geology of the€¦ · reference the recommended reference for this publication is: smithies, r....

1:100 000 GEOLOGICAL SERIES

GEOLOGY OF THEHOOLEY

1:100 000 SHEETby R. H. Smithies

EXPLANATORYNOTES

Geological Survey of Western AustraliaGeological Survey of Western Australia

Industry and ResourcesIndustry and ResourcesDepartment ofDepartment of

2455 2555

24542354

BARROWISLAND

DAMPIER BEDOUTISLAND

1 2 4

5 6 8

ONSLOW YARRALOOLA

PORTHEDLAND-

MARBLEBAR

NINGALOO YANREYWYLOO MT BRUCE

ROY HILL

12 9 10 11 12

MINILYA WINNINGPOOL

EDMUND TUREE CREEK

NEWMAN

16 13 14 15 16

MANDORA

YARRIE

BALFOURDOWNS

ROBERTSON

BULLEN

NABBERU STANLEY

TRAINOR

GUNANYA

PATERSONRANGE

ANKETELL

MUNRO

LA GRANGE

BROOME

PENDER YAMPI

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MTANDERSON

McCLARTYHILLS

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RUNTON

MADLEY

HERBERT BROWNE

WARRI

MORRIS

URAL

PERCIVAL

DUMMER

CROSSLAND

NOONKAN-BAH

LENNARDRIVER

CHARNLEY

QUOBBA KENNEDYRANGE

MT PHILLIPS MTEGERTON

COLLIER

ROBINSONRANGE

GLENBURGHWOORAMELSHARKBAY-

EDEL

HOUTMANABROLHOS

DONGARA-

GERALDTON-

AJANA

YARINGABYRO BELELE

CUEMURGOO

YALGOO KIRKALOCKA YOUANMI

SANDSTONE

WILUNAKINGSTON ROBERT

9 11 12

6 7 8

4321

13 14 15 16

10

6

2 3 4

7 8

1211

MTELIZABETH

LISSADELL

LANSDOWNE

MT RAMSAY GORDONDOWNS

MT BANNER-MAN

BILLILUNA

CORNISH LUCAS

HELENA STANSMORE

WILSON WEBB

RYAN MACDONALD

1

CAMBRIDGEGULF

ASHTON

MEDUSABANKS

MONTAGUESOUND

CAMDEN SOUNDPRINCE

12 10

16 13 14

2

5

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13 14

1 2

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4 1 2 3 4 1 2 3 4

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DUKETON THROSSELL WESTWOOD LENNIS WAIGEN

LEONORA LAVERTON RASON NEALE VERNON WANNA

5 6

12 9 10

13 14 15 16 13 14

1 2 3 4 1 2

1 2

PERENJORI NINGHAN BARLEE MENZIES

HILLRIVERMOORA BENCUBBIN

JACKSON KAL-GOORLIE

PERTH KELLER- SOUTHERNCROSS

BOOR-BERRIN ABBIN

6 7 8 5

9 10 11 12 9

14 15 16 13

EDJUDINA MINIGWAL PLUMRIDGE JUBILEE MASON

CUNDEELEESEEMORE LOONGANA

FORREST

WIDGIE-MOOLTHA

ZANTHUS NARETHA MADURA EUCLA

6 7 8 5 6

11 12 9 10

14 15 16 13 14PINJARRA CORRIGIN HYDEN LAKE

JOHNSTONNORSEMAN

COLLIE DUMBLE-YUNG

NEWDE-GATE

RAVENS-THORPE

ESPERANCE-

PEMBERTON- MT BREMERBAY

MONDRAINISLAND

IRWIN INLET

ALBANY

2 3 4 1 2

6 7 8 5

6,

12

10

BALLA-DONIA

CULVER BURN-ABBIE

NOONAERA

MALCOLM-CAPE ARID

3 4 1 2

SD 52

SE 51

SF 52

SG 52SG 51SG 50

SH 52SH 50

SI 51SI 50

SF 49

SG 49

LONDON-DERRY

114 o 120 o 126 o

32 o

28 o

24 o

20 o

16 o

5,9

15,

7, 11

DRYSDALE-

REGENT-

BARKER-10, 14 11, 15

5, 9

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8

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2355

NULLAGINE

5

COOYAPOOYA SATIRIST

PYRAMID

7SF 50

MOUNTWOHLER

MOUNTBILLROTH

HOOLEY2554

RHS240 15.05.03

PYRAMID SF 50-7

GEOLOGICAL SURVEY OF WESTERN AUSTRALIA

GEOLOGY OF THEHOOLEY1:100 000 SHEET

byR. H. Smithies

Perth 2003

MINISTER FOR STATE DEVELOPMENTHon. Clive Brown MLA

DIRECTOR GENERAL, DEPARTMENT OF INDUSTRY AND RESOURCESJim Limerick

DIRECTOR, GEOLOGICAL SURVEY OF WESTERN AUSTRALIATim Griffin

REFERENCEThe recommended reference for this publication is:SMITHIES, R. H., 2003, Geology of the Hooley 1:100 000 sheet: Western Australia Geological Survey,

1:100 000 Geological Series Explanatory Notes, 15p.

National Library of Australia Card Number and ISBN 0 7307 8932 2

ISSN 1321–299X

Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the textare referenced using Map Grid Australia (MGA) coordinates, Zone 50. All locations are quoted to at least the nearest 100 m.

Copy editor: A. ThomsonCartography: D. SuttonDesktop Publishing: K. S. NoonanPrinted by Haymarket, Perth, Western Australia

Published 2003 by Geological Survey of Western Australia

Copies available from:Information CentreDepartment of Industry and Resources100 Plain StreetEAST PERTH, WESTERN AUSTRALIA 6004Telephone: (08) 9222 3459 Facsimile: (08) 9222 3444This and other publications of the Geological Survey of Western Australia may be viewed or purchased online through theDepartment’s bookshop at www.doir.wa.gov.au

Cover photograph:Looking northwest to Mumbillina Bluff where metasedimentary rocks of the Hardey Formation unconformably overlie granite.

iii

Contents

Abstract ...................................................................................................................................................................... 1Introduction ............................................................................................................................................................... 1

Access and land use ........................................................................................................................................... 1Climate and vegetation ...................................................................................................................................... 2Physiography ...................................................................................................................................................... 2Regional geological setting and previous investigations .................................................................................. 4

Archaean rocks .......................................................................................................................................................... 5Unassigned greenstone units ............................................................................................................................. 6

Ultramafic rocks (Au, Auk, Aur) ................................................................................................................ 6Mafic rocks (Aba, Abal, Abag, Abas, Abu, Abuq) ..................................................................................... 6Sedimentary rocks (Asq, Asqn) .................................................................................................................. 6

Yule Granitoid Complex ................................................................................................................................... 7Cheearra Monzogranite (AgYchn) .............................................................................................................. 7Cockeraga Leucogranite (AgYco, AgYcor, AgYcorx) ................................................................................. 7Hornblende–biotite tonalite (AgYt) ............................................................................................................ 7Mungaroona Granodiorite (AgYmux) ......................................................................................................... 7Powdar Monzogranite (AgYpop, AgYpos) .................................................................................................. 7Unassigned granitoid (AgY) ........................................................................................................................ 8

Metamorphism ................................................................................................................................................... 8Structure ............................................................................................................................................................. 9Hamersley Basin ................................................................................................................................................ 9

Fortescue Group ......................................................................................................................................... 9Mount Roe Basalt (AFr) ...................................................................................................................... 9Hardey Formation (AFh, AFhu) .......................................................................................................... 9Kylena Formation (AFk, AFkbi, AFkh) ............................................................................................... 9Tumbiana Formation (AFt, AFtsv, AFtc, AFtsvs, AFtsvb) .................................................................. 9Maddina Formation (AFm, AFmk, AFmx) ......................................................................................... 11Jeerinah Formation (AFjslg, AFjo, AFjsl, AFjkd) .............................................................................. 11

Hamersley Group ...................................................................................................................................... 11Marra Mamba Iron Formation (AHm) .............................................................................................. 11

Structure and metamorphism ........................................................................................................................... 11Dolerite dykes (d) ............................................................................................................................................ 11

Cainozoic deposits .................................................................................................................................................. 12Residual deposits (Czru, Czrk, Czrfb) ............................................................................................................. 12Colluvium (Czc, Czcb) .................................................................................................................................... 12Alluvial deposits (Czaf, Czag, Czak) .............................................................................................................. 12Quaternary colluvium and sheetwash deposits (Qc, Qw) ............................................................................... 12Quaternary alluvial deposits (Qaa, Qao, Qab) ............................................................................................... 12

Economic geology ................................................................................................................................................... 12References ............................................................................................................................................................... 13

Appendix

Gazetteer of localities ................................................................................................................................... 15

Figures

1. Regional geological setting of HOOLEY .......................................................................................................... 22. Physiographic features of HOOLEY .................................................................................................................. 33. Igneous layering in hornblende–biotite tonalite ............................................................................................ 84. Structural overview of HOOLEY and adjacent 1:100 000 map areas ............................................................ 10

Tables

1. Summary of the geological history of HOOLEY .............................................................................................. 42. Geochronological data relevant to HOOLEY .................................................................................................... 5

1

GSWA Explanatory Notes Geology of the Hooley 1:100 000 sheet

Geology of the Hooley 1:100 000 sheet

by

R. H. Smithies

AbstractThe HOOLEY 1:100 000 sheet lies in the southwestern part of the Archaean East Pilbara Granite–Greenstone Terrane of the Pilbara Craton. Rocks of the c. 2775–2630 Ma Fortescue Group cover all butthe northeastern and southwestern corners of the map sheet. These rocks are mostly shallow dipping,weakly deformed and metamorphosed. A locally angular unconformity separates the Fortescue Grouprocks from the Yule Granitoid Complex of the East Pilbara Granite–Greenstone Terrane, which isexposed only in the northeastern part of HOOLEY. The Yule Granitoid Complex consists mainly ofc. 2945–2930 Ma granitic rocks but also includes xenoliths and roof-pendants of greenstones belongingto the Pilbara Supergroup. The Punduna greenstone pendant is the largest of these roof pendants. Thesupercrustal rocks have been metamorphosed to at least lower amphibolite facies, but are now typicallystrongly retrogressed. Their stratigraphic position within the Pilbara Supergroup is unclear. In the farsouthwestern corner of HOOLEY, rocks of the Hamersley Group conformably overlie the FortescueGroup.

KEYWORDS: Archaean, Pilbara Craton, Pilbara Supergroup, Fortescue Group, Hamersley Group,East Pilbara Granite–Greenstone Terrane, regional geology, structural geology,metamorphism, granitic rock

IntroductionThe HOOLEY* 1:100 000 geological sheet (SF 50-7, 2554)covers the southeastern part of the PYRAMID 1:250 000 mapsheet, in the northern Pilbara region (Fig. 1). Bounded bylatitudes 21°30'S and 22°00'S, and longitudes 118°00'Eand 118°30'E, the map area lies within the West PilbaraMineral Field.

Exposure is good throughout the sheet area. The north-eastern corner of HOOLEY contains outcrops of the EastPilbara Granite–Greenstone Terrane of the ArchaeanPilbara Craton. Most of the sheet area, however, is coveredby the volcano-sedimentary assemblages that form thelower to middle part of the 2775 to 2400 Ma HamersleyBasin (Arndt et al., 1991). These assemblages include theentire Fortescue Group and the Marra Mamba IronFormation, the lowest part of the overlying HamersleyGroup (see Interpreted bedrock geology on main map).The Fortescue Group unconformably overlies the YuleGranitoid Complex of the East Pilbara Granite–GreenstoneTerrane.

The area was originally mapped in 1963 as part of thePYRAMID 1:250 000 geological map sheet (Kriewaldt and

Ryan, 1967). During 2000 and 2001 the HOOLEY 1:100 000geological sheet was mapped using both 1:25 000 colour,and 1:50 000 black and white aerial photographs.Relatively easy access to the northeastern corner of thesheet facilitated mapping of that region; however, therugged topography of the Mungaroona and ChichesterRanges (which rise 500 m above sea level) impeded accessto much of HOOLEY. Mapping was restricted to traversesalong tracks and to widely spaced sites reached byhelicopter. Limited access to large parts of the map sheethave placed significant reliance on Landsat imagery andaerial photographic interpretation.

Access and land useThe unsealed road connecting the towns of Wittenoom andRoebourne passes through the southwest corner of HOOLEY.Intersecting that road, to the south of the map area, is theroad to Hooley Homestead (the only currently inhabitedhomestead), which lies in the south-central part of the sheet(Fig. 2). The only other serviced road is in the far northeastcorner of the sheet, and connects the Mugarinya AboriginalCommunity on Yandeearra Station to the north (onSATIRIST) to Yandeearra Outstation to the east (on WHITE

SPRINGS). There is limited access to areas in the northeast,south, and west of the sheet by four-wheel drive vehicleon unmaintained tracks. Large parts of the sheet area,

* Capitalized names refer to standard 1:100 000 map sheets, unlessotherwise indicated.

2

Smithies

20°

21°

22°

120°119°118°117°

100 km

INDIAN OCEAN

Mesoproterozoic–Phanerozoic rocks

Hamersley Basin

Other terranes

Greenstones

Granitoids

Greenstones Greenstones

Granitoids Granitoids

Mosquito CreekBasin

Kurrana Terrane

Pilb

ara

Cra

ton

WEST PILBARA GRANITE–GREENSTONE

TERRANE

?

?

CENTRAL PILBARA TECTONIC

ZONE

EAST PILBARA G

RANITE–GREENSTONE

TERRANE

West Pilbara Granite– East Pilbara Granite–

MallinaBasin

Geenstone Terrane Tectonic ZoneCentral Pilbara

Greenstone Terrane

Karratha

PortHedland

Terrane boundary

Town

HOOLEY

Pundunagreenstone

pendant

RHS241 21.05.03

Figure 1. Regional geological setting of HOOLEY

including most parts of the Mungaroona Range and theChichester Range, are only accessible on foot or byhelicopter.

The Mungaroona Range Nature Reserve occupies anorthwest-trending strip through the centre of HOOLEY. Theremaining land is divided between Yandeearra Station(Mugarinya Aboriginal Community) in the northeast, andHooley Station in the south. Prior permission must begranted by the Mugarinya Aboriginal Community foraccess to Yandeearra Station. Cattle grazing is the soleagricultural activity. There are no old or active mines.

Climate and vegetationThe climate of HOOLEY is arid with an average annualrainfall of 405 mm, most of it summer rainfall relating tothunderstorms or decaying tropical cyclones. Meansummer maximum temperatures are in the mid-30s (°C),whereas the winters are mild, with mean minimum Julytemperatures of around 15°C.

HOOLEY lies within the Fortescue Botanical District andis broadly divisible into three regimes (Beard, 1975). The

Fortescue River, and other major channels and associatedfloodplains, are lined with riverain Sclerophyll woodlandsof River Gum (Eucalyptus camaldulensis). The northeastcorner of the area consists of a shrub steppe of softspinifex (Triodia pungens) with scattered Acacia,Grevillea, and Hakea species. The third, and largest,regime is a tree steppe of Snappy Gum (Eucalyptusbrevifolia) with spinifex, and scattered Acacia, Grevillea,and Hakea sp. that grow on the dissected plateau thatdominates the sheet area.

PhysiographyIn the northeast of HOOLEY, tributaries to the Yule River,including the Pilbaddy Creek, drain northward, whereasthe west-draining Fortescue River cuts the southwestcorner of the sheet area (Fig. 2). These drainage systemsflow mainly during the summer wet season. Physiographicdivisions on HOOLEY match major geological divisions.Rocks of the Fortescue Group typically form a prominentdissected plateau, except in the far southwest of thesheet area, where an alluvial plain marks the FortescueRiver floodplain (Fig. 2). The dissected plateau surface

3


Figure 2. Physiographic features of HOOLEY

Fortescue River

Hooley

Cre

ek

Creek

Riv

er

Erosional

Tertiary land surface

High-level alluvial plain

473

Drainage

Unsealed road

RHS242 19.05.03

Mungaroona RangeNature Reserve

YandeearraAboriginal Land

223

266

462

467

441

281

473

384

471

473

481

Hooley Homestead

Creek

SherlockRiver

Pilbad

dy

Powda

rCre

ek

Mungo

ona

She

rlock

Depositional

Recent land surface

Dissectedplateau

Nature reserve boundary10 km

118°

30'

21°30'

22°00'

118°

00'

Sandplain with low-lying granite outcrop

476

Spot height (m)

Alluvial channel

Alluvial–colluvial plain

4

Smithies

is approximately 500 m above sea level and part ofthe peneplain that Campana et al. (1964) called theHamersley Surface. In the far northeast of the sheet area,a sandplain partly covers low-lying granitic outcrop thattypically marks the alluvial–colluvial plains division(Fig. 2).

Regional geological setting andprevious investigationsThe Archaean Pilbara Craton contains some of the oldestexposed crustal elements of Australia. It is divided intotwo components (Fig. 1) — a granite–greenstone terranethat formed between c. 3600 and c. 2800 Ma (Hickman,1983, 1990; Barley, 1997), and the unconformablyoverlying volcano-sedimentary sequences (Mount BruceSupergroup) of the c. 2775 to 2400 Ma Hamersley Basin(Arndt et al., 1991; Thorne and Trendall, 2001). Thegranite–greenstone terrane of the Pilbara Craton isexposed mainly in the north and northeast of the cratonwhere erosion has removed all but local remnants of theMount Bruce Supergroup.

Hickman (1983) provided a comprehensive interpret-ation of the geological evolution of the granite–greenstoneterranes of the Pilbara Craton, and included what wasthought to represent a regionally applicable supercrustalstratigraphy — the Pilbara Supergroup. Recently, therecognition of separate lithotectonic elements with distinctlithostratigraphy and history has led to the subdivision ofthe granite–greenstone terranes into: the East and WestPilbara Granite–Greenstone Terranes, the northeast-trending Central Pilbara Tectonic Zone, the MosquitoCreek Basin, and the Kurrana Terrane (Fig. 1; Hickman,2000). A detailed description of the subdivision,geological setting, and history of the region is presentedby Van Kranendonk et al. (2002).

HOOLEY lies in the southeastern part of the EastPilbara Granite–Greenstone Terrane (EPGGT; Fig. 1).Regionally, the terrane consists of large ovoid granitic-gneiss complexes partially surrounded by belts oftightly folded and near-vertically dipping volcanicrocks and sedimentary rocks typically metamorphosedto greenschist facies. The oldest dated greenstones inthe EPGGT are the c. 3515–3498 Ma CoonterunahGroup (Table 1; Buick et al., 1995; Van Kranendonk,1998; Nelson, 2002). Protoliths to the greenstonesuccessions accumulated until c. 2940 Ma, although themajority were deposited before c. 3240 Ma. Felsicmagmatism was also periodically active between c. 3600and c. 2830 Ma, with the majority of granitic rocks inthe eastern part of the EPGGT intruded before c. 3240 Ma.In contrast, granitic rocks dated between c. 2945 and2930 Ma form a volumetrically significant, and locallydominant, component of granitic complexes in the westernpart of the terrane, including the majority of the YuleGranitoid Complex (Table 1). Champion and Smithies(1998) interpreted these c. 2945–2930 Ma granitoids asthe products of the remelting of older-than-3240 Ma felsiccrust, associated with tectonic activity in the CentralPilbara Tectonic Zone.

The boundary between the EPGGT and the CentralPilbara Tectonic Zone is a fault, which locally may bea faulted disconformity, between the Mallina Basin andthe underlying granite–greenstone sequences. Theyoungest component of the basement to the Mallina Basinincludes a c. 3015 Ma chert assigned to the CleavervilleFormation of the Gorge Creek Group (Smithies et al.,1999).

The Mount Bruce Supergroup is the early(Neoarchaean to Palaeoproterozoic) component of theHamersley Basin. The supergroup is a cover sequence ofdominantly basaltic and sedimentary rocks, of very lowmetamorphic grade, which unconformably overlie the

Table 1. Summary of the geological history of HOOLEY

Age (Ma) Events

<3515 – >2945 Deposition of greenstone sequences (Pilbara Supergroup), and formation ofc. 3060 Ma protolith to the Cockeraga Leucogranite

c. 3420 Intrusion of protolith to the gneissic rocks of the Yule Granitoid Complex

c. 3240 Amphibolite-facies metamorphism associated with granitic magmatisminterpreted from TAMBOURAH (Van Kranendonk, 2003) and WHITE SPRINGS

(Smithies, in prep.)

<3240 – >2945 Deformation of granite/gneiss and greenstone sequences; 110–160° trending fabric.Age inferred from relationships on TAMBOURAH (Van Kranendonk, 2003)

<3060 – 2945 Amphibolite-facies metamorphism, including generation of the CockeragaLeucogranite from a c. 3060 Ma source region

c. 2945 – 2930 Voluminous granitic magmatism in the Yule Granitoid Complex, including intrusionof the Powdar Monzogranite

c. 2945 – 2930 Development of northeast-trending foliation throughout the Yule Granitoid Complex

c. 2930 – 2775 Erosion

c. 2775 – 2630 Deposition of volcanic and sedimentary rocks of the Fortescue Group

2770 and younger Dip-slip faulting along major northeasterly trending faults

c. 2600 – 2500 Deposition of lower Hamersley Group

<2600 Intrusion of dolerite dykes; east-northeast faulting

5


granite–greenstone terranes. The supergroup has beendescribed in detail by Hickman (1983), Blake (1993), andThorne and Trendall (2001). The lowest stratigraphiccomponent is the Fortescue Group that was depositedbetween c. 2775 and 2630 Ma (Arndt et al., 1991; Nelson,1997; Wingate, 1999: Thorne and Trendall, 2001; Table 2).

According to Arndt et al. (2001), Fortescue Groupvolcanism is the result of lithospheric melting duringthree successive phases of mantle plume activity. Thorneand Trendall (2001), however, cited the lithologicaldiversity of the group and the long duration of volcanism(around 140 million years) as evidence against thishypothesis, and described the tectonic setting of theFortescue Group in terms of a single, protracted riftingevent. Blake (1993) also suggested that the lower parts ofthe Mount Bruce Supergroup record a period of lateArchaean west-northwest crustal extension, followed bysouth-southwest rifting of the southern margin of thePilbara Craton.

Archaean rocksThe Archaean geology and geological history of HOOLEY

is summarized on Interpreted bedrock geology (seemain map) and in Table 1. Geochronological data relevantto HOOLEY and surrounding areas is presented in Table 2.

Approximately 70% of the EPGGT in the northeasternpart of HOOLEY is granitic rock, all of which belongs tothe Yule Granitoid Complex. Seriate-textured toK-feldspar-porphyritic monzogranites of the c. 2935 Ma(Nelson, 2000) Powdar Monzogranite (Smithies andFarrell, 2000) dominate outcrop, particularly to the westof the large area of greenstones referred to here as thePunduna greenstone pendant. North of the Pundunagreenstone pendant, the Powdar Monzogranite includeslarge xenoliths, up to 2 km long, of gneissic monzogranite.These belong to the Cheearra Monzogranite, which formsa major component of the Yule Granitoid Complex onSATIRIST. To the east and south of the Punduna greenstonependant, schlieric biotite granitic rocks of the Cockeraga

Leucogranite dominate outcrop. These granitic rockscontain gneissic xenoliths, and locally abundantgreenstone xenoliths, interpreted as derived from thegreenstone pendant into which the leucogranite hasintruded. The Cockeraga Leucogranite has a maximumage of c. 3065 Ma (Nelson, 2002), but is likely to beyounger than this (Smithies, in prep.). A hornblende–biotite tonalite forms a discrete, approximately 10 km-long, body close to the southern unconformity withthe Fortescue Group. This tonalite is intruded bythe Powdar Monzogranite, but contact relationships withthe Cockeraga Leucogranite, which is exposed to thesoutheast, could not be determined. The tonaliteis petrographically and geochemically similar —unpublished geochemical data from Geological Surveyof Western Australia (GSWA) and Geoscience Australia(GA) — to the Mungaroona Granodiorite, whichis exposed on SATIRIST (Smithies and Farrell, 2000)and which has an age of c. 2940 Ma (Nelson, 2000).

Greenstones on HOOLEY are restricted to xenoliths in,and roof-pendants on, granitic rocks of the Yule GranitoidComplex. Due to sparse outcrop and lack of continuitywith formally recognized stratigraphic components, thesegreenstones cannot be confidently assigned to groups orformations within the Pilbara Supergroup. The 12 km-long, east-trending Punduna greenstone pendant forms thelargest outcrop of greenstone. The consistent west-northwest strike of the stratigraphy suggests that thispendant can be correlated to the Cheearra greenstone beltin the southern part of SATIRIST (Smithies and Farrell,2000). The rocks of the pendant are metamorphosed toamphibolite facies and are largely derived from maficvolcanic rocks, although interleaved rocks of sedimentaryand ultramafic protolith are locally abundant. Rocks ofsedimentary or ultramafic protolith form local, discretemappable units. Relict olivine-spinifex textures indicatethat some of the ultramafic rocks are metamorphosedkomatiites.

The Neoarchaean to Palaeoproterozoic HamersleyBasin contains a volcanic and sedimentary succession —the Mount Bruce Supergroup — that is up to 10 km thick

Table 2. Precise U–Pb zircon geochronology (SHRIMP(a)) relevant to units on HOOLEY

Age (Ma) Lithology Formation/Group/Complex Sample Reference

2561 ± 8 Crystal-rich tuff Wittenoom Formation, Hamersley Group 120044 Trendall et al. (1998)2597 ± 5 Mount Newman Member Marra Mamba Iron Formation, Hamersley Group 120046 Trendall et al. (1998)2763 ± 13 Lapilli tuff Mount Roe Basalt, Fortescue Group 94792 Arndt et al. (1991)2775 ± 10 Felsic volcanic rock Mount Roe Basalt, Fortescue Group 86738 Arndt et al. (1991)2715 ± 6 Pillingini Tuff Tumbiana Formation, Fortescue Group 94775 Arndt et al. (1991)2719 ± 6 Volcaniclastic sandstone Tumbiana Formation, Fortescue Group 168935 Nelson (2001)2717 ± 2 Dacite Maddina Formation, Fortescue Group 144993 Nelson (1998)2684 ± 6 Tuffaceous sandstone Jeerinah Formation, Fortescue Group 94776 Arndt et al. (1991)2690 ± 16 Tuffaceous sandstone Jeerinah Formation, Fortescue Group 103225 Arndt et al. (1991)2935 ± 3 Powdar Monzogranite Yule Granitoid Complex 142937 Nelson (2000)2945 ± 5 Mungaroona Granodiorite Yule Granitoid Complex 142938 Nelson (2000)<3068 ± 22 Cockeraga Leucogranite Yule Granitoid Complex 169014 Nelson (2002)<3066 ± 4 Cockeraga Leucogranite Yule Granitoid Complex 169016 Nelson (2002)

NOTE: (a) Sensitive high-resolution ion microprobe

6

Smithies

and covers approximately 100 000 km2 (Trendall, 1990).This succession is subdivided into three lithostratigraphicgroups — Fortescue, Hamersley, and Turee Creek. Onlythe lower two groups are preserved on HOOLEY, with theFortescue Group dominating outcrop.

On HOOLEY, rocks of the c. 2775–2630 Ma FortescueGroup (Arndt et al., 1991; Nelson et al., 1999; Wingate,1999; Thorne and Trendall, 2001), and the lowest part ofthe Hamersley Group typically dip to the south orsouthwest at less than 10°, and are only very weaklymetamorphosed. An unconformity is well developedbetween the Fortescue Group and the underlying granite–greenstone terrane. On the map area, all recognizedformations of the Fortescue Group are preserved; however,regional topographic variations at the time the groupwas deposited have resulted in locally incompletedevelopment of the lower units. The Mount Roe Basaltis only developed in the northwest of the sheet. Elsewhereon HOOLEY the Hardey and Kylena Formations formthe base of the Fortescue Group. In the southwest corner,the contact between the Jeerinah Formation and theoverlying Marra Mamba Iron Formation marks theboundary between the Fortescue and Hamersley Groups(Thorne and Trendall, 2001). There is no evidence onthe map area of an unconformity between thesegroups. Rather, carbonaceous mudstones and siltstonesof the Jeerinah Formation pass conformably upwardsinto the ferruginous mudstones of the Marra MambaIron Formation. The Wittenoom Formation thatconformably overlies the Marra Mamba Iron Formationis not exposed on HOOLEY, but is interpreted to underlieCainozoic calcrete deposits in the far southwest of thesheet area.

Unassigned greenstone units

Ultramafic rocks (Au, Auk, Aur)

Outcrops of metamorphosed ultramafic rock that areweathered or strongly deformed have mainly been mappedas undivided ultramafic rock (Au). In areas of betterexposure, the ultramafic rocks have been subdivided intometamorphosed peridotitic komatiite (Auk) and tremolite-rich schist (Aur).

Undivided ultramafic rock (Au) includes serpentineschist, tremolite schist, and talc–tremolite–chlorite schist.These are exposed in the Punduna greenstone pendant andalso form isolated xenoliths within rocks of the YuleGranitoid Complex.

Serpentine–talc–tremolite rock (Auk) locally preservesolivine-spinifex textures and is metamorphosed peridotitickomatiite. It forms a prominent outcrop along the southernmargin of the Punduna greenstone pendant, and also formsminor xenoliths within rocks of the Yule GranitoidComplex (e.g. MGA 642000E 7605500N).

Tremolite-rich schist (Aur) is the most abundantultramafic rock type. It is typically fine grained and wellfoliated, and comprises acicular or fibrous tremolite, withsubordinate amounts of chlorite, talc, and fine-grainedopaque minerals.

Mafic rocks (Aba, Abal, Abag, Abas,Abu, Abuq)

Most of the unassigned greenstone units on HOOLEY

comprise metamorphosed mafic rock. The dominant rocktype is fine- to medium-grained, massive to stronglyfoliated amphibolite-facies mafic rock (Aba). Thiscomprises a typically granoblastic assemblage ofhornblende, plagioclase, and quartz, and locallyclinopyroxene, or less commonly orthopyroxene. Therocks are typically melanocratic to mesocratic. Leucocraticamphibolite (Abal), with less than 20% hornblende, ismapped separately along the southern part of the Pundunagreenstone pendant. Similar rock is well exposed in thefoothills of the Mungaroona Range (e.g. MGA 648000E7606800N).

Within the Punduna greenstone pendant, medium-grained amphibolite locally contains abundant layers,veins, and irregular patches of tonalite (Abag; e.g. MGA645000E 7615400N). Where tonalite is abundant the rocksresemble components of the heterogeneous CockeragaLeucogranite (AgYco).

Amphibolite is partially retrogressed, with variablealteration of hornblende to actinolite and chlorite, and ofplagioclase to sericite and epidote. Where metamorphicretrogression is associated with deformation, the rocks aretransitional to mafic schist and comprise interleavedamphibolite and actinolite schist (Abas).

Mafic and ultramafic rocks that are stratigraphicallyinterleaved at metre scale (Abu) outcrop west of thePunduna greenstone pendant (MGA 634000E 7621700N),and form the southern extension of the Cheearragreenstone belt exposed on SATIRIST. The mafic componentof these rocks can be either amphibolite or actinolite–chlorite schist. The ultramafic component is typicallytremolite schist. A similar unit dominates the northern halfof the Punduna greenstone pendant, where the mafic andultramafic rocks are also interleaved with quartz–muscovite schist and quartzite (Abuq).

Sedimentary rocks (Asq, Asqn)

Quartz–muscovite schist and quartzite (Asq), aftersubarkose, outcrop to the west of the Punduna greenstonependant (at MGA 635500E 7621700N), in association withinterleaved mafic and ultramafic rocks (Abu) of theCheearra greenstone belt. The quartz–muscovite schist andquartzite unit, which is an important component of theCheearra greenstone belt on SATIRIST (Smithies and Farrell,2000), contains between 70 and 95% quartz. Less quartz-rich components of this unit are locally well layered, withlayering defined by feldspar-rich layers, a prominentschistosity produced by alignment of muscovite, or acombination of both. The more quartz-rich rocks aretypically massive and comprise a granoblastic assemblageof quartz–plagioclase (now epidote and sericite), and raremicrocline and clinopyroxene. Actinolite is a late-crystallizing acicular mineral. Within the Pundunagreenstone pendant quartzite is interleaved with locallylayered quartz and quartz–feldspar–amphibole paragneiss(Asqn; e.g. MGA 643000E 7620500N, and MGA 647000E

7


7613500N). Layering is defined by 10 cm- to 1 m-thicklayers rich in amphibole, interpreted to be originalsedimentary bedding.

Quartz–muscovite schist and quartzite (Asq) is alsofaulted against rocks of the Fortescue Group, in thenorthwestern corner of HOOLEY (e.g. MGA 607000E7612000N). Here, metamorphic grade is notably lowerthan in the Punduna greenstone pendant. The unit alsoincludes interbeds of fine-grained tuff as well as pebbleconglomerate (Van Kranendonk, M. J., 2002, writtencomm.). It is not clear whether this outcrop belongs to thePilbara Supergroup or to the Fortescue Group.

Yule Granitoid Complex

Cheearra Monzogranite (AgYchn)

Outcrops of gneissic monzogranite to granodiorite(AgYchn) in the far northeast of HOOLEY (MGA 645500E7621000N) are interpreted as xenoliths in both the seriate-textured Powdar Monzogranite (AgYpos) and theCockeraga Leucogranite (AgYco). The gneissic unitincludes hornblende-rich granodioritic and tonaliticvarieties. It is mineralogically identical to, and texturallytransitional from, a moderately to strongly foliatedmonzogranite (AgYchm) that outcrops to the north onSATIRIST (Smithies and Farrell, 2000). Mesocratic andleucocratic bands are locally well developed withstromatic banding in some outcrops.

Cockeraga Leucogranite (AgYco,AgYcor, AgYcorx)

The Cockeraga Leucogranite outcrops sporadically nearthe northeastern boundary of HOOLEY. The unit comprisesleucocratic biotite(–hornblende) tonalite or granodiorite,with subordinate monzogranite (AgYco). These rockscommonly show a distinctive, well developed, schliericbanding (AgYcor), and locally also contain abundantxenoliths of greenstone and gneiss (AgYcorx). The preciseage of the leucogranite has not been determined. Theyoungest population of zircons from two samples collectedon WHITE SPRINGS (GSWA 169014 and 169016, both atMGA 675720E 7595740N) provided a U–Pb sensitivehigh-resolution ion microprobe (SHRIMP) age ofc. 3065 Ma (Nelson, 2002). While this may be thecrystallization age of the rocks, geochemical data(GSWA–GA unpublished data) suggests that these rocksare the result of disequilibrium melting, and might stillcontain abundant restite. Accordingly, the preferredinterpretation is that the age obtained (c. 3065 Ma)represents the minimum age of the source and themaximum age of the leucogranite, which may be as youngas c. 2940 Ma, the age of voluminous granite magmatismin the region.

The Cockeraga Leucogranite ranges from medium- tocoarse-grained tonalite or granodiorite. It is composition-ally and texturally highly variable at outcrop scale,comprising an accumulation of individual sheets andveins, readily identified by abrupt changes in grain sizeand mineralogy. Inclusions range from pea-sized clots up

to kilometre-scale blocks, and are sourced from metasedi-mentary, granite, and mafic to ultramafic igneous protolith.Schlieren typically represent variably disaggregatedxenolithic material, which in some cases is demonstrablyof local origin. In thicker leucogranite units, schlieren aretypically strongly attenuated, but become more commonand angular towards contacts with greenstone country-rockor xenoliths. The greenstone country-rock or xenoliths arethemselves metamorphosed to at least lower amphibolitefacies, and become increasingly invaded (net-veined), orswamped and disaggregated by leucogranite, close toleucogranite sheets. Biotite is the predominant maficmineral in schlieren, but is accompanied by hornblendewhere the leucogranite has intruded mafic xenoliths. Aflow foliation is particularly well defined in the schlieren-rich rocks. It locally wraps around xenoliths and showsirregular ‘swirls’ that do not conform to regional structuraltrends.

Hornblende–biotite tonalite (AgYt)

Coarse-grained and massive, this hornblende–biotitetonalite (AgYt) forms a discrete, approximately 10 km-longbody, to the south of Punduna Pool (e.g. MGA 645000E7608000N). This mesocratic rock has locally welldeveloped 10 cm to metre-scale layering that parallels thestrike of greenstone units within the Punduna greenstonependant. The layering is defined by variations in thecombined abundance of mafic minerals (Fig. 3) and almostcertainly reflects emplacement of at least parts of thetonalite body via sheeted intrusion. The tonalite isundeformed, and so is younger than the greenstones andgneissic rocks, but older than the c. 2935 Ma (Nelson,2000) porphyritic monzogranite of the PowdarMonzogranite (AgYpos), which intrudes it. Mineralogic-ally, the tonalite differs from the Mungaroona Granodiorite(AgYmux) only in containing a relatively higher proportionof plagioclase; however, the two rocks are geochemicallyvery similar (GSWA–GA, unpublished data). Accordingly,it is speculated that the tonalite is similar in age to thec. 2945 Ma Mungaroona Granodiorite (Nelson, 2000).

Mungaroona Granodiorite (AgYmux)

A small outcrop of the Mungaroona Granodiorite, locallycontaining abundant greenstone xenoliths and rafts(AgYmux), in the northwest of HOOLEY (MGA 611600E7622100N), is fault-bounded against rocks of the FortescueGroup. The rock is typically a medium- to coarse-grainedand mostly equigranular hornblende–(biotite) granodioriteor (rarely) biotite monzogranite. A sample of MungaroonaGranodiorite from SATIRIST was dated at c. 2945 Ma(Nelson, 2000)

Powdar Monzogranite (AgYpop,AgYpos)

On SATIRIST, the Powdar Monzogranite (AgYpo) includesfour distinct mineralogical and textural varieties, but onHOOLEY only a porphyritic monzogranite (AgYpop) andseriate-textured monzogranite (AgYpos) are exposed,differing only in the abundance of K-feldspar phenocrysts.

8

Smithies

These rocks are typically leucocratic with biotite, the solemafic silicate mineral (now mostly chlorite), comprisingless than 5% of the rock. The rocks are commonly massiveto weakly deformed, but locally have a strong foliationdefined by flow alignment of K-feldspar phenocrysts. Asample of the Powdar Monzogranite (GSWA 142937)from SATIRIST was dated at c. 2935 Ma (Nelson, 2000).

Unassigned granitoid (AgY )

Surrounded by outcrop of the lower parts of the FortescueGroup, this strongly weathered granitic rock is ofuncertain age and relationship to other granitic rocks ofthe Yule Granitoid Complex (AgY; e.g. MGA 629000E7603000N). It is interpreted to have formed topographichighs at the time of early Fortescue Group deposition.

MetamorphismMost rocks of the EPGGT are metamorphosed to low- tomiddle-greenschist facies, characterized by the presenceof chlorite–actinolite–albite(–epidote) in mafic rocks,and albite–biotite(–white mica – chlorite) in peliticmetasedimentary rocks. Amphibolite-facies assemblagesare locally developed close to contacts with granitic rocks,

and particularly to larger bodies of tonalitic togranodioritic composition. Metamorphic temperatures inthe northwestern part of the EPGGT (e.g. SATIRIST), andin the Mallina Basin region, peaked at c. 2950 Ma,approximately coincident with voluminous magmatism(Smithies and Farrell, 2000).

All greenstone assemblages (in xenoliths and roofpendants) on HOOLEY have been metamorphosed to at leastlower-amphibolite facies. Although the mineralogy ofmost rocks reflects extensive retrogression, preservationof the peak metamorphic assemblage, hornblende–plagioclase(–clinopyroxene), is widespread. Smithies andFarrell (2000) noted that on SATIRIST the metamorphicmineral assemblages in the pre-metamorphic componentof the Cheearra Monzogranite (AgYch), and in theCheearra greenstone belt, show a progressive southerlyincrease in metamorphic grade. It appears that this trendcontinues onto HOOLEY as evidenced by the prevalence ofamphibolite-facies mineral assemblages in rocks of thePunduna greenstone pendant. It is not clear if thismetamorphic trend is related to local intrusion of graniticrocks or is more regional in nature, reflecting a northerlydecrease in structural depth.

Furthermore, structures defined by amphibolite-faciesassemblages of the Western Shaw greenstone belt on

RHS246 29.05.03

Figure 3. Layering in hornblende–biotite tonalite defined by variations in the relative proportions of hornblendeand plagioclase (typically on a 10–50 cm scale). Mafic xenoliths (left of lens cap) are rounded cognateinclusions of diorite and gabbro

9


TAMBOURAH can be related to an earlier c. 3240 Ma phaseof deformation (Wijbrams and McDougall, 1987; VanKranendonk, 2003). Hence, the metamorphic history ofthe EPGGT in the HOOLEY region may have been long andcomplex.

StructureAll phases of the Yule Granitoid Complex on HOOLEY

show a weak east-northeasterly trending foliation (S3), andexcept for foliations developed adjacent to late faults, thisis the only deformational fabric developed in the c. 2945to 2930 Ma granitic rocks that dominate the complex.

In the greenstones, this late east-northeasterly trendingfoliation overprints a strongly developed foliation. In thePunduna greenstone pendant, the greenstones are foldedwith steep east-southeasterly trending axial planes (Fig. 4),with a strongly developed axial-planar foliation (S2). Theage of this early foliation is unknown, but a similarlyoriented fabric developed in greenstone xenoliths in theeastern part of WHITE SPRINGS (Fig. 4) overprints a fabric(S1) that Van Kranendonk (2003) related to a c. 3240 Maphase of deformation. On this evidence, the age of theeast-southeast fabric is constrained between c. 3240 and2945 Ma, as there is no other known phase of deformationduring that period in the EPGGT (Van Kranendonk et al.,2002).

Hamersley Basin

Fortescue Group

The Fortescue Group is a c. 2775–2630 Ma (see Table 2;Arndt et al., 1991; Nelson et al., 1999; Wingate, 1999;Thorne and Trendall, 2001) succession of dominantlybasaltic rocks that extends across much of the PilbaraCraton. An angular unconformity defines its contact withthe granite–greenstone terrane. Polymictic conglomeratecontaining subrounded clasts derived from the underlyinggranite–greenstone terrane, and a medium- to coarse-grained, poorly sorted sandstone, locally mark the base ofthe group on HOOLEY. These units are generally too thinand irregular to be represented at 1:100 000 scale. Rocksof the Fortescue Group typically dip shallowly southwardwith a resultant gradual southerly progression to higherstratigraphic levels. All recognized formations of theFortescue Group are preserved.

Mount Roe Basalt (AFr)

The Mount Roe Basalt (AFr) forms the basal unit of theFortescue Group. It comprises both subaerial andsubaqueous lava facies, but no reliable indicators wereobserved on HOOLEY to establish the local environment ofdeposition.

This unit is only preserved in the far northwest cornerof the sheet area. Much of the Mount Roe Basalt iscomposed of either massive, vesicular or glomero-porphyritic basalt. The vesicular basalt contains rare,squat, subhedral phenocrysts of plagioclase andclinopyroxene in a plagioclase-rich groundmass that also

includes interstitial chlorite and epidote (after mafic phasesand glass). The glomeroporphyritic rocks differ from thevesicular variety only in that they contain abundantaggregates of plagioclase up to 2 cm in size. Both thevesicular and glomeroporphyritic basalt are locallypillowed.

Hardey Formation (AFh, AFhu)

Regionally, the Hardey Formation (AFh) includes a widerange of sedimentary and volcanic rocks deposited invarious alluvial (including fan), fluvial, lacustrine, deltaic,and shoreline environments (Thorne and Trendall, 2001).It overlies the Mount Roe Basalt in northwestern HOOLEY,but in the central-northern part of the sheet it unconform-ably overlies the EPGGT. This unit was originally referredto as the Hardey Sandstone, but was later renamed byThorne et al. (1991). On HOOLEY the Hardey Formationcomprises medium- to coarse-grained, poorly sortedsubarkose, with locally developed conglomerate, well-laminated siltstone, shale, and felsic tuff. It is, however,dominated by a sequence of poorly sorted, medium- tocoarse-grained, volcanolithic sandstone, interbedded withwell-laminated siltstone, fine-grained tuffaceoussedimentary rock, and conglomerate (AFhu).

Kylena Formation (AFk, AFkbi, AFkh)

The Kylena Formation (AFk), previously the Kylena Basalt(Kojan and Hickman, 1998), conformably or disconform-ably overlies the Hardey Formation in the northwesternpart of HOOLEY. Farther to the southeast it forms the basalunit of the Fortescue Group, in direct contact withbasement rocks of the EPGGT. The unit typicallycomprises flows of massive to amygdaloidal basalt andbasaltic andesite, and is known regionally to contain minorintercalations of high-Mg basalt, dacite, and rhyolite(Kojan and Hickman, 1998). Layers in which basalticandesite, with minor basalt and andesite (AFkbi) aredominant were mapped separately. Basalt and basalticvolcaniclastic rocks, including breccia, locally containsericite and pyrophyllite alteration along epithermal veinsand bedding planes (AFkh). This hydrothermal alterationproduces bleached zones that are readily identifiableon aerial photography (e.g. MGA 646000E 7601300N)and is interpreted as syn- to late-volcanic, epithermal-stylealteration.

Tumbiana Formation (AFt, AFtsv, AFtc, AFtsvs,AFtsvb)

On HOOLEY, the Tumbiana Formation (AFt) is a thin(<200 m) unit comprising mainly coastal and nearshoreshelf facies, clastic and volcaniclastic rocks. It includes adistinctive stromatolitic carbonate horizon and a minormafic lava component (Thorne and Trendall, 2001) thatbecomes a locally volumetrically significant componenton HOOLEY, and further east on WHITE SPRINGS. The contactbetween the Tumbiana Formation and Kylena Formationhas been regarded as a conformity, as it appears onHOOLEY; however, Hickman (in prep.) documented alocally unconformable relationship between these twounits on COOYA POOYA, in the West Pilbara Granite–Greenstone Terrane.

10

Sm

ithies

Figure 4. Structural overview of HOOLEY and adjacent 1:100 000 map areas. Also shown are major greenstone outcrops, and in boxes, areas of abundantgreenstone xenoliths and pendants

RHS243 19.05.03

Fault

Western Shawgreenstone belt

extension

Mount Gratwickxenolith field

Pundunagreenstone pendant

118°

30'

21° 30'

22° 00'

118°

00'

Fold hinge

119'

00°

Cheearragreenstone belt

SSS

12

3

SATIRIST

HOOLEY

HOOLEYWHITE

SPRINGS

Trend of mainfoliations

10 km

Areas of abundantgreenstone xenolithsand roof pendants

Mount BruceSupergroup

Granitic rock

Greenstone

Dyke

11


Four subdivisions of this formation are recognized onHOOLEY. The dominant and locally basal packagecomprises metre- to tens of metre-scale interbeds ofvolcaniclastic sandstone, carbonate-rich tuff, andvolcaniclastic mudstone and siltstone (AFtsv). This lowerpackage also includes distinct layers of dark-grey,siliceous stromatolitic dolomite and limestone. Wherethese carbonate units are abundant or dominant, they weremapped as the Meentheena Carbonate Member (AFtc).

The upper part of the Tumbiana Formation on HOOLEY

comprises fine- to coarse-grained volcaniclastic sandstone,tuff, and fine-to medium-grained clastic sedimentaryrock (AFtsvs), with rare carbonate-rich interbeds. This unitappears to combine parts or all of the upper units, asmapped to the northwest on COOYA POOYA (Hickman,in prep.). These include sandstone and siltstone (AFtss),tuff, and tuffaceous siltstone, commonly with accretionarylapilli (AFtt), and arenaceous siltstone and tuff (AFtsl).

In the area around Wonga Well, in the central part ofHOOLEY, the volcaniclastic sandstone, tuff, and clasticsedimentary rock unit (AFtsvs) contains abundantbasalt sheets and dykes (AFtsvb). Contacts betweenbasalt and sedimentary rocks are locally peperitic,evidence of synchronous clastic sedimentation and maficvolcanism.

Maddina Formation (AFm, AFmk, AFmx)

The Maddina Formation (AFm) outcrops over much of thesouthwestern quarter of HOOLEY. Regionally, the formationconsists mainly of basalt flows, pillow lavas, and fine- tocoarse-grained mafic volcaniclastic rocks. Subordinatedacite, rhyolite, and non-volcanic sedimentary rock,including stromatolitic carbonate and quartz sandstone arepresent (Thorne and Trendall, 2001).

On HOOLEY, the Maddina Formation typically consistsof massive, vesicular, and amydaloidal basalt, and basalticandesite (AFm). Included is a distinct layer of maficvolcanicalstic sandstone, mudstone, chert, and dolomitecalled the Kuruna Member (AFmk), which Thorne andTrendall (2001) interpreted to have accumulated in a low-energy shallow coastal setting. In the southeast corner ofthe sheet, the Maddina Formation includes extensivedeposits of basaltic volcaniclastic breccia (AFmx)consisting of angular basalt fragments, up to 30 cm across,with a chlorite- and carbonate-rich mafic matrix.

Jeerinah Formation (AFjslg, AFjo, AFjsl, AFjkd)

Outcrop of the Jeerinah Formation is confined to thesouthwest corner of HOOLEY. Regionally, this formationincludes argillite, sandstone, dolomite, chert, and a varietyof volcanic rocks including basalt flows, as well as maficto felsic volcaniclastic rocks (Thorne and Trendall, 2001).

On HOOLEY the basal unit of the formation — theWoodiana Member (AFjo) — appears to conformablyoverly the Maddina Formation. It comprises quartz-richsandstone interbedded with subordinate chert, chertbreccia, mudstone, and volcanogenic lithic sandstone, andis locally well preserved (e.g. MGA 606000E 7584000N).

According to Thorne and Trendall (2001), the WoodianaMember reflects deposition in a nearshore shelfenvironment, whereas the middle and upper parts of theJeerinah Formation reflect deposition within an offshoreshelf environment. On HOOLEY, rocks characteristic of thelatter facies include variegated, light-coloured mudstoneand siltstone (AFjsl), and an overlying unit comprisingcarbonaceous mudstone and siltstone, chert, and localdolomite beds (AFjslg). Within this carbonaceousmudstone and siltstone unit, dolomite and dolomitic shale(AFjkd) form local mappable layers (e.g. MGA 607800E7577000N).

Hamersley Group

Marra Mamba Iron Formation (AHm)

Outcrop of the Hamersley Group on HOOLEY is restrictedto the far southwest corner of the sheet. The grouptypically comprises poorly outcropping interbeds of chert,banded iron-formation, mudstone, and siltstone of theMarra Mamba Iron Formation (AHm). No evidence ispreserved of an unconformity between this unit and theunderlying Jeerinah Formation, although there aresignificant changes from north to south in the thicknessof units within the latter formation (particularly in AFjslg).

Structure and metamorphismFor both the Fortescue and Hamersley Groups, beddingsurfaces typically dip at a shallow angle, predominantlysouthwards. The rocks show gentle folding (Fig. 4) andbroad domal features are locally present (MGA 604500E7612000N). North-northeasterly trending faults show adip-slip component that has locally juxtaposed quartz–muscovite schist and quartzite (Asq), in the northwesternpart of HOOLEY, against rocks of the Tumbiana Formation(MGA 606600E 7611000N), and has uplifted a wedge ofMount Roe Basalt. These faults typically do not affect theMaddina Formation, and it is likely that fault movementpre-dates deposition of that formation.

Northeast-trending faults are a common and significantfeature throughout HOOLEY, and for many of these thelatest phase of movement probably post-dated depositionof the Fortescue Group. These faults contain evidence ofboth strike-slip and dip-slip displacements; however, onlythe latter appears to typify displacement after depositionof the Fortescue Group.

The rocks of the Fortescue and Hamersley Groupshave been subject to low-grade metamorphism, character-ized in mafic rocks by an assemblage containing chloriteand epidote.

Dolerite dykes (d)Dolerite dykes (d), of undetermined age are recognizedin the southern and northern parts of HOOLEY. Theytypically trend either east-northeast or north, and areassociated with a late phase of faulting (e.g. MGA647500E 7577500N).

12

Smithies

Cainozoic deposits

Residual deposits (Czru, Czrk,Czrfb)Massive, grey, siliceous caprock over ultramafic rock(Czru) is associated with altered outcrop of tremolite-richschist (Aur) in the northern part of HOOLEY (MGA643000E 7619400N).

Massive, nodular, and cavernous limestone of residualorigin (Czrk) in the far northeast corner of the map areais developed over rocks of the EPGGT. The deposit ismore extensively developed in the southwestern part of thesheet, mainly over mafic rocks of the Maddina Formation.

Ferruginous caprock (Czrfb), developed over basalt,forms small exposures in the northwestern part of HOOLEY

(MGA 615000E 7622000N), is more extensively developedto the north, on SATIRIST. It forms laterite platforms thatare slightly elevated compared to adjacent colluvialdeposits developed over basaltic rocks of the FortescueGroup.

Colluvium (Czc, Czcb)Dissected and consolidated colluvium (Czc) formsoutwash fans, flanking elevated outcrop in the northeasternand southwestern parts of the sheet. These deposits consistof clay- or silica-cemented, poorly stratified silt, sand, andgravel, typically with a high proportion of mafic (chloritic)detritus, except where derived from granitic rocks. In thesouthwest part of HOOLEY, a gilgai surface has locallydeveloped over colluvial deposits (Czcb). Gilgai is a clay-rich silt or sand deposit characterized by the developmentof numerous cracks and sinkholes. The clay expands andcontracts according to water content, and in dry conditionsproduces an irregular ‘crabhole’ surface.

Alluvial deposits (Czaf, Czag,Czak )Alluvial deposits dissected by recent drainage are a minorcomponent on HOOLEY. Pisolitic limonite deposits (Czaf )form two small mesas 1–2 km to the southeast of HooleyHomestead. Alluvial gravel (Czag) is only in thenortheastern part of the map, where it overlies rocks of

the EPGGT, particularly adjacent to the present channelof Pilbaddy Creek. Alluvial calcrete (Czak) is exposedalong the southwestern bank of the Fortescue River, in thefar southwest corner of the sheet, where it is interpretedto overlie the Wittenoom Formation of the HamersleyGroup.

Quaternary colluvium andsheetwash deposits (Qc, Qw)Colluvium, consisting of sand, silt, and gravel, is locallyderived from elevated outcrops and deposited on outwashfans, and talus slopes (Qc). In more distal regions,sheetwash deposits (Qw) of silt, sand, and pebbles aredeposited on outwash fans. Locally reworked by windaction, sand deposits have generally been stabilized byextensive grass and shrub cover.

Quaternary alluvial deposits (Qaa,Qao, Qab)Present-day drainage channels contain alluvial clay, silt,and sand in channels on floodplains, or sand and gravelin rivers and creeks (Qaa). Alluvial clay, silt, and sandform overbank deposits on floodplains (Qao) and locallyinclude gilgai (Qab).

Economic geologyThere are no known gold occurrences on HOOLEY, nor arethere any currently working mines or prospects. In the pastthe late (c. 2935 Ma) granitic rocks of the Yule GranitoidComplex (AgYpos) have been prospected for pegmatite-hosted beryl (MGA 636900E 7612300N); alluvialcorundum has been found in Corung Creek (MGA647500E 7609810N; Kriewaldt and Ryan, 1967), and iron-rich regolith deposits have been investigated over rocksof the Marra Mamba Iron Formation, in the southwest ofHOOLEY (MGA 604200E 7575800N; Ruddock, 1999). Fora detailed description of the mineral occurrences andexploration potential of the EPGGT see Ruddock (1999).

13


References

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ARNDT, N., BRUZAK, G., and REICHMANN, T., 2001, The oldestcontintental and oceanic plateaus: Geochemistry of basalts andkomatiites of the Pilbara Craton, Australia: Geological Society ofAmerica, Special Paper 352, p. 359–387.

BARLEY, M. E., 1997, The Pilbara Craton, in Greenstone belts editedby M. J. DE WIT and L. D. ASHWALL: Oxford University Press,p. 657–664.

BEARD, J. S., 1975, The vegetation of the Pilbara area: University ofWestern Australia, 1:100 000 Vegetation Series Map and ExplanatoryNotes, University of Western Australia Press, 120p.

BLAKE, T. S., 1993, Late Archaean crustal extension, sedimentarybasin formation, flood basalt volcanism, and continental rifting: theNullagine and Mount Jope supersequences, Western Australia:Precambrian Research, v. 60, p. 185–242.

BUICK, R., THORNETT, J. R., McNAUGHTON, N. J., SMITH, J. B.,BARLEY, M. E., and SAVAGE, M., 1995, Record of emergentcontinental crust ~3.5 billion years ago in the Pilbara Craton ofAustralia: Nature, v. 375, p. 574–577.

CAMPANA, B., HUGHES, F. E., BURNS, W. G., WHITCHER, I. G.,and MUCENIEKAS, E., 1964, Discovery of the Hamersley irondeposits (Duck Creek – Mt Pyrton – Mt Turner areas): AustralasianInstitute of Mining and Metallurgy, Proceedings, v. 210, p. 1–30.

CHAMPION, D. C., and SMITHIES, R. H., 1998, Archaean granitesof the Yilgarn and Pilbara Cratons, in Granites, island arcs, themantle and ore deposits, The Bruce Chappell SymposiumAbstracts: Australian Geological Survey Organisation, Record1998/33, p. 24–25.

CHAMPION, D. C., and SMITHIES, R. H., 2000, The geochemistryof the Yule Granitoid Complex, East Pilbara Granite–GreenstoneTerrane; evidence for early felsic crust: Western Australia GeologicalSurvey, Annual Review 1999–2000, p. 42–48.

HICKMAN, A. H., 1983, Geology of the Pilbara Block and its environs:Western Australia Geological Survey, Bulletin 127, 268p.

HICKMAN, A. H., 1990, Geology of the Pilbara Craton, in ThirdInternational Archaean Symposium, Perth, 1990, ExcursionGuidebook No. 5: Pilbara and Hamersley Basin edited by S. E. HO,J. E. GLOVER, J. S. MYERS, and J. R. MUHLING: University ofWestern Australia, Geology Department and University Extension,Publication no. 21, p. 2–13.

HICKMAN, A. H., 2000, Geology of the Dampier 1:100 000 sheet:Western Australia Geological Survey, 1:100 000 Geological SeriesExplanatory Notes, 39p.

HICKMAN, A. H., in prep., Geology of the Cooya Pooya 1:100 000sheet: Western Australia Geological Survey, 1:100 000 GeologicalSeries Explanatory Notes.

KOJAN, C. J., and HICKMAN, A. H., 1998, Late Archaean volcanismin the Kylena and Maddina Formations, Fortescue Group, westPilbara: Western Australia Geological Survey, Annual Review1997–98, p. 43–53.

KRIEWALDT, M., and RYAN, G. R., 1967, Pyramid, W.A.: WesternAustralia Geological Survey, 1:250 000 Geological SeriesExplanatory Notes, 39p.

NELSON, D. R., 1997, Compilation of SHRIMP U–Pb zircongeochronology data, 1996: Western Australia Geological Survey,Record 1997/2, 189p.

NELSON, D. R., 1998, Compilation of SHRIMP U–Pb zircongeochronology data, 1997: Western Australia Geological Survey,Record 1998/2, 242p.

NELSON, D. R., 2000, Compilation of geochronology data, 1999:Western Australia Geological Survey, Record 2000/2, 205p.



NELSON, D. R., TRENDALL, A. F., and ALTERMANN, W., 1999,Chronological correlations between the Pilbara and KaapvaalCratons: Precambrian Research, v. 97, p. 165-189.

RUDDOCK, I., 1999, Mineral occurrences and exploration potential ofthe west Pilbara: Western Australia Geological Survey, Report 70,63p.

SMITHIES, R. H., in prep., Geology of the White Springs 1:100 000sheet: Western Australia Geological Survey, 1:100 000 GeologicalSeries Explanatory Notes.

SMITHIES, R. H., and FARRELL, T. R., 2000, Geology of the Satirist1:100 000 sheet: Western Australia Geological Survey, 1:100 000Geological Series Explanatory Notes, 42p.

SMITHIES, R. H., HICKMAN, A. H., and NELSON, D. R., 1999,New constraints on the evolution of the Mallina Basin, and theirbearing on relationships between the contrasting eastern and westerngranite–greenstone terranes of the Archaean Pilbara Craton, WesternAustralia: Precambrian Research, v. 94, p. 11–28.

THORNE, A. M., and TRENDALL, A. F., 2001, Geology of theFortescue Group, Pilbara Craton, Western Australia: WesternAustralia Geological Survey, Bulletin 144, 249p.

THORNE, A. M., TYLER, I. M., and HUNTER, W. M., 1991,Turee Creek, W.A. (2nd edition): Western Australia GeologicalSurvey, 1:250 000 Geological Series Explanatory Notes, 29p.

TRENDALL, A. F., 1990, Hamersley Basin, in Geology and mineralresources of Western Australia: Western Australia Geological Survey,Memoir 3, p. 163–189.

TRENDALL, A. F., NELSON, D. R., de LAETER, J. R., andHASSLER, S., 1998, Precise zircon U–Pb ages from the MarraMamba Iron Formation and the Wittenoom Formation, HamersleyGroup, Western Australia: Australian Journal of Earth Sciences,v. 45, p. 137–142.

VAN KRANENDONK, M. J., 1998, Litho-tectonic and structural mapcomponents of the North Shaw 1:100 000 sheet, Archaean PilbaraCraton: Western Australia Geological Survey, Annual Review1997–1998, p. 63–70.

VAN KRANENDONK, M. J., 2003, Geology of the Tambourah1:100 000 sheet: Western Australia Geological Survey, 1:100 000Geological Series Explanatory Notes, 57p.

14

Smithies

VAN KRANENDONK, M. J., HICKMAN, A. H., SMITHIES, R. H.,NELSON, D. R., and PIKE, G., 2002, Geology and tectonic evolutionof the Archaean North Pilbara Terrain, Pilbara Craton, WesternAustralia: Economic Geology, v. 97, p. 695–732.

WIJBRANS, J. R., and McDOUGALL, I., 1987, On the metamorphichistory of an Archean granitoid greenstone terrane, East Pilbara,Western Australia, using the 40Ar/39Ar age spectrum technique: Earthand Planetary Science Letters, v. 84, p. 226–242.

WINGATE, M. T. D., 1999, Ion microprobe baddeleyite and zirconages for Late Archaean mafic dykes of the Pilbara Craton, WesternAustralia: Australian Journal of Earth Sciences, v. 46, p. 493–500.

15


Appendix 1

Gazetteer of localities

Place name MGA coordinatesEasting Northing

Grimms Bore 643600 7575000Hooley Homestead 626300 7579600Punduna Pool 642000 7612700Wonga Well 624100 7592700

Further details of geological publications and maps produced by theGeological Survey of Western Australia can be obtained by contacting:

Information CentreDepartment of Industry and Resources100 Plain StreetEast Perth WA 6004Phone: (08) 9222 3459 Fax: (08) 9222 3444www.doir.wa.gov.au

The 1:100 000 sheet covers the southeast corner of the1:250 000 sheet. These Notes describe the stratigraphy, structure,and mineralization of the area, which lies in the central part ofthe Archaean Pilbara Craton. The Yule Granitoid Complex(2945-2930 Ma) is a major feature of the East PilbaraGranite–Greenstone Terrane on , andcontains unassigned greenstones asxenoliths or roof pendants. The FortescueGroup (2775-2630 Ma), and the MarraMamba Iron Formation of the HamersleyGroup unconformably overlie these rocksas part of the Hamersley Basin. They dipshallowly south-southwest with the FortescueGroup dominating outcrop on asa plateau. Pegmatite-hosted beryl, iron-richregolith, and alluvial corundum have previouslybeen of economic interest on the map area

HOOLEY PYRAMID

HOOLEY

HOOLEY

.

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Creek

Pilba

ddy

Cree

k

Corun

g

Creek

Hope

Cree

k

MungoonaCreek

SHER

LOCK

RIVE

R

Pilbaddy

Creek

Powd

ar

Cree

k

SHERLOCK

RIVER

SHERLOCK

RIVER

Hooley

Creek

FORTESCUE

RIVER

Hoole

y Creek

Pilbaddy

Creek

Ellina

Creek

Hooley

Creek

Yammera

CreekPilbara

Creek

Yard (abd)

Yard (abd)

Yards (abd)

Hutt Yards

Yard

Yards

Yards

YardYards

Yard

Yard

Yard

Yard

Yard

Yard

Yard Yard

Yard

landing ground (abd)




ROEBOURNE

WITTENOOM

ROAD

landing ground

Hooley

fence

(abd

)

fenc

e(a

bd)

fence(abd)

fence (abd)


fence (abd)

Wittenoom 54 km

Mou

nt F

lore

nce

Hom

este

ad 1

9 km

Hooley

Yard

MUMBILLINA BLUFF

WHINGAWARRENA HILL

PEELANGOOTHARANA PEAK

MUNGAROONA RANGE

M U N G A R O O N A R A N G E

C H I C H E S T E R

R A N G E

Aboriginal Reserve

Aboriginal Reserve

Pilbaddy Well (abd)

Powd

ar

Cree

k

Punduna Pool

Bore

Spring

Peahwarrinah Spring

Miaguarina Pool

Table Top Bore (abd)

Billadunna Spring

Bore (abd)

Tarraninnia Spring

Tanama Spring

Warrina Spring

Mountbatten Well

Mooliana WellCheetawona Pool

Windinginna Well

Goanna Well

Burgess Bore

Well (abd)

Hancocks Dam

Carboy Well (abd)

Tank (abd)

Centenary Bore

Sherlock Bore (abd) Hood Well (abd)(PD)

Cheedy WellCheedy Pool

Gap Pool

CarlercaleraPool

CheeranaPool Marie Louise Bore

Kyalina PoolCorkbark Well (abd)

Pindrinna Well (PD)

Yandina Bore

Clark Well (abd)

Bore

Kelly Well (abd)

Cottage Well

Brookanthana Well

NgulkaminningthaPool

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Grim Well (abd)

Grimms Bore

Mooliande Well

Panthangoona Tank

Salt Spring Well (abd)Spring

Bore (abd)

Wonga Well

Jeffries Well

SnakewoodWell

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Bore Well

Spring

(abd)

(PD)

Pool

ChudyearinaPool

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MumbillinaBrl

WEST PILBARA MINERAL FIELD

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Z

40

40

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Ôc

d

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ñgY

ñgYcor

ñgYcorx

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10

30

COOYA POOYA MOUNT WOHLER NORTH SHAW MARBLE BAR

WHITE SPRINGSMOUNT BILLROTH

MOUNT GEORGE

ROY HILLWEELI WOLLIMOUNT BRUCE

MOUNT MARSH

MOUNT LIONEL

2353

2354

2355

2453

2454

2455

2552

2553

2554

2555

2652

2653

2654

2655

2752

2753

2754

2755

2852

2853

2854

2855

ROCKLEA

JEERINAH

MILLSTREAM

McRAE WITTENOOM

HOOLEY

SATIRIST

MUNJINA

WODGINA

TAMBOURAH

WARRIE

SPLIT ROCK

2352 2452

PYRAMID

ROY HILL

MARBLE BAR

MOUNT BRUCE

SF 50-7 SF 50-8

SF 50-11 SF 50-12

1:100Ý000 maps shown in black

1:250Ý000 maps shown in brown

W.A.

N.T.

S.A.

N.S.W.

Vic.

Qld

Tas.

A.C.T.

GN

GRID / MAGNETIC

GRIDCONVERGENCE

True north, grid north and magnetic north

are shown diagrammatically for the centreof the map. Magnetic north is correct for

2 years.2002 and moves easterly by about 0.1° in

TN

Ôw

80

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d

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ñFkbi

ñFk

ñu ñbal

d

ñsqn

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ñu

ñbuqñur

ñsqnñba

ñba

ñu

0.5°

ANGLE 2°

5

85

80

85

40

ñba ñgY

ñgYco

GEOLO

G IC A L SURVEY

WE

ST

E R N A U S T R AL

IA

TIM GRIFFIN

DIRECTOR

Geological Survey ofWestern Australia

ñgYt

ñgYch

22°00À 22°00À

21°30À 21°30À

118°00À

118°00À

118°30À

118°30À

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Óc

ÓrfbÓrkÓru

ñsqñsqn

ñba

ñbalñbas

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ñukñur

ñu

YULE GRANITOID COMPLEX

QUAT

ERNA

RY

CAIN

OZOI

C

PHAN

EROZ

OIC

Ham

ersle

y Gro

upFo

rtesc

ue G

roup

ARCH

AEAN

c.

Alluvial sand and gravel in rivers and creeks; clay, silt, and sand in channels on floodplains

Alluvial sand, silt, and clay in floodplains, with gilgai surface in areas of expansive clay

ÓcbFerruginous caprock over basaltResidual calcrete; massive, nodular, and cavernous limestone; mainly silicifiedSiliceous caprock over ultramafic rock

JEERINAH FORMATION

Woodiana Member:

MADDINA FORMATION:

Kuruna Member:

TUMBIANA FORMATION:

KYLENA FORMATION:

HARDEY FORMATION:

MOUNT ROE BASALT:

QuartzÊmuscovite schist and quartzite

Leucocratic amphibolite; medium grained; massive to strongly foliatedAmphibolite and actinolitic schist

Ultramafic rock, undivided; metamorphosed

Tremolite-rich schist; after ultramafic rock

Porphyritic monzograniteSeriate-textured monzogranite

MUNGAROONA GRANODIORITE

Meentheena Carbonate Member:

Mou

nt B

ruce

Sup

ergr

oup

Pilb

ara

Supe

rgro

up (n

o st

ratig

raph

ic su

bdivi

sion)

AUSTRALIA 1Ý:Ý100Ý000 GEOLOGICAL SERIES SHEET 2554GEOLOGICAL SURVEY OF WESTERN AUSTRALIA

40À

50À

40À

50À

10À 20À

10À 20À

Fault

Bedding, showing strike and dip

Metamorphic foliation, showing strike and dip

Airphoto lineament

Grid lines indicate 1000 metre interval of the Map Grid Australia Zone 50

VERTICAL DATUM: AUSTRALIAN HEIGHT DATUM

0 1 2 3 4 5 6 7 8 9 10

KilometresMetres

1000

SCALE 1:100Ý000

HORIZONTAL DATUM: GEOCENTRIC DATUM OF AUSTRALIA 1994UNIVERSAL TRANSVERSE MERCATOR PROJECTION

SHEET INDEX

The recommended reference for this map is:

WebÝ www.mpr.wa.gov.au EmailÝ geological [email protected]

Topography from the Department of Land Administration Sheet SF 50-7, 2554,with modifications from geological field survey

Óag

CHEEARA MONZOGRANITE

SEA LEVEL

2 km

4 km

SEA LEVEL

2 km

4 km

DA

INTERPRETED BEDROCK GEOLOGY

Geological boundary

strike and dip estimated from aerial photography

exposed......................................................................................................................

exposed......................................................................................................................

concealed...................................................................................................................

inclined.......................................................................................................................

vertical........................................................................................................................

5Ê15°....................................................................................................................

15Ê45°..................................................................................................................

inclined.......................................................................................................................

overturned..................................................................................................................

fracture pattern..........................................................................................................

Formed road.....................................................................................................................

Track..................................................................................................................................

Fence, generally with track.............................................................................................

Homestead........................................................................................................................

Building..............................................................................................................................

Yard....................................................................................................................................

Contour line, 20 metre interval........................................................................................

Watercourse with ephemeral pool or waterhole...........................................................

Pool....................................................................................................................................

Spring.................................................................................................................................

Bore, well...........................................................................................................................

Windpump.........................................................................................................................

Dam, tank..........................................................................................................................

Abandoned........................................................................................................................

Position doubtful...............................................................................................................

Basaltic andesite with minor basalt and andesite

POWDAR MONZOGRANITE

Dolerite dyke

Jeerinah Formation

Maddina Formation

Tumbiana Formation

Kylena Formation

Hardey Formation

Mount Roe Basalt

Powdar Monzogranite

HornblendeÊbiotite tonalite

Chearra Monzogranite

YULE GRANITOID COMPLEX

Forte

scue

Gro

up

0 5 10 15 20

Kilometres

SCALE 1:Ý500Ý000

B C

inclined.......................................................................................................................

Igneous layering, showing strike and dip

inclined.......................................................................................................................

Igneous flow banding, showing strike and dip

vertical........................................................................................................................

inclined.......................................................................................................................

vertical........................................................................................................................

Cleavage, showing strike and dip

inclined.......................................................................................................................

Crenulation cleavage, showing strike and dip

inclined.......................................................................................................................

Gneissic banding, showing strike and dip

A

B

C

D

Fold, showing axial trace

c.

c.

c.

c.

QuartzÊmuscovite schist and quartziteGranitoid rock, unassigned

Cockeraga Leucogranite

PILB

ARA

CRAT

ON

MARRA MAMBA IRON FORMATION:

2686Ê2629 MaÝäÝå

c.

Geochronology by:

(7) M. T. D. Wingate, 1999, Australian Journal of Earth Sciences, v. 46, p. 493Ê500.

(2) N. T. Arndt et al., 1991, Australian Journal of Earth Sciences, v. 38, p. 261Ê281.

Marra Mamba Iron Formation

Major track........................................................................................................................

DIAGRAMMATIC SECTIONS

ñu

ñbag

Z-vergence..................................................................................................................

Small-scale fold axis, showing strike and dip

Beryl............................................................................................................................

chert, banded iron-formation, mudstone, and siltstone

Dolomite and dolomitic shale

massive, vesicular, and amygdaloidal basalt and basaltic andesite

Basaltic volcaniclastic breccia

basaltic to andesitic volcaniclastic sandstone, mudstone, chert, and dolomite

Volcaniclastic sandstone, tuff, and fine- to medium-grained clastic sedimentary rock

sandstone, conglomerate, siltstone, shale, and felsic tuff

Felsic tuff, tuffaceous sandstone, siltstone, and shale; interbedded; locally conglomerate

massive, vesicular, and glomeroporphyritic basalt

Variegated, light-coloured mudstone and siltstone

Cartography by S. Coldicutt, G. Wright, and B. Williams

Amphibolite; fine to medium grained; massive to strongly foliated

ñsqn

(1) A. F. Trendall et al., 1998, Australian Journal of Earth Sciences, v. 45, p. 137Ê142.

(3) D. R. Nelson et al., 1999, Precambrian Research, v. 97, p. 165Ê189.(4) D. R. Nelson, 1998, GSWA Record 1998/2, p. 133Ê135.(5) D. R. Nelson, 2001, GSWA Record 2001/2, p. 175Ê177.(6) R. T. Pidgeon, 1984, Australian Journal of Earth Sciences, v. 31, p. 237Ê242.

(8) D. R. Nelson, 2000, GSWA Record 2000/2, p. 82Ê85.

Edited by C. Strong and G. Loan

Mineralization and rock commodity information from non-confidential data held in the WAMINdatabase, GSWA, at 15 May 2002

antiform; exposed, concealed..................................................................................

syncline.......................................................................................................................

Corundum...................................................................................................................

Iron..............................................................................................................................

Mineral occurrence...........................................................................................................

Mineral deposit.................................................................................................................

Prospect............................................................................................................................

ñgYmu Mungaroona Granodiorite

ñbuAmphibolite

ñu

Overbank deposits; alluvial sand, silt, and clay in floodplains adjacent to main drainage channels

Colluvium _ sand, silt, and gravel on outwash fans; scree and talusSheetwash deposits _ silt, sand, and pebbles in distal outwash fans; no defined drainage

Pisolitic limonite deposits, developed along palaeodrainage lines; dissected by recent drainage

Colluvium _ sand, silt, and gravel on outwash fans; scree and talusColluvium with gilgai surface in areas of expansive clay; dissected by recent drainage

Volcaniclastic sandstone, tuff, and clastic sedimentary rock with locally abundant basalt sheets and dykes with peperitic margins

dark grey stromatolitic dolomite and limestone, carbonate-rich tuff, mudstone, and siltstone

Interleaved mafic and ultramafic rocks; metamorphosedInterleaved mafic and ultramafic rocks, quartzÊmuscovite schist, and quartzite

Metamorphosed peridotitic komatiite; olivine spinifex texture; serpentineÊtalcÊtremolite rock

Mineral exploration drillhole, showing subsurface data...............................................

Mineral and rock commodities

Geology by R. H. Smithies 2000Ê2001

SMITHIES, R. H., 2002, Hooley, W.A. Sheet 2554: Western Australia Geological Survey,1:100Ý000 Geological Series.

Wittenoom Formation

HAM

ERSL

EY B

ASIN

Department ofMineral and Petroleum Resources

CLIVE BROWN, M.L.A.

MINISTER FOR STATE DEVELOPMENT

JIM LIMERICK

DIRECTOR GENERAL

HornblendeÊbiotite tonalite

Gneissic monzogranite to granodiorite

Quartzite with locall banded quartz and quartzÊfeldsparÊamphibole paragneiss

Medium-grained amphibolite with abundant layers, veins, and irregular patches of tonalite; massive to strongly foliated

Alluvial gravel, unrelated to recent drainage; variably consolidated; dissected by recent drainage

Carbonaceous mudstone and siltstone, chert, and local dolomite beds

2595 MaÝâ

2717 MaÝè

2719 MaÝê

2760 MaÝäÝì

2770 MaÝäÝî

massive and amygdaloidal basalt, basaltic andesite, and dacite; local high-Mg basalt and rhyolite

PILB

ARA

CRAT

ON

HAM

ERSL

EY B

ASIN

Volcaniclastic sandstone, carbonate-rich tuff, and volcaniclastic mudstone, and siltstone; locally abundant layers of dark greysiliceous stromatolitic dolomite and limestone

mafic to felsic volcaniclastic sandstone, tuff, and fine- to medium-grained clastic sedimentary rock; minorbasalt, chert, dolomite, and limestone

Massive and amygdaloidal basalt, and mafic volcaniclastic rocks with sericite and pyrophyllite (hydrothermal) alteration along

Leucocratic biotite(Êhornblende) tonalite and granodiorite and subordinate monzogranite with well-developed schlieric banding; locallyabundant granitoid gneiss xenolithsLeucocratic biotite(Êhornblende) tonalite and granodiorite and subordinate monzogranite with well-developed schlieric banding and

locally abundant greenstone and granitoid gneiss xenoliths

ñFkh

Ôaa Ôao Ôab Ôc

Óaf Óc Órfb Órk Óru

ñHm

ñFjo

ñFjkd

ñFm

ñFmx

ñFmk

ñFt

ñFtsvb

ñFk

ñFh

ñFhu

ñFr

ñsq ñsqn

ñba ñbal ñbasñbag ñbu ñbuq

ñuk ñurñu

ñgY

ñgYcor

ñgYtñgYmux

ÓcbÓag

Ôw

ñFkbi

ñHm

ñFj

ñFm

ñFt

ñFk

ñFh

ñFr

ñgY

ñgYco

ñgYpoñgYi

ñgYt

ñgYch

ñgY

ñgYpos

ñFmñFm

ñFtsv

ñFk

ñgYpos

ñgYcorx

ñgYt

ñgYpos

ñuñuk

ñbal

ñba

ñbas

ñgYchn

ñbuq

ñur

ñur

ñbuq

ñgYchn

ñbas

ñFtsvb

ñsq ñba

ñHd

ñFtsv

ñFtc

ñFjslg

ñFjsl

ñgYmu

ñbu ñu

ñFtsvs

ñgYchn

ñFtsvs

ñgYpop ñgYpos

Dolerite dyke; interpreted from aeromagnetic data where dashed

Óak

Óak Alluvial calcrete; massive, nodular, and cavernous limestone; variably silicified and dissected

Granitoid rock, unassigned; age uncertain; typically strongly weathered; metamorphosed

Hornblende(Êbiotite)-bearing granodiorite and monzogranite with greenstone and granitoid gneiss rafts and xenoliths

2935 MaÝð

Unas

signe

dPi

lbar

a Su

perg

roup

Ham

ersle

yGr

oup

epithermal veins and bedding planes

ñgYcorxñgYco

ñgYco COCKERAGA LEUCOGRANITE: leucocratic biotite(Êhornblende) tonalite and granodiorite and subordinate monzogranite; locally abundant pegmatite, andgreenstone and granitoid gneiss xenoliths; weakly metamorphosed

Published by the Geological Survey of Western Australia. Digital and hard copies of this map

100 Plain Street, East Perth, WA, 6004. Phone (08) 9222 3459, Fax (08) 9222 3444are available from the Information Centre, Department of Mineral and Petroleum Resources,

Ultramafic rock, metamorphosed

Metamorphosed interleaved mafic andultramafic rocks

Breakaway.........................................................................................................................

Reserve boundary.............................................................................................................

Interleaved granodiorite, granitoid, and pegmatite

quartz-rich sandstone, chert, chert breccia, and mudstone; locally includes volcanogenic lithic sandstone

¦ Western Australia 2002

Version 1 Ê June 2002

PRODUCT OF THE NATIONAL

GEOSCIENCE AGREEMENTG E O S C I E N C EA U S T R A L I A

SHEET 2554 FIRST EDITION 2002

The Map Grid Australia (MGA) is based on the Geocentric Datum of Australia 1994 (GDA94)

GEOCENTRIC DATUM OF AUSTRALIA

GDA94 positions are compatible within one metre of the datum WGS84 positions

geology of the€¦ · reference the recommended reference for this publication is: smithies, r....

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