic to Palaeozoic rocks of the east Kimberley region of Western Australia. The Halls Creek Orogen initially formed in the Palaeoproterozoic between the Kimberley Craton to the northwest and the North Australian Craton to the east. Rocks of the c. 1910 to 1790 Ma Lamboo Complex share many features with convergent Phanerozoic plate margins associated with the subduction of oceanic crust. The Lamboo Complex has been divided into the parallel Western, Central and Eastern zones, with only the Central and Eastern zones outcropping on DIXON.
The oldest rocks on DIXON are the Halls Creek Group in the Eastern zone of the Lamboo Complex, that represent deposition on a passive continental margin. The low-grade mafic metavolcanic and metasedimentary rocks of the c. 1880 Ma Biscay Formation of the Halls Creek Group are overlain by the turbiditic metasedimentary rocks of the Olympio Formation, which include alkaline metavolcanic rocks of the c. 1857 Ma Maude Headley Member. The Halls Creek Group is intruded by the Woodward Dolerite. In the Central zone of the Lamboo Complex on DIXON, sedimentary and volcanic protoliths of the Tickalara Metamorphics were deposited at c. 1865 Ma. At c. 1850 Ma they were intruded by sheets of tonalite and monzogranite, with peak metamorphic conditions, ranging from epidote–amphibolite facies up to the granulite facies transition, reached at c. 1845 Ma. Accompanying deformation produced northeasterly verging recumbent folds. The deformation and metamorphism are consistent with the accretion of an island arc to the eastern edge of the Kimberley Craton.
The Central and Eastern zones of the Lamboo Complex on DIXON were deformed and metamorphosed during the c. 1835 to 1805 Ma Halls Creek Orogeny, reflecting the suturing of the Kimberley and North Australian Cratons at c. 1820 Ma. Large-scale easterly verging folding (including the Black Rock Anticline and the Biscay Anticlinorium) and thrusting was accompanied by mylonite formation along major shear zones. The c. 1800 Ma sedimentary and mafic volcanic rocks of the Red Rock Formation were deposited in the Red Rock Basin. They are preserved on DIXON as fault-bounded slivers along major strike-slip fault zones that developed during the c. 1000 Ma Yampi Orogeny. The Lamboo Complex is unconformably overlain by Neoproterozoic sedimentary rocks deposited in the Wolfe Creek Basin. The oldest group is the c. 830 Ma Ruby Plains Group, equivalent to Supersequence 1 of the Centralian Superbasin. These rocks are unconformably overlain by the Duerdin Group, which includes glacigene rocks correlated with the Marinoan glaciation, and then the Albert Edward Group. These are equivalent to Supersequences 3 and 4 of the Centralian Superbasin. Sinistral reactivation of the large-scale faults took place during the c. 560 Ma King Leopold Orogeny, deforming the Neoproterozoic sedimentary rocks. This was followed by the eruption of the basaltic rocks of the c. 513 Ma Antrim Plateau Volcanics in the Ord Basin, and deposition of the shallow marine to fluvial Middle to Upper Cambrian Goose Hole Group. Further sinistral strike-slip faulting and associated thrusting took place during the c. 400 to 300 Ma Alice Springs Orogeny, and was accompanied by the deposition of the fluvial rocks of the Devonian Mahony Group. An extensive erosion surface, the Sturt Plateau, formed between c. 250 and 24 Ma. Uplift and erosion after 24 Ma has produced the sandstone karst of the Bungle Bungle Range.
Minor occurrences of precious and base metal mineralization are present on DIXON. Mining for gold has taken place in the Halls Creek Group, and in associated alluvial deposits within the present drainage system.
KEYWORDS: Halls Creek Orogen, Lamboo Complex, Red Rock Basin, Wolfe Creek Basin, Ord Basin, Tickalara Metamorphics, Halls Creek Group, Ruby Plains Group, Duerdin Group, Albert Edward Group, Antrim Plateau Volcanics, Goose Hole Group, Mahony Group, regional geology
1 Tyler
and the Mahony Group in the eastern part of the sheet Introduction were recompiled on the 1:50 000 black-and-white photographs by A. M. Thorne (GSWA) from the mapping The DIXON* 1:100 000 map sheet (SE 52-6, 4562) is bounded by latitudes 17°30'S and 18°00'S and longitudes of Mory and Beere (1988). The mapping by R. G. Warren 128°00'E and 128°30'E. The map sheet lies within the was described in an AGSO record (Warren, 1997). DIXON RANGE 1:250 000 sheet in the east Kimberley region of Western Australia. Physiography, vegetation, and Tourism and cattle grazing for beef are the main commercial activities in the east Kimberley region, and climate the northeastern part of DIXON is within the Purnululu DIXON lies within the Ordland physiographic division National Park. Hoatson et al. (1997) detailed the (Beard, 1979). The sheet area includes parts of the Ord attractions and facilities within the park, and provided a Plains province, and the Bow River Hills, the Halls Creek guide to the rocks, landforms, plants, animals, and human Ridges, and the Albert Edward Range subprovinces of the impact. Tourist camping facilities at the Bellburn and Lamboo Hills province (Fig. 1). The Bow River Hills and Walardi campsites, and an airstrip used for scenic tourist the Halls Creek Ridges occupy the western part of the flights were not shown on the published geological map sheet and consist of low hills and ridges, the summits of (Tyler et al., 1998d), but are present along ‘Bellburn which are remnants of the Sturt Plateau, that falls from Creek’ to the northeast of Blue Hole Yards (see Hoatson about 400 m AHD† in the south and west to about 260 m et al., 1997, p. 10). The Sophie Downs, Alice Downs, and near the Ord River (Warren, 1997). The Sturt Plateau is Mabel Downs pastoral leases extend into the sheet, part of a series of ancient subdued land surfaces that were although none of their homesteads are located on it. The established in the Kimberley region during prolonged abandoned Turner Homestead is located on the Turner subaerial erosion that followed glaciation during the River, at the northwestern end of the Hardman Range. Permian, at c. 280 Ma (Plumb and Gemuts, 1976; Appendix 1 is a gazetteer of localities on DIXON. Playford, 2001). The Albert Edward Range in the central No major roads occur within the map sheet and access part of the sheet consists of steep ridges rising to over is limited to sparse, poorly maintained station tracks 540 m, and deep valleys. The Ord Plains occupy the within the pastoral leases. Vehicle access in the Purnululu eastern part of the sheet and, at around 200–220 m, National Park is restricted to tracks to campsites and generally have little relief other than the prominent points of interest between April and September. Hardman Range, which is an outlier of the Sturt Plateau, and the Dixon Range, which is an extension of the Geological investigations prior to 1969 are summar- Lamboo Hills (Warren, 1997). ized in the Explanatory Notes for the first edition of DIXON RANGE and in a bulletin on the geology of the east Erosion of the Sturt Plateau took place after 24 Ma, Kimberley region (Dow and Gemuts, 1967, 1969). More after a relative lowering of sea level by more than 300 m. recent work is referred to as appropriate in the following Creeks and rivers draining into the Joseph Bonaparte Gulf, Notes. which generally flow to the north and west as part of the Ord drainage basin, incised the old peneplanation surface The present survey was carried out during the (the Wave Hill Surface), and the Early Miocene or younger remapping of the King Leopold and Halls Creek Orogens White Mountain Formation deposited on the surface that was commenced in 1986 by the Geological Survey (Mory and Beere, 1988; Blake, 1996). Warren (1994a) of Western Australia (GSWA). The mapping also formed suggested that the major rivers draining the Lamboo Hills, part of a joint project with the Australian Geological including the westerly flowing upper Ord River and Survey Organisation (AGSO, now Geoscience Australia: Panton River, were originally headwaters to the inland GA) as part of the National Geoscience Mapping Accord Sturt drainage basin, but were captured by the northerly (NGMA) Kimberley–Arunta project. Fieldwork on DIXON flowing Ord River. This period of erosion has produced was carried out in 1992 and 1993. The Palaeoproterozoic the spectacular ‘beehives’ sandstone karst scenery of the Tickalara Metamorphics and Red Rock Formation rocks Purnululu National Park (Young 1986, 1987; Blake, 1996; in the northwestern part of the sheet were mapped by Hoatson et al., 1997). I. M. Tyler (GSWA), with the Palaeoproterozoic Halls Creek Group rocks in the western part being mapped by The vegetation of the Kimberley region has been R. G. Warren (AGSO), both using 1:25 000 colour aerial described by Beard (1979). The Lamboo Hills are covered photography flown in 1991 and available from the Western by low-tree savanna and sparse tree steppe comprising Australian Department of Land Information (DLI). The spinifex and eucalypts. The vegetation covering the Ord Neoproterozoic rocks of the Ruby Plains, Duerdin, and Plain is strongly controlled by the underlying geology. Albert Edward Groups in the southeastern part of the sheet Short-grass, low-tree savanna and tree steppe grow on the were mapped and recompiled by R. G. Warren and basalt of the Antrim Plateau Volcanics, steppe with D. H. Blake (AGSO) using DLI 1:50 000 black-and-white scattered low trees on the Headleys Limestone, grass aerial photography flown in 1988. The Phanerozoic rocks savanna on the rest of the Goose Hole Group, and low tree of the Antrim Plateau Volcanics, the Goose Hole Group, savanna and sparse tree steppe on the sandstones of the Mahony Group.
* Capitalized names refer to standard 1:100 000 map sheets, unless otherwise indicated. † Australian Height Datum
2 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
17° 30' Black
Point Frank Creek Creek River
Black Hills Rock Blue Hole Wills PURNULULU NATIONAL PARK
Black
RANGE
DIXON
Ord Black River
Duck Edle Creek
Creek
Grant Peak Panton
Turner (abd) River BAY OF BISCAY HILLS HARDMAN RANGE Turner
Turner Hill RANGE Kartung Rija
Elvire Aboriginal Reserve River
Creek
River EDWARD
Mt Forster
Saunders 128° 30' 128° 00'
ALBERT 18° 00' IMT88 16.01.04
Bow River Hills Topographic feature LAMBOO HILLS Halls Creek ridges Major track PROVINCE Homestead (abd) Albert Edward Range National Park boundary ORD PLAINS PROVINCE 20 km
Figure 1. Physiography and drainage sketch map of DIXON (after Warren, 1997)
3 Tyler 126° 129°
SOUTHERN BONAPARTE BASIN The climate is semi-arid monsoonal having a ‘wet’ C a season when temperatures are hot and humidity is high, rlton S
h and a ‘dry’ season when temperatures are warm to hot and elf humidity is low. Rainfall averages between 600 and ASHTON CAMBRIDGE GULF Pincombe 900 mm per annum, and is mainly generated from Inlier thunderstorms and cyclones between November and April. Burt Average daily maximum temperatures vary from 36–39°C Range KIMBERLEY BASIN Bastion Shelf in December and January to 27–30°C in June and July. Basin Mount Rob Outlier Carr 16° Boyd Watercourses generally only flow after prolonged Basin Revolver heavy rain. Permanent pools occur in some of the rivers, MOUNT ELIZABETH LISSADELL Creek Basin however wells and bores provide water supplies for stock. Ragged Range Outlier
Regional geological setting Osmond Basin Durack Fold Belt MOUNT TURKEY OSMAND Mount House REMARKABLE CREEK Group Victoria River The regional geological setting and the main tectonic units LANSDOWNE DIXON RANGE Basin IXON found on D are shown in Figure 2, and the tectonic Red Rock and one units and simplified geology of the map sheet are shown Z Texas Downs Basins Zone KING LEOPOLD OROGEN in Figure 3. A summary of the geological history of DIXON McINTOSH LINACRE HOOPEROROGEN DIXON COMPLEX ORD is presented in Table 1, geochronology for units on DIXON ORD Speewah Basin
Central Western BASIN is summarized in Table 2 and the stratigraphy of the 18° Palaeoproterozoic to Palaeozoic sedimentary rocks is CREEK Zone summarized in Table 3. The map sheet lies almost entirely MOUNT RAMSAY GORDON DOWNS within the Halls Creek Orogen (Fig. 2), a major north- Crowhurst Eastern Belt Basin Moola Bulla Wolfe Creek Basin easterly trending orogenic belt developed within the Pillara Basin Inlier old F Proterozoic and Palaeozoic rocks of northern Australia Louisa Basin HALLS (Myers et al., 1996; Tyler et al., 1998c; Tyler and Hocking, 2001). The orogen formed initially in the Palaeo- Birrindudu Basin Hardman LAMBOO COMPLEX proterozoic during a collision between the Kimberley Lucas Craton Craton to the northwest, and a composite Archaean craton Jones Arch to the east, to form the North Australian Craton (Tyler Billiluna Shelf et al., 1995; Myers et al., 1996; Blake et al., 2000; Griffin IMT92 30.03.04 et al., 2000; Sheppard et al., 1999, 2001). Following Phanerozoic 1:250 000 sedimentary and ASHTON collision, the orogen was the locus of repeated sedimentary Neoproterozoic map sheet volcanic rocks basin formation, orogenic deformation and associated fault 1:100 000 reactivation during the Palaeoproterozoic, Mesoprotero- Mesoproterozoic McINTOSH map sheet zoic, Neoproterozoic, and Phanerozoic (Tyler et al., 1995; igneous and Palaeoproterozoic Thorne and Tyler, 1996; Blake et al., 2000). metamorphic rocks Archaean granite–gneiss 200 km The oldest component of the Halls Creek Orogen is King Leopold Orogen the c. 1910 to 1790 Ma Lamboo Complex, a north- northeasterly trending belt of igneous and low- to high- Halls Creek Orogen grade meta-igneous and metasedimentary rocks that underlie the western part of DIXON (Dow and Gemuts, 1969; Griffin and Grey, 1990; Blake et al., 1999, 2000; Figure 2. Location of 1:100 000 and 1:250 000 map sheets Griffin et al., 2000; Page et al., 2001). Earlier models for in the east Kimberley and their relationship to the formation of the Lamboo Complex, and other belts of tectonic units similar age in northern Australia, proposed extension and crustal thinning, then convergence without subduction of oceanic crust (Hancock and Rutland, 1984; Etheridge events, the c. 1865 to 1850 Ma Hooper Orogeny and the et al., 1987; Wyborn, 1988). However Ogasawara (1988) c. 1835 to 1805 Ma Halls Creek Orogeny. noted that the chemistry of tonalites in the Lamboo Complex is similar to that of tonalites formed by partial Before the collision of the Kimberley Craton with the melting of basaltic rock above Phanerozoic subduction rest of the North Australian Craton, sedimentary rocks zones, and suggested that the Halls Creek Orogen may were being deposited in the c. 1835 Ma Speewah Basin represent the site of a Palaeoproterozoic convergent to the west of the orogen, at the same time as the intrusion margin. More recently Tyler et al. (1995, 1999), Griffin of granitic and gabbroic rocks into the Lamboo Complex et al. (2000), and Sheppard et al. (1999, 2001) have argued during the Halls Creek Orogeny (Tyler et al., 1995; Blake that the Lamboo Complex shares many features with et al., 2000; Tyler, 2000). The overlying post-orogenic convergent Phanerozoic plate margins associated with the sedimentary rocks of the c. 1830 to 1790 Ma Kimberley subduction of oceanic crust. These authors presented a Basin extended across the Lamboo Complex, being equiv- plate tectonic model for the c. 1910 to 1790 Ma evolution alent to the rocks of the Red Rock, Texas Downs, and of the Halls Creek Orogen, which involved two orogenic Revolver Creek Basins (Blake et al., 2000; Tyler, 2000).
4 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
17°30'
Fault 128°30'
Downs BlackAnticline Rock
Alice
Fault
Creek
Halls Hardman Syncline 128°00' 18°00' IMT90 01.04.04 Mahoney Group Tickalara Metamorphics
ORD BASIN Goose Hole Group Woodward Dolerite
Antrim Plateau Volcanics LAMBOO Halls Creek Group COMPLEX Albert Edward Group Fault, strike-slip Duerdin Group WOLFE CREEK BASIN Fault Anticline Ruby Plains Group 20 km Syncline Red Rock Formation RED ROCK BASIN
Figure 3. Simplified geological map of DIXON
5 Tyler
Table 1. Summary of the geological history of DIXON
______Lamboo Complex ______Age (Ma) Central zone Eastern zone c. 1880(a) Deposition of the Biscay Formation mafic volcanic and sedimentary rocks c. 1865(b) Deposition of the mafic volcanic and siliciclastic and carbonate sedimentary protoliths to the Tickalara Metamorphics (c) 1863–1850 Early layer-parallel deformation (D1); greenschist facies
metamorphism (M1) <1873–1857(d) Deposition of the lower Olympio Formation turbiditic sedimentary rocks. Eruption of the Maude Headley Member alkaline volcanic rocks c. 1850(e) Intrusion of the Dougalls Tonalite, Monkey Yard Tonalite, and Fletcher Creek Monzogranite as sheet-like intrusions; associated contact metamorphism and metasomatism (f) c. 1845 Northeasterly verging recumbent folding (D2); epidote– amphibolite to granulite facies high T/low P
metamorphism (M2) <1847(g) Deposition of the upper Olympio Formation turbiditic sedimentary rocks Intrusion of Woodward Dolerite
1835–1805(e) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ HALLS CREEK OROGENY ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Formation of upright, SSW-plunging folds (D3) Layer-parallel shearing, related to SW-directed under epidote–amphibolite facies conditions (M3). extension (D3) Formation of the tight to isoclinal, east-facing, NNE- Upright to moderately inclined SSE-facing, NNE-
plunging Black Rock Anticline (D4); epidote–amphibolite plunging open to isoclinal folds and associated thrusts to greenschist facies mylonitic rocks along major fault zones (D4); associated low-grade metamorphism ?1800 Deposition of Red Rock Formation sedimentary and mafic volcanic rocks Red Rock Basin c. 1000(h) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ YAMPI OROGENY ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Large-scale sinistral strike-slip faulting, associated folding, and local cleavage development (D5) c. 830(i) Deposition of the Ruby Plains Group Wolfe Creek Basin c. 610(j) Deposition of the Duerdin Group and the Albert Edward Group c. 560(h) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ KING LEOPOLD OROGENY ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Sinistral strike-slip reactivation of major faults (D6) c. 513(k) Eruption of the mafic Antrim Plateau Volcanics Ord Basin 513–495(l) Deposition of the Goose Hole Group
300–400 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ALICE SPRINGS OROGENY ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Sinistral strike-slip reactivation of major faults (D7) c. 370(l) Deposition of the Mahony Group Ord Basin 250–24(m) Formation of plateau surface 24–present(n) Uplift and erosion of plateau surface
NOTES: (a) Blake et al. (1999) (h) Shaw et al. (1992) (b) Page et al. (1995), Page and Hoatson (2000), Bodorkos et al. (2000a) (i) Grey and Blake (1999) (c) Page and Hoatson (2000), Page et al. (2001) (j) Grey and Corkeron (1998) (d) Page and Sun (1994), Griffin et al. (1998), Blake et al. (1999), R. W. Page in (k) Hanley and Wingate (2000) Geoscience Australia’s OZCHRON database (l) Mory and Beere (1988) (e) Page et al. (2001) (m) Plumb and Gemuts (1979), Playford (2001) (f) Oliver et al. (1999), Bodorkos et al. (2000a) (n) Mory and Beere (1988), Blake (1996) (g) Blake et al. (1999), R. W. Page in Geoscience Australia’s OZCHRON database
6 GSWA Explanatory Geology ofNotes the Dixon 1:100 000 sheet e and Hoatson (2000) e and Hoatson (2000) OZCHRON metamorphism 2 metamorphism 2 IXON 3444al. (1999) et Blake al. (2000) et Bodorkos al. (2000) et Bodorkos 5al. (2000) et Bodorkos al. (1999) et Blake ± 2 Page et al. (2001) zircon: igneous crystallization zircon: maximum deposition zircon: igneous crystallization monazite: peak high-grade M zircon: igneous crystallization zircon: maximum depositional age 1847 ± 6 zircon: maximum deposition zircon: maximum deposition zircon: peak high-grade M zircon: igneous crystallization zircon: igneous crystallization 00800 1880 ± 47730 1865 ± 377400 1864 ± 69500 1867 ± 69500 1845 ± 865003 ± 1845 31584 1863 ± 363200 1849 ± 364600 Pag 1850 13400 1873 ± 507900 1857 ± 38100 et al. (1999) Oliver Pag Page al. et (2001) OZCHRON 80 80 80 80 80 80 80 80 80 80 80 80 79200 84510 10400 98600 98600 93700 74866 94800 94500 88400 86100 05800 Easting Northing 3 3 4 3 3 3 3 3 3 3 3 4 fragmental volcanic rock fragmental volcanic eldspathic wacke Garnet-bearing migmatitic metasedi- Garnet-bearing migmatitic Garnet–sillimanite pelite Garnet–sillimanite pelite Hypersthene granulite Garnet–biotite monzogranite sandstone Coarse arkosic (GA) mentary rock (palaeosome) zircon: maximum deposition 9352601293525043 felsic Foliated 97SB12595SB11 Psammite 95SB11 SM25H113349 migmatite Stromatic 93526006 Gneissic metagranite 93526007 93525128B85598001 F 92524896 rock felsic volcanic Porphyritic (GA) Table 2. Summary of SHRIMP U–Pb zircon and monazite dating of samples relevant to units on U–Pb zircon and monazite dating of Table 2. Summary of SHRIMP D REEK REEK REEK REEK REEK REEK C C C C C C NTOSH NTOSH NTOSH I I I C C C IXON IXON IXON ALLS ALLS URKEY URKEY URKEY URKEY Dougalls Tonalite D Rose Bore Granite M Unit Map sheet Sample Lithology AMG coordinates(Ma) Age Reference Tickalara MetamorphicsTickalara M Fletcher Creek Monzogranite D Maude Headley Member H Tickalara MetamorphicsTickalara T Tickalara MetamorphicsTickalara MetamorphicsTickalara T T Olympio FormationLower M Upper Olympio Formation D Tickalara MetamorphicsTickalara T Biscay Formation H
7 Tyler
In the northwestern part of DIXON, sedimentary rock and volcanic rocks of the c. 1855 Ma Whitewater Volcanics basalt, which outcrop in fault-bounded slivers along the (Griffin et al., 1993; Tyler et al., 1999; Griffin et al., 2000). Halls Creek and Alice Downs Faults, were deposited in The metasedimentary and volcanic rocks were deformed the Red Rock Basin (Dow and Gemuts, 1969; Tyler et al., and metamorphosed, and were extensively intruded by 1995, 1997b; Blake et al., 2000). granitic and gabbroic rocks of the Paperbark supersuite, as well as by subvolcanic porphyries and by layered Large-scale sinistral strike-slip faulting took place in mafic–ultramafic intrusions, during the Hooper Orogeny the Halls Creek Orogen during the Mesoproterozoic Yampi between c. 1865 and 1850 Ma (Tyler and Page, 1996; Orogeny (1400–1000 Ma). During this orogeny a pattern Tyler et al., 1999; Griffin et al., 2000; Page and Hoatson, of north-northeasterly trending synthetic sinistral faults, 2000; Page et al., 2001). and east-northeasterly trending antithetic dextral faults was established (Tyler et al., 1995; Thorne and Tyler, 1996). The Central zone (Fig. 4) is dominated by medium- to high-grade metasedimentary and meta-igneous rocks In the eastern part of the sheet the Lamboo Complex of the Tickalara Metamorphics, which were intruded is unconformably overlain by Neoproterozoic sedimentary by granitic sheet-like intrusions, and deformed rocks of the Wolfe Creek Basin (Shaw et al., 1994; Grey and metamorphosed between c. 1865 and 1856 Ma and and Blake, 1999), which are part of the Centralian at 1850–1845 Ma (Tyler and Page, 1996; Bodorkos Superbasin. This superbasin was interpreted by Walter et al., 1999, 2000a; Blake et al., 2000; Page et al., 2001). et al. (1995) as a broad intracratonic sag-basin that In the southern part of the Central zone, low-grade meta- extended throughout much of central Australia between sedimentary and mafic and felsic volcanic rocks of the c. 800 Ma and the earliest Cambrian. The c. 560 Ma King Koongie Park Formation were deposited at 1845–1840 Ma Leopold Orogeny affected rocks throughout the King (Page et al., 1994). Layered mafic–ultramafic bodies were Leopold and Halls Creek Orogens, giving rise to a intruded into the Central zone at c. 1856 Ma, c. 1845 Ma, widespread unconformity at the base of the succeeding and c. 1830 Ma (Page and Hoatson, 2000). Large volumes c. 515 Ma Lower Cambrian basaltic volcanic rocks and of granite and gabbro of the Sally Downs supersuite Middle to Upper Cambrian sedimentary rocks in the Ord intruded the Central zone during the Halls Creek Orogeny Basin. The volcanic rocks form part of an extensive at 1835–1805 Ma (Tyler and Page, 1996; Page et al., continental flood basalt province that originally extended 2001). The c. 1804 Ma Eastmans Granite intruded the across 300 000 km2 of northern Australia (Hanley and southeastern end of the Central zone (Tyler et al., 1998a; Wingate, 2000). Devonian sedimentary rocks of the Ord Page et al., 2001). Basin were deposited in sub-basins formed by extensive sinistral strike-slip faulting and associated folding and The Eastern zone (Fig. 4) is composed of low-grade thrusting related to the c. 400 to 300 Ma Alice Springs metasedimentary and metavolcanic rocks of the Halls Orogeny in central Australia (Mory and Beere, 1988; Creek Group, which unconformably overlie c. 1910 Ma Thorne and Tyler, 1996). The Hardman Fold Belt (Tyler mafic and felsic volcanic rocks of the Ding Dong Downs and Hocking, 2001) formed at this time. Volcanics, together with associated granitic rocks (Tyler et al., 1998b; Blake et al., 1999). Mafic volcanic rocks in the lower part of the Halls Creek Group were erupted at c. 1880 Ma, with alkaline volcanic rocks within turbiditic Palaeoproterozoic Lamboo metasedimentary rocks in the middle and upper part erupted between c. 1857 Ma and c. 1848 Ma (Blake et al., Complex 1999). The Woodward Dolerite forms a series of dolerite sills intruded into the Halls Creek Group. Both the Halls Introduction Creek Group and the Woodward Dolerite were deformed and metamorphosed during the 1835–1805 Ma Halls Hancock and Rutland (1984) divided the Lamboo Creek Orogeny, and were intruded by c. 1820 to 1810 Ma Complex into four zones. Griffin and Tyler (1992) granites of the Sally Downs supersuite, and by the amalgamated zones II and III, and Tyler et al. (1994, 1995) c. 1788 Ma San Sou Monzogranite, at the southern end of and Tyler (2000) subsequently modified their zone the Lamboo Complex (Tyler et al., 1998b; Blake et al., boundaries. The three zones (Western, Central and 1999; Page et al., 2001). Eastern) trend north-northeasterly (Fig. 2) along the length of the complex and are separated by major fault systems. On DIXON, only the Central and Eastern zones are present, Eastern zone separated by the Halls Creek Fault (Fig. 3). Stratigraphic units cannot be correlated across the zone boundaries, Halls Creek Group and this is consistent with the zones forming Palaeo- proterozoic tectonostratigraphic terranes (Tyler et al., On DIXON the Eastern zone lies to the east of the Halls 1995; Fig. 4). Creek Fault and trends north-northeasterly, occupying most of the western third of the sheet (Fig. 3). The rocks The Western zone of the Lamboo Complex (Fig. 4) is exposed within the zone belong predominantly to the a continuation of the Hooper Complex in the King Palaeoproterozoic Halls Creek Group. Leopold Orogen of the west Kimberley region (Griffin et al., 2000). It is composed of low- to high-grade The rocks of the Halls Creek Group were defined and turbiditic metasedimentary rocks of the c. 1870 Ma described by Dow and Gemuts (1969), and the group was Marboo Formation, unconformably overlain by felsic redefined by Griffin and Tyler (1992). The Halls Creek
8 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
WESTERN ZONE CENTRAL ZONE EASTERN ZONE Ma
1790 Hart Dolerite 1790
1800 Kimberley Group and equivalents 1800
1810 1810 D /M D4 /M4 4 4 1820 1820
Speewah D3 /M3 1830 Group 1830 Koongie Park Woodward Dolerite 1840 Whitewater Formation ?? ?1840 Volcanics Olympio Formation D2 /M2 1850 Butchers Gully Member 1850 D1 /M1 Maude Headley Volcanic Member 1860 1860 D2 /M2 D1 /M1 1870 Marboo Tickalara 1870 Formation Metamorphics ?? ? 1880 Ruins Biscay Formation 1880 Dolerite Saunders Creek Formation ?? ? 1890 1890
1900 1900
1910 1910
IMT89 01.04.04
Sally Downs supersuite Dougalls suite Turbidite
Paperbark supersuite Alkaline volcanic rock Mafic volcanic rock
Dolerite sills Felsic and mafic volcanic rock Deformation/metamorphism
Terrigenous clastic rock Felsic volcanic rock
Figure 4. Simplified time-space plot for the three zones of the Lamboo Complex. Layered mafic–ultramafic intrusions have been omitted for clarity; they intruded the Western zone at c. 1856 Ma, and the Central zone at c. 1856 Ma, 1841 Ma and 1830–1810 Ma (after Sheppard et al., 2001; references for ages are given in Table 2, and in the text)
Group now consists of three formations: the Saunders Sensitive High-Resolution Ion MicroProbe (SHRIMP) Creek Formation (not present on DIXON), the Biscay U–Pb zircon age of 1880 ± 3 Ma (Blake et al., 1999), Formation, and the Olympio Formation. The upper part interpreted as the age of volcanism, for the Biscay of the mafic volcanic-dominated Biscay Formation is Formation, making it the oldest rock unit on DIXON. Page exposed in the southwestern corner of the sheet and is and Hancock (1988) reported a conventional U–Pb zircon overlain by the extensive turbiditic metasedimentary rocks age of 1856 ± 5 Ma for a felsic ‘sill’ within ‘Biscay of the Olympio Formation. Alkaline volcanic rocks of the Formation tuffs’ in the northeastern part of HALLS CREEK. Maude Headley Member occur in the lower part of the Owing to uncertainty as to whether the ‘sill’ was coeval Olympio Formation. with the surrounding rocks, it was regarded as a minimum age for the Halls Creek Group. Blake et al. (1999) mapped A deformed felsic volcanic rock from the Ilmars the ‘sill’ as a lava flow, and both the flow and the copper–lead–zinc prospect on HALLS CREEK gives a fragmental volcanics that enclose it belong to the Maude
9 Tyler
Headley Member of the Olympio Formation. SHRIMP TiO2, P2O5, Cr, Y, Nb, and Zr contents, and trace element U–Pb zircon ages of 1857 ± 5 Ma and 1857 ± 2 Ma have ratios similar to low-TiO2 continental flood-basalts. been obtained from the same rock and from a pyroclastic Sheppard et al. (1999) considered that they were erupted rock sampled on MCINTOSH respectively (Page and Sun, on a passive continental margin along the western edge 1994; Griffin et al., 1998; Blake et al., 1999; R. W. Page of the North Australian Craton prior to its collision with in Geoscience Australia’s OZCHRON database), providing the Kimberley Craton. a depositional age for the lower part of the Olympio Formation. Olympio Formation (PLHo) A detrital zircon population from an Olympio The following description is based on Warren (1997), Formation turbiditic sandstone sampled on MCINTOSH that Tyler et al. (1998b), and Blake et al. (1999). The Olympio underlies the Maude Headley Member gave a SHRIMP Formation (#Ho) is the youngest and most widespread U–Pb age of 1873 ± 5 Ma (Blake et al., 1999; R. W. Page unit of the Halls Creek Group on DIXON. The contact in Geoscience Australia’s OZCHRON database) providing with the underlying Biscay Formation on DIXON is con- a maximum depositional age for the lower part of the formable, either with the <1873 Ma lower Olympio Olympio Formation. On DIXON a detrital zircon population Formation turbiditic sedimentary rocks, or with the from an Olympio Formation turbiditic sandstone sampled c. 1857 Ma Maude Headley Member volcanic rocks. The above the Maude Headley Member gave a SHRIMP geochronological data suggest that there may be a time U–Pb age of 1847 ± 6 Ma (Table 2; Blake et al., 1999; gap of up to 20 Ma separating the two formations (Blake R. W. Page in Geoscience Australia’s OZCHRON et al., 2000). Due to the lack of persistent marker horizons database) providing a maximum depositional age for the and the possibility of structural repetition, the thickness upper part of the Olympio Formation. of the Olympio Formation is difficult to estimate. However, Dow and Gemuts (1969) suggested that the unit Tight to isoclinally folded rocks of the Halls Creek was 4000 m (12 000 feet) thick. Hancock and Rutland Group are intruded by the Mount Christine Granitoid (1984) and Hancock (1991) give similar thickness on DOCKRELL (Tyler et al., 1998b), the oldest component estimates for the formation. of which has given a SHRIMP U–Pb zircon age of 1817 ± 4 Ma (Page et al., 2001) providing a minimum The Olympio Formation consists predominantly of depositional age for the Halls Creek Group. Deformation thin- to very thick bedded (up to 10 m), fine- to coarse- took place during the c. 1835 to 1805 Ma Halls Creek grained turbiditic mudstone, siltstone, quartz wacke, Orogeny. Deformed Halls Creek Group rocks are greywacke, quartz sandstone, lithic sandstone, and arkosic unconformably overlain by the ?1835–1800 Ma Moola sandstone, with minor pebbly sandstone. Warren (1997) Bulla Formation on HALLS CREEK (Blake et al., 1999). records the presence of a boulder bed exposed in the Ord River, although a precise location is not given. Sandstone layers show graded bedding, with flame structures and rip- Biscay Formation (PLHr, PLHrb) up clasts occuring at the contacts with underlying The following description is based on Warren (1997) and mudstone. Thinner, finer grained sandstone layers show Blake et al. (1999). The c. 1880 Ma Biscay Formation is graded bedding and, locally, ripple cross-lamination. in excess of 1000 m thick on HALLS CREEK (Blake et al., Clasts are commonly angular to subrounded, and 1999), reaching 1500 m further south on DOCKRELL (Tyler consist predominantly of quartz and feldspar in a matrix et al., 1998b). On DIXON only the upper part of the Biscay of quartz, chlorite, and clay minerals. Cubes of iron oxides Formation is present and consists predominantly of mafic or cube-shaped voids up to 0.5 cm across after sulfide volcanic rocks metamorphosed under low- to medium- occur locally. The metamorphic grade of the Olympio grade conditions (#Hr). These were originally fine grained Formation on DIXON is very low to low, probably reaching basalt lava flows, mafic volcaniclastic rocks, and the middle greenschist facies (Dow and Gemuts, 1969). volcanogenic sedimentary rocks derived from Minor clast components in the sandstones are jasper, vein contemporaneous erosion of the volcanic rocks. Pillow quartz, chert, microgranite, shale and fine-grained mafic lavas are not preserved on DIXON, but have been rock, tourmaline, and flakes of detrital muscovite. Locally, recognized in the Biscay Formation on DOCKRELL (Tyler clasts of the Maude Headley Member may be seen in the et al., 1998b). Some coarser grained flows have basal part of the upper Olympio Formation. The boulder amygdaloidal tops. Cyclic units occur at the top of the bed in the Ord River section contains granite clasts and Biscay Formation where a basalt lava flow was followed blocks of limestone up to 0.5 m long. by mafic volcaniclastic rocks and volcanogenic sedimentary rocks capped by thin layers of chert, with or The Olympio Formation has been interpreted as being without thin layers and pods of carbonate (#Hrb). The deposited by turbidity currents as part of a submarine fan uppermost unit in the Dry Creek area on DIXON is a fine system (Dow and Gemuts, 1969; Hancock and Rutland, grained chert or siliceous volcaniclastic sandstone. 1984; Hancock, 1991). Complete Bouma sequences (Walker, 1984) are uncommon, but divisions A, D, and E The Biscay Formation may represent mainly shallow- are usually represented. Hancock (1991) tentatively water shelf sedimentation and subaqueous to subaerial reported that palaeocurrents obtained from outcrops in the volcanism (Blake et al., 1999). Geochemically the upper Olympio Formation to the northeast of Halls Creek metabasalts can be divided into two groups (Sheppard townsite were from the northwest. The petrography of et al., 1999). One group has compositions similar to clasts within the sandstone units indicated a continental, enriched (E-) MORB, while the second group has lower largely crystalline source predominantly composed of
10 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet granitic rocks, with variable input of felsic volcanic rocks (1997) described the rock in outcrop as a dark green, and muscovite-bearing sedimentary rocks (Hancock, medium-grained, even-textured metadolerite. A second sill 1991). Clast composition on DIXON is also consistent with is present in the Grants Patch area on MCINTOSH and may rapid erosion of a proximal, predominantly granitic source. extend onto DIXON. It has fine-grained margins and a relict The detrital zircon ages of c. 1873 Ma for the lower ophitic texture. Olympio Formation and c. 1847 Ma for the upper Olympio Formation indicate that they were derived from The Woodward Dolerite forms a series of sills intruded different source regions. The c. 1847 Ma age from the throughout the Halls Creek Group on HALLS CREEK and upper Olympio Formation is too young for derivation from DOCKRELL, and these may be of different ages ranging from the underlying units of the Halls Creek Group or from the c. 1910 Ma to <1847 Ma (Tyler et al., 1998b; Blake et al., Western zone of the Lamboo Complex. It is also not 1999). They have been affected by, and therefore predate, consistent with a provenance in the Central zone, which the earliest deformation and metamorphism that affects the includes extensive mafic volcanic rocks and granitic rocks Halls Creek Group, and are probably older than with tonalitic compositions, and from which a more c. 1835 Ma. complex detrital zircon population might be expected. The source area does not appear to be exposed within the Halls Creek Orogen at present and was probably removed during Central zone possibly contemporaneous strike-slip movements along a proto-Halls Creek Fault system. Tickalara Metamorphics (ìmTa, ìmTan, ìmTav, ìmToa, ìmTpa, ìmTps, ìmTpn, Maude Headley Member (ìHov) ìmTpc, ìmTgd, ìmTgm, ìmTog, ìmTgl, The following description is based on Warren (1997) and ìmTss, ìmTgs) Blake et al. (1999). The c. 1857 Ma Maude Headley Member of the Olympio Formation consists of alkaline The Central zone of the Lamboo Complex occurs in the volcanic rocks that either conformably overlie the Biscay northwestern part of DIXON to the west of the Halls Creek Formation, or occur 50–100 m above the base of the Fault (Fig. 3). The Tickalara Metamorphics outcrop within Olympio Formation. It ranges from several hundreds to a the Central zone and consist of interlayered low- to high- few tens of metres in thickness. grade metavolcanic and metasedimentary rocks, intruded by sheet-like mafic and felsic meta-igneous bodies. Lavas range in composition from amygdaloidal trachyte to rhyolite. Pillows in metarhyolite indicate Metamorphosed mafic volcanic rocks interlayered with subaqueous eruption from a nearby volcanic centre. A siliciclastic and calcareous metasedimentary rocks distinctive unit of fragmental volcanics, with flattened and dominate the Tickalara Metamorphics on DIXON. A bent porphyritic clasts cemented by a carbonate matrix, sequence of turbiditic siliciclastic metasedimentary rocks forms prominent dark outcrops. The top of the member within the Tickalara Metamorphics on McINTOSH to the is marked by laminated chert and carbonate. Northwest west does not extend onto DIXON. Amphibolite (#mTa) of Grant Peak the laminated rocks are capped by 20 m of may be interlayered with either upper amphibolite to black carbonate and a thin crystal-rich volcaniclastic granulite facies migmatitic pelitic, psammitic, and calc- sandstone. silicate gneisses (#mTan), or with amphibolite facies pelite, psammite, calc-silicate rock, and marble (#mTav). Northeast of Dry Creek thin layers of chert or fine- At low to medium grades in the Tickalara Metamorphics grained siliceous volcanic ashstone occur near the base of on MCINTOSH, volcanic structures may be preserved the upper Olympio Formation. These may represent very including amygdales, pillows, and fragmental textures late-stage activity from the Maude Headley Member with interstitial carbonate (see also Plumb et al., 1985; volcanic centre. Carbonate rocks in the Olympio Allen, 1986; Blake et al., 2000; Tyler et al., in prep.a). Formation southwest and north of Black Point had been Amygdales are preserved in amphibolite on DIXON considered to be high in the Olympio Formation (Dow and (Fig. 9). Amphibolite with relict primary layering and Gemuts, 1969). These may actually be low in the gabbroic textures (#mToa) is also present. Interlayered succession and could be a northern extension of the Maude pelite and psammite characterized by epidote–amphibolite Headley Member. facies mineral assemblages (#mTpa) and by middle The Maude Headley Member has chemical amphibolite facies mineral assemblages (#mTps), occur characteristics of A-type felsic rocks, formed by with banded iron-formation, calc-silicate rock, marble, and fractionation of an intraplate mafic magma modified by a minor amphibolite. Upper amphibolite facies to granulite minor crustal input (Warren, 1997). The presence of cherty facies migmatitic pelitic gneiss contain layers and pods rocks, and carbonates and carbonate-matrix fragmental of amphibolite and psammitic gneiss (#mTpn). Units of calc-silicate rock and marble interlayered with minor volcanics may reflect the presence of siliceous and CO2- rich volcanic-related fluids. banded iron-formation and quartzite (#mTpc) are present within the metasedimentary sequence. Sedimentary structures, other than compositional layering that Woodward Dolerite (ìdw) represents original bedding, are not preserved on DIXON.
The Woodward Dolerite (#dw) on DIXON forms a sill Sheet-like meta-igneous bodies belonging to the intruded into the uppermost Biscay Formation at the Dougalls suite (Sheppard et al., 1995, 1997a, 2001) consist western edge of the sheet, north of Grant Peak. Warren of the Dougalls Tonalite (#mTgd) and the Monkey Yard
11 Tyler
2000), suggesting rapid tectonic evolution of the Central zone at that time. The Dougalls Tonalite and the Fletcher Creek Monzogranite on DIXON (Table 2), have SHRIMP U–Pb zircon igneous crystallization ages of 1849 ± 3 Ma and 1850 ± 2 Ma respectively. Both units intrude the metasedimentary and metavolcanic units of the Tickalara Metamorphics on DIXON (Page et al., 2001). Previous workers have assumed the metasedimentary and metavolcanic units of the Tickalara Metamorphics to be the metamorphosed medium- to high-grade equivalents of the Halls Creek Group (Dow and Gemuts, 1969; Hancock and Rutland, 1984; Plumb et al., 1985; Allen, 1986), which is exposed within the Eastern zone of the Lamboo Complex (see Eastern zone below). However the Biscay Formation, in the lower part of the Halls Creek Group, has been dated at c. 1880 Ma (Page and Sun, 1994; Blake et al., 1999). In the upper part of the Halls Creek Group, felsic volcanic units of the Olympio Formation were erupted between 1857 Ma and 1848 Ma (Blake et al., 1999). The conformably overlying turbiditic sedimentary rocks contain detrital zircons as young as c. 1847 Ma (Blake et al., 1999). Deformation and metamorphism of the Tickalara Metamorphics took place between c. 1863 and 1845 Ma (Tyler and Page, 1996; Bodorkos et al., 1999, 2000a;
IMT93 19.02.04 see Early deformation and metamorphism in the Central zone below), and occurred, therefore, while the Figure 5. Inclusion of amphibolite, veined by upper part of the Halls Creek Group was still being metamorphosed tonalite and trondhjemite, within deposited. Allen (1986) suggested that quartzose the Dougalls Tonalite (AMG 394800E 8063200N) metasedimentary rocks that apparently occur within the Tickalara Metamorphics on DIXON and TURKEY CREEK were part of the Saunders Creek Formation at the base of the Halls Creek Group. However, these outcrops are considered here to be low-strain pods of c. 1800 Ma Red Tonalite (#mTgm) on DIXON. Also present is amphibolite Rock Formation sandstones, strung out within mylonitic and dioritic to gabbroic granulite (#mTog), which is cut rocks along the Halls Creek and Alice Downs Faults (see by extensive veins and patches of metamorphosed tonalite Red Rock Formation below). and trondhjemite, and occurs as widespread inclusions within the Dougalls Tonalite (Fig. 5; see also Blake et al., 2000, fig. 3.9A). The relationship between the leucocratic and melanocratic phases is complex and the range of structures present is consistent with mingling of two magmas (Sparks and Marshall, 1986; Frost and Mahood, 1987; Blake et al., 2000). The Fletcher Creek Monzo- granite (#mTgl) represents a separate, more felsic intrusion, which may also contain inclusions of the amphibolite and dioritic to gabbroic granulite veined by tonalite and trondhjemite (Fig. 6).
Mylonites derived from both metasedimentary and meta-igneous rocks (#mTss, #mTgs) are also present along the Alice Downs and Halls Creek Faults.
A depositional age for the sedimentary and volcanic protoliths of the Tickalara Metamorphics has not been obtained. Nevertheless, detrital zircons from metasedi- mentary rocks on MCINTOSH and TURKEY CREEK indicate a maximum depositional age of c. 1865 Ma from SHRIMP
U–Pb ages (Page et al., 1995; Page and Hoatson, 2000; IMT94 19.02.04 Bodorkos et al., 2000a). A minimum depositional age is provided by the Rose Bore Granite, a deformed and Figure 6. Inclusion of amphibolite veined by metamorphosed intrusive granitic sheet exposed on metamorphosed tonalite and trondhjemite, within MCINTOSH, which has a SHRIMP U–Pb zircon igneous the Fletcher Creek Monzogranite (AMG 394200E crystallization age of 1863 ± 3 Ma (Page and Hoatson, 8063700N)
12 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
Tyler et al. (1995) concluded that the differences Western zone (Bodorkos et al., 1999, 2000a; Oliver et al., between the Tickalara Metamorphics and the Halls Creek 1999). Group were consistent with their deposition in geographically separate tectonostratigraphic terranes that In the Central zone a maximum age for the first were juxtaposed during subsequent tectonism. Sheppard deformation is provided by the c. 1863 Ma Rose Bore et al. (1999) interpreted the metamorphosed basaltic rocks Granite on MCINTOSH, which pre-dates D1 (Tyler and Page, of the Tickalara Metamorphics as forming in an oceanic 1996). A minimum age for D1 is provided by the island arc/back-arc basin or ensialic marginal basin setting, c. 1850 Ma age for the intrusion of the granitoids of the based on their geochemistry. In contrast they interpreted Dougalls suite and the Fletcher Creek Monzogranite, the basaltic rocks of the Biscay Formation of the Halls which post-date D1 but pre-date D2 (Tyler and Page, 1996). Creek Group as being erupted on a passive continental D1 in the Central zone therefore has similar time margin. Sheppard et al. (2001) suggested that the constraints to D2 in the Western zone (Table 1). geochemical and isotopic composition of the tonalites and D in the Central zone post-dates the intrusion of the trondhjemites of the Dougalls suite resemble crustally 2 Dougalls suite and is synchronous with peak meta- derived adakites and low- to medium-K, calc-alkaline rocks from Phanerozoic continental margins and island morphism. Oliver et al. (1999) and Bodorkos et al. (2000a) dated peak M metamorphism in the Tickalara arcs. They interpreted the suite as the product of melting 2 Metamorphics at c. 1845 Ma. This indicates that of a package of mafic volcanic rocks in the deep crust (>40 km depth), implying a substantially tectonically deformation and metamorphism in the Central zone continued after the Hooper Orogeny in the Western zone and/or magmatically thickened crust in the Central zone had finished. Bodorkos et al. (1999) suggested that peak at c. 1850 Ma. metamorphism was prolonged with the repeated injection Bodorkos et al. (1999) have pointed out that although of mafic magma ensuring that the rocks remained very hot ≥ the tectonic evolution of the Lamboo Complex has been ( 650°C) for at least 10 m.y., with the Central zone M2 interpreted in terms of two separate orogenic events, in event merging into D3/M3 of the Halls Creek Orogeny. the Central zone the high temperature/low pressure metamorphism can be attributed to a single long-lived Sheppard et al. (1999) suggested that the metasedi- thermal anomaly spanning the two events. This is mentary and metabasaltic rocks of the Tickalara consistent with the large volumes of mafic magma, as both Metamorphics represent a c. 1865 Ma intra-oceanic island layered mafic–ultramafic intrusions and gabbroic bodies, arc. The Hooper Orogeny in the Western zone and the that have been intruded into the Tickalara Metamorphics early deformation and metamorphism in the Central zone almost continuously over a period from c. 1860 Ma to may correspond to the accretion of the island arc to the c. 1830 Ma (Hoatson and Blake, 2000). The maintenance edge of the Kimberley Craton (Myers et al., 1996; of the anomaly over such a long time period suggests a Sheppard et al., 1997a). From the relative position of the major mantle perturbation at the base of the crust of the zones within the Lamboo Complex, subduction of oceanic Central zone (Bodorkos et al., 1999), although it is unclear crust at this time was probably to the southeast (Sheppard how this was achieved in the interpreted rapidly evolving et al., 2001). The early deformations in the Central zone island arc to plate margin to collisional setting. It may were interpreted as being related to large-scale easterly reflect the different nature of the oceanic crust and of directed thrusting by Hancock and Rutland (1984). subduction processes in the Palaeoproterozoic (Sheppard and Tyler, 2002). Deformation (D1/D2) The petrography and the structural and metamorphic The earliest deformation (D1) has produced a pervasive history of the Tickalara Metamorphics is described under layer-parallel foliation to gneissic banding (S1) to the the Early deformation and metamorphism in the northwest of the Alice Downs Fault. No D1 folds have Central zone and Halls Creek Orogeny sections below. been recognized. In carbonate units boudins of more
competent layers are wrapped by the S1 fabric (e.g. Gemuts, 1971, plate 9, figure 1). The S fabric is locally Early deformation and metamorphism 1 truncated by veins of Dougalls Tonalite and Fletcher Creek in the Central zone Monzogranite. The Hooper Orogeny in the Hooper Complex of the King Large-scale D2 fold closures are not recognized to the Leopold Orogen took place between c. 1870 and 1850 Ma northwest of the Alice Downs Fault, but small-scale D2 (Tyler and Griffin, 1990, 1993; Griffin et al., 1993; Tyler folds are present in metasedimentary rocks (Plumb et al., et al., 1999; Griffin et al., 2000). Tyler et al. (1995) noted 1985; Allen, 1986; Bodorkos, 2001). Folds are char- the similarities in the geological evolution of the Hooper acterized by a variably developed axial planar foliation Complex and the Western zone of the Lamboo Complex. (S2) defined usually by aligned biotite, and locally by Rocks of the Marboo Formation in the Western zone of sillimanite crystals. The Fletcher Creek Monzogranite and the Lamboo Complex, and those of the Tickalara the Dougalls Tonalite both contain a well developed S2 Metamorphics within the Central zone are both affected fabric. by two early phases of deformation, and Tyler and Page (1996) correlated these events with the Hooper Orogeny. To the southeast of the Alice Downs Fault the earliest However, zircon and monazite SHRIMP U–Pb ages from deformation is not well preserved, with a ubiquitous the Central zone suggest that, although there is overlap, schistosity probably representing a combined S1/S2 fabric. it has a tectonic history that differs from that of the Large scale D1 folds are not recognized, but S2 crenulates
13 Tyler
have been intruded at a shallow crustal level into relatively cold (300–350°C) country rocks, consistent with the
greenschist facies metamorphic conditions for D1 that are indicated by the fine inclusion trails within later garnet porphyroblasts. Mineral assemblages within the Tickalara Metamorphics between the Alice Downs and Halls Creek Faults are indicative of epidote–amphibolite facies conditions. Pelitic and psammitic metasedimentary rocks typically consist of biotite, muscovite, and quartz with accessory iron oxides, tourmaline, and zircon. Garnet is often present as subhedral to rounded porphyroblasts up to 10 mm across in pelitic rocks, wrapped by intergrown fine- to medium-grained mica, quartz, and iron oxide defining a well developed schistosity (Fig. 8). Mafic metavolcanic rocks are thoroughly recrystallized, having IMT95 19.02.04 fine- to medium-grained assemblages of chlorite, epidote, blue-green (edenitic) to green amphibole (hornblende), Figure 7. Small-scale, isoclinal D fold closures in pelitic 2 plagioclase (albite to oligoclase), and quartz with minor schist, Tickalara Metamorphics (AMG 398900E 8054500N)
a) a layer-parallel S1 in small-scale, isoclinal D2 fold closures (Fig. 7). Garnet porphyroblasts, which are wrapped by the crenulation cleavage, preserve earlier straight to sigmoidal inclusion trails of fine-grained quartz or iron oxide (Fig. 8), which are interpreted as the remnants of a low-grade, probably greenschist facies S1. The Monkey Yard Tonalite outcrops within large-scale, elongate, doubly-plunging fold closures around the D4 Black Rock Anticline, between the Alice Downs and Halls Creek Faults. These structures have been interpreted as S4 originally recumbent, east-verging, isoclinal D2 folds (Hancock and Rutland, 1984; Bodorkos, 2001), although S2 unfolding D3 and D4 as recognized here would suggest a northeasterly vergence. 1 mm
Metamorphism (M1/2 ) b) Bodorkos et al. (1999) and Bodorkos (2001) recognized that mineral assemblages representing the highest metamorphic grades in the Tickalara Metamorphics are typical of metamorphism at high temperatures and low pressures (750–800°C at 350–500 MPa). These assembl- ages grew syn- to post-D2 (c. 1845 Ma) during a single thermal event (M1/2) that encompassed both D1 and D2. On DIXON, metamorphic grade increases towards the northwest corner of the map sheet. Between the Halls Creek Fault and the Alice Downs Fault, mineral assemblages are indicative of the epidote–amphibolite facies (Zone B of Gemuts, 1971). To the northwest of the Alice Downs Fault, mineral assemblages represent an increase in grade from the middle amphibolite facies to the amphibolite- to granulite-facies transition (Zone A of Gemuts, 1971). 1 mm
IMT96 19.02.04 The Fletcher Creek Monzogranite was intruded at c. 1850 Ma following D , and Magart (1994) and Bodorkos 1 Figure 8. (a) Garnet porphyroblast wrapped by the S and et al. (1999) recognized a narrow (100 m) pyroxene 2 S4 crenulation cleavages. Crossed nicols. (b) hornfels facies contact aureole in the surrounding calc- Garnet preserves earlier straight to sigmoidal silicate rocks and marbles. They inferred that for the inclusion trails of fine-grained quartz or iron aureole to develop, the Fletcher Creek Monzogranite must oxide. Plane-polarized light (GSWA 108376)
14 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
In the north, medium- to coarse-grained pelitic rocks are interlayered with psammite, calc-silicate rocks and marble, and amphibolite, and become migmatitic with anatectic leucosomes developed both parallel to, and crosscutting layering (Bodorkos, 2001). The pelites consist of garnet, biotite, plagioclase, and quartz, with or without cordierite, sillimanite, and K-feldspar, reflecting the locally K-poor nature of the metasedimentary rocks (Plumb et al., 1985; Sheppard et al., 1997b). The appearance of cordierite with garnet is controlled by the reaction: biotite + sillimanite = garnet + cordierite + melt (3) Calc-silicate rocks interlayered with pelite and psammite typically contain ragged and irregular garnet porphyroblasts up to 5 mm across intergrown with quartz. Depending on how calcareous these rocks are, the porphyroblasts are wrapped by foliations characterized by biotite, quartz, plagioclase (oligoclase–andesine), and iron oxide, or biotite, quartz, epidote, calcite, and iron oxides, together with accessory tourmaline and zircon. Irregular crystals of hornblende may be present locally. Magart (1994) and Bodorkos (2001) have interpreted calc-silicate rocks, and compositionally layered impure marble associated with pure marble around the Fletcher IMT97 19.02.04 Creek Monzogranite, as the result of metasomatism due to pervasive infiltration of fluids at high temperatures Figure 9. Stretched amygdales in amphibolite derived from within a contact aureole. Magart (1994) recognized basalt lava in the Tickalara Metamorphics (AMG carbonate-absent, silica-dominated wollastonite–quartz– 404100E 8055700N) garnet–clinopyroxene–epidote, and quartz–garnet– clinopyroxene(–scapolite–plagioclase) rocks at the intrusion margins. Associated impure marble is characterized by alternating calcite- and silicate-rich titanite and iron oxides. Blebs of intergrown quartz and layers, interpreted to represent increasingly channellized epidote, which may be stretched (Fig. 9), probably fluid flow away from the intrusion. Silicate phases include represent recrystallized amygdales. The Monkey Yard clinopyroxene, garnet, and scapolite. Unmetasomatized Tonalite is variably foliated, and consists of medium- to pure marble is characterized by coarse-grained, coarse-grained quartz, plagioclase (oligoclase), blue-green amphibole, epidote, and K-feldspar, with minor titanite and iron oxides. K-feldspar occurs locally intergrown with plagioclase and quartz, and myrmekite.
To the northwest of the Alice Downs Fault, mineral assemblages are indicative of conditions ranging from the middle amphibolite facies in the south to the amphibolite- Bt to granulite-facies transition in the north. Medium- to St coarse-grained pelitic and psammitic rocks in the south consist of biotite, quartz, and iron oxides with or without muscovite, and with sillimanite, garnet, and staurolite Sil occurring in more pelitic lithologies. Plagioclase may also be present intergrown with quartz. Rounded to subhedral garnet porphyroblasts can be up to 10 mm across, wrapped by anastomosing trails of intergrown fibrolitic sillimanite, biotite, and iron oxide (Fig. 10) consistent with the reaction: Grt garnet + muscovite = sillimanite + biotite (1)
Crystalline sillimanite can occur in rounded to elongate 1 mm patches up to 20 mm across. Locally garnet may be IMT98 19.02.04 surrounded by sillimanite. Irregular to subhedral crystals of staurolite are intergrown with biotite (Fig. 10) Figure 10. Garnet (Grt) surrounded by sillimanite (Sil) and suggesting the operation of reaction 2, irregular to subhedral crystals of staurolite (St) intergrown with biotite (Bt) (GSWA 108361), plane- garnet + chlorite = staurolite + biotite (2) polarized light
15 Tyler
Orogeny may be the result of a collision between the combined Central and Western zones and the Eastern zone, the earliest stages of which began at c. 1835 Ma (Page et al., 2001; Sheppard et al., 2001). The collision, which involved the suturing of the Kimberley Craton to the rest of the North Australian Craton, was completed by 1805 Ma (Myers et al., 1996; Tyler et al., 1998c; Sheppard et al., 2001).
Deformation Griffin and Tyler (1992) established a sequence of
deformation events (D1 to D7) for the southern part of the Halls Creek Orogen. Their nomenclature is followed here. Deformation that affected the Halls Creek Group in the 1 mm Eastern zone must have occurred after c. 1847 Ma, the age IMT99 19.02.04 of the youngest detrital zircons in the Olympio Formation,
and has been attributed to D3 and D4 (Tyler et al., 1998b), Figure 11. Irregular to rounded orthopyroxene in Dougalls equivalent to DH1 and DH2 of Blake et al. (1999). In the Tonalite (GSWA 113593), plane-polarized light Central zone the intrusion of the c. 1835 Ma Mabel Downs
Tonalite was synchronous with D3 (Bodorkos et al., 2000b). A minimum age for deformation is provided by the c. 1808 Ma age for the Mount Christine Granitoid granoblastic calcite, and silicate phases include olivine (Page et al., 2001), which cuts across the trend of D4 (variably altered to serpentine), spinel, garnet, clino- structures in the Halls Creek Group on DOCKRELL (Tyler pyroxene, plagioclase, scapolite, amphibole, epidote, and et al., 1998b). titanite.
Amphibolites northwest of the Alice Downs Fault are First deformation (D3 ) typically medium to coarse grained with granoblastic The first deformation to affect rocks in the Eastern textures. Mineral assemblages include green hornblende, zone (D ) was low-angle normal faulting and layer- plagioclase (andesine to labradorite), quartz, and iron 3 parallel shearing (Hancock, 1991; Warren, 1994b, 1997; oxides, with or without garnet or clinopyroxene, indicative Tyler et al., 1998b; Blake et al., 1999, 2000). Warren of the upper amphibolite facies. (1997) noted that there were gaps in the expected strati- The Dougalls Tonalite is metamorphosed and is a graphic sequence between the upper Biscay Formation and medium- to coarse-grained rock consisting of quartz, the Olympio Formation, which corresponded to thin plagioclase (oligoclase to andesine), biotite, hypersthene, (c. 3 m) zones of laminated or brecciated rock. These were and iron oxides with either hornblende or garnet. Sheppard interpreted as bedding-parallel faults, which on a regional et al. (1995) suggested that hypersthene might be a relict scale together form a low-angle normal fault that cuts igneous phase. However, in samples from DIXON (113593 progressively down-section from north to south and from and 108368, Fig. 11) hypersthene has a similar irregular east to west (Warren, 1994b). to rounded form to accompanying metamorphic garnet, In the Central zone D is characterized by large-scale and is intergrown with biotite and hornblende as well as 3 quartz and plagioclase, suggesting that it has recrystallized folding and the local development of shear zones (Plumb during prograde metamorphism, indicating transitional et al., 1985; Tyler and Page, 1996; Sheppard et al., 1997b; granulite facies conditions. Locally it may be rimmed by Bodorkos et al., 1999, 2000b; Bodorkos, 2001). On DIXON, structures attributable to D are present between the Halls iron oxide. 3 Creek Fault and the Alice Downs Fault, and have produced The Fletcher Creek Monzogranite consists of quartz, refolding of recumbent D2 folds around the D4 Black Rock plagioclase (oligoclase), K-feldspar, garnet, biotite, Anticline to produce elongate basin and dome structures muscovite, and iron oxides. The garnets are rounded, picked out by fold cores of Monkey Yard Tonalite. euhedral to subhedral grains up to 3 mm in diameter, and Unfolding the anticline suggests that the original are relatively rich in Mn (up to 34.2 mol.%; Ogasawara, orientation of D3 was as upright, north-northeasterly 1988), consistent with their initial formation as magmatic trending structures with gentle plunges to the south- crystals (Sheppard et al., 1995). Where garnet is present southwest. Locally a crenulation (S3) of S2 may be biotite is typically absent. recognized, cutting across D2 fold hinges at an angle to the more widespread S4 crenulation. Halls Creek Orogeny Second deformation (D4 )
Deformation and metamorphism during the Halls Creek The second deformation to affect the Eastern zone (D4) Orogeny (Tyler and Page, 1996; Blake et al., 2000) has was compressional and was marked by the formation of affected the entire Lamboo Complex. The Halls Creek open to tight, upright to overturned, north-northeasterly
16 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet trending folds (Warren, 1997). In the southwestern corner of the map sheet the most obvious D4 structures are a series of anticlines and synclines forming the Biscay Anticlinorium of Dow and Gemuts (1969). The structures forming the anticlinorium plunge gently to moderately to the north-northeast, with the anticlines marked by narrow outcrops of the Biscay Formation and the Maude Headley Member, separated by synclines within the Olympio Formation.
The folds change in style to the north-northeast probably reflecting the more massive nature of the lower Halls Creek Group and its basement, compared with the Olympio Formation (Tyler et al., 1998b). Warren (1997) reported that a cleavage is absent in the southwest, but to the north-northeast the intersection of an axial plane fracture cleavage with bedding in Olympio 1 mm Formation rocks produces ‘pencil slates’ (Blake et al., IMT100 19.02.04 2000, fig. 3.7B). Beds dip steeply to the west, with the asymmetric folds becoming overturned, facing to the east. Figure 12. Asymmetric ‘mica-fish’ in mylonitic pelite (GSWA Typically, anticlines are preserved with the intervening 108355, plane-polarized light). Arrows indicate synclines removed by local thrusting (Warren, 1997). This sense of shear is consistent with the suggestion by Blake et al. (1999) that
D4 was the result of an easterly verging fold and thrust system. facies conditions similar to M3 in the northwest, to greenschist facies adjacent to the Halls Creek Fault. In In the Central zone, the regional-scale D4 Black Rock Anticline lies between the Alice Downs Fault and the metasedimentary rocks in the northwest, an S4 crenulation Halls Creek Fault. This structure is picked out by is typically picked out by muscovite and biotite. In metacarbonate, amphibolite layers, and the Monkey Yard shear zones along the Alice Downs Fault, garnet, epidote, Tonalite and is an antiform produced by refolding of or muscovite porphyroclasts may be present, with muscovite ranging from large (up to 3.5 mm diameter) recumbent D2 folds. It was referred to as the Black Rock ‘Antiform’ by Hancock and Rutland (1984), but Tyler et al. broken crystals with bent and fractured cleavages, to (1998d) retained the original nomenclature of Gemuts smaller (1 mm diameter) asymmetric ‘mica-fish’ (Fig. 12; (1971) on the published geological map. The ‘anticline’ see Passchier and Trouw, 1996). The porphyroclasts is a tight to isoclinal, asymmetric structure, which is are wrapped by a fine schistose matrix of muscovite, locally overturned to the east (Gemuts, 1971, fig. 8). It quartz, and iron oxides with or without biotite or plunges gently to moderately to the north-northeast, and epidote. At lower strains, transposed isoclinal, small- scale D2 fold hinges may be preserved, wrapped by a is parallel to the D4 structures in the adjacent Eastern zone. A well-developed crenulation is present, axial planar to strong schistosity (Fig. 13). In metatonalitic rocks, the fold structure (Fig. 8). lozenge-shaped porphyroclasts of quartz and plagioclase
Extensive zones of mylonitic rocks, developed within both metasedimentary and meta-igneous rocks in the Tickalara Metamorphics, are found associated with both the Alice Downs Fault and the Halls Creek Fault on DIXON. Locally the mylonitic fabrics grade into protomylonitic rocks where the fabric can be identified as an S4 crenul- ation, consistent with the mylonitization occurring during
D4. S–C fabrics and asymmetric tails on porphyroclasts typically indicate west-side-up movement on shear zones, consistent with the exposure of higher grade rocks to the west, and with easterly directed thrusting in the Eastern zone to the east.
Metamorphism (M3 and M4)
There is little evidence of retrogression of M1/2 mineral assemblages during M3 on DIXON suggesting that similar 1 mm epidote–amphibolite facies metamorphic conditions were IMT101 19.02.04 developed.
Figure 13. Transposed, isoclinal, small-scale D2 fold hinges During D4, extensive recrystallization took place with wrapped by a strong schistosity in mylonitic pelite metamorphic grade ranging from epidote–amphibolite (GSWA 108358, plane-polarized light)
17 Tyler
differences in stratigraphy and provenance may reflect contemporaneous activity along a proto-Halls Creek Fault (Tyler et al., in prep.b). Outcrops of variably deformed sandstone, conglomerate, siltstone, and mudstone (#k) occur as strips along the Alice Downs Fault in the northwestern corner of DIXON. These are up to 2 km long, and 300 to 400 m wide. A 21 km-long strip of massive to amygdaloidal basalt and basaltic breccia (#kb) reaches up to 2 km in width along the Halls Creek Fault. A layer of carbonate (#kc) is present within the basalt unit, adjacent to the Halls Creek Fault at the western edge of DIXON.
1 mm Mesoproterozoic IMT102 19.02.04 Yampi Orogeny Figure 14. Lozenge-shaped porphyroclasts of quartz and plagioclase in metatonalitic rocks wrapped by an The Mesoproterozoic Yampi Orogeny was recognized in asymmetric, finely schistose to laminated the King Leopold Orogen in the west Kimberley region mylonitic fabric (GSWA 108353, plane-polarized by Tyler and Griffin (1990, 1993) and by Griffin et al. light) (1993), and is equivalent to D5 of Griffin and Tyler (1992) in the Halls Creek Orogen. Structures assigned to this
event were referred to by Warren (1997) as D3 and by (oligoclase, sieved by fine muscovite, epidote, and biotite) Blake et al. (1999) as DY. up to 15 mm in diameter are wrapped by an asymmetric, The system of regional-scale, north-northeasterly finely schistose to laminated mylonitic fabric with strings trending sinistral faults and easterly trending dextral faults and ribbons of garnet, epidote, quartz, iron oxides, titanite, in the Halls Creek Orogen affects rocks as young as and biotite with muscovite or chlorite (Fig. 14). Devonian (Dow and Gemuts, 1969; Plumb and Gemuts, In mylonitic metatonalite along the Halls Creek Fault, 1976; Tyler et al., 1995; Thorne and Tyler, 1996). rounded to angular (often broken) porphyroclasts of quartz However, Dow and Gemuts (1969) noted that younger and plagioclase (oligoclase) are wrapped by a fine, rocks were displaced less than older rocks, suggesting that schistose matrix of chlorite, muscovite, quartz, epidote, the faults have long, complex histories. Direct dating of calcite, and iron oxide. Adjacent pelitic rocks have D5 faults in the Halls Creek Orogen is not available, but retrograde greenschist facies assemblages with an S4 K–Ar dating by Shaw et al. (1992) placed constraints of schistosity picked out by chlorite, muscovite, and quartz, between 1475 ± 12 Ma and 999 ± 9 Ma on the Yampi wrapping ovoid patches up to 5 mm across consisting of Orogeny in the King Leopold Orogen. sericite intergrown with iron oxide and some relict garnet. Curvilinear trails of iron oxide may be preserved from an original M1/2 garnet porphyroblast (Fig. 15). Biotite is preserved in some chlorite grains.
Palaeoproterozoic Red Rock Basin Red Rock Formation (ìk, ìkc, ìkb) Fault-bounded strips of conglomerate, sandstone, relict mudstone, siltstone, metabasalt, and carbonate occur along garnet the Halls Creek Fault and the Alice Downs Fault on DIXON, MCINTOSH, and TURKEY CREEK (Tyler et al., 1997a, 1997b, 1998d). At one locality on TURKEY CREEK, conglomerate and sandstone unconformably overlie the Tickalara Metamorphics (Tyler et al., 1997b). These rocks are 1 mm correlated with the Red Rock Formation (#k), which was IMT103 26.02.04 deposited in the Red Rock Basin, and which is now Figure 15. S4 schistosity wrapping ovoid patches of sericite exposed in the Osmand Range on TURKEY CREEK (Tyler intergrown with iron oxide and relict garnet. et al., 1997b). The Red Rock Formation and the Texas Curvilinear trails of iron oxide may be preserved
Downs Formation are probably equivalent to the from an original M1/2 garnet porphyroblast (GSWA c. 1800 Ma Kimberley Group to the west, but the 108407, plane-polarized light)
18 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
Tyler et al. (1995) suggested that the pattern of strike- Centralian Superbasin (Walter et al., 1995; Plumb, 1996; slip faulting was controlled by major northeasterly Corkeron et al., 1996; Grey and Corkeron, 1998; Corkeron trending structures that developed during the Palaeo- and George, 2001). Rocks in the upper part of the Albert proterozoic, and whose position is now marked by the Edward Group, above and including the Boonall Dolomite, zone boundaries in the Lamboo Complex. The current may represent at least the lower part of Supersequence 4 fault pattern was interpreted to have developed first as (Grey and Corkeron, 1998). ductile structures in the Mesoproterozoic, accompanying northeasterly directed folding and thrusting in the King Leopold Orogen. Later Neoproterozoic and Palaeozoic Ruby Plains Group reactivations of the faults were more brittle. The Ruby Plains Group consists of three formations: the In the Halls Creek Group in the Eastern zone, Warren Mount Kinahan Sandstone, the Eliot Range Dolomite, and (1997) recognized northerly trending, steeply dipping the Illjarra Sandstone (Blake et al., 1997, 1999). Only the faults. On their eastern side are narrow zones, up to 1 km lower two units are exposed on DIXON (Table 3). They are wide, of open to tight folds with axial surfaces parallel to equivalent to the c. 830 Ma Supersequence 1 of the the faults, and with variable plunges. D3 and D4 structures Centralian Superbasin and probably represent intertidal, are overprinted, with their lineations reoriented and the fluvial, lacustrine, and shallow marine sediments (Walter earlier fabrics crenulated to produce pencil slates. In the et al., 1995; Grey and Blake, 1999; Blake et al., 1999). vicinity of Grants Peak, Warren (1997) suggested that large-scale sheath folding could be related to strike-slip movements between two northerly to north-northeasterly Mount Kinahan Sandstone (ìPk) trending D5 faults. Small-scale sheath folds are present locally in the Maude Headley Member. Warren (1997) also Outcrops of the Mount Kinahan Sandstone (#Pk) are reported that metamorphic grade may be higher near D5 discontinuous and are restricted to a zone between two sets faults with an increase in grain size and the development of northeasterly trending faults in the central part of the of phyllites from fine-grained sedimentary rocks. A zone southern half of DIXON. Previously these outcrops were of quartz–chlorite–calcite veins occurs adjacent to a D5 mapped as either Mount Parker Sandstone or as Mount fault near the Slinkey Hill prospect. Forster Sandstone (Dow and Gemuts, 1967). Stromatolite biostratigraphy indicates that the unit cannot be correlated with the Mount Parker Sandstone in the Osmand Range to the north (Grey and Blake, 1999). The most northerly Neoproterozoic outcrop is overlain by the Moonlight Valley Tillite, and therefore cannot be the stratigraphically higher Mount Wolfe Creek Basin Forster Formation (Warren, 1997). A third exposure is Neoproterozoic rocks form a narrow strip running north– within a fault-bounded thrust sheet 3.5 km north of Mount Forster. Other exposures of ‘Mount Parker Sandstone’ south through the central part of DIXON, and are represented by the Ruby Plains, Duerdin, and Albert shown by Dow and Gemuts (1967) have been identified Edward Groups, all of which were deposited in the Wolfe as Olympio Formation by Warren (1997). Creek Basin (Shaw et al., 1994; Tyler and Hocking, 2001; The Mount Kinahan Sandstone forms prominent equivalent to the ‘Wolfe Basin’ of Blake et al., 1997, cuestas unconformably overlying tightly folded Olympio 1999). On DIXON, the Ruby Plains Group unconformably Formation rocks. On HALLS CREEK to the south it has a overlies the Palaeoproterozoic Halls Creek Group, maximum thickness of 150 m (Blake et al., 1999). On while the glacigene Duerdin Group unconformably DIXON it consists of up to 200 m of medium-grained, overlies either the Halls Creek Group or the Ruby Plains medium- to thick-bedded, cross-bedded, quartz sandstone. Group. The Albert Edward Group conformably overlies the Duerdin Group, and is overlain unconformably by the Cambrian Antrim Plateau Volcanics. The Ruby Plains Eliot Range Dolomite (ìPi ) Group has been equated with the c. 830 Ma Super- sequence 1 of the Centralian Superbasin of Walter et al. Carbonate rock of the Eliot Range Dolomite (#Pi) (1995), following identification within it (Grey and Blake, outcrops within a thrust slice, 4 km north of Mount 1999) of the stromatolite Linella avis (Krylov 1967). Forster. Blake et al. (1999) described the unit on HALLS Previously the rocks now mapped as Neoproterozoic Ruby CREEK as consisting of thin- to thick-bedded and locally Plains Group on DIXON had been correlated with the brecciated dolomitic mudstone, siltstone, and sandstone Mesoproterozoic Mount Parker Sandstone and Bungle with thin bands and lenses of nodular black chert present Bungle Dolomite (Dow and Gemuts, 1967). in places. Stromatolites are common locally. Coates and Preiss (1980) equated the combined Duerdin and Albert Edward Groups with the c. 610 Ma Illjarra Sandstone (ìPj ) Marinoan Glaciation in South Australia. However, Grey and Corkeron (1998), on the basis of stromatolite The Illjarra Sandstone (#Pj) is not exposed on DIXON, but biostratigraphy, suggested that the Marinoan Glaciation is is shown on the cross section. It is exposed on HALLS represented by the Fargoo and Moonlight Valley Tillites CREEK to the south where it consists of lithic sandstone, only, with the Duerdin Group and the lower Albert with siltstone and dolomitic sandstone and mudstone as Edward Group equivalent to Supersequence 3 of the minor components (Blake et al., 1999).
19 Tyler
Table 3. Stratigraphy of the Palaeoproterozoic to Palaeozoic sedimentary rocks on DIXON(a)
Basin Group Formation Thickness Lithology (m)
Ord Basin Mahony Group Glass Hill Sandstone (DMg) 200 Pebbly quartz sandstone, conglomerate, siltstone
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ unconformity/disconformity ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Goose Hole Group Elder Subgroup Overland Sandstone (_Go) 190 Lithic arkose Eagle Hawk Sandstone (_Ge) 10 Feldspathic sandstone, siltstone Negri Subgroup Panton Formation (_Gp) 24 Siltstone and mudstone; feldspathic sandstone and limestone Linnekar Limestone (_Gl) 124 Limestone, shale; chert; stromatolites and macrofossils Nelson Shale (_Gn) 100 Siltstone and mudstone; feldspathic sandstone Headleys Limestone (_Gh) 50 Limestone; chert; stromatolites
Antrim Plateau Volcanics (_a) 340 Massive and amygdaloidal, locally porphyritic basalt and basaltic breccia; sandstone, siltstone; stromatolitic chert Blackfella Rockhole Member (_ar) <130 Basalt and basaltic breccia Bingy Bingy Member (_ab) <140 Glomeroporphyritic basalt
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ unconformity/disconformity ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Wolfe Creek Basin Albert Edward Group Nyuless Sandstone (#Ly) 40 Quartz sandstone, lithic sandstone; siltstone and conglomerate Timperley Shale (#Lj) 1 000 Mudstone, siltstone; sandstone Boonall Dolomite (#Lb) 30–60 Laminated dolomite, dolorudite; mudstone Elvire Formation (#Le) 60 Mudstone; quartz sandstone Mount Forster Sandstone (#Lo) 100 Quartz sandstone; pebbly sandstone and conglomerate
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ disconformity ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Duerdin Group Ranford Formation (#Eo) 650 Siltstone and mudstone; feldspathic wacke, lithic sandstone, quartz sandstone, dolomitic sandstone and dolomite Jarrad Sandstone Member (#Eoj) 60 Dolomitic sandstone, and quartz sandstone, siltstone, and mudstone Moonlight Valley Tillite (#Em) 0–>10 Matrix-supported, polymictic pebble to boulder conglomerate, sandstone; larger clasts polished and striated locally
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ unconformity/disconformity ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Fargoo Tillite (#Ef) 52 Matrix-supported pebble to boulder conglomerate, sandstone; clasts polished and striated locally
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ unconformity/disconformity ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Ruby Plains Group Illjarra Sandstone – Lithic sandstone, minor siltstone and dolomite (subsurface only) Eliot Range Dolomite (#Pe) – Dolomitic mudstone, siltstone and sandstone Mount Kinahan Sandstone (#Pk) 200 Quartz sandstone
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ unconformity ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Red Rock Basin Red Rock Formation (#k, #kc, #kb) – Lithic quartz sandstone, feldspathic quartz sandstone, pebbly sandstone, conglomerate, siltstone, mudstone, basalt, basaltic breccia
SOURCE: (a) after Dow and Gemuts, 1969; Mory and Beere, 1988; Blake et al., 1997, 1999)
20 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet Duerdin Group Yards, a sandstone with a calcareous matrix replaces the dolomite. In outcrop the tillite consists of predominantly The Duerdin Group on DIXON consists of three formations: quartzite clasts in a clay matrix (Warren, 1997). Other the Fargoo Tillite, the Moonlight Valley Tillite and the clasts include lithologies recognizable as coming from the Ranford Formation (Dow and Gemuts, 1969; Table 3). The Olympio Formation. Ranford Formation contains the Jarrad Sandstone Member. The group consists of glacigene rocks that are equivalent The Moonlight Valley Tillite has been interpreted by to the c. 610 Ma Marinoan Glaciation and it is correlated Plumb (1981) as being deposited in hollows on an with the lower part of Supersequence 3 of the Centralian irregular surface from ablation of a grounded, and locally Superbasin (Plumb, 1996; Walter et al., 1995; Grey and floating, retreating ice sheet. Ice movement was from ice- Corkeron, 1998). capped land to the north or northeast with clasts being derived from rocks in the Victoria River Basin. The Dow and Gemuts (1969) considered that the Fargoo widespread deposition of the unit, which extends from Tillite and the overlying Moonlight Valley Tillite were Kununurra to south of Halls Creek, suggests a broad, low- deposited in a marine environment from a floating ice relief continental ice sheet. sheet. However Plumb and Gemuts (1976) considered that the main tillites were subglacial deposits onto bedrock at or near the edge of a marine basin. Plumb (1981) presented Ranford Formation (ìEo) a model involving marine transgression accompanying glacial retreat. The Ranford Formation (#Eo) either conformably overlies the Moonlight Valley Tillite or steps onto the underlying Mount Kinahan Sandstone or the Olympio Formation. On Fargoo Tillite (ìEf ) DIXON it is conformably overlain by the Mount Forster Sandstone of the Albert Edward Group. It can consist of The Fargoo Tillite (#Ef ) on DIXON outcrops to the west 650 m of thin-bedded siltstone, shale, mudstone, and fine- of the Dixon Range where it unconformably overlies grained quartz sandstone, with thin beds of dolomitic tightly folded Olympio Formation. In this area the Fargoo sandstone and dolomite, and thin- to thick-bedded Tillite is disconformably overlain by the Moonlight Valley greywacke (Dow and Gemuts, 1969; Blake et al., 1999). Tillite. Sedimentation and subsequent erosion may have Load casts, graded bedding, convolute bedding, ripple- been controlled by an adjacent northeasterly trending fault marks, and low-angle cross-bedding are common. (Warren, 1997). The unit here is 52 m (170 feet) thick and Sheppard et al. (1999) reported palaeocurrents from north consists of 3 m of a basal medium-grained quartz to south on BOW. sandstone, overlain by 12 m of boulder conglomerate, 6 m of dolomitic sandstone, and 31 m of interbedded shale, The Ranford Formation represents a deepening marine siltstone, and quartz sandstone, which may be equivalent shelf or lake, following melting of the ice sheets (Plumb, to the Frank River Sandstone (Dow and Gemuts, 1969). 1993). The boulder conglomerate is composed of well-rounded boulders of quartz, quartzite, dolomite, and chert, which are rarely polished and striated, set in a matrix of dolomitic Jarrad Sandstone Member (ìEoj ) sandstone. The Jarrad Sandstone Member (#Eoj) overlies the The Fargoo Tillite in the Osmand Range to the north Moonlight Valley Tillite north of the Ord River. One of DIXON has been interpreted as the deposit of a terrestrial, outcrop on the published map (Tyler et al., 1998d; AMG or at least grounded, mountain-fed glacier. It is overlain 421500E 8060000N) has been wrongly labelled as #Lj. It there by the probably fluvioglacial Frank River Sandstone consists of 60 m of dolomitic sandstone, with rare glacial (Plumb, 1981). Clasts were derived from the adjacent erratics in sandstone lenses near the base (Dow and Lamboo Complex, which was probably ice-capped land. Gemuts, 1969). It probably represents a migrating delta fan (Plumb, 1993; Blake et al., 1999). Moonlight Valley Tillite (ìEm) The Moonlight Valley Tillite (#Em) outcrops Albert Edward Group discontinuously, resting unconformably on the Olympio Formation and stepping onto the Mount Kinahan The Albert Edward Group consists of five formations: the Sandstone and the Fargoo Tillite across northeasterly Mount Forster Sandstone, the Elvire Formation, the trending faults. This relationship suggests a period of Boonall Dolomite, the Timperley Shale, and the Nyuless active faulting and erosion prior to its deposition. It is Sandstone (Dow and Gemuts, 1969; Table 3). Glacigene overlain conformably by the Ranford Formation. Warren rocks are not present, nevertheless the Boonall Dolomite (1997) reported the occurrence of a fragment of glaciated is correlated with the glacigene Egan Formation of the pavement on the underlying Olympio Formation near Louisa Downs Group on the MOUNT RAMSAY 1:250 000 AMG 315900E 8046000N. The tillite is poorly exposed, map sheet to the southwest (Plumb, 1996; Grey and with its presence indicated by a thin veneer of rounded Corkeron, 1998; Tyler et al., 1998a). The group is equiv- quartzite cobbles, and by the distinctive ‘cap dolomite’, a alent to the upper part of Supersequence 3 and at least the less than 10 m-thick, cream or pale pink flaggy dolomite lower part of Supersequence 4 of the Centralian Super- at the top of the tillite (Warren, 1997). North of Blue Hole basin (Walter et al., 1995; Grey and Corkeron, 1998).
21 Tyler Mount Forster Sandstone (ìLo) Neoproterozoic On DIXON, the Mount Forster Sandstone (#Lo) overlies the King Leopold Orogeny Ranford Formation disconformably, and is conformably overlain by the Elvire Formation, and unconformably The King Leopold Orogeny (Tyler and Griffin, 1993; overlain by the Antrim Plateau Volcanics. It consists of Griffin et al., 1993) produced extensive, well-exposed, 100 m of fine- to coarse-grained quartz sandstone with west-northwesterly trending folding and thrusting in the abundant ripple marks and ubiquitous cross-bedding, and King Leopold Ranges, along the southwestern margin of quartz pebble conglomerate, which forms prominent strike the Kimberley Basin (Griffin and Myers, 1988; Tyler and ridges and cuestas (Dow and Gemuts, 1969; Blake et al., Griffin, 1990), together with the reactivation of shear zones 1999). Sheppard et al. (1999) reported palaeocurrents on in the Hooper Complex (Tyler et al., 1991; Shaw et al., BOW indicating that sediment transport was dominantly 1992). Deformation affected Neoproterozoic glacigene towards the south-southwest. Plumb (1993) interpreted rocks, and Shaw et al. (1992) obtained K–Ar ages of deposition as taking place on a shallow marine shelf, c. 560 Ma from reactivated shear zones and interpreted this passing up into tidal and alluvial flats. date as the age of deformation. Coates and Preiss (1980) and Plumb (1981) recalculated and reinterpreted Rb–Sr ì data from Bofinger (1967) and reported ages of 568 Ma Elvire Formation ( Le) and 576 ± 80 Ma from the McAlly Shale of the Louisa The Elvire Formation (#Le) conformably overlies the Downs Group, equivalent to the Timperley Shale of the Mount Forster Sandstone and is overlain conformably by Albert Edward Group. These ages were interpreted as the Boonall Dolomite. It consists of 60 m of maroon and reflecting a metamorphic cleavage-forming event, which chocolate-brown shale and siltstone, with minor thin beds was correlated by Shaw et al. (1992) with the King of fine- to medium-grained quartz sandstone representing Leopold Orogeny. Thrusting in the west Kimberley region deposition on a flood plain (Dow and Gemuts, 1969; was linked to sinistral strike-slip faulting in the east Blake et al., 1997, 1999). Kimberley region (Tyler and Griffin, 1990; Tyler et al., 1991). Deformation occurred at about the same time as the Paterson Orogeny at the eastern edge of the Pilbara Craton Boonall Dolomite (ìLb) and the Petermann Ranges Orogeny in central Australia (Myers et al., 1996; Tyler et al., 1998c). The Boonall Dolomite (#Lb) forms low cuestas on the eastern side of the Albert Edward Range. It conformably Small-scale structures that can be attributed to the King overlies the Elvire Formation and is conformably overlain Leopold Orogeny (D6; DL of Blake et al., 1997, 1999, by the Timperley Shale. It consists of between 30 and 2000) have not been recognized on DIXON. On HALLS 60 m of fine-grained dolomite with minor dolomitic CREEK and RUBY PLAINS to the south, large-scale fold inter- conglomerate and dolomitic breccia, and may contain ference patterns are present within Neoproterozoic rocks poorly preserved stromatolitic structures, including algal between generally west-northwesterly trending King mats (Dow and Gemuts, 1969; Blake et al., 1999). Leopold Orogeny structures and northeasterly trending late Palaeozoic Alice Springs Orogeny structures (Blake et al., The unit is regarded as equivalent to the Egan 1997, 1999, 2000). The King Leopold Orogeny structures Formation in the Louisa Downs Group, which represents appear to die out in intensity northwards. Plunge reversals deposition on a shallow, warm-water carbonate platform of D4 folds in the Olympio Formation across west- that was interrupted by glaciation (Corkeron and George, northwesterly trending axes (Fig. 3) may be related to D6. 2001). Uplift and erosion at this time is indicated by the unconformity at the base of the Cambrian Antrim Plateau Volcanics. Timperley Shale (ìLj )
The Timperley Shale (#Lj) conformably overlies the Boonall Dolomite, and is overlain conformably by the Palaeozoic Ord Basin Nyuless Sandstone, and unconformably by the Antrim Palaeozoic sedimentary and volcanic rocks belonging to Plateau Volcanics. It consists of 1000 m of thinly bedded, the Ord Basin are exposed in the eastern half of DIXON. green or dark-grey shale, siltstone, and mudstone The Ord Basin lies to the east of the Halls Creek Fault and deposited in a below-wave-base marine or lacustrine contains rocks of latest Early to ?Late Cambrian and Late environment (Dow and Gemuts, 1969; Plumb, 1993; Blake Devonian age. The following descriptions are based on the et al., 1999). work of Mory and Beere (1985, 1988) who extensively revised and redefined the stratigraphy from that of Dow and Gemuts (1967). Nyuless Sandstone (ìLy)
The Nyuless Sandstone (#Ly) on DIXON is restricted to the southern edge of the sheet where it conformably overlies Lower Cambrian Antrim Plateau the Timperley Shale. The unit is unconformably overlain Volcanics (êa) by the Antrim Plateau Volcanics. It consists of 40 m of fine- to medium-grained quartz sandstone deposited by The Antrim Plateau Volcanics (_a) unconformably overlie braided streams (Dow and Gemuts, 1969; Plumb, 1993). the Neoproterozoic Albert Edward Group rocks, progress-
22 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet ively stepping down from the Nyuless Sandstone to the exposed in the eastern half of the map sheet, and Mount Forster Sandstone from north to south across comprises the Middle Cambrian Negri Subgroup, which DIXON. They are conformably overlain by the Middle includes the Headleys Limestone, the Nelson Shale, the Cambrian Headleys Limestone. On DIXON the Antrim Linnekar Limestone, and the Panton Formation, and the Plateau Volcanics include the Blackfella Rockhole Member overlying Upper Cambrian Elder Subgroup, which and the Bingy Bingy Member. The unit is 340 m thick includes the Eagle Hawk Sandstone and the Overland south of the abandoned Turner Homestead and thins to the Sandstone. It is unconformably overlain by the Upper southeast (Mory and Beere, 1988). Hanley and Wingate Devonian Glass Hill Sandstone of the Mahony Group. The (2000) gave a SHRIMP U–Pb zircon date of 513 ± 12 Ma entire group is 630 m thick west of the Dixon Range, with for a dolerite dyke in the west Kimberley, which they inter- the Negri Subgroup being 440 m thick and the Elder preted as a feeder to the Antrim Plateau Volcanics. They Subgroup 190 m thick (Mory and Beere, 1988, fig. 14). suggested that lava flows must have originally extended across at least part of the Kimberley Basin. The Antrim The Negri Subgroup was deposited in laterally Plateau Volcanics are part of the Kalkarinji continental continuous intertidal to shallow subtidal environments in flood basalt province, Australia’s largest, which originally an intracratonic basin on a stable basement. The upper part covered an area of 300 000 km2 and extended as far east of the Linnekar Limestone represents a basin-wide marine as the Northern Territory – Queensland border (Hanley and incursion. A second marine incursion from the northwest Wingate, 2000; Glass, 2002). The thickest sections are in occurred during the deposition of the Panton Formation the Osmand Range, suggesting that the major eruptive but did not reach the southwestern part of the basin, which centres may have been to the north of DIXON. includes DIXON. The Elder Subgroup was deposited on intertidal sand and mudflats that were succeeded by a The unit consists predominantly of fine- to medium- braided fluvial system flowing from a low-relief hinterland grained, massive, vesicular, amygdaloidal and porphyritic to the northeast. tholeiitic basalt, interbedded with minor basaltic breccia, siltstone, sandstone, tuff, and stromatolitic chert (Bultitude, 1971; Mory and Beere, 1988). Lava flows range from 5 Negri Subgroup to 80 m thick, averaging 25 to 35 m. The lavas consist of plagioclase, clinopyroxene, and opaques, within a matrix Headleys Limestone (êGh) of devitrified glass. Flow tops are highly vesicular or amygdaloidal, with amygdales filled with coarse quartz, The Headleys Limestone (_Gh) on DIXON conformably chert, calcite, agate, chlorite, prehnite, and pumpellyite. overlies the Antrim Plateau Volcanics and is conformably Pipe vesicles may occur at the bottoms of flows. The overlain by the Nelson Shale. The unit consist of 50 m of presence of prehnite and pumpellyite suggests depths of grey, laminated or massive micrite with chert nodules, and burial for the lavas of between 5 and 7 km (Mory and locally contains simple, non-branching stromatolites. Beere, 1988). Nelson Shale (êGn) Bingy Bingy Member (êab) The Nelson Shale (_Gn) conformably overlies the Headleys Limestone, and is overlain conformably by the _ The Bingy Bingy Member ( ab) outcrops within the Linnekar Limestone. On DIXON it consists of 100 m of Antrim Plateau Volcanics in the southeastern corner of purple siltstone with minor thin beds of sandstone and DIXON. It consists of a massive fine- to medium-grained micrite. The cyanobacteria or calcimicrobe Girvanella has glomeroporphyritic basalt flow with clots of plagioclase been recorded from the Nelson Shale (Dow, 1980). crystals up to 1 cm in diameter. The unit reaches a maxi- mum thickness of 130 m to the northeast of DIXON near Chara Rockhole on LINACRE (Mory and Beere, 1988). Linnekar Limestone (êGl) The Linnekar Limestone (_Gl) conformably overlies the Blackfella Rockhole Member (êar ) Nelson Shale and is conformably overlain by the Panton Formation. On DIXON it consists of 24 m of fossiliferous The Blackfella Rockhole Member (_ar) occurs at or near limestone and shale. The presence of the trilobite the top of the Antrim Plateau Volcanics on DIXON. It Redlichia forresti has been interpreted as indicating an consists of a number of very fine grained lava flows with early Middle Cambrian age (Öpik, 1967). Girvanella, the basaltic breccias at their tops. The unit reaches a maximum narrow, conical shell of the holoplanktonic mollusc thickness of 140 m to the northeast of DIXON near Chara Biconulites hardmani, and unnamed stromatolites are also Rockhole on LINACRE (Mory and Beere, 1988). present (Mory and Beere, 1988).
Middle to Upper Cambrian Panton Formation (êGp) Goose Hole Group The Panton Formation (_Gp) conformably overlies the Linnekar Limestone and is conformably overlain by the The Goose Hole Group (Mory and Beere, 1985, 1988) Eagle Hawk Sandstone of the Elder Subgroup, or incorporates all sedimentary rocks within the Ord Basin unconformably overlain by the Glass Hill Sandstone of the that conformably overlie the Antrim Plateau Volcanics and Upper Devonian Mahony Group. On DIXON it consists of are considered to be of Cambrian age. On DIXON it is 124 m of purple siltstone, flaggy sandstone, and limestone
23 Tyler
(Mory and Beere, 1988). Locally the Panton Formation the Elder Subgroup, and locally the Panton Formation may be highly fossiliferous, containing the Middle of the Negri Subgroup of the Cambrian Goose Hole Cambrian assemblage of the trilobites Redlichia and Group (Mory and Beere, 1985, 1988). Overlying strata are Xystridura (documented by Öpik, 1967; Jell, 1983). Also not known; however, the interpretation of the Piccaninny present (Traves, 1955) are the brachiopods Billingsella and Structure to the north as a deeply eroded meteorite Wimanella, girvanellids, stromatolites, and Biconulites impact structure (Beere, 1983), implies the erosion of hardmani. several kilometres of strata from above the Glass Hill Sandstone forming the Bungle Bungle Range on TURKEY CREEK. Elder Subgroup The Glass Hill Sandstone is the only formation of the Eagle Hawk Sandstone (êGe) Mahony Group outcropping on DIXON. It is 200 m thick at its type section at the south end of the Dixon Range, The Eagle Hawk Sandstone (_Ge) conformably overlies the Panton Formation, and is conformably overlain by the and it is dominated by pebbly quartz sandstone, with Overland Sandstone, or unconformably overlain by the minor siltstone and conglomerate. Pebbly sandstone is Glass Hill Sandstone of the Upper Devonian Mahony friable, medium to fine grained, and well sorted. Pebbles generally comprise from 1% to 5% of the rock. They are Group (Mory and Beere, 1988). On DIXON it consists of 190 m of red, fine-grained, trough cross-bedded to parallel up to 3 cm in diameter with rare cobbles up to 15 cm, and laminated, medium- to thin-bedded, micaceous, arkosic consist of quartzite and locally abundant shale intraclasts. sandstone and minor siltstone and mudstone. Trilobite Medium trough and planar cross-bedding are dominant tracks are present on bedding planes, which also show with minor, thick parallel bedding and low-angle cross- wave-generated ripples and sand-filled desiccation cracks. bedding. Siltstone occurs as thin lenses and is massive, rippled and contains mudcracks. Conglomerate is parallel and trough cross-bedded in thin to medium lenses. Overland Sandstone (êGo) The Overland Sandstone (_Go) conformably overlies the Eagle Hawk Sandstone and is unconformably overlain by Palaeozoic the Glass Hill Sandstone of the Upper Devonian Mahony Group. On DIXON its outcrop is restricted to the east of Alice Springs Orogeny the Ord River. It consists of up to 10 m of white to fawn, fine- to medium-grained, clayey, lithic arkose and The youngest phase of major faulting and folding (D7; DA sandstone. Lithic fragments make up to 20% of the rock of Blake et al., 1997, 1999, 2000) in the east Kimberley and include quartz–mica schist, fine-grained region is attributed to the Late Devonian to Carboniferous metasedimentary rock, and quartzite. The sandstone is (400–300 Ma) Alice Springs Orogeny (Shaw et al., 1991; medium to thin bedded and trough cross-bedded, planar Tyler et al., 1995; Thorne et al., 1999). On DIXON, the cross-bedded or parallel laminated. Cambrian rocks of the Antrim Plateau Volcanics and the Goose Hole Group, and the Devonian rocks of the Glass Hill Sandstone, are folded into a gentle to open, large- scale, northeasterly plunging syncline, which represents Upper Devonian Mahony Group the southwesterly closure of the regional-scale Hardman The Mahony Group (Mory and Beere, 1985, 1988) on Syncline (Fig. 3). The fold is bounded by thrusting within the Osmand Range to the north and can be related to a DIXON consists of the Glass Hill Sandstone, which unconformably overlies the Elder Subgroup, and locally compression direction consistent with regional-scale the Negri Subgroup of the Cambrian Goose Hole Group. sinistral strike-slip movements on the Halls Creek Fault Correlation of the Mahony Group with the Cockatoo system (Thorne and Tyler, 1996). The folding represents Group in the Bonaparte Basin to the north suggests a Late the final stages of deformation. Initially a depositional Devonian, Frasnian age (Mory and Beere, 1988). basin was produced by flexural subsidence to the south of the Osmond Fault, with the Late Devonian alluvial fan, Sediment in the Mahony Group was derived mainly alluvial plain, and braided stream deposits of the Mahony from a highland in the Osmand Range. Initially braided Group being deposited in response to the initiation of streams and rivers flowed to the southwest, parallel to the southeasterly directed thrusting (Mory and Beere, 1988; highland. Contemporaneous eolian sandstone indicates an Thorne and Tyler, 1996). arid climate. Later movement on the east-northeasterly trending Osmond Fault in the Osmand Range resulted in In the Albert Edward Range and to the west of the the development of alluvial fans passing southwards into Dixon Range, west-southwesterly directed folding and alluvial plain deposits, and then fluvial deposits where thrusting is developed, which becomes more intense broad, shallow rivers flowed southeast, transverse to the towards an easterly trending dextral fault on HALLS CREEK fans. to the south (Blake et al., 1999). The folding and thrusting occurs locally between easterly to north-northeasterly trending faults that show dextral offset. The deformation Glass Hill Sandstone (DMg) may reflect compression between originally easterly trending dextral fault structures, antithetic to regional-scale The Glass Hill Sandstone (DMg) on DIXON unconformably sinistral movement on the Halls Creek Fault. The faults overlies the Eagle Hawk and Overland Sandstones of were rotated during continued sinistral movements.
24 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
Olympio Formation contact. Occurrences such as Slinkey Quartz veins (q) Hill may be situated in the Olympio Formation just above the Maude Headley Member in a culmination produced Quartz veins (q) are not widespread on DIXON. A large mass of vein quartz forms a prominent outcrop adjacent by the interference of D4 folds with cross-folding produced to a splay of the Halls Creek Fault within the Tickalara during D6. Metamorphics (AMG 403400E 8056600N). Quartz veins At Slinkey Hill (AMG 407000E 8045500N) gold are present along a fault within the Olympio Formation mining took place within the sandstones, siltstones, and southeast of the Bay of Biscay Hills. mudstones of the Olympio Formation of the Halls Creek Group. Mineralization is present at the intersection of ladder-like quartz veins and the Slinkey Hill Fault, Cainozoic surficial deposits associated with chlorite–hematite–sericite–carbonate alteration. At Black Duck Creek D (AMG 408700E Semiconsolidated low-angle slope deposits, scree and 8032800N) low-grade gold mineralization occurs in a large rubble (Czc) outcrop below scarps and in valleys, and quartz vein and quartz stockwork associated with a consist of sand, gravel, conglomerate, and sedimentary northerly trending fault. breccia. Colluvial sand and gravel (Czcv) forms dissected valley-fill deposits above the present-day In the Dry Creek area a number of abandoned gold alluvium-filled drainage channels (Qa). Semiconsolidated workings on quartz veins are present in sedimentary rocks and unconsolidated silt, sand, and gravel (Czs) covers of the Olympio Formation (Dry Creek 1 to 6, around valley floors and plains. Treeless black soil plains (Czb) AMG 394500E 8015400N) and in volcanic rocks of the formed by clay and silt cover broad flood plains adjacent Maude Headley Member (Kangaroo Hole, AMG 394700E to the larger creeks and rivers. These plains consist of 8015500N). black and dark grey-brown soils and expanding clays that produce cracking soils, and are largely developed over the Gold and silver mineralization at Wills Creek B2 Antrim Plateau Volcanics, the Nelson Shale, and the (AMG 401600E 8062600N) occurs within a pegmatitic Panton Formation. A landslip breccia (Czx) occurs below quartz breccia vein in the Tickalara Metamorphics. a scarp of Mount Forster Sandstone in the Albert Edward At Wills Creek C2 (AMG 401100E 8060200N) gold Range. mineralization occurs in thin limonitic quartz veins within amphibolite of the Tickalara Metamorphics. Calcrete (Czk) is restricted to an outcrop within alluvium and colluvium forming an older, dissected flood plain of the Ord River. Massive and pisolitic ferruginous Regolith — alluvial to beach placers duricrust (Czl) overlies outcrops of the Nelson Shale in Alluvial gold has been worked in the Dry Creek area. A the southeastern part of DIXON. Extensive consolidated and number of other deposits and occurrences are known on partly consolidated sandplain deposits (Czn) surround the DIXON, principally to the north of Slinkey Hill, and along outcrops of the Glass Hill Sandstone in the northeastern creeks and rivers draining from areas of known bedrock part of DIXON. mineralization in the Halls Creek Group.
Economic geology Base metal The mineral occurrences and exploration potential of the Orthomagmatic mafic and layered east Kimberley region have been documented in detail by mafic–ultramafic Sanders (1999) and by Hassan (2000). The following brief summary is based on open file exploration reports held The geology, mineralization, and economic potential of the in the WAMEX database (http://www.doir.wa.gov.au/ mafic–ultramafic layered intrusions in the Lamboo wamex/) and summarized by Hassan (2000). Most of the Complex have been discussed in detail by Hoatson and occurrences described here do not appear on the published Blake (2000). Copper, nickel, and gold mineralization map sheet (Tyler et. al., 1998d), but they are shown on the occurs in the Tickalara Metamorphics at Wills Creek D 1:500 000 map accompanying Hassan (2000). (AMG 401900E 8062600N). Minor malachite staining and gossanous veins are associated with massive biotite pods in amphibolite after gabbro. Precious metal Vein and hydrothermal — undivided Skarn
Warren (1994b,c, 1997) has suggested that gold in the Base metal occurrences classified as skarns on DIXON are Halls Creek Orogen may have been sourced from the within calc-silicate and marble units of the Tickalara A-type volcanics of the Maude Headley Member, with Metamorphics. These include copper as chrysocolla, fluids circulating through reactivated D5/6/7 faults malachite staining, and disseminated chalcopyrite at Sally reconcentrating gold at favourable structurally controlled Downs A (AMG 398600E 8063100N) and Wills Creek B4 sites. Typically these sites are close to the Maude Headley (AMG 397800E 8052900N), zinc and silver in gossan at Member, in the vicinity of the Biscay Formation – Wills Creek B5 (AMG 397800E 8052200N), and copper
25 Tyler and silver as malachite and chalcopyrite in association Stratabound sedimentary — undivided with quartz and tonalite veins at Wills Creek B6 (AMG 397000E 8051300N). Copper, zinc, lead, silver, (tin) mineralization was reported in a gossan in metasedimentary rocks of the Tickalara Metamorphics at Wills Creek A (AMG 401300E Stratabound volcanic and sedimentary 8061500N). — undivided The Antrim Plateau Volcanics form part of the Kalkarinji Vein and hydrothermal — undivided continental flood basalt province and have potential for the discovery of Noril’sk type nickel–copper sulfides and Copper and zinc are associated with gossanous stringers platinum group elements (Naldrett and Lightfoot, 1993). within metasedimentary rocks of the Tickalara Metamorphics at Wills Creek B3 (AMG 402100E At the Panton–Elvire copper prospect (AMG 416800E 8060400N). Finely disseminated sulfides and associated 8026100N), segregations of cuprite and chrysocolla up to malachite staining occur within amphibolites at Ord 30 cm wide occur in a 5 m-thick zone in basaltic agglom- (copper). erate. Mineralization occurs over a strike length of 5 km within the Antrim Plateau Volcanics.
At Panton River (gossan) 1 (AMG 394400E 8012900N) zinc mineralization occurs associated with gossanous carbonate rock in the upper part of the Biscay Formation.
26 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
References
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28 GSWA Explanatory Notes Geology of the Dixon 1:100 000 sheet
SHEPPARD, S., GRIFFIN, T. J., and TYLER, I. M., 1995, TYLER, I. M., HOATSON, D. M., GRIFFIN, T. J., SHEPPARD, S., Geochemistry of felsic igneous rocks from the southern Halls Creek BLAKE, D. H., and WARREN, R. G., 1997a, McIntosh, W.A. Orogen: Western Australia Geological Survey, Record 1995/4, 81p. Sheet 4462: Western Australia Geological Survey 1:100 000 SHEPPARD, S., GRIFFIN, T. J., and TYLER, I. M., 1997a, The tectonic Geological Series. setting of granites in the Halls Creek and King Leopold Orogens, TYLER, I. M., HOATSON, D. M., SHEPPARD, S., BLAKE, D. H., Northwest Australia: Australian Geological Survey Organisation, and WARREN, R. G., in prep.a, The geology of the McIntosh Record 1997/44, p. 107–109. 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 SHEPPARD, S., TYLER, I. M., GRIFFIN, T. J., and TAYLOR, W. R., Geological Series Explanatory Notes. 1999, Palaeoproterozoic subduction-related and passive margin TYLER, I. M., and HOCKING, R. 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M., and BLAKE, Journal of Volcanology and Geothermal Research, v. 29, p. 99–124. D. H., 1997b, Turkey Creek, W.A. Sheet 4563: Western Australia THORNE, A. M., SHEPPARD, S., and TYLER, I. M., 1999, Lissadell, Geological Survey 1:100 000 Geological Series. W.A. (2nd edition): Western Australia Geological Survey, 1:250 000 TYLER, I. M., THORNE, A. M., HOATSON, D. M., and BLAKE, Geological Series Explanatory Notes, 68p. D. H., in prep.b, The geology of the Turkey Creek 1:100 000 sheet: THORNE, A. M., and TYLER, I. M., 1996, Mesoproterozoic and Western Australia Geological Survey, 1:100 000 Geological Series Phanerozoic sedimentary basins in the northern Halls Creek Orogen: Explanatory Notes. constraints on the timing of strike-slip movement on the Halls Creek TYLER, I. M., WARREN, R. G., and BLAKE, D. H., 1998d, Dixon, Fault system: Western Australia Geological Survey, Annual Review W.A. Sheet 4562: Western Australia Geological Survey, 1:100 000 1995–96, p. 156–168. Geological Series. 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29 Tyler
Appendix
Gazetteer of localities on DIXON
Locality AMG coordinates Easting Northing
Airstrip/helipad (Purnululu National Park) 426000 8058500 Bay of Biscay Hills 397500 8028000 Bellburn campsite (Purnululu National Park) 424700 8061000 Black Hills 410000 8062000 Black Point 411500 8062000 Blue Hole 420500 8058000 Blue Hole Yards 421500 8059100 Dixon Range 427000 8046000 Dry Creek 394500 8015400 Dry Swamp Yard 439500 8059500 Eight Mile Yard 431900 8020200 Grant Peak 395000 8032200 Hardman Range 431500 8024100 Monkey Yard 397300 8058000 Mount Forster 415100 8014100 Piccaninny Yard 437500 8049200 Seven Mile Yard 445300 8028100 Slinkey Hill 407000 8045500 The Island 437000 8039500 The Island Yard 430900 8041800 Turner Hill 431500 8024100 Turner Homestead (abandoned) 425000 8028000 Walardi campsite (Purnululu National Park) 425400 8062100
30 TYLER
The Dixon 1:100 000 sheet lies within the central southern portion of the Dixon Range 1:250 000 sheet in the East Kimberley region. The mapped area falls within the Halls Creek Orogen, a major northeasterly trending orogenic belt developed in Palaeo- proterozoic to Palaeozoic rocks. The oldest components lie within the Central and Eastern zones of the Lamboo Complex. Successively younger Neoproterozoic and Palaeozoic basins are exposed in the eastern and northeastern parts of the sheet, each separated from the previous basin suite by four successive orogenies. These Notes describe the lith- ology, geological history, and relationships of these successions, and the deformation and metamorphism associated with the four orogenies. Mineralization in the sheet area is also briefly outlined. Geology of the Dixon 1:100 000 sheet
These Explanatory Notes are published in digital format (PDF) and are available online at: www.doir.wa.gov.au/gswa. This copy is provided for reference only. Laser-printed copies can be ordered from the Information Centre for the cost of printing and binding.
Further details of geological publications and maps produced by the Geological Survey of Western Australia can be obtained by contacting: EXPLANATORY NOTES
Information Centre Department of Industry and Resources 100 Plain Street East Perth WA 6004 Phone: (08) 9222 3459 Fax: (08) 9222 3444 www.doir.wa.gov.au/gswa AUSTRALIA 1Ý:Ý100Ý000 GEOLOGICAL SERIES GEOLOGICAL SURVEY OF WESTERN AUSTRALIA SHEET 4562
128^00À 10À 20À 128^30À
A 94 96 98 è00 02 04 06 08 è10 12 14 16 18 è20 22 24 26
17^30À 28 è30 32 34 36 38 è40 42 44 46 Geological boundary ìmTog 280
57 70 44 280 Ós Óc ìmTpc ìLo 280 17^30À
2 300 çMg 4 Ôa ìmTpc exposed...... ìmTan ìk ìmTpa êa280 Ôa Ócv ìmTgm 15 ìEo çMg
300 53 P êGh Ón Ón çMg Structural symbols are labelled according to the sequence of 64 260
ìmTgl 260
280
Ôa 80 76 êGl 400 Ócv 28 deformation events, where known
3 ìmTpa ìEm 260 64 ìmTpc 300 0 Ós Óc Ôa Alluvium _ unconsolidated silt, sand, and gravel 50 Ós ìmTpc 300 15 ìmTa 2 QUATERNARY 2 83 RIVER Yampi Orogeny ( c. 1000 Ma) Ócv 2 300
Ós 70 Ócv 320 320
ìmTa 73 260 240 Dë...... 5
ìmTpc ìmTa 4 280 ìmTgd Ôa 260 Ón 280 280 Ób Óc Ók Ól Ón Óx Ós 60 Ócv ìk 4 Black Halls Creek Orogeny (1835Ê1805 Ma)
ìmTan HILLS 75 Point ìEm 60 çMg
ìmTan 87 4 K 280 Dé...... 62 Ócv êGh Ób Black soil _ clay and silt; includes swelling clay soil on basalt ìmTpc BLAC9 êGe CAINOZOIC 60 Ôa ORD Dç...... 3 ìmTpc 80 75 çMg 260 62 Óc Colluvium and rubble _ sand, gravel, conglomerate, and sedimentary breccia forming sheetwash fans and scree slopes 65 Creek P RIVER çMg 300 ìmTa 4 ìEo 280
320 3 82 75 FRANK Ós çMg Ócv Colluvium and alluvium _ clay, silt, sand, and gravel forming dissected valley-fill deposits Hooper Orogeny (1865Ê1850 Ma)
Creek 340 4 P 240 300 70 320 240 Rock 80 70 Ók Calcrete _ sheet carbonate associated with alluvium, and colluvium
Ôa 74 ìEoj êGh DÛ...... 2 300 70 Ól Laterite _ massive and pisolitic ferruginous duricrust 300 ìmTpa 5
Wills 300 Ôa Óc 300 Ón Unconsolidated and partly consolidated sandplain deposits Fault or shear Ócv P 240
85 ìLj Piccaninny 380 Óx Landslip breccia exposed......
3 ðô60 260 57 50 êa êGl Ós Colluvium and alluvium _ partly consolidated clay, silt, sand, and gravel; adjacent to drainage; includes calcrete locally ìmTpn P concealed...... 33 ìHo Ôa ðô60 Ób Ôa Dry Swamp Yd 260 thrust...... Black ìHov Blue Hole Yds (abd)
q Quartz vein 340 280 Fold, showing axial trace and generalized plunge direction ìmTgm P Ócv 280
ìmTa 320 çMg 280 300 320 anticline; exposed, concealed...... 320 êGn Óc Monkey Yd 280
58 ìmTa syncline; exposed......
38 320 ìLo êar
340 340 2 ìEo 240 260 Ón çMg GLASS HILL SANDSTONE: medium- to fine-grained quartz arenite; minor pebbly sandstone, conglomerate, and siltstone
80 ìmTps ìmTss overturned syncline; exposed......
2 LATE
240 58 4 52 ìmTa 280 êGe 75 Ócv FRASNIAN ìmTog DEVONIAN
êGh Mahony Group Small-scale fold axial surface, showing strike and dip ìmTgm q 240 37 260 inclined...... ìmTpa 240 260 çMg êGo OVERLAND SANDSTONE: white, fine- to medium-grained lithic arkose
2 Creek Small-scale fold axis, showing trend and plunge 30 ìHov 280 êa 240 40 Ócv PHANEROZOIC 75 240 minor anticline...... 65 56 87 38 ìLo 3 4 47 ìHov 340 Z
4 Z 74 êGe EAGLE HAWK SANDSTONE: fine-grained, micaceous, feldspathic sandstone; minor siltstone Z-vergence...... 38
260 56
Elder Subgroup 300
ìmTa 0 240 ìmTgs 280 54 0 WH TEMPLETONIAN LATE CAMBRIAN 3 M
BOOMERANGIAN_ M-vergence...... 54 Ôa 280 2 54 2 70 400 Bedding, showing strike and dip 4 65 çMg êGp PANTON FORMATION: siltstone and mudstone; minor feldspathic sandstone, and limestone 2
Ón 10 340 M ìmTpc 260 inclined...... 47 êGp LINNEKAR LIMESTONE: laminated micritic limestone, shale, and calcareous shale; contains chert, stromatolites, and vertical...... 54 60 êGl
2 260 Goose Hole Group macrofossils locally
340 360
0 horizontal......
260 260 54
320 60 40
73 320 P U R N U L U L U N A T I O N A L P A R K
4 3 77
85 ORD BASIN Ócv 280 overturned......
ORDIAN PALAEOZOIC
260 purple siltstone and mudstone; minor feldspathic sandstone Ócv 240 êGn NELSON SHALE:
Negri Subgroup strike and dip estimated from aerial photography 320 300 360 240 70 260 Ôa MIDDLE CAMBRIAN êa horizontal...... ìmTss 220 Óc êGh HEADLEYS LIMESTONE: grey massive to laminated limestone; contains minor chert and stromatolites locally
52 Ôa Ón Ón 0Ê5°......
êa 260 320 Ós 240 Óc 52 5Ê15°...... 80 300 20 400 ìmTpc P ìEm 15Ê45°...... ìmTgm 40 260 Óc çMg êar Blackfella Rockhole Member: fine-grained basalt and basaltic breccia
ìEo êar êGp 220 êGe
320 trend of bedding......
380 ìmTa 18
340 340 55 280
38 ìHo 40 Foliation, showing strike and dip 280 0
300 240 êab Bingy Bingy Member: glomeroporphyritic basalt
260 êGl 280 68 ðô50 inclined...... 40
320 ANTRIM PLATEAU VOLCANICS: massive or amygdaloidal, locally porphyritic basalt and basaltic breccia; includes thin 60 Ôa êGh Óc ðô50 vertical...... 400 P 300 ìEf ìLo EARLY CAMBRIAN êa 50 ìEo interbeds of sandstone, siltstone, and stromatolitic chert 320 Piccaninny Yd Cleavage, showing strike and dip 340 çMg 300 40 Ón êGp 74 65 Ôa Ós inclined......
ìmTpa 75 260 P R A N G E 2 2
êGn 320 vertical......
260 340 280 240 êGo
35 200 380 ìkb ìLy NYULESS SANDSTONE: quartz sandstone and lithic sandstone; minor siltstone and conglomerate Crenulation cleavage, showing strike and dip
48 340 71
êGl 240 48 inclined......
360 220 êGe 5 220 Lineation, showing trend and plunge direction ìEm êGn Ócv 200 2 ìLj TIMPERLEY SHALE: grey-green mudstone and siltstone; minor sandstone 55 êGp ìmToa 00 300 stretching lineation; inclined...... 30 3 320 Creek
180
Óc 260 Ón
400 Ón beddingÊcleavage intersection; inclined...... 20
40À 360 340 300 40À ìLb BOONALL DOLOMITE: yellow or grey laminated dolomite, dolorudite, and argillite ìmTpc Piccaninny Ón 46 ìmTav axis of crenulation; inclined...... 32 300 çMg
240 46 Fossil locality...... 380 êGh çMg Albert Edward Group
340 Óc ìEo 35 5 Ón êGp 180 ìLe ELVIRE FORMATION: thin-bedded argillite; minor quartz sandstone 380 40 Ócv 240 êGe D I X O N 400 32 êGp Track...... 20 ìLo
Slinkey Hill Ób 340 240
380 320 çMg Ôa ìLo MOUNT FORSTER SANDSTONE: fine- to medium-grained quartz sandstone; minor pebbly sandstone and conglomerate Fence, generally with track...... 240 Ôa 220 Ós Ós 28 70 Ón Ócv ìmTpa 200 220 Homestead...... Turner
80 ìLo 44 380 ìEo 240 êGo ìmTpa Ón êGp êGo Black Point 340 280 êGh 44 Locality...... 400 Óc Ón RANFORD FORMATION: thin-bedded siltstone and mudstone, and thin- to thick-bedded greywacke, lithic sandstone, Ós 22 53 Ócv Ón
ìEm 220 Ób ìEo Building...... 2 380 êar 5 quartz sandstone, dolomitic quartz sandstone, and dolomite 16 40 êGe
65 êGe Yard...... Yd
00
êGh Óc 5 2 ORD Jarrad Sandstone Member: thin- to thick-bedded, fine- to medium-grained, dolomitic sandstone and quartz sandstone;
280 National park boundary......
260 ìEoj 300 200 220 êGp Ócv siltstone and mudstone
êGl Ós WOLFE CREEK BASIN Reserve boundary...... 42 380 Ós 75 380 380 200 320 Ócv 42 massive, matrix-supported, polymictic pebble- to boulder-conglomerate, and poorly sorted, Breakaway...... Blac Ócv MOONLIGHT VALLEY TILLITE: 3 êar The Island Yd êGe c. 610 Ma ìEm
Ós k 360 Ócv massive sandstone; larger clasts in conglomerate are polished and striated locally Contour line, 20 metre interval...... 300 380 Ós 180 ìHo êGn Ób Ócv Abandoned...... (abd) ìHov ìLj 360 Ós FARGOO TILLITE: matrix-supported, polymictic pebble- to boulder-conglomerate, and 9 êa Ôa Ób RIVER ìEf
Ób 200 êGp sandstone; clasts in conglomerate are polished and striated locally 70 Óc Ób Ós êGl P Ók Watercourse; pool...... P ðô40 êGh Ôa Ócv Duck 300 200 340 ðô40 Waterhole...... WH
360 Ós 220 ìPi ILLJARRA SANDSTONE: lithic sandstone; minor siltstone and dolomite (section only)
ìLe êGl Swamp...... Ôa 240 Creek ìEo 280 êGl PANTON Well...... W 280 200 70 10
300 Ób c. ?800 Ma ìPe ELIOT RANGE DOLOMITE: dolomitic mudstone, siltstone, and sandstone Windpump...... 55 ìEm êGp 200 71 êar êGl Ord River Homestead 63 km 5 ìkc 40 Ós Óc 14 (PD) 38 40 ìLe Position doubtful...... 70 360 70 30 ìLj RIVER Ruby Plains Group Duerdin Group
75 38 quartz sandstone
500 ìPk MOUNT KINAHAN SANDSTONE: ìLb Ós 4 200 Palm P (PD)
70 ìPk Ôa êGp 200 P Alluvial workings (gold)...... Dry Creek
80 17 220 280 ìLb Óc ìLo
4 Prospect...... 10 êGl 220 Edle Creek 80 20 240 Ócv
Ócv 200 fine- to coarse-grained lithic quartz-sandstone, pink feldspathic quartz sandstone, pebbly 360 êGl RED ROCK FORMATION: 540 85 êa ìdw ìk sandstone, conglomerate, siltstone, mudstone, basalt flows, and basaltic breccia.
40
340 45 45 ìLj 36 340 B 20 4 P 36 Ócv P Ób ìkc Carbonate rock
ìdw 5 8 êGl 220 360 ìLo êGh
ìHov 3 êGn 220 RED ROCK BASIN 220 3 Ób ìLe ìkb Massive to amygdaloidal basalt flows and basaltic breccia
65 260 êar Ós
30 50 400 80 ìLb
34 ìHo ìPk Ób
45 70 20 Ób 220 TN 300 15 34 320 ìLo êGn Ócv ìmTss ìmTgs
Black K I M B E R L E Y M I N E R A L F I E L D Ôa êGn GN Duck 220
260
340 MN
PROTEROZOIC SHEET INDEX 320 Ôa Ócv ìmTss Strongly sheared rocks; mylonitized
ìHov 25 Óc P Ós 220 260 ìEo ìmTgs Strongly sheared granitoid rock; mylonitized GRANT PEAK MOUNT
340 RIVER GLENROY TABLELAND BEDFORD REMARKABLE TURKEY CREEK OSMAND
32 Ôa 500 Óc GRID / MAGNETIC 340 220 4163 4263 4363 4463 4563 4663 Creek 32 LANSDOWNE DIXON RANGE ANGLE 3.3¾ êGn c. 1850 Ma ìmTgd ìmTgl ìmTgm ìmTog êar SE 52-5 SE 52-6 280 P LERIDA LAPTZ TUNGANARY McINTOSH DIXON LINACRE ìLo GRID
4162 4262 4362 4462 4562 4662 340 ìLb 220 ìmTgd DOUGALLS TONALITE: foliated and metamorphosed hyperstheneÊhornblendeÊbiotite tonalite; abundant pyroxene amphibolite 60 260 ìLe CONVERGENCE
WH ìLe 300 and country rock inclusions 0.2¾ êGh TURNER Ób
H I L L S 60 70 Óc 320 êa ìmTgl FLETCHER CREEK MONZOGRANITE: foliated and metamorphosed, leucocratic, biotiteÊmuscovite(ÊgarnetÊmagnetite) monzogranite; ELMA MOUNT CUMMINGS ANGELO HALLS CREEK ANTRIM NICHOLSON 30 ðô30 65 WH contains rounded- to angular-inclusions of amphibolite and country rock 4161 60 WHs 4261 4361 4461 4561 4661 80 P ìLb Turner landing ground ðô30 ìmTgm MONKEY YARD TONALITE: foliated and metamorphosed hornblendeÊbiotite(Êepidote) tonalite; epidote amphibolite inclusions MOUNT RAMSAY GORDON DOWNS 260 P SE 52-9 SE 52-10 P WH Ócv 220 ìmTog Amphibolite and dioritic to gabbroic granulite; cut by abundant veins of metatonalite and metatrondhjemite B I S C A Y BOHEMIA RAMSAY DOCKRELL RUBY PLAINS COW CREEK GORDON DOWNS
50 260 P Ób Yd 4160 4260 4360 4460 4560 4660 40 NICHOLSON
340 70 P 220 O F Ós Amphibolite; garnet- or clinopyroxene-bearing; relict primary layering and gabbroic textures
340 ìmToa 300 Ócv Turner (abd) 240 çMg Central zone 1:100Ý000 maps shown in black
260 Ócv 7 True north, grid north and magnetic north
50À 28 300 Ôa 7 Mile Yd 1:250Ý000 maps shown in brown
280 50À are shown diagrammatically for the centre
80 75 260 5
50 B A Y 260 Tickalara Metamorphics Óc 280 Óc 240 28 ìLb Yd Óc of the map. Magnetic north is correct for q 67 Yd (abd) 60 55 Ôa RIVER c. 1865 Ma ìmTa ìmTpa ìmTpc ìmTpn ìmTps 1998 and moves easterly by about 0.1^ in WHs 68 ìmTan ìmTav 300 Óc 9 years.
260 êa 340 (all units may be extensively veined by granitoid material)
300 Amphibolite; epidote-, garnet-, or clinopyroxene-bearing
80 70 260 çMg ìmTa 320 êa Óc ìmTan Amphibolite; interlayered with migmatitic pelitic, psammitic, and calc-silicate gneiss, includes epidote, garnet, or clinopyroxene 26
ìLe P 240
R 300 ìmTav Amphibolite; containing local pillows and fragmental volcanic textures with interstitial carbonate; interlayered with pelite, psammite,
WH 70 260 5 240 êar 260 WH RIVE 26
q ìLo ìEo Ób calc-silicate rock, and marble Lamboo Complex
WHs 240
340 êGn ìmTpa Interlayered pelite and psammite, with banded iron-formation, calc-silicate rock, and marble; minor amphibolite; includes crenulated garnetÊ 340
280 êa biotiteÊmuscoviteÊquartz schist and garnetÊchloriteÊmuscoviteÊquartz schist
340 30
WH WH 40 360 2 ìmTpc Calc-silicate and marble; minor banded iron-formation, quartzite, and amphibolite
P Ócv ìHov 340 êar Ól
WH ìmTpn BiotiteÊplagioclaseÊquartz(ÊK-feldsparÊsillimaniteÊgarnetÊcordierite) migmatitic pelitic gneiss; numerous layers and pods of amphibolite
WHs W TURNER HILL 40 240 and psammitic gneiss 320 24 300 ìEm 280 260 40 411 m H A R D M A N ìmTps Interlayered pelite and psammite, with banded iron-formation, calc-silicate rock, and marble; minor amphibolite; includes sillimaniteÊgarnetÊ 400
340 ìEm Ócv Óc 24 N.T.
360 300 stauroliteÊbiotiteÊplagioclaseÊquartz schist and sillimaniteÊbiotiteÊmuscoviteÊquartz schist WH 45
PANTON êa 260 Qld
ìHo 60 WH 260 Ós 280 P 260 70 ìLo Ób Óc WHs 400 ìdw WOODWARD DOLERITE: medium- to coarse-grained metadolerite W.A.
260
80
35 2 360 S.A.
WH 380 22 360 70 85 WHs 80 70 êa R A N G E 300 êGn Kartung Rija 22 metamorphosed (low- to medium-grade) thin- to very thick-bedded, fine- to coarse-grained, turbiditic, 85 ìHo Ób OLYMPIO FORMATION: N.S.W. 340 Óc P Aboriginal Reserve êGh ìHo Ós 5 lithic sandstone, greywacke, quartz wacke, and arkosic sandstone; siltstone and mudstone; minor pebbly sandstone
ELVIRE A.C.T. 240
Óc ìEm ìLe 300 360 çMg
ìEm 25 Ós Maude Headley Member: metamorphosed andesitic to trachytic volcanic and volcaniclastic rock with carbonate-rich Vic. 340
ìHo 400 360 êar Ôa Ós 280 c. 1855 Ma ìHov Ôa êa Ôa Óc matrix; minor ferruginous chert 85 340 20 P êGn êar êGh Eastern zone ìLo 8 Mile Yd Ób
ðô20 70 70 ìLj ìEo 300 Tas. 80 P ìHo BISCAY FORMATION: metamorphosed (low- to medium-grade) basaltic volcanic rock and sedimentary rock; minor
Óc ìEm ðô20 c. 1880 Ma
WHs 400 Ócv 25 ìHr 260
320 êGh 80 500 280 Ócv metadolerite sills 65 400 2 êGh Halls Creek Group 60 80 Ôa
80 3 P ìPk ìLj
260 320 360 ìLb RIVER ìHrb Metamorphosed basaltic volcanic and volcaniclastic rock; minor pelite and metadolerite; carbonate and chert lenses 50 85 êar 260 85 Creek 70
70 65 ìPe 300 440 êa 25 340 P êGh Óc
85 300 WH 420 260 18 380
ìHov 400 60
360 Ós 280 18
ìPk êar 320
340 260
300 êar
280
WHs 280 Ó400 c 320
440 Ôa 320
340 êGh TURNER 300
340 êGh GOVERNMENT OF WESTERN AUSTRALIA
400
80 240 75 400 ìEm êa
70 65 Ól HON. NORMAN MOORE, M.L.C. ìLb 340 300
MINISTER FOR MINES
16 Ôa 400 55 75 Saunders 300 ìLj 280 80 Dry Creek 60 85 16
65 ìEo ìLe ìLo 340
60 60 300 280 ìHrb 400 ìEm
360 ìLo ìLo 320
500
340
280 3
360 420 R A N G E 60 IC A L S 340 320 G U
400 L O R
400 320 V
320 O E 400 Ôa E
ìLb Y
360
Óx G ìLj 300 ìEm 300
30 ìHov êab W
A
14 E SIMPLIFIED GEOLOGY I MT FORSTER 300 êGh 15 S L
RIVER A
400 P T 400 14 E R
ìEm 340 ìmTo R N A U S T 340 Fault 340 ìmTg ìmTa ìHo Óc êar 340 Ób çM Mahoney Group
ìEo DEPARTMENT OF MINERALS GEOLOGICAL SURVEY OF 360 320
ìLo 240 êGh Downs Black Rock
420 Ôa ìEm Anticline
340 320 360 AND ENERGY WESTERN AUSTRALIA ìHr 420 P 300 4 ìk êG Goose Hole Group ORD BASIN
Ós 300 ìmTo
300 280 ìmTg êG 300 ìmTs
E D W A R D 300 ìmTg L. C. RANFORD, DIRECTOR GENERAL PRODUCT OF THE NATIONAL DAVID BLIGHT, DIRECTOR 340 340 Alice Antrim Plateau Volcanics 320 êa GEOSCIENCE MAPPING ACCORD 12 440 400 çM
300 êGh 320 Ôa
P ìLj 12 êa ìL Albert Edward Group
ìEm P 320 êa
320 Fault Ôa 420 ìLj 320 ìL 360 êa ìmTg WOLFE CREEK SCALE 1:100Ý000
ìHo 300 ìLb êar ìE Duerdin Group Ôa 320 280 360 BASIN
300 ìmTa Creek ìE 1000 0 1 2 34 567 8910
380 400 ìk ìLy 320 320 340 êar Ôa ìP Ruby Plains Group ìEm
300 320 Metres
ìEm ìLj 300 Kilometres A L B E R T ìEo 9 7 320 Halls UNIVERSAL TRANSVERSE MERCATOR PROJECTION êar êGh Ócv 3 Hardman RED ROCK 20 320 ìk Red Rock Formation êa BASIN HORIZONTAL DATUM: GEOCENTRIC DATUM OF AUSTRALIA 1994 ðô10ôôôÜN ìLb Syncline ðô10 VERTICAL DATUM: AUSTRALIAN HEIGHT DATUM 18^00À 18^00À ìmTg ìmTo ìmTa ìmTs å96ôôôÜE 98 è00 02 04 06 08 è10 12 14 16 18 è20 22 24 26 28 è30 32 34 36 38 è40 42 44 46 Grid lines indicate 1000 metre interval of the Map Grid Australia Zone 52 ìmTg Felsic intrusive sheets Gordon Downs Homestead 95 km ìmTo Amphibolite 128^00À 20À 128^30À The Map Grid Australia (MGA) is based on the Geocentric Datum of Australia 1994 (GDA94) 10À ìHo ìE ìL ìmTa Mafic metavolcanic, amphibolite, and metamorphosed ìHr Central zone GDA94 positions are compatible within one metre of the datum WGS84 positions sedimentary and carbonate rocks ìP GEOCENTRIC DATUM OF AUSTRALIA ìmTs Metasedimentary rock ìdw Tickalara Metamorphics Reference points to align maps based on the previous datum, AGD84, have been placed near the map corners ìdw Woodward Dolerite êG Lamboo Complex ìHo Olympio Formation DIAGRAMMATIC SECTION ìHov Maude Headley Member Compiled by I. M. Tyler, R. G. Warren (AGSO), D. H. Blake (AGSO), A B Eastern zone and A. M. Thorne, 1993Ê1997 ìHr Biscay Formation Alice Downs Fault Black Rock Anticline Halls Creek Fault BLACK HILLS Hardman Syncline DIXON RANGE ORD RIVER PANTON RIVER
Halls Creek Group Geology by R. G. Warren (AGSO), I. M. Tyler, and D. H. Blake (AGSO), 1992Ê1993 ìk êGo ìmTpa êGp êa Ord Basin geology modified from MORY, A. J., and BEERE, G. M., 1987, SEA LEVEL ìmTa ìmTpa çMg SEA LEVEL çM ìmTgd Western Australia Geological Survey, Bulletin 134, Plates 1 and 2 ìmTpa ìmTpa ìmTgm êGe ìmTa ìEf ìEm êGl ìP Edited by N. Tetlaw and G. Loan êGn ìHov ìmTss êGh êar ìHr Cartography by E. Green and C. Brien ìmTan ìLo êa êa Topography from the Department of Land Administration Sheet SE 52-6, 4562, SCALE 1:Ý500Ý000 ìmTpc ìmTpc ìL with modifications from geological field survey 2 km ìHo ìLo 0 5 10 15 20 2 km ìE Published by the Geological Survey of Western Australia. Copies available from Kilometres ìmTpa ìEo the Information Centre, Department of Minerals and Energy, 100 Plain Street, ìmTpc ìPk East Perth, WA, 6004. Phone (08) 9222 3459, Fax (08) 9222 3444 ìmTa ìmTa ìmTa ìPi ìmTpc ìPe This map is also available in digital form Printed by the Sands Print Group, Western Australia ìmTpn ìHo SHEET 4562 FIRST EDITION 1998 The recommended reference for this map is: 4 km 4 km TYLER, I. M., WARREN, R. G., and BLAKE, D. H., 1998, Dixon, W.A. Sheet 4562: Version 1.1 _ April 2004 Western Australia Geological Survey, 1:100Ý000 Geological Series ¦ Western Australia 2002