Departmentof Industryand Resources
EXPLANATORY NOTES GEOLOGY OF THE EASTERN CREEK 1:100 000 SHEET
by T. R. Farrell
1:100 000 GEOLOGICAL SERIES
Keep 3 mm border around photo. Resize white box as required.
GeologicalSurvey of Western Australia
GEOLOGICAL SURVEY OF WESTERN AUSTRALIA
GEOLOGY OF THE EASTERN CREEK 1:100 000 SHEET
by T. R. Farrell
Perth 2006 MINISTER FOR RESOURCES Hon. John Bowler MLA
DIRECTOR GENERAL, DEPARTMENT OF INDUSTRY AND RESOURCES Jim Limerick
EXECUTIVE DIRECTOR, GEOLOGICAL SURVEY OF WESTERN AUSTRALIA Tim Griffi n
REFERENCE The recommended reference for this publication is: FARRELL, T. R., 2006, Geology of the Eastern Creek 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 33p.
National Library of Australia Card Number and ISBN 1 74168 054 9
ISSN 1321Ð229X
Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the text are referenced using Map Grid Australia (MGA) coordinates, Zone 51. All locations are quoted to at least the nearest 100 m.
Copy editor: D. P. Reddy Cartography: A. Blake Desktop publishing: K. S. Noonan
Published 2006 by Geological Survey of Western Australia This Explanatory Note is published in digital format (PDF) and is available online at www.doir.wa.gov.au/gswa/ onlinepublications. 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 are available from: Information Centre Department of Industry and Resources 100 Plain Street EAST PERTH, WESTERN AUSTRALIA 6004 Telephone: +61 8 9222 3459 Facsimile: +61 8 9222 3444 www.doir.wa.gov.au/gswa/onlinepublications
Cover photograph: View to the south-southeast over rocks of the Mosquito Creek Formation near the Eastern Creek mining centre Contents
Abstract ...... 1 Introduction ...... 1 Climate and vegetation ...... 3 Physiography ...... 4 Previous work ...... 4 Archean Pilbara Craton ...... 4 East Pilbara Granite–Greenstone Terrane ...... 5 Pilbara Supergroup ...... 5 Warrawoona Group ...... 5 Euro Basalt (AWebk, AWebs, AWed, AWeb, AWebkc, AWebx, AWebkz, AWeu, AWeuk, AWeup, AWeux, AWesl, AWefv, AWeccw) ...... 6 Wyman Formation (AWwssz, AWwcc, AWwb, AWwd) ...... 9 Unassigned Warrawoona Group (AW(bk), AW(cc)) ...... 10 Yilgalong Granitic Complex (AgAm, AgApf) ...... 10 Structure of the East Pilbara Granite–Greenstone Terrane ...... 10
DEP1 (<3325 Ma) ...... 10
DEP2 (c. 3291–3274 Ma) ...... 11 DEP3 (<3274 Ma) ...... 11
DEP4 ...... 11 DEP5 ...... 11 Metamorphism of the East Pilbara Granite–Greenstone Terrane ...... 11 Kurrana Terrane ...... 12 Kurrana Granitic Complex ...... 12 Golden Eagle Orthogneiss (AgKge) ...... 12 Bonney Downs Granite (AgKbd) ...... 12 Mosquito Creek Basin ...... 12 De Grey Group ...... 12 Coondamar Formation (ADncc, ADnb, ADnbk, ADnup, ADnux, ADnur, ADnlb, ADnstb, ADnstbc, ADnss, ADnlbn, ADnu, ADnba, ADnog, ADnsl, ADnst, ADnfv) ...... 13 Mosquito Creek Formation (ADqs, ADqsc, ADqsl, ADqst, ADqss) ...... 14 Unassigned felsic igneous rocks (Agh) ...... 15 Structure of the Mosquito Creek Basin and Kurrana Terrane ...... 15
DMB1 (<3178 Ma) ...... 16 DMB2 (2926–2905 Ma) ...... 16 DMB3 ...... 17 DMB4 (c. 2905 Ma) ...... 17
DMB5 (c. 2860–2775 Ma) ...... 18 DMB6 ...... 19 Metamorphism of the Mosquito Creek Basin ...... 19 Coondamar Formation ...... 19 Mosquito Creek Formation ...... 19 Neoarchean to Paleoproterozoic Hamersley Basin ...... 20 Mount Bruce Supergroup ...... 20 Fortescue Group ...... 20 Mount Roe Basalt (AFr, AFrsc, AFrst, AFrsl) ...... 20 Hardey Formation (AFh) ...... 21 Bamboo Creek Member (AFhb) ...... 21 Kylena Formation (AFkbk, AFkkl, AFkbi) ...... 21 Tumbiana Formation (AFt) ...... 22 Maddina Formation (AFmbk, AFm, AFmbi, AFmcc, AFmk) ...... 22 Jeerinah Formation (AFj) ...... 23 Structure of the Fortescue Group ...... 23
DFG1 (c. 2730 Ma) ...... 23 DFG2 (c. 2690–2629 Ma) ...... 23 Hamersley Group ...... 23 Carawine Dolomite (AHc) ...... 23 Minor intrusions of Archean or Proterozoic age ...... 23 Mafi c dykes (d, Ad) ...... 23 Hornblende–quartz monzodiorite and diorite (Agd) ...... 24 Quartz veins (q) ...... 24 Neoarchean to Paleoproterozoic Pinjian Chert Breccia (!cb) ...... 24 Paleoproterozoic Bridget Suite (#gBmh) ...... 24 Phanerozoic Canning Basin ...... 24 Paterson Formation (Pa) ...... 24
iii Cenozoic regolith geology ...... 24 Residual deposits (Czrf, Czrk, Czrz, Czc, Czoc) ...... 24 Quaternary colluvium and sheetwash deposits (Qc, Qcf, Qw, Qwf) ...... 25 Quaternary alluvial deposits (Qaa, Qao) ...... 25 Economic geology ...... 25 Vein and hydrothermal mineralization ...... 25 Precious metal — gold(–antimony) ...... 25 Stratabound volcanic and sedimentary mineralization ...... 25 Base metals — copper, lead, zinc ...... 25 Regolith-hosted mineralization ...... 26 Steel industry metal — manganese ...... 26 References ...... 27
Appendices
1. Gazetteer of localities on EASTERN CREEK ...... 30 2. Correlation of rock codes and stratigraphic names on EASTERN CREEK with rock codes and stratigraphic names used in the GSWA databases ...... 31 3. Defi nition of stratigraphic names on EASTERN CREEK ...... 33
Figures
1. Location of EASTERN CREEK and regional geological setting in the Pilbara Craton ...... 2 2. Simplifi ed physiographic map of EASTERN CREEK ...... 3 3. Geological and radiometric maps of EASTERN CREEK ...... 5 4. Simplifi ed geological interpretation map of EASTERN CREEK ...... 7 5. Partly silicifi ed komatiite with relict bladed olivine-spinifex texture, Mount Elsie greenstone belt ...... 8 6. Typical exposure of tabular-bedded turbidites, Mosquito Creek Formation ...... 14 7. Ferruginous nodule in a metasiltstone, Mosquito Creek Formation ...... 15 8. Mineral lineation in phyllite, Mosquito Creek Formation ...... 16
9. Dismembered DMB2 fold in a sandstone bed, Mosquito Creek Formation ...... 16 10. Composite SMB2–3 fabric in a slate with isoclinally folded quartz veins, Mosquito Creek Formation ...... 17 11. Pseudomorph of a former (?)carbonate porphyroblast with curved inclusion trails, phyllite, Mosquito Creek Formation ...... 17 12. Biotite porphyroblast with asymmetric chlorite tails, chlorite–actinolite schist, Coondamar Formation ...... 18
13. Thrust fault (DMB4) in thin-bedded sandstone and siltstone, Mosquito Creek Formation ...... 18 14. Quartz slickenfi bres on a D MB3 thrust fault, Mosquito Creek Formation ...... 18 15. Well-developed kink bands (DMB5) overprinting a fi ne crenulation (LMB3), phyllite, Mosquito Creek Formation ...... 19 16. Poorly sorted, polymictic boulder conglomerate at the base of the Mount Roe Basalt ...... 21 17. Mafi c dyke with angular xenoliths of chert, Mount Elsie greenstone belt ...... 23
Table
1. Summary of the geological history of EASTERN CREEK ...... 6
iv Geology of the Eastern Creek 1:100 000 sheet
by T. R. Farrell
Abstract
The EASTERN CREEK 1:100 000 geological map sheet covers part of the eastern margin of the Archean Pilbara Craton in Western Australia, straddling the boundary between the granite–greenstone basement and the overlying Hamersley Basin. Three major tectonic subdivisions of the granite–greenstone basement are present on EASTERN CREEK: the East Pilbara Granite–Greenstone Terrane, the Mosquito Creek Basin, and the Kurrana Terrane. The East Pilbara Granite–Greenstone Terrane outcrops in the northwest of the sheet, and is represented by deformed monzogranite and granodiorite (Yilgalong Granitic Complex, c. 3.29 Ga), and a belt of metamorphosed basalt, ultramafi c rock, chert, and clastic sedimentary rock (Mount Elsie greenstone belt, c. 3.40 – 3.31 Ga). Deeply weathered exposures of strongly deformed monzogranite and orthogneiss in the southwest corner of EASTERN CREEK belong to the Kurrana Terrane. Separating the two terranes is the Mosquito Creek Basin, which contains a basal sediment–mafi c–ultramafi c succession (Coondamar Formation) and an upper turbidite succession (Mosquito Creek Formation). Rocks of the Mosquito Creek Basin are in tectonic contact with adjacent terranes, except on the northeast margin of the basin, where the Mosquito Creek Formation lies unconformably on the East Pilbara Granite–Greenstone Terrane. The three tectonic units have a long history of deformation and metamorphism with at least eleven recognizable tectonic events. The early events, which affected the Mount Elsie greenstone belt and the Yilgalong Granitic Complex, involved the development of a strong bedding-parallel foliation, followed by the development of north-northwesterly trending folds and shear zones. Later deformation events were focused mainly on the Kurrana Terrane and Mosquito Creek Basin to the south. Intense deformation during north–south shortening of the Mosquito Creek Basin at c. 2.90 Ga produced tight east–west chevron folds, and culminated in south-over-north thrusting. Greenstones in the Mount Elsie greenstone belt were predominantly metamorphosed under ?lower greenschist facies conditions, with higher grades, up to amphibolite facies, attained only near the contact with the Yilgalong Granitic Complex. Within the Mosquito Creek Basin, metamorphism in the Coondamar Formation ranged from lowermost greenschist facies to amphibolite facies along the contact with the Kurrana Granitic Complex. Low-pressure-style metamorphism in the Mosquito Creek Formation reached a peak prior to folding and south-over-north thrusting, ranging from zeolite facies in some areas through to lower greenschist facies.
The Hamersley Basin is represented on EASTERN CREEK by the Fortescue Group and the Carawine Dolomite of the Hamersley Group. The Fortescue Group lies unconformably on the granite–greenstone basement, and dips gently to the east and southeast. It is conformably overlain by the Carawine Dolomite and a related Proterozoic chert breccia, which are exposed in the northeast and southeast corners of the sheet.
KEYWORDS: Pilbara Craton, Mosquito Creek Formation, Coondamar Formation, Nullagine, Archean, greenstone.
Introduction mining centre in the centre of the map area. The nearest town is Nullagine, which lies about 45 km to the west of The EASTERN CREEK* 1:100 000 geological map sheet the western boundary of the sheet. (SF 51-05, 3054) covers the area between latitudes 21°30'S and 22°00'S, and longitudes 120°30'E and 121°00'E Access to EASTERN CREEK is either by the Skull (Fig. 1) in the Pilbara region of Western Australia. The Springs road from Nullagine (Fig. 2), or via the Nullagine map occupies the central-southern part of the NULLAGINE – Woodie Woodie road from the east. The area can also 1:250 000 sheet, and is named after the Eastern Creek be reached by station tracks from the Balfour Downs and Noreena Downs homesteads to the south and southeast (Fig. 2). Much of the map area is diffi cult to access due * Capitalized names refer to standard 1:100 000 map sheets, unless to the rugged nature of the terrain and a scarcity of tracks. otherwise indicated. Easy access to the Mount Elsie greenstone belt is limited
1 Farrell
20° 117° 118° NE 119° 120° 121° ? INDIAN ENSTO ? OCEAN MB E–GRE
GRANIT NIC TERRANE NE TO
WEST PILBARA ONE Z REENS 21° MB TE–G CENTRAL PILBARA TECTO YILGALONG BRAESIDE T ANE ERR MOUNT Yilgalong Granitic T PGG ARA GRANI EDGAR Complex W MB T PILB EAS NULLAGINE
EPGGT EASTERN PEARANA MCB CREEK 22° P I L B A R A C R A T O N KURRANA TERRANE Rat Hill Inlier
T Wyloo Dome EPGG Turkey, Rooney, and MCB Springo Inliers Milli Milli Dome Billinooka Rocklea ana 23° ne Cooninia Inlier Dome Inlier Kurr Terra
MAP PILBARA CRATON AREA
CAPRICORN O ROG EN Sylvania Inlier 100 km YILGARN CRATON
TRF68 22.06.06 Mesoproterozoic–Phanerozoic rocks
Hamersley Basin
West Pilbara Granite– Central Pilbara East Pilbara Granite– Other terranes Greenstone Terrane Tectonic Zone Greenstone Terrane (WPGGT) (EPGGT)
Mosquito Creek Mallina Basin (MB) MCB Basin (MCB)
De Grey
upergroup
S Whim Creek Group
Pilbara Craton Greenstone Greenstone Greenstone Kurrana Terrane
North Pilbara Craton GraniteGranite Granite Unassigned Greenstone Granite
Major fault Proposed, concealed basin boundary
Figure 1. Location of EASTERN CREEK and regional geological setting in the Pilbara Craton
2 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet
Elsie 21°30'
121°00' er Creek
Creek
Creek
Elsie Little Riv Boodalyerrie MOUNT ELSIE (502 m) ie err
Boodaly
Eastern Creek
Cooke
Creek
Snake
ie 36 km Woodie Hill Mosquito Springs
Creek Skull Wood
Road Nullagine 45 km HALLCOMES MOUNT Sunset PEAK HAYS (460 m) Hill
Coondamar Donkey Redmond
Coondamar iver Creek Davis R
Creek 10 km 120°30' 22°00' TRF50 26.06.06 Ranges Road or track Drainage Low hills over granite Prominent hill Dissected plateau Mining centre Deposit
Figure 2. Simplifi ed physiographic map of EASTERN CREEK
to areas adjacent to the track between Mount Elsie* and Mapping of EASTERN CREEK was carried out between the Warrawagine homestead north of EASTERN CREEK, and July 1999 and September 2001 using 1:25 000-scale a few mineral exploration tracks around Mount Elsie. The colour aerial photographs from the Department of Land central-western part of the area, along the Skull Springs Information (DLI, formerly DOLA) 1998, Landsat TM5 road and the road to the Mosquito Creek mining centre on (Thematic Mapper) images, and 1996 400 m line-spaced NULLAGINE to the west, is easily accessible along numerous radiometric data from Geoscience Australia (formerly gold prospecting tracks. However, areas west and AGSO) and the Geological Survey of Western Australia northwest of the Eastern Creek mining centre, north and (GSWA). west of Hallcomes Peak, and large parts of the northeast quadrant of EASTERN CREEK are virtually inaccessible to four-wheel drive vehicles. Climate and vegetation
* MGA coordinates of localities mentioned in the text are listed in EASTERN CREEK has a hot (‘winter drought’), desert Appendix 1. to grassland climate characterized by relatively low
3 Farrell rainfall, dry winters, and mean temperatures above 18°C aspects of the structural geology (Hickman, 1975) and (Commonwealth Bureau of Meteorology, 2003). Data sedimentology (Eriksson, 1982; Eriksson et al., 1994). for the town of Nullagine, west of EASTERN CREEK, show The structure of lode-gold deposits in the western end of that December is the hottest summer month on average, the Mosquito Creek Formation, just to the west of EASTERN with a mean maximum temperature of 39.7°C. Winters CREEK, was described by Blewett et al. (2002), and isotope are cool to mild, with rare nights where the temperature chemistry and Sm–Nd dating of the granitic rocks in the falls below zero. The coldest month, on average, is July, Kurrana Terrane, which extend onto the southwest corner with a mean maximum temperature of 24°C, and a mean of EASTERN CREEK, was presented by Tyler et al. (1992). daily minimum of 7.5°C. The average annual rainfall is Previous work on the lithostratigraphy and chemistry of about 327 mm, most of which falls between December the Fortescue Group relevant to EASTERN CREEK includes and June (Commonwealth Bureau of Meteorology, 2003). a regional synthesis by Thorne and Trendall (2001), and a The rainfall is extremely variable, depending on the geochemical traverse through the Kylena, Tumbiana, and development of monsoonal lows and tropical cyclones Maddina Formations near Mount Hays by Glikson et al. between December and April. (1986).
EASTERN CREEK lies in the eastern part of the Pilbara A summary of mineral occurrences and mining on Region (or Fortescue Botanical District) of the Eremaean EASTERN CREEK was presented by Ferguson and Ruddock Province of Beard (1990). The region is typified by (2001), and a limited number of open-fi le company reports extensive spinifex grassland (Triodia sp.) with scattered are available in the Western Australian mineral exploration small trees (Eucalyptus leucoploia and E. brevifolia) (WAMEX) database held by GSWA. Descriptions of and shrubs (mainly Acacia sp.). Denser vegetation is old mine workings in the Elsie, Eastern Creek, and commonly found along drainage lines. Boodalyerrie mining centres can be found in Finucane (1939a,b).
Physiography
EASTERN CREEK is undulating to hilly, with local areas of Archean Pilbara Craton rugged rangeland with high relative relief (Fig. 2). The EASTERN CREEK encompasses parts of three major tectonic altitude above sea level ranges from a maximum of just components of the Archean Pilbara Craton (Fig. 3a), which over 500 m at Mount Elsie in the northwest, and in the forms the granite–greenstone basement to the Hamersley southwest, to a minimum of about 240 m in the northeast. Basin. The craton has been studied extensively, particularly There are two main drainage catchments on EASTERN in the last 15 years (e.g. Arndt et al. 1991; Blake and CREEK (Fig. 2), separated by a divide that follows a line Barley, 1992; Thorpe et al., 1992a; Barley, 1993; Krapez, between Little River Creek and Elsie Creek in the north, 1993; McNaughton et al., 1993; Buick et al., 1995; Barley along the western edge of the Fortescue Group between et al., 1998; Collins et al., 1998; van Haften and White, Mount Elsie and Hallcomes Peak, and then trends west- 1998; Barley and Pickard, 1999; Blake, 2001; Kloppenburg southwesterly to the western edge of the sheet. East of the et al., 2001; Zegers et al., 2001; Blewett, 2002; Buick et al., divide the watercourses fl ow into the Davis and Oakover 2002; Huston et al., 2002; Van Kranendonk et al., 2002; rivers, whereas west of the divide they drain into the Blake et al., 2004). The oldest components of the craton Nullagine River. are the 3.58 – 2.83 Ga East Pilbara Granite–Greenstone Terrane (EPGGT, which includes the Yilgalong Granitic* The physiography of EASTERN CREEK (Fig. 2) is largely Complex and the Mount Elsie greenstone belt), exposed in controlled by the underlying geology. Areas underlain the northwest of the sheet, and the 3.23 – 2.84 Ga Kurrana by greenstone and metamorphosed sedimentary rocks Terrane in the southwest. These terranes are separated by are characterized by long strike ridges of resistant rock the c. ?3.04 – 2.90 Ga Mosquito Creek Basin (Fig. 3a). with narrow intervening valleys. Areas underlain by granitic rocks are typifi ed by subdued rocky hills, and are All Archean rocks in the Pilbara Craton on EASTERN traversed by sandy creeks. In contrast, the area underlain CREEK have been metamorphosed and deformed. Multiple by the Fortescue Group is best described as a dissected phases of deformation have been identified using the plateau, with scattered plateau remnants capped by deeply overprinting of outcrop-scale structures, geochronological weathered rock that are possibly relics of an old erosional age constraints, and broad-scale stratigraphic and surface. structural relationships (Table 1). The complete sequence of deformation events is not recognized in all tectonic units; the fi rst three deformation events are thought to Previous work have occurred in the East Pilbara Granite–Greenstone Terrane, prior to development of the Mosquito Creek Noldart and Wyatt (1962) fi rst mapped the area covered Basin. Subsequent deformation appears to have focused by EASTERN CREEK during the preparation of the first mainly on the Mosquito Creek Basin and Kurrana Terrane, edition of the NULLAGINE 1:250 000 geological sheet. A and later generations of structures are not common in the second edition of the map was prepared by Thom et al. granite–greenstone terrane. The last recognized event (1973), and a brief description of the main rock types involved extensive faulting that affected all Archean rocks, on EASTERN CREEK was presented in the accompanying explanatory notes (Hickman, 1978). More detailed studies * Granitic Complexes were labelled as Granitoid Complexes on the on parts of the Mosquito Creek Formation have examined EASTERN CREEK map (Farrell, 2005).
4 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet
a) b)
Yilgalong Granitic 21°30' 21°30' Complex
121°00' Mount 121°00' Elsie greenstone belt
Hamersley Basin
Mosquito Creek Basin
Kurrana
120°30' 10 km 120°30' 22°00' Terrane 22°00' TRF51 Fault 07.06.06
Figure 3. Geological and radiometric maps of EASTERN CREEK: a) geological sketch map showing the principal tectonic subdivisions; b) ternary radiometric map (400-m line spacing, AGSO/GSWA, 1996, with K, Th, U as red, green, blue) highlights the differences in chemistry between the various units in the Hamersley Basin
and probably occurred during, and shortly after, deposition Group, Wyman Formation, Golden Cockatoo Formation, of the Fortescue Group (Table 1). Sulphur Springs Group, Gorge Creek Group, and De Grey Group (Van Kranendonk et al., 2001, 2002). On EASTERN CREEK the Pilbara Supergroup was represented by the Warrawoona Group, in the Mount Elsie greenstone belt East Pilbara GraniteÐGreenstone in the northwest corner of the map sheet (Fig. 3), and the Terrane De Grey Group, in the Mosquito Creek Basin. The East Pilbara Granite–Greenstone Terrane comprises In a subsequent revision of the stratigraphy of the ovoid granitic complexes separated by linear to arcuate Pilbara Craton (Van Kranendonk et al., 2004), the belts of multiply deformed and metamorphosed greenstone successions in the Pilbara Craton were divided greenstones. The granitic complexes show evidence for a into two supergroups: the Pilbara Supergroup, comprising long history of magmatism and deformation, and contain the Warrawoona, Kelly, Sulphur Springs, and Gorge the oldest rocks in the Pilbara Craton, ranging in age from Creek Groups; and the De Grey Supergroup, which is a 3.58 Ga (McNaughton et al., 1988) to 2.83 Ga (Nelson, redefi nition of the former De Grey Group. However, for 2004a). The greenstones were deposited between 3.52 Ga consistency with Version 2.0 of the EASTERN CREEK map (Buick et al., 1995) and c. 2.94 Ga (Van Kranendonk (Farrell, 2005), the stratigraphic scheme in these Notes et al., 2002), and are dominated by basalt, chert–BIF follows that of Van Kranendonk et al. (2001, 2002), (banded iron-formation), and ultramafi c rocks, with locally although it should be noted that in the revised stratigraphy abundant felsic and sedimentary rock. The greenstone of Van Kranendonk et al. (2004), all rocks assigned to the successions were assigned by Hickman (1983) to the Warrawoona Group on EASTERN CREEK (Farrell, 2005) are Pilbara Supergroup. now part of the Kelly Group (formerly the Kelly Subgroup of the Warrawoona Group). Appendix 2 contains a table showing the translation of stratigraphic names into the Pilbara Supergroup revised scheme of Van Kranendonk et al. (2004). The Pilbara Supergroup, as defi ned by Hickman (1983), Warrawoona Group comprised the Archean layered succession in the granite– greenstone basement exposed in the northern part of the The Warrawoona Group (Hickman, 1983; Barley, 1993) Pilbara Craton. At the time that Version 2.0 of the EASTERN is a thick succession of mafic volcanic rocks, with CREEK 1:100 000 map (Farrell, 2005) was compiled, subordinate chert and felsic rocks, that accumulated the supergroup was subdivided into the following units, between 3.49 and 3.33 Ga (McNaughton et al., 1993; from base to top: Coonterunah Group, Warrawoona Van Kranendonk et al., 2002, and references therein).
5 Farrell
Table 1. Summary of the geological history of EASTERN CREEK
Age (Ma) Event
c. 3395–3312 Deposition of greenstones in Mount Elsie greenstone belt (Euro Basalt, Wyman Formation, and unassigned Warrawoona Group)
? Early foliation in Yilgalong Granitic Complex and Mount Elsie greenstone belt (DEP1) c. 3291–3274 Intrusion of Yilgalong Granitic Complex ?3280–3260 ?Intrusion of older components of Golden Eagle Orthogneiss
Main foliation in Mount Elsie greenstone belt (DEP2)
Northerly to northwesterly trending folds and shear zones in Mount Elsie greenstone belt (DEP3)
? (?Localized) uplift of Yilgalong Granitic Complex (DEP4) 3225–3178 Intrusion of granite precursor to Golden Eagle Orthogneiss >c. ?3035 Deposition of the Coondamar Formation
Early foliation in Golden Eagle Orthogneiss and Coondamar Formation (DMB1) ?during development of the Kurrana Shear Zone Creek Formation (DMB2) ?Local reclined folds in Golden Eagle Orthogneiss and Coondamar Formation Peak metamorphism of the Mosquito Creek Formation c. 2905 East–west folding and south-over-north thrusting in Mosquito Creek Basin (DMB4) and local thrusting in Yilgalong Granitic Complex (DEP5) c. 2860 Intrusion of Bonney Downs Granite 2860–2775 Dextral shearing in Kurrana Granitic Complex and Mosquito Creek Basin and kink folds in Mosquito Creek Formation (DMB5) 2775–2629 Deposition of Fortescue Group 2755 Intrusion of diorite plugs (?related to Bamboo Creek Member) c. 2541 Deposition of Carawine Dolomite (Hamersley Group) 1803 Intrusion of Bridget Suite Regionally, the group has been subdivided into several The top of the basalt is either a paraconformity with the formations based on lithostratigraphic correlations and Wyman Formation or an angular unconformity with rocks geochronological data. Correlations were not attempted of the Fortescue Group. Estimates of the thickness of on Version 1.0 of EASTERN CREEK (Farrell, 2003) due to the the basalt are complicated by multiple deformation, and uncertainty in assigning the rocks to specifi c formations possible loss of section due to faulting. A thickness of up to in the absence of geochemical and geochronological 9 km has been inferred on NORTH SHAW (Van Kranendonk, data. The rocks in the Mount Elsie greenstone belt were 2000) to the west-northwest. The Euro Basalt has not mapped as undivided Warrawoona Group, although it was been directly dated on EASTERN CREEK, but a depositional recognized that the lower part of the succession shows age of c. 3395 to 3325 Ma has been interpreted by similarities to the Euro Basalt (Hickman, 1977, 1983). Van Kranendonk et al. (2002). Subsequent mapping of adjacent NULLAGINE (Bagas et al., 2004a) and YILGALONG (Williams, 2005) has more strongly On EASTERN CREEK the Euro Basalt consists mainly supported the stratigraphic subdivision of the greenstone of basalt and mafic schist, with subordinate gabbro, belt, and these changes were incorporated into Version 2.0 chert, ultramafi c rocks, and clastic sedimentary rocks. of EASTERN CREEK (Farrell, 2005). Units of the Warrawoona Metamorphosed komatiitic basalt (AWebk) is the dominant Group that outcrop on Eastern Creek are the Euro Basalt mafi c rock, constituting about 60–70% of the succession. and the Wyman Formation. Mafi c schist (AWebs) and fi ne-grained gabbro (AWed) are common, but much less volumetrically abundant. Euro Basalt (AWebk, AWebs, AWed, AWeb, Metamorphosed komatiitic basalt (AWebk) in the AWebkc, AWebx, AWebkz, AWeu, AWeuk, AWeup, Euro Basalt is variously foliated, grey-green in colour, AWeux, AWesl, AWefv, AWeccw) and contains locally abundant varioles (up to 5 mm in The Euro Basalt is the oldest unit of the Warrawoona diameter) and vesicular zones. Pyroxene-spinifex textures Group on EASTERN CREEK, occupying the lower part of the are recognizable in many outcrops. Carbonate alteration succession in the Mount Elsie greenstone belt (Fig. 4). is widespread and strongly affected rocks are typically The base of the unit is not exposed on EASTERN CREEK, foliated and deeply weathered. Partial silicifi cation of and to the north and northeast of Mount Elsie the basalt is the basalt is also common in some areas, as evidenced intruded by granites of the Yilgalong Granitic Complex. by bleaching and cherty fracture characteristics. Pillow 6 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet 21°30' 121°00' lt Spec Fau Blue Redmond Fault lt Fau Coondamar 10 km 120°30' 22°00' TRF52 26.06.06 Mosquito Creek Formation Hamersley Group and y Pinjian Chert Breccia Coondamar Formation Bridget Suite Group Metagabbro and De Gre Jeerinah Formation roup amphibolite Golden Eagle rgroup Orthogneiss Maddina Formation Yilgalong Granitic Tumbiana Formation a Superg Complex Undivided Kylena Formation ona uce Supe Pilbar Hardey Formation Wyman Formation Bamboo Creek Group Euro Basalt Fortescue Group Member Warrawo Ultramafic rocks Mount Br Mount Roe Basalt Fault Bonney Downs Dolerite dyke Granite Figure 4. Simplifi ed geological interpretation map of EASTERN CREEK 7 Farrell structures are well preserved in many locations, commonly Outcrops of metamorphosed gabbro and dolerite with chilled margins and radial concentrations of vesicles (AWed) are common throughout the greenstone belt, but now fi lled with various proportions of chlorite, actinolite, are mostly too small to be shown separately on the map. epidote, albite, and carbonates. In a few areas the pillows The rocks are typically fi ne to medium grained, massive, have elongate, partly quartz-fi lled, convex cavities close to and granular to intergranular textured. The gabbro and the upper margin. These cavities may have originally been dolerite bodies may represent small, shallow-level sills or fi lled with quartz and calcite, with subsequent dissolution plugs emplaced in the mafi c volcanic pile during ongoing of the calcite during surface weathering. In a few areas volcanic activity. the komatiitic basalt has small, relict ?olivine phenocrysts (<0.5 mm) replaced by aggregates of chlorite and calcite, Narrow vein-like zones of fractured, strongly silicifi ed, or albite and calcite. and weathered komatiitic basalt (AWebkz) are common in the area around Mount Elsie. These zones contain veins In areas of more extensive outcrop the komatiitic of chert and milky quartz, and are locally brecciated and basalt appears to be in fl ows between 1 and 3 m thick, associated with deeply weathered altered rock. They are with local concentrations of vesicles towards the tops of mostly confi ned to one stratigraphic interval, and may individual fl ows. A good exposure of a succession of fl ows possibly represent synvolcanic faults and associated zones up to 1.5 m thick is about 3 km south-southwest of Mount of hydrothermal alteration. Elsie (MGA 247490 7607310). At this location there is a succession of columnar-jointed fl ows with vesicular tops, Ultramafi c rocks typically form small elongate pods interspersed with pillowed intervals. and thin layers that outcrop discontinuously over strike lengths of up to 3 km. Larger bodies of ultramafi c rock Tholeiitic basalt (AWeb) is more abundant in the are present in a narrow sliver of greenstone exposed along western part of the Mount Elsie greenstone belt, the southern margin of the Yilgalong Granitic Complex particularly along the western edge of the map. Here, (Fig. 4). The ultramafi c rocks have a weak to moderate the basalt is dark blue-green to grey-green, and weakly foliation in the central part of the belt, but are more highly foliated with local zones of quartz veining. deformed in areas of higher metamorphic grade close to the contact with the Yilgalong Granitic Complex north of Thin units of mafic schist interleaved with minor Mount Elsie. A range of ultramafi c rock types are exposed amounts of metamorphosed komatiitic basalt and slate on EASTERN CREEK, including peridotite, pyroxenite, (AWebs) are exposed near Mount Elsie. The mafic and minor talc–carbonate and tremolite–chlorite schist. schist is a strongly foliated rock containing chlorite, Undivided ultramafi c rocks (AWeu) are generally either albite, accessory opaque minerals and actinolite, and weathered or poorly exposed. locally abundant carbonate. The schist commonly has zones of strong carbonate alteration, and in places Thin layers of metamorphosed komatiite (AWeuk), with contains weathered carbonate veins and Fe-hydroxide relict olivine-spinifex textures, are locally within units of pseudomorphs of (?)pyrite up to 3 mm (MGA 250070E mafi c schist (Fig. 5). The only signifi cant exposure lies 7611990N). The protolith is uncertain due to the effects 500 m southeast of Mount Elsie, where partly silicifi ed of metamorphism, strong deformation, and carbonate komatiite is intercalated with mafi c schist and (?)talc– alteration, but it may have originally been a fine- carbonate schist. grained mafic volcaniclastic rock. The interleaved komatiitic basalt is also strongly deformed, but has a Metamorphosed peridotite (AWeup) forms thin relict pyroxene-spinifex texture in some areas. Thin layers layers in the central part of the Mount Elsie greenstone of associated very fi ne grained, chloritic slaty rock are belt, and two large lenses on the southern margin of possibly metamorphosed penecontemporaneous interfl ow the Yilgalong Granitic Complex east of Mount Elsie. sediments. Some locations also contain poorly exposed thin units of talc-bearing ultramafi c rock. Minor mafic rock types include metamorphosed carbonate-altered komatiitic basalt (AWebkc) and metamorphosed basaltic fragmental rock (AWebx). Carbonate-altered komatiitic basalt (AWebkc) is typically weathered and partly capped by calcrete. Carbonate alteration is common in the mafic rocks, but in most cases carbonate-altered mafi c rocks do not form readily mappable units. Metamorphosed basaltic fragmental rock (AWebx) forms thin units at several locations within the Mount Elsie greenstone belt. The best exposure lies 5 km southwest of Mount Elsie, where a 2–3 m-thick layer of fragmental rock contains a variety of clasts, including fl ow-banded (?)basalt, up to 300 mm in size. At another location, 3 km west-southwest of Mount Elsie, a poorly TRF53 04.05.06 sorted fragmental rock has well-rounded to angular clasts of vesicular and variolitic basalt up to 400 mm. Figure 5. Partly silicifi ed komatiite with relict bladed olivine- Some of the clasts at this location also show flow spinifex texture, Mount Elsie greenstone belt (MGA banding. 252360E 7610850N) 8 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet The rock is characteristically fi ne to medium grained, 1983). On EASTERN CREEK the basal contacts with the Euro granular textured, and weakly foliated. Most exposures Basalt are either strongly faulted or poorly exposed, such are pervasively serpentinized and appear to be relatively that the relationship between the two units is unclear. homogeneous, apart from a few talc-bearing horizons. The Relationships with the overlying units range from an peridotite is locally associated with metapyroxenite. In a apparently conformable contact with a succession of few locations metamorphosed peridotite contains actinolite unassigned pillow basalts of the Warrawoona Group pseudomorphs of pyroxene phenocrysts up to 40 mm (e.g. (AW(bk)), to a faulted contact with the Coondamar 4 km north of Mount Elsie, MGA 250220E 7611940N). Formation, or to unconformable contacts with the Mosquito Creek Formation and rocks of the Fortescue Metamorphosed pyroxenite (AWeux) in the Mount Group. Estimates of the thickness are uncertain due to Elsie greenstone belt is typically medium grained, with a folding and disruption of the unit; however, a value up variously developed foliation, and commonly associated to 1 km is probable. The Wyman Formation has not been with metamorphosed peridotite. In places the pyroxenite dated on EASTERN CREEK. A depositional age range of 3325 is coarsely porphyritic, containing pseudomorphs of to 3315 Ma is indicated by a conventional U–Pb zircon pyroxene phenocrysts and skeletal (?)ilmenite, replaced date of 3325 ± 3 Ma (Thorpe et al., 1992a), and sensitive by metamorphic actinolite and sphene respectively. The high-resolution ion microprobe (SHRIMP) U–Pb zircon rock appears to be in layers and lenses in metamorphosed dates of 3325 ± 4, 3324 ± 4 (McNaughton et al., 1993), melanocratic gabbro. 3318 ± 4 (Nelson, 2002a), and 3315 ± 3 Ma (Nelson, 2002b) from other areas in the East Pilbara Granite– Sedimentary rocks are a minor component of the Euro Greenstone Terrane. Basalt on EASTERN CREEK. Metamorphosed fi ne-grained clastic sedimentary rocks (AWesl) are typically weathered On EASTERN CREEK the Wyman Formation consists and poorly exposed, except in the extreme northwest of the of silicifi ed clastic sedimentary rock, with subordinate sheet. The rocks typically contain white mica, with thin komatiitic basalt and gabbro, and thin bands of chert and cherty layers, and local fuchsitic zones. In less weathered very minor amounts of ultramafi c rock. Metamorphosed exposures they are pale grey-green, locally laminated, clastic sedimentary rock (AWwssz) is the dominant and interbedded with sandstone. Four kilometres west lithotype. Much of the outcrop is weathered, strongly of Mount Elsie (MGA 246090E 7609010N), a weathered silicified, and cut by chert veins, and includes layers exposure of thin-bedded siltstone and medium-grained of chert (silicifi ed ?metashale), and minor amounts of sandstone has sporadically distributed chert layers up strongly silicifi ed basalt. In fresh creek exposures the to 200 mm thick. Sandstone beds are characteristically rocks are thin to medium bedded, commonly well foliated, kaolinized, whereas the siltstone layers tend to be partly and include mudstone, sandy siltstone, poorly sorted silicifi ed. fi ne- to coarse-grained sandstone, and pebbly sandstone. The sequence typically contains chert layers up to about Thin layers of foliated, pale, siliceous metamorphosed 70 mm thick, and has local chertifi ed zones and beds of felsic (?)volcaniclastic rock (AWefv) are exposed in layered chert. In a creek exposure 8 km west-southwest of the northwestern corner of EASTERN CREEK. Optical Mount Elsie (MGA 242910E 7606180N), fresh outcrops microscopy reveals that the rock consists almost entirely of well-foliated metamorphosed siltstone and fi ne-grained of metamorphic white mica and quartz, with minor chlorite sandstone are grey to grey-brown in colour. The sandstone and sphene, suggesting derivation from a felsic protolith. typically contains clasts of quartz, plagioclase, and minor Metamorphosed layered chert (AWeccw) is widespread tourmaline in a recrystallized, fine-grained foliated in the Euro Basalt on EASTERN CREEK, typically forming matrix of quartz, white mica, chlorite, albite, and opaque thin units along specific stratigraphic horizons in minerals. In the pebbly sandstone the clasts are up to association with poorly exposed metasedimentary 20 mm in size, and are dominated by chert. The mudstone rocks. The chert typically has black-and-white or grey- is completely recrystallized to fi ne-grained quartz, white and-white layering on a 10 to 150 mm scale, with fi ne mica, chlorite, and opaque minerals. internal laminae in many of the layers. Locally, it contains Thin bands of metamorphosed chert (AWwcc) are hydrous Fe-oxides after (?)pyrite. The chert also includes common in some parts of the Wyman Formation. The chert some poorly layered grey to brown or green-grey chert ranges in colour from light brown or grey-brown through with milky quartz veins. The layered chert is commonly to dark grey or green-grey. The rock locally contains associated with fi ne-grained, light-grey to pale-brown crosscutting veins of grey chert or milky quartz, as well as silicifi ed rocks containing thin chert layers up to 30 mm porous zones dominated by Fe-hydroxides (after ?pyrite) that may be silicifi ed clastic sedimentary rocks. and breccia zones with abundant quartz veins. The chert is commonly associated with pale-brown, intensely silicifi ed Wyman Formation (AWwssz, AWwcc, AWwb, rock of uncertain origin. In some layers vague pillow-like AWwd) structures suggest that, locally, the chert may have formed through extreme silicifi cation of basalt. The chert also The Wyman Formation (Lipple, 1975; Hickman and includes thin bands of layered chert that are too small to Lipple, 1978) is distributed along the southern edge be shown separately at map scale. of the Mount Elsie greenstone belt, and in a narrow, north-northwesterly trending corridor west of Mount Basalt in the Wyman Formation (AWwb) is variously Elsie. Regionally, the Wyman Formation is generally foliated, grey-green in colour, and has scattered varioles conformable on the Euro Basalt, although locally (up to 5 mm), localized vesicular zones, and relict pillow unconformable relationships have been reported (Hickman, structures. Patchy carbonate alteration is widespread 9 Farrell and silicifi cation is common adjacent to chert layers and of Mount Elsie is grey on fresh surfaces, and contains contacts with clastic sedimentary rocks (AWwssz). Small phenocrysts of plagioclase and quartz up to 3 mm in an bodies of metamorphosed equigranular gabbro and dolerite aphanitic groundmass. The rock has a SHRIMP U–Pb (AWwd) are common. A typical exposure 6 km southwest zircon age of 3279 ± 3 Ma (Nelson, 2005j). Based on of Mount Elsie (MGA 246980E 7604180N) is massive and their similar age and closeness to the granite–greenstone homogeneous, apart from minor quartz–epidote alteration contact, these dykes are thought to be related to the in thin veins and small patches. Yilgalong Granitic Complex. Unassigned Warrawoona Group (AW(bk), AW(cc)) Structure of the East Pilbara GraniteÐ Rocks in the Mount Elsie greenstone belt that could not Greenstone Terrane be confi dently assigned to a specifi c formation include komatiitic basalt (AW(bk)) and nonlayered chert and Five deformation episodes have been identifi ed in the East associated silicifi ed rock of uncertain origin (AW(cc)). Pilbara Granite–Greenstone Terrane on EASTERN CREEK: These rocks outcrop in an area about 7 km west-northwest DEP1 to DEP5 (Table 1). The three main deformation events of Eastern Creek Well (MGA 247500E 7601500N), and in (DEP1–DEP3) must have occurred before the development a north to northwesterly trending, fault-bound belt close to of the Mosquito Creek Basin, which truncates DEP2–3 the northwestern margin of EASTERN CREEK. structural trends at the southern end of the Mount Elsie greenstone belt. Most of the deformation events recognized in the Mosquito Creek Basin and Kurrana Terrane have Yilgalong Granitic Complex (AgAm, no expression in the greenstone succession, suggesting AgApf) that the East Pilbara Granite–Greenstone Terrane was stabilized by the time deformation began in the south. 2 The Yilgalong Granitic Complex occupies about 200 km Localized crenulations that overprint DEP2 and DEP3 fabrics in the central-northern margin of EASTERN CREEK. The are recognized in a few areas, but it is uncertain if they are complex has a variously deformed intrusive contact with the result of a deformation prior to the formation of the the Euro Basalt, and is overlain nonconformably by rocks Mosquito Creek Basin or related to one of the events that of the Fortescue Group in the east. Crystallization of the have been recognized in the basin. Minor, south-dipping granites between 3291 and 3274 Ma is indicated by a thrust faults in the Yilgalong Granitic Complex (DEP5) are SHRIMP U–Pb zircon date of 3292 ± 4 Ma (Nelson, 2005e) probably related to the DMB4 event in the Mosquito Creek from EASTERN CREEK, and dates of 3274 ± 5 (Nelson, in Basin (see below). prep.), 3277 ± 6 (Nelson, 2005f), 3290 ± 4 (Nelson, 2005g), and 3291 ± 4 Ma (Nelson, 2005h,i) obtained on YILGALONG The large-scale structure of the Mount Elsie greenstone (Williams, 2005) to the north. belt is dominated by three features: a partially preserved dome-like structure near Mount Elsie, the fl anks of a dome On EASTERN CREEK the majority of the complex consists extending onto the western edge of EASTERN CREEK from of strongly deformed, fi ne- to medium-grained, biotite NULLAGINE, and an intervening, north to northwesterly granodiorite and biotite monzogranite (AgAm). Tonalite trending corridor of folding and faulting that runs the and granodiorite are dominant along the western margin of length of the belt. The Mount Elsie dome-like structure the complex near Steel Well. Pegmatite zones are common is outlined by concentric units of chert, mafic schist, throughout and some outcrops have thin aplite dykes. A ultramafic rock, and sedimentary rock, which young vague layering, defi ned by variations in grain size and away from the centre of the dome to the northwest, west, abundance of biotite, is present in areas close to the margin and southwest. The dome is truncated along the northern of the granitic complex (e.g. 3.5 km northeast of Mount side by granites of the Yilgalong Granitic Complex, and Elsie, MGA 253260E 7611610N). Local variants include obscured by overlying rocks of the Fortescue Group in hornblende–biotite monzogranite and a weakly porphyritic the southeast. monzogranite. Small areas of a fi ne- to medium-grained, weakly foliated leucocratic granodiorite may be a younger phase. Quartz veins and mafi c dykes are common in the DEP1 (<3325 Ma) Yilgalong Granitic Complex, particularly adjacent to the Structures produced in the fi rst phase of deformation southeast margin. are preserved in parts of the greenstone belt around An isolated body of microporphyritic biotite Mount Elsie. The principal outcrop-scale DEP1 structures granodiorite about 3 km east of Mount Elsie (MGA are a foliation (SEP1, mainly preserved in mafi c schist) 253160E 7609530N) is assigned to the Yilgalong Granitic and a mineral lineation (LEP1). The foliation trends Complex. Outcrop in this area is poor, due to extensive approximately westerly to northwesterly and dips to the fracturing. The rock is relatively leucocratic, containing south or southwest at 20° to 55°. The mineral lineation is about 1–2 vol.% of biotite extensively retrogressed typically down-dip on SEP1 and is mainly defi ned in mafi c to aggregates of white mica and fine-grained opaque rocks by the alignment of amphibole. SEP1 is crenulated minerals. and largely overprinted by SEP2 in most areas. Along the contact with the Yilgalong Granitic Complex, due north Thin dykes and small plugs of feldspar porphyry of Mount Elsie, SEP1 is preserved as intrafolial folds of (AgApf) have intruded the greenstone succession to the thin leucosomes in a composite SEP1–2 fabric. The timing north and east of Mount Elsie. Most of these dykes are too of this event is unknown, but must be post-3325 Ma — the small to be shown on the map. A dyke 2 km east-northeast minimum age for the host Euro Basalt. 10 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet DEP2 (c. 3291–3274 Ma) are gently plunging, have a weak, west-southwesterly dipping axial-planar cleavage (S ), and verge to the west- The second deformation event resulted in the development EP4 southwest, consistent with uplift of the granitic complex of tight folds, a regionally extensive foliation, and a along shallow-dipping structures. The exact timing of this series of arcuate zones of high strain that wrap around event relative to D is not clear, and the structures are the western side of the Mount Elsie dome. D folds EP3 EP2 tentatively assigned to D . Similar structures have not are outlined by units of chert and silicifi ed sedimentary EP4 been observed in other parts of the greenstone belt. rock, and are commonly upright, open to tight, and plunge moderately to the south and southeast. A strong axial-planar foliation (S ) is present in most parts of the EP2 DEP5 greenstone belt. In the Mount Elsie area the foliation is broadly parallel to stratigraphy and follows the arcuate The Yilgalong Granitic Complex has shallow-dipping trend of the broad-scale structure of the dome. It overprints thrust faults in an area 4 km east-northeast of Mount Elsie (MGA 253300 7611600). The faults cut an early SEP1, resulting in the development of a pronounced east-trending, steeply dipping foliation (SEP2), and are intersection lineation (LEP2), which is parallel to a locally developed mineral lineation. associated with north-verging, recumbent asymmetric folds that have a spaced, anastomosing axial-planar cleavage Constraints on the age of DEP2 are provided by enclosing lenses of less deformed rock with an asymmetry relationships with granites in the Yilgalong Granitic consistent with south-over-north movement. These thrusts Complex. Close to the granite–greenstone contact, have only been observed at this location, and are thought 5 km north-northwest of Mount Elsie, the granites have to be equivalent to the late DMB4 thrust and reverse faults a foliation similar in orientation to SEP1–2 and mineral in the Mosquito Creek Basin succession. lineation similar to LEP2 in the greenstone belt, indicating that some components of the granitic complex pre-date DEP2. Conversely, northeast of Mount Elsie the dome- Metamorphism of the East Pilbara like structure and SEP2 are truncated by younger granites, suggesting that there are also some granites in the GraniteÐGreenstone Terrane complex that post-date DEP2. These relationships suggest Greenstones on EASTERN CREEK have mostly been that the second deformation event was broadly coeval metamorphosed to lower greenschist facies, and basalts with intrusion of the Yilgalong Granitic Complex, and and ultramafi c rocks commonly display well-preserved is therefore constrained to 3291–3274 Ma. A correlation primary igneous textures. Amphibolite-facies rocks are with the deformation sequence of Van Kranendonk et al. restricted to a narrow zone along the contact with the (2002) is problematic because the timing constraints for Yilgalong Granitic Complex, from north of Mount Elsie DEP2 place it between their D2 and D3. This raises the to the northern margin of the sheet. There is no apparent possibility that DEP2 belongs to an as-yet unrecognized difference in metamorphic grade between the main deformation event that affected the easternmost part of the deformation events in the Mount Elsie greenstone belt Pilbara Craton in the area around the Yilgalong dome of (DEP1–DEP3, see Structure of the East Pilbara Granite– Van Kranendonk et al. (2002). Greenstone Terrane). In rocks that show both SEP1 and SEP2, the foliations are defi ned by the same metamorphic mineral assemblages. DEP3 (<3274 Ma) The third deformation event resulted in large-scale shear Mafi c rocks are typically replaced by metamorphic zones in the centre of the greenstone belt, and along the assemblages of chlorite–albite–epidote–actinolite granite contact west and northwest of Steel Well, and a (–quartz–sphene), which is diagnostic of greenschist- locally well developed foliation (SEP3). Rocks in the DEP3 facies conditions and indicates a metamorphic temperature shear zones have a strong foliation and a well-developed, range of about 280° to 500°C (Bucher and Frey, 1994). gently south-plunging mineral–stretching lineation (LEP3). In rocks with well-preserved igneous textures, igneous Possible S–C fabrics indicating dextral movement are clinopyroxene is commonly replaced by actinolite(–chlorite) present in some outcrops. In the shear zones strongly and plagioclase by albite(–epidote). Replacement of the deformed metabasalt locally contains σ-porphyroclasts primary igneous minerals is typically complete, except in consisting of aggregates of calc-silicate minerals, such as some outcrops of metamorphosed gabbro and pyroxenite, epidote, sphene, and calcite, after primary pyroxene. The which may contain relict clinopyroxene. Amphibolite- shear zones are assigned to DEP3 because they truncate or facies metabasalt is strongly foliated with local, thin overprint DEP2 structures (e.g. 5 km northwest of Mount leucosomes, and is composed of metamorphic assemblages Elsie). The third deformation event probably occurred after of hornblende–plagioclase(–epidote–sphene–quartz– 3274 Ma (the minimum age for the Yilgalong Granitic carbonate minerals). Complex) because DEP3 structures are well developed in granites along the western edge of the complex. Metamorphosed peridotite characteristically contains assemblages of a serpentine-group mineral (probably antigorite), magnetite, and various amounts of carbonate, D EP4 talc, and (?)diopside. Much of the primary igneous Low-angle normal faults and asymmetric folds in SEP2 are textures have been obliterated during serpentinization, but developed along the granite–greenstone contact north of mesocumulate textures are locally preserved. The general Mount Elsie. The faults trend easterly to southeasterly absence of tremolite suggests a maximum temperature in and dip to the south at about 20°. The asymmetric folds the order of 500°C (Bucher and Frey, 1994). 11 Farrell Kurrana Terrane 1980; Split Rock Supersuite of Van Kranendonk et al., 2004) that were emplaced across the East Pilbara Granite– The Kurrana Terrane is dominated by granite and gneiss Greenstone Terrane and Kurrana Terrane at 2.89 – 2.83 Ga. (Kurrana Granitic Complex), and greenstones are a very The Bonney Downs Granite is deformed and interleaved minor constituent. The age of this component of the with the Golden Eagle Orthogneiss and is faulted against Pilbara Craton is not well constrained, but recent SHRIMP the Coondamar Formation along the Coondamar Fault U–Pb zircon dating (Nelson, 2004h, 2005a,b) indicates an (Fig. 4), which is a zone of late dextral movement (and age range of 3.23 to 2.84 Ga. probable reactivation of the Kurrana Shear Zone (Bagas, 2005) along the edge of the Mosquito Creek Basin (see Structure of the Mosquito Creek Basin and Kurrana Kurrana Granitic Complex Terrane). The Kurrana Granitic Complex is exposed in the On EASTERN CREEK the Bonney Downs Granite is southwestern corner of EASTERN CREEK. In this area the a strongly deformed, fi ne- to medium-grained, weakly rocks are deeply weathered and information on their porphyritic monzogranite with local pegmatitic zones and petrology is limited. The granites have been assigned to sparse aplite veins. It has a distinct radiometric signature two units using fi eld observations and radiometric data (Fig. 3b), characterized by high potassium, thorium, (Fig. 3b) — the Golden Eagle Orthogneiss (AgKge), and and uranium counts. Petrographic identifi cation of the a weakly porphyritic monzogranite (AgKbd) with a high granite on EASTERN CREEK is uncertain, due to the extreme radiometric signature, which is interpreted to be part of the weathering, but it has been classifi ed as a monzogranite Bonney Downs Granite (Hickman, 1983; Bagas, 2005). based on the presence of roughly equal proportions of two different types of feldspars (now replaced by clay minerals). Golden Eagle Orthogneiss (AgKge) Farther to the west and southwest, on NULLAGINE The Golden Eagle Orthogneiss (AgKge) is a strongly foliated layered orthogneiss, tectonically juxtaposed against (Bagas et al., 2004a) and NOREENA DOWNS (Farrell and rocks of the Mosquito Creek Basin. The orthogneiss is Smithies, 2005), the granite is largely undeformed and intruded by the Bonney Downs Granite and unconformably in some areas contains feldspar phenocrysts up to 30 mm overlain by rocks of the Fortescue Group. SHRIMP U–Pb in size. A crystallization age of c. 2860 Ma is indicated zircon dating on individual components of the gneiss have by a SHRIMP U–Pb zircon date of 2861 ± 4 Ma for two given ages of 3225 ± 5 (Nelson, 2005a) and 3178 ± 3 Ma concordant analyses of a single zircon crystal (Nelson, (Nelson, 2004h). Dates of 3283 and 3260 Ma obtained 2005b) from a sample collected on NULLAGINE. A date of 2838 ± 6 Ma for a group of discordant analyses with high by Sm–Nd whole-rock dating (Tyler et al., 1992), and the 208 206 presence of a single c. 3379 Ma zircon xenocryst in one Pb/ Pb values from the same sample gives a minimum sample of orthogneiss (GSWA 178013, Nelson, 2005a), estimate of the crystallization age. suggest that the orthogneiss may also contain slightly older components. Mosquito Creek Basin All exposures of the Golden Eagle Orthogneiss on EASTERN CREEK are extremely weathered, and it is difficult The Mosquito Creek Basin is a Mesoarchean, easterly to distinguish the various components of the gneiss in trending structure containing a package of predominantly outcrop. In fresh outcrops on NULLAGINE (Bagas et al., clastic sedimentary rocks assigned to the De Grey 2004a) and NOREENA DOWNS (Farrell and Smithies, 2005), Group. The basin fill consists of two contrasting to the west and southwest, the orthogneiss consists mainly successions: a lower package of mafi c–ultramafi c rocks of strongly foliated and metamorphosed biotite-bearing and consanguineous sedimentary rocks (Coondamar monzogranite, granodiorite, and tonalite. Petrographically, Formation, >c. 3.04 Ga), and an upper package of the monzogranite is composed of dynamically recrystallized siliciclastic sedimentary rocks (Mosquito Creek Formation, quartz and various proportions of plagioclase and c. 2.93 – 2.90 Ga). The upper package is similar in age and K-feldspar. Small amounts of recrystallized brown biotite lithology to the Mallina Formation (Smithies et al., 2001) are scattered throughout. The orthogneiss is (?tectonically) in the Mallina Basin. The appearance of large volumes of interleaved with quartz–muscovite schist, amphibolite, and clastic sedimentary rocks at c. 2.95 Ga and the paucity of rare pelitic schist and ultramafi c schist close to the contact mafi c volcanism in this part of the stratigraphic record are with the Coondamar Formation. Amphibolite is typically indicative of a major change in the tectonics of the Pilbara in discontinuous layers less than 5 m thick, whereas the Craton. ultramafi c rocks form narrow lenses. The orthogneiss also contains more extensive areas of weathered chlorite– actinolite schist, quartz–muscovite schist, and amphibolite De Grey Group interleaved with strongly foliated granites (ADnlbn). The De Grey Group (subsequently revised to the De Grey Supergroup, Van Kranendonk et al., 2004) is a succession of sedimentary rocks that was deposited unconformably Bonney Downs Granite (AgKbd) on the West Pilbara and East Pilbara Granite–Greenstone The Bonney Downs Granite (Hickman, 1983; AgKbd) Terranes at c. 2.97 – 2.92 Ga (Van Kranendonk et al., belongs to a group of late- to post-tectonic tin–tantalum– 2002). Deposition occurred in three major depocentres: lithium-bearing monzogranites (‘tin granites’ of Blockley, the Mallina (Smithies et al., 1999, 2001), Lalla Rookh 12 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet (Krapez, 1984, 1989), and Mosquito Creek Basins, as well Coondamar Formation along anticlinal axes in the northern as in several smaller basins. half of the basin. Minor components of the formation include metamorphosed chert (ADncc), tholeiitic basalt On EASTERN CREEK rocks of the De Grey Group (ADnb), komatiitic basalt (ADnbk), peridotite (ADnup), and outcropping in the Mosquito Creek Basin have been pyroxenite (ADnux), as well as tremolite–chlorite schist assigned to two formal stratigraphic units: the volcano- (ADnur), and minor talc–chlorite schist and phyllite. sedimentary Coondamar Formation (see Appendix 3) at the base, and the paraconformably overlying siliciclastic Metamorphosed layered chert (ADncc) is restricted Mosquito Creek Formation (Noldart and Wyatt, 1962; to the southern margin of the Mosquito Creek Basin in Hickman, 1978, 1983). The Coondamar Formation is a the southwest of EASTERN CREEK, where it is exposed subdivision of the Mosquito Creek Formation as defi ned in the hinge zone of a large upright, northeast-plunging by Hickman (1978), and is equivalent to the informally antiform. The chert has layers up to 80 mm thick with named Middle Creek Formation of Blewett et al. (2002). fine, regular, and continuous internal laminae up to 2 mm. The rock is typically ferruginous and is associated The stratigraphy of the Mosquito Creek Basin was with poorly exposed amphibole-rich schist (probable originally interpreted in terms of a broadly synclinal metapyroxenite or metagabbro), and outcrops in an area structure, with the mafi c to ultramafi c rocks along the of deeply weathered, poorly exposed, and strongly foliated margins (now assigned to the Coondamar Formation) metamorphic rocks (ADnlb). at the base, and the siliciclastic rocks (Mosquito Creek Formation) at the top of the sequence in the core of A recessive unit of metamorphosed, poorly sorted the syncline. The Coondamar Formation has now been basaltic lithic sandstone and granulestone (ADnstb) is separated from the Mosquito Creek Formation based on exposed close to the northern edge of the Mosquito Creek new geochronological data (Nelson, 2005c) and fi eld data Basin. Outcrop is poor, but in rare creek exposures it is collected in the mapping of EASTERN CREEK (Farrell, 2003, a green-grey, relatively massive rock with subangular to 2005), NULLAGINE (Bagas et al., 2004a), and NOREENA subrounded mafi c lithic clasts. Basaltic lithic sandstone DOWNS (Farrell and Smithies, 2005). with local carbonate alteration and minor layers of chert (ADnstbc) is exposed a few kilometres farther south, along the track to the Eastern Creek mining centre. In this area Coondamar Formation (ADncc, ADnb, ADnbk, the rocks are variously deformed and contain abundant ADnup, ADnux, ADnur, ADnlb, ADnstb, ADnstbc, small brown spots due to weathering of carbonate ADnss, ADnlbn, ADnu, ADnba, ADnog, ADnsl, porphyroblasts. The rocks are locally rich in carbonates ADnst, ADnfv) and in places contain carbonate veining. Also present in some locations are layers of pale grey-brown cherty rock The Coondamar Formation outcrops along the southern with a local boxwork of Fe-hydroxides or quartz. margin of the Mosquito Creek Basin in the southwest of EASTERN CREEK, and in elongate structural windows close Narrow windows of well-foliated, metamorphosed to and along the northern margin of the basin, near the chloritic sandstone and siltstone (ADnss) outcrop along Eastern Creek mining centre. The formation is in faulted thrust faults and in the hinge zones of D3 anticlines in basal contact with the East Pilbara Granite–Greenstone the northern part of the basin. The siltstone is typically Terrane in the north, and with the Kurrana Terrane in metamorphosed to a chlorite phyllite. In the fi eld the the south. The upper boundary is a paraconformity with sandstone is distinguished by a characteristic pale the Mosquito Creek Formation. The thickness of the green-grey to blue-grey colour, a flinty fracture, and Coondamar Formation is uncertain due to the combined a scaly foliation. In some areas sandstone beds have a effects of strong deformation, tight folding, and faulted conglomeratic base with grey or white cherty clasts up to basal contacts, but a thickness of up to 2 km is indicated 50 mm in size. for the type area near Hallcomes Peak (see Appendix 3). The formation has not been directly dated, but must be A mixed unit of strongly foliated metamorphic rocks younger than the 3325–3315 Ma Wyman Formation, the (ADnlb) outcrops on the southern margin of the Mosquito youngest dated unit in the East Pilbara Granite–Greenstone Creek Basin along the Coondamar Fault. A wide range Terrane immediately north of the Mosquito Creek Basin, of rock types is present, including chlorite–actinolite and older than the overlying Mosquito Creek Formation, schist, amphibolite, phyllite, and semipelitic schist. which has an interpreted age of c. 2926–2905 (Bagas Minor components include biotite schist and andalusite– et al., 2004b). A tentative date of 3035 ± 6 Ma (Nelson muscovite schist. A similar rock association, but with 2005c) for a single zircon crystal from a small foliated interleaved strongly deformed granite (ADnlbn), forms granodiorite intrusion in the Coondamar Formation on rafts within the Kurrana Granitic Complex. NOREENA DOWNS (Farrell and Smithies, 2005), to the southwest, provides a possible tighter constraint on the Metamorphosed ultramafic rocks are a distinctive minimum age of the formation. minor component of the Coondamar Formation. On EASTERN CREEK the ultramafic rocks are restricted to On EASTERN CREEK the Coondamar Formation contains the southern part of the basin, and are interleaved with a variety of metamorphosed mafic and sedimentary strongly deformed and metamorphosed mafic and rocks. It is dominated by chloritic metasedimentary sedimentary rocks. Ultramafi c rock types recognized in the rocks, metagabbro, and amphibolite in the southern area, fi eld include undivided ultramafi c rocks (ADnu, typically and basaltic lithic sandstone in the northern exposures. fi ne-grained rocks with a high magnetic susceptibility), Detailed mapping has also revealed narrow windows of tremolite–chlorite schist (ADnur), metamorphosed 13 Farrell peridotite (ADnup), and metamorphosed pyroxenite Much of the Mosquito Creek Formation consists of (ADnux). a monotonous sequence of metamorphosed sandstone, siltstone, and shale (ADqs), with well-preserved graded Amphibolite (ADnba) and metagabbro (ADnog) bedding (Fig. 6), and local cross-bedding and sole are mainly exposed along the southern margin of the marks. The rocks are mainly thin bedded (typically 10 Mosquito Creek Basin in two belts of intercalated mafi c to 150 mm), but parts of the succession are more thickly and metasedimentary rock. The metagabbro forms large bedded (up to about 1 m) with a greater predominance of individual bodies up to about 600 m wide and 3 km long, sandstone, and scattered pebbly beds. Graded bedding is and numerous small lenses or thin layers, too small to ubiquitous and, in some locations, there are well developed show at map scale, interleaved with metasedimentary Bouma sequences (Bouma, 1962) showing a complete rocks. Associated with the metagabbro is a unit of gradation from massive coarse-grained sandstone, through metasedimentary rock with thin layers of amphibolite and parallel-laminated and convolute-laminated siltstones, tremolite–chlorite schist (ADnsl). A unit of metasandstone to shale (A, B, C, and E Bouma divisions). Many beds, with minor siltstone (ADnst) extends along the centre of however, range from coarse-grained sandstone to fi ne- the northern belt of metagabbro and amphibolite. The grained sandstone or siltstone (B, C and B, C, D Bouma metasandstone contains relict quartz clasts enclosed by a divisions), and the shaly tops are missing. Inverse grading foliation defi ned by white mica, plagioclase, and actinolite. and low-angle cross-lamination can be seen within Locally preserved graded bedding indicates that the individual beds in a few locations (e.g. MGA 250880E sequence youngs to the south. A thin discontinuous unit 7590360N). Tabular beds of sandstone up to 1 or 2 m thick, of metamorphosed felsic volcaniclastic sandstone (ADnfv) with a massive or cross-bedded base and a thin silty top outcrops about 3 km south-southwest of Hallcomes Peak. may be channel deposits (e.g. MGA 253280E 7592690N). The rock is partly silicifi ed and contains abundant relict Black to dark-brown ferruginous nodules after (?)pyrite clasts of quartz as well as ?plagioclase. are locally abundant in fi ne-grained sandstone, siltstone, and shale (Fig. 7). They commonly reach up to 15 mm in size (70 mm in extreme cases) and possibly represent Mosquito Creek Formation (ADqs, ADqsc, ADqsl, metamorphosed diagenetic pyrite nodules. ADqst, ADqss) The Mosquito Creek Formation is a metamorphosed Siltstone and shale are typically metamorphosed to succession of siliciclastic sedimentary rocks that occupies slate or phyllite, depending on the metamorphic grade most of the central part of the Mosquito Creek Basin. The and protolith composition, whereas sandstone is partly base of the formation is either a paraconformity with the recrystallized and foliated. Metashale is commonly dark Coondamar Formation or an angular unconformity with grey in colour, probably due to the presence of extremely rocks of the East Pilbara Granite–Greenstone Terrane. fi ne graphite after carbonaceous material, and typically Interpretation of the stratigraphy has been hindered by contains numerous deformed quartz veins. Optical the effects of complex deformation and the absence of microscopy, scanning electron microscopy, and X-ray distinctive marker units. Original estimates of the thickness diffraction studies (T. R. Farrell and R. Offl er, unpublished of the formation were greater than 5 km (Hickman, 1978), data) reveal that the slate and phyllite consist of fi ne- but mapping of EASTERN CREEK has revealed that much of grained chlorite, illite – white mica, albite, carbonaceous the formation is tightly folded at wavelengths of 1–2 km, matter (probably graphite), quartz (in most rocks), and and that there are narrow windows of the Coondamar accessory monazite and rutile. In the lowest grade rocks Formation along anticlinal hinge zones in the northern half the ‘chlorite’ is probably a mixture of chlorite and mixed- of the formation. These observations suggest that, in the layer chlorite–smectite (Merriman and Peacor, 1999). north, the preserved thickness of the formation is probably in the order of 1–1.5 km. The age of the Mosquito Creek Formation is not tightly constrained, but recent work on the dating of detrital zircon in sandstones (Nelson, 2004b,c,d,e,f, 2005d) and Pb–Pb dating of galena (Thorpe et al., 1992b; Huston et al., 2002) has shown that it must have been deposited between c. 2926 and 2905 Ma (Bagas et al., 2004b). The Mosquito Creek Formation has previously been described by Hickman (1975, 1978, 1983) and Eriksson et al. (1994), and the rocks have commonly been interpreted as turbidite deposits. The sedimentology has not been studied in detail, but based on previous work (Eriksson et al., 1994), and additional work carried out ASTERN REEK in the mapping of E C (Farrell, 2003, 2005), TRF54 26.06.06 deposition is thought to have occurred in a submarine fan system. Upper-fan deposits are distributed along Figure 6. Typical exposure of tabular-bedded turbidites, the northern margin of the basin, in the area around the grading from coarse-grained sandstone to siltstone Eastern Creek mining centre, and lower- and mid-fan or shale (dark grey), Mosquito Creek Formation deposits occupy the central and southern parts of the (younging to the right in the photo; MGA 261980E basin. 7589850N) 14 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet having low-angle cross-bedding. There are also rare fl ute casts and ripple marks. Graded bedding is not common. In a few locations the thin-bedded succession (ADqsl) is incised by channel deposits of pebble conglomerate (ADqsc). This succession possibly represents a lower, mid- fan lobe deposit. Also outcropping in the area around the Eastern Creek mining centre is a massive, tabular-bedded sandstone (ADqst). The rock is typically medium to coarse grained, with local pebbly zones and sparse beds of pebble conglomerate. Individual beds are about 5–10 m thick. The sandstone grades laterally to thin-bedded, fi ne-grained TRF55 04.05.06 sandstone, and is interspersed with thin units of thin- bedded sandstone and siltstone. The lack of grain-size Figure 7. Ferruginous nodule in a metasiltstone (phyllite) grading and the general absence of other depositional with well-developed kink bands, Mosquito Creek structures suggest rapid deposition, possibly in depositional Formation (MGA 248410E 7587720N) lobes at the termination of mid-fan channels. In the area around Eastern Creek Well, and to the west and northwest, is a sandstone–siltstone(–shale) succession Many slates contain both K-white mica and Na-white mica (ADqss) that shows repeated coarsening-up and thickening- (T. R. Farrell and R. Offl er, unpublished data). up cycles. Each cycle shows a gradation from a base of thin-bedded (typically 20–50 mm), fi ne-grained sandstone, Sandstone typically contains detrital white mica, siltstone, and minor ferruginous shale to thicker bedded quartz, and clasts of grey or black chert, and in many (typically 50–500 mm, but up to 2000 mm), medium- to areas is poorly sorted and matrix supported (e.g. MGA coarse-grained sandstone with scattered chert granules 249160E 7581230N). It is locally ferruginous or siliceous. and local beds of pebbly sandstone and conglomerate. The In thin section it contains various proportions of quartz, coarse-grained intervals are commonly graded, and locally plagioclase, and chert clasts, plus rare fragments of ripple marked. Individual cycles are 30–50 m thick. These biotite and granitic rock. Petrographically, the sandstones rocks are tentatively interpreted to represent suprafan lobe can be classifi ed as lithic wacke or lithic arenite, but deposits in a prograding submarine fan system. may range through to quartz wacke or subarkosic wacke (classifi cation after Pettijohn et al., 1987). Discontinuous layers and lenses of pebble Unassigned felsic igneous rocks (Agh) conglomerate (ADqsc) outcrop in three belts in the north — along the northern edge of the basin and on both A suite of felsic dykes are exposed in the northern part fl anks of a west-southwesterly trending, doubly plunging of the Mosquito Creek Basin about 7 km west-southwest anticline that passes through the Eastern Creek mining of the Eastern Creek mining centre. Dykes of hornblende centre. The conglomerates are associated with coarse- (–plagioclase) porphyry (Agh) in this area are commonly grained sandstone, granulestone, pebbly sandstone, and conformable, but locally cut across stratigraphy in the host minor cobble conglomerate, in tabular beds or channel metasedimentary rocks. The dykes are variously foliated deposits up to about 10 m thick. They contain chert clasts and extensively altered (probably during metamorphism). (~90–95 vol.%), some vein quartz, and minor amounts of Primary subhedral to euhedral hornblende phenocrysts basalt, granitic rock, sandstone, and kaolinized felsic rock are pseudomorphed by assemblages of chlorite–Fe oxides (including quartz porphyry). Along the northern margin of (–carbonates–albite), whereas plagioclase phenocrysts the basin the conglomerates are poorly sorted and matrix are replaced by albite – white mica – carbonates. The supported, with angular to subrounded clasts in a coarse groundmass is extensively replaced by fine-grained sandy matrix. Farther south, along the anticline near the chlorite, albite, quartz, carbonates, white mica, and Eastern Creek mining centre, the conglomerates tend to be opaque minerals. Locally, the dykes contain clots of ferro- more texturally mature and are typically clast supported, magnesian minerals and small mafi c enclaves up to 30 mm with rounded to well-rounded clasts. In some areas in size. Some dykes have possible amygdales, in the form the conglomerates are brecciated and silicifi ed (MGA of irregular ‘pools’ of coarser grained, radially arranged quartz–carbonate – white mica. The dykes are interpreted 247850E 7595550N) or ferruginized (MGA 248150E to be Archean in age, on the basis of a pronounced 7600170N), probably due to later faulting and weathering. The conglomerates are interpreted to be upper-fan channel foliation in some outcrops, and probably pre-date the DMB4 deposits in a submarine fan system. deformation event in the Mosquito Creek Basin. Interbedded with the pebble conglomerate is an extensive succession of thin-bedded, siliceous fi ne-grained Structure of the Mosquito Creek Basin sandstone, siltstone, and shale (ADqsl). The shale is and Kurrana Terrane commonly ferruginous, with alternating grey and dark- red laminae. Bed thickness is mostly 20–50 mm, but may Up to six phases of deformation (DMB1–6) are recognized attain a maximum of about 100 mm. Locally, the rocks in the rocks from the eastern part of the Mosquito Creek have a convolute or wavy lamination, with some beds Basin and the Kurrana Terrane (Table 1). Evidence for 15 Farrell the earliest phase of deformation (DMB1) is found only in the Golden Eagle Orthogneiss (c. ?3270–3178 Ma), and possibly in the lowermost parts of the Coondamar Formation (>c. 3035 Ma). DMB1 (<3178 Ma) The Golden Eagle Orthogneiss has a strongly developed, composite fabric (SMB1–2) with intrafolial, tight to isoclinally folded relics of an early high-grade foliation (SMB1) defined by thin monzogranite leucosomes. A composite fabric, tentatively correlated with SMB1–2, is also present in the Coondamar Formation, where it is TRF59 04.05.06 preserved in the hinge zone of mesoscale DMB4 folds as an anastomosing disjunctive schistosity or cleavage (foliation terminology after Passchier and Trouw, 1996). Chlorite– Figure 8. Mineral lineation in phyllite, Mosquito Creek Formation (MGA 252820E 7578340N). The lineation actinolite schist in the Coondamar Formation locally has is defi ned by the preferred alignment of carbonate a zonal crenulation cleavage (SMB2) with microlithons rhombs (dark grey), now largely replaced by iron containing crenulated relics of SMB1. oxides and quartz. Note the later fi ne crenulation to the right The tectonic setting and timing of DMB1 is not clear due to the effects of later strong deformation, but it must have occurred after c. 3178 Ma, which is the inferred minimum age of the Golden Eagle Orthogneiss. Argon–argon are now pseudomorphed by fi ne-grained aggregates of hornblende cooling ages of 3.2 – 3.0 Ga (Wijbrans et al., quartz(–chlorite – white mica) or Fe-oxides–quartz. The 2000) for the Kurrana Terrane suggest uplift at this time, lineation is typically steep plunging and in some outcrops possibly related to DMB1. The Kurrana Shear Zone (Bagas, is overprinted by a crenulation lineation (LMB3). 2005), along the contact between the Kurrana Terrane and the Coondamar Formation, may have formed at this time. Mesoscale DMB2 folds are typically asymmetric, upright, and open to isoclinal, with steep-plunging axes parallel to a bedding–cleavage intersection lineation DMB2 (2926–2905 Ma) (Fig. 9). The folds are locally boudinaged, either during D or in a later event. Macroscale D folds are exposed The second deformation event affected the entire basin. MB2 MB2 in a few locations. The folds typically have wavelengths D structures are best developed in the Coondamar MB2 of 100–300 m, and are angular and asymmetric, with an Formation and the Golden Eagle Orthogneiss, and are not axial-planar foliation subparallel to the long limb and as prominent in the Mosquito Creek Formation, where oblique to the short limb. The fold shapes persist along they have largely been obliterated during D . The main MB4 strike (down-profi le), resulting in discrete zones, broadly structures attributed to D are: a strong composite fabric MB2 parallel to stratigraphy, where bedding and cleavage are at (S ) in the southern part of the basin, a steep-plunging MB1–2 angles of 10° to 20°. bedding–cleavage intersection (LMB2), steep-plunging folds (FMB2), and a weak mineral lineation (LMB2). The tectonic setting during DMB2 and the original orientation of DMB2 structures are uncertain, but, by The most prominent DMB2 structure in the southern part of the basin is a strong composite foliation (SMB1–2) subparallel to the basin margin. The foliation trends east to northeasterly, and typically dips to the north or northwest, towards the centre of the basin. In the Golden Eagle Orthogneiss the foliation is a continuous planar schistosity defi ned mainly by the alignment of thin leucosomes, quartz ribbons, and the lattice-preferred orientation of biotite. The SMB2 foliation in the Coondamar Formation is typically a well-developed, continuous schistosity in fi ne-grained rocks, and a disjunctive schistosity in metasandstone. In contrast, in the Mosquito Creek Formation SMB2 is mostly parallel to, and partly overprinted by, SMB3. In a few locations, particularly in the hinge zone of DMB4 folds, SMB2 is preserved as a spaced cleavage at an angle to SMB3 (e.g. 2 km southeast of Eastern Creek Well, MGA 255500E 7597300N). In most areas of the Mosquito Creek TRF60 26.06.06 Formation SMB2 is also parallel to bedding. Figure 9. Dismembered DMB2 fold in a sandstone bed, A weak mineral lineation defi ned by the alignment Mosquito Creek Formation (MGA 248400E 7586330N; of elongate former (?)carbonate porphyroblasts (LMB2) is view from above). The fold is upright and steeply tentatively assigned to DMB2 (Fig. 8). The porphyroblasts plunging with an axial-planar cleavage 16 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet necessity, SMB2 must have been shallow-dipping in order for it to be deformed into shallow-plunging upright folds during DMB4. If the DMB2 folds are restored to their original orientation by unfolding of FMB4, then they would have been recumbent, with axes plunging gently either north or south. The absolute age of DMB2 is constrained to c. 2926– 2905 Ma by the maximum age of the Mosquito Creek Formation, and Pb–Pb galena model ages of 2905 ± 9 Ma for mineralization associated with structures related to DMB4 (Bagas, 2005). 1 mm TRF61 04.05.06 DMB3 Rare, reclined, isoclinal folds in the Coondamar Formation Figure 10. Composite SMB2Ð3 fabric in a slate with isoclinally and Golden Eagle Orthogneiss on NULLAGINE have been folded quartz veins, Mosquito Creek Formation (GSWA 161193, MGA 253530E 7586690N). In most assigned by Bagas (2005) to DMB3. These structures have not been observed on EASTERN CREEK and may be of the rock the fabric is a continuous cleavage, and crenulated relics of S are only preserved adjacent D folds that have not been re-oriented during later MB2 MB2 to the quartz veins (plane-polarized light) deformation. DMB4 (c. 2905 Ma) actinolite schist and phyllite in the Coondamar Formation The fourth event was an intense pervasive deformation typically have a well-developed schistosity, defi ned by the that affected all rocks in the basin, largely overprinting assemblage chlorite–albite–actinolite, wrapping around DMB2 structures, and resulted in the formation of the relict biotite porphyroblasts with curved inclusion trails predominant east–west to northeast–southwest structural (Fig. 12). grain. The principal DMB4 structures include shallow- plunging, angular, open to isoclinal folds (FMB4), an axial- Mesoscale DMB4 folds are angular, open to very planar foliation (SMB4), and a shallow-plunging crenulation tight, upright to steeply inclined, and typically shallow and mineral lineation (LMB4). plunging. The orientation of the fold axes varies across the basin from south to north. Along the southern margin Within the Mosquito Creek Formation, SMB4 is a of the basin, the folds are open to tight, and plunge to continuous cleavage in metasiltstone, slate, and phyllite, the east-northeast or northeast. They have an axial- an anastomosing spaced cleavage in metasandstone, and planar disjunctive cleavage (SMB4), and there is a a weakly developed, spaced cleavage in very low grade pronounced, combined mineral–crenulation lineation rocks north of Eastern Creek Well. The foliation trends (LMB4) parallel to the fold axes. In the central part of the approximately east–west in the centre of the basin, and basin the fold axes plunge gently either east or west, and northeast–southwest along the northern and southern margins, and is broadly parallel to bedding (S0), but more steeply dipping near the basin margins. In some outcrops, isoclinally folded beds have an axial-planar continuous crenulation cleavage, suggesting that the foliation seen in outcrop is, in many cases, probably a composite fabric (SMB2–4). Isoclinally folded quartz veinlets, with an axial-planar continuous cleavage are also common (Fig. 10). In some areas, phyllites have a spaced cleavage and contain small relict porphyroblasts aligned at a low angle to the cleavage (Fig. 11). The porphyroblasts are pseudomorphed by fine-grained aggregates of quartz (–chlorite – white mica) or Fe-oxides–quartz, but preserve inclusion trails that are contiguous with the external TRF62 04.05.06 foliation (SMB2–4). The inclusion trails typically curve into the external foliation and are fi ner grained, suggesting that the porphyroblasts have either grown post-DMB2 and pre- Figure 11. Pseudomorph of a former (?)carbonate porphyroblast with curved inclusion trails, phyllite, DMB4, or early syn-DMB4. Porphyroblast growth may have been coeval with the development of the chlorite–mica Mosquito Creek Formation (GSWA 161104, MGA 254170E 7586720N). The porphyroblast now consists stacks (Jiang and Peacor, 1994; Li et al., 1994) commonly of extremely fi ne aggregates of quartz, chlorite, found in phyllites from the Mosquito Creek Formation. white mica, and carbonaceous material. Note the Similar porphyroblast–inclusion trail relationships also marked obliquity between the porphyroblast and the occur in the southern part of the basin, where chlorite– external foliation (SMB2Ð3; plane-polarized light) 17 Farrell by thrust or reverse faults that displace the north-facing limb. The faults appear to have formed in the latter stages of DMB4 because they are commonly subparallel to the axial surfaces of DMB4 folds. Mesoscale faults typically cut across bedding at a low angle and anastomose around sigmoidal-shaped blocks of less deformed rock (Fig. 13). The fault zones have a variety of localized structures, including quartz slickenfi bres (Fig. 14), striations, and fault breccia, as well as tectonic ‘ripples’ or undulations on striated surfaces. Quartz slickenfi bres show a spread of plunge directions, but consistently indicate a broadly south-over-north to southeast-over-northwest sense of movement. TRF63 04.05.06 Figure 12. Biotite porphyroblast with asymmetric chlorite DMB5 (c. 2860–2775 Ma) tails, chloriteÐactinolite schist, Coondamar Formation (GSWA 174926, MGA 252210E 7574080N). The fi fth deformation event involved dextral movement Porphyroblast has an internal fabric defi ned by along east- to northeast-trending shear zones (with the alignment of small grains of graphite (plane- probable reactivation of late-DMB4 faults) and resulted in polarized light) the development of upright, steep-plunging monoclinal kinks and box folds (FMB5), a locally developed spaced crenulation cleavage (SMB5), and small-scale kink bands and crenulations (LMB5; Fig. 15). are subparallel to a fi ne crenulation lineation (LMB4) in metasiltstone and phyllite. In contrast, along the northern Mesoscale indicators of dextral movement are margin the DMB4 folds typically plunge gently to the west- exposed at various locations in the southern part of the southwest. basin, including the Blue Spec Fault zone (Fig. 4), but are best developed along the southern margin of the Large-scale DMB4 folds are mostly recognized in the basin, and appear to affect rocks from both the Golden fi eld by younging reversals, although there are some well- Eagle Orthogneiss and the Bonney Downs Granite. exposed periclinal folds outlined by resistant conglomerate Dextral shearing is evidenced by S–C mylonites with beds in the northeast part of the basin. Good younging σ-porphyroclasts in granites, asymmetric pinch-and- criteria (graded beds, scour-and-fill structures, ripple swell structures in psammitic layers in thin-bedded marks, cross-beds, and channels) are preserved in many metasedimentary rocks, asymmetrically boudinaged quartz outcrops. In the north-central part of the basin, rocks of veins, and dextral offsets on metre-scale anastomosing the Coondamar Formation are exposed in narrow windows shear zones. through the Mosquito Creek Formation along the anticlinal culminations of major DMB4 folds. Box folds in the central part of the basin have wavelengths of about 0.5 m, amplitudes in the order Many of the larger DMB4 folds in the northern half of 0.1 m, and are in rocks where the main foliation is of the basin are overturned to the north and disrupted oriented at 90°–100°, indicating approximately east–west TRF65 04.05.06 TRF64 28.06.06 Figure 14. Quartz slickenfi bres on a D MB3 thrust fault, Mosquito Figure 13. Thrust fault (DMB4) in thin-bedded sandstone and Creek Formation (MGA 250980E 7597820N). The siltstone, Mosquito Creek Formation (MGA 250980E slickenfi bres at this location show a relatively 7597820N). The rocks are fractured and variously consistent orientation, but in other outcrops foliated adjacent to individual fault planes, which there may be up to three sets of fi bres in different anastomose around blocks of relatively undeformed orientations. View from above looking down onto rock. View to the west of a subvertical face a shallow-dipping fault surface 18 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet Metamorphism of the Mosquito Creek Basin Coondamar Formation Metamorphism of the Coondamar Formation occurred under conditions ranging from subgreenschist facies in the north of the Mosquito Creek Basin to amphibolite facies on the southernmost edge of the basin adjacent to the Kurrana Terrane. In the northern part of the basin, near Eastern Creek Well, basaltic lithic sandstone is partially recrystallized and replaced by metamorphic assemblages of chlorite– TRF66 07.06.06 carbonate–quartz(–albite), indicating a metamorphic grade Figure 15. Well-developed kink bands (DMB5) overprinting of lower greenschist facies or lower. Farther south, in the a fine crenulation (LMB3), phyllite, Mosquito central and southern parts of the basin, chlorite–actinolite Creek Formation (MGA 261190E 7585870N). The phyllite and schist consist principally of fine-grained crenulation runs from top right to bottom left chlorite, actinolite, quartz, and albite, with accessory magnetite, sphene, and apatite. In contrast, in the south near Hallcomes Peak, chlorite–actinolite phyllite locally contains one or both of small porphyroblasts of biotite (commonly shortening. The SMB5 crenulation cleavage is steep dipping, <1 mm in width) or aggregates of chlorite(–K-feldspar). subparallel to the axial surfaces of DMB5 folds, and in two The porphyroblasts are partially replaced by chlorite principal strike directions (340°–360° and 020°–045°), (–K-feldspar–quartz), commonly have chlorite fringes, and similar in orientation to the axial-surface traces of the contain inclusion trails defi ned by chlorite, actinolite, and box folds. The kink bands overprint both the LMB3 sphene that are oblique to the external foliation. These crenulation lineation and the L mineral lineation MB2 inclusion trails are interpreted to be relics of SMB2 because (Fig. 15). the porphyroblasts are deformed and enclosed by the matrix foliation (S ). Biotite is absent from the matrix, The timing of D is constrained to after c. 2860 Ma MB2–4 MB5 indicating that higher grades (mid-greenschist facies or (the maximum crystallization age of the Bonney Downs higher) were attained close to the southern boundary of Granite) and before c. 2775 Ma when deposition of the basin before the development of S . the Fortescue Group commenced. The relative timing MB4 of dextral shearing with respect to the kink folding is Amphibolite-facies rocks are restricted to a narrow not entirely clear. The two sets of structures have been zone (<500 m wide) close to the boundary with the assigned to the same event because kink folds in the Kurrana Terrane, where pelitic rocks are metamorphosed southern part of the basin are dominantly monoclinic to coarse-grained andalusite–muscovite schist, and mafi c dextral, and kink fold axes are subparallel to the axes of rocks to amphibolite. undulations in outcrop-scale anastomosing dextral shear zones. Mosquito Creek Formation The Mosquito Creek Formation has been metamorphosed DMB6 under very low to low-grade conditions. Shale and The last major deformation was a ductile–brittle event siltstone are typically metamorphosed to slate or phyllite associated with the formation of late-stage faults that depending on metamorphic grade and bulk composition, affect all Archean rocks on EASTERN CREEK (see Structure and sandstone is partly recrystallized and foliated. of the Fortescue Group). Tight to open folds (FMB6a) are present along north-trending faults associated with Slate and phyllite typically contain fine-grained small satellite basins of Fortescue Group rocks, and along chlorite, white mica, albite, graphite, quartz (in most the Redmond Fault (Fig. 4), which is a younger (DMB6b) rocks), and small amounts of fi ne-grained K-feldspar, west-northwesterly trending oblique slip fault that cuts monazite, rutile, tourmaline, and magnetite. Muscovite and across both the Mosquito Creek Basin and the Fortescue paragonite co-exist in many slates, and some samples also Group. A sinistral displacement on the Redmond Fault contain intermediate K–Na-white mica. Slate and phyllite of about 4.6 km is indicated by the offset of a large locally display small chlorite–mica stacks and retrogressed mafi c dyke. An apparent dextral offset by about 2.5 km porphyroblasts (<1.0 mm) enclosed by the main foliation of the Fortescue unconformity, which dips shallowly to (SMB2–4). The porphyroblasts are pseudomorphed by fi ne- the southeast (about 15°), can be accommodated by a grained aggregates of quartz(–chlorite–white mica–rutile) component of north-side-up vertical movement in the order or Fe-oxides–quartz, and have inclusion trails defi ned by of 1.9 km. Along the northeast side of the Redmond Fault concentrations of graphite that are contiguous with the DMB6b folds are upright, open to tight, and typically plunge external foliation (SMB2–4). The inclusion trails typically moderately to steeply to the northwest. Macroscopic curve into the external foliation and are fi ner grained, S-shaped folds in this area are consistent with fl exuring suggesting that the porphyroblasts developed pre- or early during sinistral north-side-up oblique movement on the syn-DMB4. The original mineralogy of the porphyroblasts fault. is uncertain, but it is possible that they were carbonates. 19 Farrell Chlorite–mica stacks reach up to 0.6 mm in length and volcanic rocks, and related sedimentary rocks, up to are lens or spindle shaped, with long axes parallel to the 6.5 km thick that was deposited unconformably on the enclosing foliation (SMB2–4). Mineralogically, they consist granite–greenstone basement. Deposition of the Fortescue of various proportions of chlorite, muscovite, paragonite, Group spanned the period from about 2.78 to 2.63 Ga intermediate K–Na-mica, and some quartz. The constituent (Arndt et al., 1991; A. F. Trendall, quoted in Nelson et al., phyllosilicates are typically stacked in bundles at a high 1999), and occurred during rifting of the Pilbara Craton angle to the enclosing foliation, and in many cases are and its evolution into a subsiding, passive continental kinked or folded, indicating development before DMB4. margin (Tyler and Thorne, 1990; Blake and Barley, 1992; Blake, 1993; Thorne and Trendall, 2001, and references Preliminary illite crystallinity (IC = 0.31, s.d. = 0.060, therein). n = 17) and white mica b cell parameter (b = 8.989, s.d. = 0.008, n = 12) studies on slate and phyllite indicate low- Rocks assigned to the Fortescue Group cover about pressure/high-temperature-style metamorphism under two-thirds of EASTERN CREEK, and lie unconformably on diagenetic to epizonal (zeolite- to lower greenschist-facies) rocks of the East Pilbara Granite–Greenstone Terrane, conditions (Farrell and Offl er, 2001). Mosquito Creek Basin, and Kurrana Terrane (Fig. 3). In general, the Fortescue Group succession dips moderately to the east and southeast, and the youngest exposed rocks in the group lie in the southeast corner of the map Neoarchean to sheet, close to the Davis River. In the northwest, adjacent to the Yilgalong Granitic Complex, the stratigraphy is Paleoproterozoic complicated by the presence of a shallow basin-like structure, and by post-depositional faulting. In addition, Hamersley Basin two outliers of the Fortescue Group occupy small, The Hamersley Basin (Trendall, 1983) contains a fault-related basins close to the northwest boundary of Neoarchean succession of mafi c to intermediate volcanic the sheet. On EASTERN CREEK the Fortescue Group is rocks, and subordinate felsic and sedimentary rocks represented, from base to top, by the Mount Roe Basalt, (Fortescue Group), and a conformably overlying package and the Hardey, Kylena, Tumbiana, Maddina, and Jeerinah of sedimentary rocks dominated by banded iron-formation, Formations. ferruginous shale, and dolomite (Hamersley Group). The basin is interpreted to have developed by rifting of the Pilbara Craton at c. 2.78 Ga, with concomitant extrusion Mount Roe Basalt (AFr, AFrsc, AFrst, AFrsl) of fl ood basalts (Tyler and Thorne, 1990; Thorne and The Mount Roe Basalt (Kriewaldt, 1964) is a succession, Trendall, 2001, and references therein). Subordinate felsic up to 2.5 km thick, of subaerial basaltic lavas, and sedimentary rocks are thought to have been deposited volcaniclastic rocks, and minor subaqueous basaltic lavas in intracratonic basins. Break-up of the Pilbara Craton is (Thorne and Trendall, 2001). Epiclastic sedimentary rocks generally considered to have occurred by c. 2.72 Ga, by are a minor component, and are thought to constitute no which time an ocean basin was developed to the south of more than about 1% of the unit (Thorne and Trendall, the present-day craton margin (Tyler and Thorne, 1990; 2001). On EASTERN CREEK the Mount Roe Basalt is locally Blake and Barley, 1992). Deposition of the upper part at the base of the Fortescue Group, and lies unconformably of the Fortescue Group (Jeerinah Formation) and the on rocks of the Mount Elsie greenstone belt, Yilgalong Hamersley Group is then interpreted to have occurred on a Granitic Complex, and Mosquito Creek Formation in the thermally subsiding continental margin (Tyler and Thorne, northwest of the map. A maximum thickness of about 1990; Blake and Barley, 1992). 500 m is indicated for an area north of Mount Olive. The unit consists of a basal sandstone and polymictic conglomerate, and an upper succession of basalt and minor Mount Bruce Supergroup gabbro. The sedimentary rocks have been included in the Mount Roe Basalt, although they could also belong to The Mount Bruce Supergroup (Trendall, 1979; Mount the pre-Mount Roe Basalt package of sedimentary rocks Bruce Megasequence of Blake and Barley, 1992) described by Thorne and Trendall (2001). The basalt has is a gently dipping supracrustal sequence that lies not been dated on EASTERN CREEK, but a SHRIMP U–Pb unconformably on the granite–greenstone basement. zircon date of 2775 ± 10 Ma (Arndt et al., 1991) indicates The supergroup encompasses all the stratigraphic units a depositional age of c. 2.78 Ga. that occupy the Hamersley Basin, and comprises a basal volcano-sedimentary succession (Fortescue Group), and an Undivided Mount Roe Basalt (AFr) outcrops in the overlying succession of chert – banded iron-formation and northwest corner of EASTERN CREEK, in an area north of dolomite (Hamersley Group). the Eastern Creek mining centre, and on the margins of two small outliers of the Fortescue Group close to the western margin of the sheet. The exposure north of the Fortescue Group Eastern Creek mining centre is dominated by fi ne-grained, aphyric, dark green-grey to blue-grey basalt with sparse The Fortescue Group (MacLeod et al., 1963; Thorne vesicles up to about 8 mm in diameter. The basalt is mostly and Trendall, 2001; the Nullagine and Mount Jope homogeneous, apart from a locally developed, vague Supersequences of Blake and Barley, 1992; Blake, 1993, compositional layering close to the top of some fl ows. 2001) is a thick sequence of Neoarchean mafi c and felsic Undivided Mount Roe Basalt (AFr) in the outliers near the 20 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet the Bamboo Creek Member (Thorne and Trendall, 2001; formerly the Bamboo Creek Porphyry, Noldart and Wyatt, 1962). On EASTERN CREEK the Hardey Formation unconformably overlies the Mount Roe Basalt, and parts of the East Pilbara Granite–Greenstone Terrane and Mosquito Creek Basin. Outcrop is discontinuous and the thickness of the unit varies up to a maximum of about 800 m near the southern boundary of the Yilgalong Granitic Complex. The formation is unconformably overlain by rocks of the Kylena Formation. Uranium–lead zircon dating in other areas of the Pilbara Craton indicates a depositional age range of c. 2768 to 2752 Ma (Pidgeon, 1984; Arndt et al., 1991; Blake et al., 2004). TRF57 07.06.06 Undivided Hardey Formation on EASTERN CREEK (AFh) Figure 16. Poorly sorted, polymictic boulder conglomerate at consists of a mixed succession of conglomerate, sandstone, the base of the Mount Roe Basalt, dominated by siltstone, and local tuffaceous sandstone. Medium-bedded clasts of vesicular or variolitic basalt derived from intervals of polymictic conglomerate, medium- to coarse- the underlying Mount Elsie greenstone belt (MGA grained sandstone, and pebbly sandstone alternate with 244360E 7604760N) thin-bedded intervals of fine-grained sandstone and siltstone. The conglomerate contains a wide range of clast types, not all of which are present in each outcrop. Clast types include felsic volcanic rock, granitic rock, vesicular western edge of the map comprises fi ne-grained vesicular basalt, chert, sandstone, and vein quartz. The clasts are basalt with local zones of fi ne- to medium-grained, weakly typically rounded to well rounded and up to 200 mm porphyritic gabbro. in size. In some areas the Hardey Formation contains a At the base of the Mount Roe Basalt there are siliceous, dark-grey to green-grey, medium- to coarse- local isolated exposures of polymictic pebble and grained tuffaceous sandstone, with local pebbly beds. cobble conglomerate (AFrsc, Fig. 16). Beds of boulder This rock is distinguished by clasts of accretionary conglomerate are also present in some areas. The most lapilli. extensive exposures of this rock type are 1 km northwest of Mount Olive, and along the southern margin of the Bamboo Creek Member (AFhb) Yilgalong Granitic Complex. The composition of the conglomerate is directly related to that of the basement On EASTERN CREEK the Bamboo Creek Member (AFhb) rocks nearby. Adjacent to the Mosquito Creek Basin, near overlies and locally intrudes the sedimentary rocks of Mount Olive, the conglomerate contains clasts of pebble the Hardey Formation. There are large exposures in the conglomerate and sandstone derived from the Mosquito central-northern area, but much of the outcrop is deeply Creek Formation, as well as basalt from the Mount Elsie weathered. In fresh outcrops the porphyry is a dark green- greenstone belt. The clasts are set in a coarse-grained grey rock crowded with phenocrysts of pinkish feldspar sandy matrix. Along the margin of the Yilgalong Granitic (?K-feldspar) and quartz in a fi ne-grained groundmass. Complex the conglomerate is up to about 200 m thick and The rock is typically massive, and possible columnar dips gently to the south at 10° to 20°. It comprises pebble jointing is preserved in several locations. In some areas the and cobble conglomerate, with interbedded coarse-grained porphyry is cut by closely spaced joints, and in others it feldspathic sandstone, as well as boulder conglomerate has a crude layering. Contacts with the Hardey Formation with clasts greater than 1 m in diameter. The conglomerate are locally discordant, suggesting that the porphyry may is locally dominated by granitic clasts, but can contain a be locally intrusive. wide variety of clasts, including basalt, felsic volcanic rock, layered chert, and vein quartz. Kylena Formation (AFkbk, AFkkl, AFkbi) Tuffaceous sandstone (AFrst) conformably overlies The Kylena Formation (Kojan and Hickman, 1998; the basal conglomerate of the Mount Roe Basalt. The formerly the Kylena Basalt, MacLeod and de la Hunty, sandstone contains angular fragments of quartz, feldspar, 1966; Hickman, 1983) outcrops in the central and and probable mafi c rock, as well as (?)devitrifi ed vitric central-northern parts of EASTERN CREEK. The formation clasts. Also present are local beds containing (?)reworked lies unconformably on the Yilgalong Granitic Complex, accretionary lapilli up to about 3 mm in size. The Mosquito Creek Formation, and Golden Eagle Orthogneiss. tuffaceous sandstone is interbedded with ripple-marked For the most part the Kylena Formation is unconformable siliceous siltstone and shale (AFrsl), and minor sandstone on the Hardey Formation, although there are locally and pebbly sandstone. conformable relationships in the Fortescue Group outlier west of Mount Elsie. Contact with the overlying Tumbiana Formation appears to be conformable. The formation is Hardey Formation (AFh) from about 0.5 to 2.5 km thick. The age of the formation is The Hardey Formation (Thorne et al., 1991) is a succession constrained by a date of 2741 ± 3 Ma for a mafi c tuff with of clastic sedimentary and volcanic rocks up to 3 km thick a detrital component, interpreted by Blake et al. (2004) that locally includes a quartz–feldspar porphyry, named as a maximum age, and the c. 2724–2715 Ma age (Arndt 21 Farrell et al, 1991; Blake et al., 2004) for the overlying Tumbiana fi ne-grained volcaniclastic rocks with minor carbonate Formation. (named the Mingah Tuff Member by Lipple, 1975) and an upper unit of stromatolitic carbonate and calcareous The mafic rocks of the Kylena Formation are sandstone (named the Meentheena Carbonate Member petrographically similar to the basalts of the Mount Roe by Lipple, 1975). An age of 2724–2715 Ma for the Basalt. They have been subdivided using geochemical Tumbiana Formation is indicated by SHRIMP U–Pb zircon (Glikson et al., 1986) and radiometric data (Fig. 3b), as dates of 2715 ± 6 Ma (Arndt et al., 1991) on a tuffaceous has been done in the west Pilbara (Kojan and Hickman, sandstone from the middle of the formation, and 2724 ± 5 1998). On EASTERN CREEK the Kylena Formation comprises and 2721 ± 4 Ma (Blake et al., 2004) on felsic tuffs a lower succession of basalt, local mafi c tuff, and probable from the base and mid-section of the formation komatiitic basalt (AFkbk), a thin unit of limestone and respectively. calcareous shale and siltstone (AFkkl), and an upper succession of tholeiitic basalt, basaltic andesite, and andesite On EASTERN CREEK the Tumbiana Formation (AFt) (AFkbi), with the more differentiated rocks towards the top outcrops in a northeasterly to east-northeasterly trending of the succession. belt that extends from Coondamar Creek to a point 20 km northeast of Mount Hays. The main rock types AFkbk The lower succession ( ) consists mainly of fi ne- are fi ne-grained sandstone, siltstone, and a distinctive grained, blue-grey, vesicular or amygdaloidal basalt. The tuffaceous sandstone or granulestone containing abundant vesicles are typically less than about 5 mm in size, but up accretionary lapilli. The latter is blue-grey or green- to 50 mm in some areas, and are concentrated in narrow grey and has individual beds, packed with accretionary zones, parallel to layering. Amygdales are fi lled with the lapilli, showing weak grain-size grading. Thorne and assemblages quartz, quartz–epidote, quartz–carbonate, Trendall (2001) interpreted similar rock types as primary or quartz–amphibole. Rare zones of brecciation with or pyroclastic fall deposits. The sandstone is typically basaltic without large elongate cavities up to 200 mm long may in composition and is locally intercalated with thin basalt represent the tops of individual fl ows. Locally, the basalt is fl ows. weakly plagioclase-phyric and may have a wispy layering. Some parts of the lower succession contain lapilli tuff with fl attened accretionary lapilli, shard-like fragments, Maddina Formation (AFmbk, AFm, AFmbi, and angular to subrounded rock fragments up to 15 mm. AFmcc, AFmk) Minor rock types not shown separately include massive fine-grained gabbro and laminated siliceous fine ash The Maddina Formation (AFm; Kojan and Hickman, (?)tuff. 1998; Thorne and Trendall, 2001, and references therein) consists mainly of subaerial basaltic lavas and mafic The limestone unit in the middle of the Kylena volcaniclastic rocks. The formation conformably overlies Formation (AFkkl) consists of thin-bedded stromatolitic the Tumbiana Formation, is up to about 1 km thick, and limestone with interbedded, ripple-marked shale and encompasses the former Nymerina Basalt, Maddina siltstone. The shale and siltstone commonly have thin Basalt, and Kuruna Siltstone (MacLeod and de la Hunty, interbeds of limestone. Fine-grained sandstone is near the 1966; Hickman, 1983). A SHRIMP U–Pb zircon date of top of the unit in some locations. The maximum thickness 2717 ± 2 Ma (Nelson, 1998) from near the base of the of the unit is about 10–15 m. The stromatolites and ripple Maddina Formation shows that it is similar in age to the marks suggest that the unit was deposited in a shallow- underlying Tumbiana Formation. water environment. The Maddina Formation covers an extensive area The upper part of the Kylena Formation (AFkbi) in the east and southeast of EASTERN CREEK. Outcrop in consists of a differentiated succession of extrusive rocks this area is very good, and the unit is clearly defi ned on ranging in composition from basalt through to andesite radiometric images (Fig. 3b). The formation is dominated (Glikson et al., 1986). This change in composition is by locally vesicular or plagioclase-phyric mafi c rocks, refl ected in the potassium and thorium concentrations and superficially appears to be relatively uniform in determined from airborne radiometric data. The uppermost composition. However, two major subunits have been part of the succession has a thorium content similar to that distinguished using whole-rock geochemistry (Glikson of the Bamboo Creek Member (AFhb), and a potassium et al., 1986) and radiometric data. These subunits are, content comparable to parts of the Yilgalong Granitic from base to top: komatiitic basalt (AFmbk), and basaltic Complex (AgAm). In the fi eld the rocks are very similar to andesite and andesite, with minor basalt (AFmbi). Minor those in the lower succession, and are typically vesicular rock units in the Maddina Formation include silicifi ed or amygdaloidal with local zones of brecciation and, in siltstone and chert (AFmcc), and siltstone and tuffaceous a few locations, possible pillow structures. Minor rock siltstone (AFmk). types in this unit include fi ne-grained laminated clastic sedimentary rock and coarse lapilli tuff. A unit of siltstone and probable tuffaceous siltstone with accretionary lapilli (AFmk) is exposed within the Maddina Formation in the northeast corner of EASTERN Tumbiana Formation (AFt) CREEK, between Boodalyerrie Creek and the eastern The Tumbiana Formation (Lipple, 1975; Thorne and boundary of the sheet. On the easternmost edge of Trendall, 2001) conformably overlies the Kylena EASTERN CREEK, and on PEARANA to the east, the siltstone Formation, and reaches a maximum thickness of about is underlain and partly intruded by a dolerite sill (Ad; 250 m. In the east Pilbara it consists of a lower unit of Williams and Trendall, 1998). 22 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet Jeerinah Formation (AFj) southeast corner of the sheet, south-southeast of the Sunset Hill manganese prospect. More extensive exposures of The Jeerinah Formation (MacLeod et al., 1963; Thorne and the dolomite on PEARANA, to the east, have been described Trendall, 2001), formerly the Lewin Shale (de la Hunty, by Williams and Trendall (1998, and references therein). 1964; Hickman, 1983), consists mainly of fi ne-grained The Carawine Dolomite has not been directly dated, but clastic sedimentary rocks with minor chert. It is widely a minimum age of c. 2540 Ma is inferred from a Pb–Pb thought to be conformable on the Maddina Formation isochron date of 2541 ± 32 Ma, which is interpreted to be (Thorne and Trendall, 2001, and references therein) and the age of diagenesis of the carbonate sediments (Jahn and attains a thickness of up to 1250 m. A depositional age Simonson, 1995). range of 2690 to 2629 Ma is indicated by SHRIMP U–Pb zircon dates of 2690 ± 16, 2684 ± 6 (Arndt et al., 1991), On EASTERN CREEK the dolomite is a grey recrystallized and 2629 ± 5 Ma (A. F. Trendall, quoted in Nelson et al., rock with minor amounts of shale and nodular chert. The 1999). dolomite is locally variegated due to impurities of iron The Jeerinah Formation (AFj) forms prominent hills and manganese, and contains a variety of sedimentary along the western boundary of the Davis River valley, in structures suggestive of deposition in a shallow-water, platform setting (Williams and Trendall, 1998). the southeast corner of EASTERN CREEK. In this area the formation consists of bedded chert, siltstone, shale, and minor medium- to coarse-grained sandstone. The chert is thin to thick bedded and grey to pale green-grey, with a Minor intrusions of Archean vague lamination, and typically forms a resistant cap over deeply weathered shale and siltstone. or Proterozoic age Structure of the Fortescue Group Mafi c dykes (d, Ad) DFG1 (c. 2730 Ma) Numerous mafi c dykes of uncertain age (d) cut across rocks of the East Pilbara Granite–Greenstone Terrane, A gentle basin-like structure south of the Yilgalong Mosquito Creek Basin, Kurrana Terrane, and Hamersley Granitic Complex has affected rocks in the lower part Basin. Most dyke outcrops are deeply weathered and of the Fortescue Group, up to and including the Kylena poorly exposed. Apart from a few exceptions, the majority Formation. The absence of similar structures in the have a low magnetic susceptibility. In fresh outcrop the overlying Tumbiana Formation suggests development of dykes are mostly composed of massive, homogeneous the structure before c. 2724 Ma, which is the maximum age dolerite or gabbro. One unusual mafic dyke 9 km of rocks in the Tumbiana Formation (Blake et al., 2004). southwest of Mount Elsie contains angular and highly irregular fragments of quartz and subordinate chert DFG2 (c. 2690–2629 Ma) (Fig. 17). These fragments are thought to be greenstone Rocks of the Fortescue Group are cut by numerous faults. xenoliths. In many locations mafi c dykes are associated North- to northwest-trending dextral faults are interpreted with quartz veins that follow the same trend. In a few to be structures formed during deposition of the Jeerinah areas airphoto lineaments are defi ned by subparallel mafi c Formation. The faults cut through the Maddina Formation dykes and quartz veins. A dolerite of inferred Archean and are locally associated with small basins of Jeerinah age (Ad) in the northeast corner of EASTERN CREEK is the Formation that unconformably overlie the lower parts continuation of a large dolerite sill on PEARANA (Williams of the Maddina Formation (e.g. 3.5 km southeast of and Trendall, 1998) that has intruded along the contact Hallcomes Peak). Subsidiary northeasterly trending faults between the Maddina and Jeerinah Formations. also probably formed at about the same time. Hamersley Group The Hamersley Group lies conformably on the Fortescue Group and is a package of sedimentary rocks, up to 2.5 km thick, characterized by abundant banded iron- formation and iron-rich shale. The lower part of the group consists mainly of banded iron-formation assigned to the Marra Mamba Iron Formation and dolomitic rocks of the Wittenoom Formation (Trendall, 1983). In the northeast part of the Hamersley Basin, which is exposed on EASTERN CREEK, the basal unit is the Carawine Dolomite, which is the easterly correlative of the Wittenoom Formation. TRF58 28.06.06 Carawine Dolomite (AHc) Figure 17. Mafi c dyke with angular xenoliths of chert, probably The Carawine Dolomite (AHc; Noldart and Wyatt, 1962; derived from metamorphosed chert in the host Hickman, 1983) is the only unit of the Hamersley Group on greenstones, Mount Elsie greenstone belt (MGA EASTERN CREEK. The only exposures of the unit are in the 242330E 7605280N) 23 Farrell HornblendeÐquartz monzodiorite suggesting that they are the surface exposures of much more extensive igneous bodies. The dominant rock type and diorite (Agd) is a fi ne- to medium-grained, massive hornblende-bearing Mafi c plugs up to 250 m wide have intruded the Coondamar granodiorite to monzogranite. The largest exposure, Formation about 8 km west-southwest of Eastern Creek Well 4 km south-southeast of the Parnell mining centre, is weakly porphyritic and contains scattered, rounded mafi c (MGA 246500E 7595200N and MGA 247300E 7594800N). The intrusions range in composition from hornblende–quartz enclaves up to 130 mm, as well as sparse xenoliths of monzodiorite to hornblende diorite, and are granular and metamorphosed sandstone and vein-quartz. An intrusive seriate textured with a quartz content locally up to 10%. age of c. 1800 Ma is indicated by a SHRIMP U–Pb zircon Small rounded mafi c enclaves up to 30 mm are common, date of 1803 ± 19 Ma (Nelson, 2002c) from an intrusion in and there are rare xenoliths of Mosquito Creek Formation the Granite Hills on NULLAGINE (Bagas, 2005), immediately in some outcrops. A crystallization age of c. 2755 Ma is west of EASTERN CREEK. indicated by a SHRIMP U–Pb zircon date of 2755 ± 7 Ma (Nelson, 2004g), suggesting that the intrusions may have been feeders for the Hardey Formation in the Fortescue Phanerozoic Canning Basin Group. Paterson Formation (Pa) The Paterson Formation (Pa) of the Canning Basin is the Quartz veins (q) only Permian–Carboniferous unit on EASTERN CREEK. It Quartz veins (q) are abundant in the Mount Elsie is poorly exposed in the northeast corner. More extensive greenstone belt, the Coondamar and Mosquito Creek exposures on PEARANA to the east have been described in Formations, and the Yilgalong and Kurrana Granitic more detail (Williams and Trendall, 1998). It is interpreted Complexes. There are several distinct sets of quartz veins as a fl uvioglacial deposit on the basis of a basal diamictite of contrasting age. There is an older set of foliation- with scattered boulders, and polished grooved pavements parallel deformed veins in the Mount Elsie greenstone on the underlying Pinjian Chert Breccia. belt, a later set of foliation-parallel veins in the Coondamar and Mosquito Creek Formations, and a younger set of veins associated with crosscutting mafi c dykes (d). Most foliation-parallel veins are too small to be shown Cenozoic regolith geology individually, and hence only the larger quartz veins Parts of EASTERN CREEK are mantled by Cenozoic regolith, associated with the mafi c dykes are shown on the map. including residual indurated deposits exposed by erosion, and a range of younger alluvial and eluvial deposits. Individual regolith units have been mapped using fi eld observations in conjunction with airphoto and Landsat-TM Neoarchean to image interpretation. Paleoproterozoic Pinjian Chert Breccia (!cb) Residual deposits (Czrf, Czrk, The Pinjian Chert Breccia (!cb; Williams and Trendall, Czrz, Czc, Czoc) 1998) overlies the Carawine Dolomite (AHc) along the Davis River in the southeast of EASTERN CREEK. The The oldest regolith units typically form residual deposits breccia consists of angular fragments of chert and layered on low hills and plateau remnants. They include chert in a siliceous matrix. The breccia is locally rich in ferruginous duricrust (Czrf), calcrete (Czrk), silcrete and iron and manganese oxides, giving the rock a black to siliceous duricrust (Czrz), weakly consolidated colluvium dark-brown colour and semimetallic lustre. Subeconomic (Czc), and a unit of limestone and calcareous sandstone concentrations of manganese occur in the Sunset Hill, (Czoc) called the Oakover Formation (Noldart and Wyatt, Redmond, Snake Hill, and Donkey prospects. The 1962; Williams and Trendall, 1998). Pinjian Chert Breccia is thought to have formed by deep Ferruginous duricrust (Czrf) caps deeply weathered weathering of the Carawine Dolomite (Williams and rocks of the Fortescue Group along the Davis River Trendall, 1998). valley, and along Coondamar Creek in the central- southern margin of EASTERN CREEK. Isolated outcrops of ferruginous duricrust are also on the northern edge of Paleoproterozoic Bridget the Mosquito Creek Formation, near Mount Olive. These deposits probably represent an ancient weathering surface, Suite (#gBmh) possibly related to the ‘Hamersley Surface’ (Campana et al., 1964). A north-northwesterly trending suite of small, post-tectonic monzogranite intrusions (#gBmh) lies within the Mosquito Calcrete (Czrk) forms rubbly deposits on undulating Creek Formation close to the western margin of EASTERN country adjacent to the Davis River, about 2.5 km CREEK. Many of the intrusions, even though relatively east of the Redmond manganese prospect. Siliceous small, have wide, biotite-grade metamorphic aureoles, duricrust, including silcrete and secondary chert breccia 24 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet (Czrz), overlies the Pinjian Chert Breccia (!cb) in the Eastern Creek, Elsie, and Mosquito Creek. Additionally, southeastern corner of the area. It is thought to be derived substantial amounts of alluvial gold have been extracted from the Pinjian Chert Breccia by deep weathering and through prospecting activity up to the present time. Most secondary silicifi cation (Williams and Trendall, 1998). of the hard-rock mining occurred in the early 1900s, although some mines have been worked sporadically since Partly consolidated deposits of silt, sand, and gravel then. (Czc) are largely restricted to a few areas in the northeast corner of EASTERN CREEK, and near Coondamar Creek, The Boodalyerrie mining centre encompasses a group where they are on low hills above the level of the present- of small workings within the Yilgalong Granitic Complex day drainage system. The deposits are partly dissected and (MGA 270750E 7613200N) that were active from 1901 eroded, and are interpreted to be the remnants of colluvial to 1910. Gold was extracted from thin quartz veins in deposits that pre-date the present-day erosional regime. granitic rock with a yellow-green alteration (Finucane, 1939a). Alluvial gold was also produced from the adjacent The lower unit of the Oakover Formation (Czoc) is creeks. Total gold production was 25.992 kg (Ferguson only in the northeasternmost corner of EASTERN CREEK, and and Ruddock, 2001). occupies a paleovalley of the Oakover River (Williams and Trendall, 1998). The formation is estimated to be at least The Elsie mining centre is in the Mount Elsie 30–40 m thick, and is considered a lacustrine deposit. greenstone belt, close to Mount Elsie. Mining activity occurred mainly between 1899 and 1906, and was focused on quartz veins in foliated metabasalt and mafi c schist with Quaternary colluvium and carbonate alteration (Finucane, 1939b). Total production up to 1998 was 52.388 kg of gold (Ferguson and Ruddock, sheetwash deposits (Qc, Qcf, 2001). Qw, Qwf) Larger amounts of gold were found in the Mosquito Proximal slope deposits, comprising unconsolidated rock Creek Formation, which continues to be an area of active debris, sand, and silt, lie on steep slopes and in adjacent gold prospecting. There are two historic mining centres areas on the valley fl oor. They have been mapped either on EASTERN CREEK and several others on NULLAGINE to the as colluvium (Qc), or as ferruginous colluvium (Qcf) if west. The Eastern Creek mining centre lies in the northeast dominated by ferruginous debris and iron-rich nodules. corner of the Mosquito Creek Formation, close to Eastern The latter unit is typically developed in the southeast part Creek Well. In this area the gold is in quartz veins in slate, of EASTERN CREEK, adjacent to ferruginous duricrust (Czrf), and metamorphosed siltstone and sandstone. The mining and outcrops of the Maddina and Jeerinah Formations. centre was active mainly between 1908 and 1924 for a total gold production of 308.132 kg, although a few of More distal parts of the regolith, along valley fl oors, are the shafts have been worked sporadically since then by dominated by sheetwash (Qw) and ferruginous sheetwash prospectors. The Mosquito Creek mining centre extends deposits (Qwf). Sheetwash deposits are typically along the onto the western edge of EASTERN CREEK from NULLAGINE major creeks and rivers. They consist of sand, silt with a and encompasses the Federal and Parnell mines. These poorly defi ned drainage, and are locally gradational into mines lie on the eastern extension of a line of gold and alluvium (Qaa) or overbank deposits (Qao). antimony deposits, called the Blue Spec line (Ferguson and Ruddock, 2001). Several other small workings are present along the eastern extension of this line towards the Quaternary alluvial deposits centre of EASTERN CREEK. On NULLAGINE the mineralized lodes contain quartz, stibnite, aurostibite, native gold, (Qaa, Qao) pyrite, pyrrhotite, and carbonate, as well as minor Recent deposits of unconsolidated to semiconsolidated amounts of scheelite, arsenopyrite, marcasite, sphalerite, clay, silt, sand, and gravel (Qaa) of probable Quaternary chalcopyrite, magnetite, mackinawite, calvarite, rickardite, age lie along intermittently active fl uvial channels and on and gudmundite (Hickman, 1983; Gifford, 1990). adjacent fl oodplains. These deposits may grade laterally into overbank deposits (Qao) or sheetwash (Qw and Qwf). Broad areas of clay, silt, and sand on fl oodplains adjacent Stratabound volcanic and to major creek systems are mapped as overbank deposits. sedimentary mineralization Base metals — copper, lead, zinc Economic geology Subeconomic base metal mineralization has been discovered in the Coondamar Formation and the lower Vein and hydrothermal part of the Mosquito Creek Formation at several locations mineralization near Coondamar Creek, in the southwest corner of EASTERN CREEK. Assays of drillhole chips gave up to Precious metal — gold(–antimony) 18% Cu, 1.7% Pb, 19.5% Zn, 210 g/t Ag, and 1.75 g/t Au in the Coondamar Horse Creek prospect (Ferguson and Significant historical gold production has come from Ruddock, 2001). A gossan at the Coondamar Creek Mogul four mining centres on EASTERN CREEK — Boodalyerrie, prospect contains malachite, azurite, chrysacolla, cuprite, 25 Farrell hydrozincite, smithsonite, and cerussite. At depth the surface sheets and lens-shaped mounds. They are thought primary mineralization consists of pyrite, chalcopyrite, to have formed by remobilization and precipitation of sphalerite, and galena (Ferguson and Ruddock, 2001). manganese during deep weathering of the Carawine Dolomite in the Paleoproterozoic, followed by further surface enrichment during deep weathering in the Regolith-hosted mineralization Cenozoic (Ferguson and Ruddock, 2001). Mineralogical studies have shown that the manganese deposits are Steel industry metal — manganese dominated by cryptomelane, pyrolusite, and goethite (Ostwald, 1993). Supergene manganese mineralization in the southeast corner of EASTERN CREEK belongs to the Pilbara Manganese Province (de la Hunty, 1963). These occurrences have formed largely by supergene enrichment of manganese- bearing Archean sedimentary rocks of the Hamersley Group. On EASTERN CREEK the manganese deposits are hosted by the Pinjian Chert Breccia (!cb), and form 26 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet References ARNDT, N. T., NELSON, D. R., COMPSTON, W., TRENDALL, BUCHER, K., and FREY, M., 1994, Petrogenesis of metamorphic rocks A. F., and THORNE, A. M., 1991, The age of the Fortescue Group, (6th edition): Berlin, Springer–Verlag, 318p. Hamersley Basin, Western Australia, from ion microprobe zircon BUICK, R., THORNETT, J. R., McNAUGHTON, N. J., SMITH, U–Pb results: Australian Journal of Earth Sciences, v. 38, J. B., BARLEY, M. E., and SAVAGE, M., 1995, Record of emergent p. 261–281. continental crust ~3.5 billion years ago in the Pilbara Craton of BAGAS, L., BEUKENHORST, O., and HOS, K., 2004a, Nullagine, Australia: Nature, v. 375, p. 574–577. W.A. Sheet 2954: Western Australia Geological Survey, 1:100 000 BUICK, R., BRAUHART, C. W., MORANT, P., THORNETT, J. R., Geological Series. MANIW, J. G., ARCHIBALD, N. J., DOEPEL, M. G., FLETCHER, I. R., BAGAS, L., FARRELL, T. R., and NELSON, D. R., 2004b, Age and PICKARD, A. L., SMITH, J. B., BARLEY, M. E., McNAUGHTON, provenance of the Mosquito Creek Formation: Western Australia N. J., and GROVES, D. I., 2002, Geochronology and stratigraphic Geological Survey, Annual Review 2003–04, p. 62–70. relationships of the Sulphur Springs Group and Strelley Granite: a temporally distinct igneous province in the Archaean Pilbara Craton, BAGAS, L., 2005, Geology of the Nullagine 1:100 000 sheet: Australia: Precambrian Research, v. 114, p. 87–120. Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 33p. CAMPANA, B., HUGHES, F. E., BURNS, W. G., WHITCHER, I. G., and MUCENIEKAS, E., 1964, Discovery of the Hamersley iron BARLEY, M. E., 1993, Volcanic, sedimentary and tectonostratigraphic deposits (Duck Creek – Mt Pyrton – Mt Turner area): The Australasian environments of the ~3.46 Ga Warrawoona Megasequence — a Institute of Mining and Metallurgy, Proceedings, no. 210, p. 1–30. review: Precambrian Research, v. 60, p. 47–67. COLLINS, W. J., VAN KRANENDONK, M. J., and TEYSSIER, C., BARLEY, M. E., LOADER, S. E., and McNAUGHTON, N. J., 1998, 1998, Partial convective overturn of Archaean crust in the east Pilbara 3430 to 3417 Ma calc-alkaline volcanism in the McPhee Dome and Craton, Western Australia — driving mechanisms and tectonic Kelly Belt, and growth of the eastern Pilbara Craton: Precambrian implications: Journal of Structural Geology, v. 20, p. 1405–1424. Research, v. 88, p. 3–23. COMMONWEALTH BUREAU OF METEOROLOGY, 2003, BARLEY, M. E., and PICKARD, A. L., 1999, An extensive, crustally- Commonwealth Bureau of Meteorology, Canberra, viewed derived, 3325 to 3310 Ma silicic volcanoplutonic suite in the eastern 18 December 2003, 27 Farrell GIFFORD, A. C., 1990, Blue Spec – Golden Spec gold–antimony from Central Wales, U.K.: Journal of Structural Geology, v. 16, deposit, in Geology of the mineral deposits of Australia and Papua p. 1339–1357. New Guinea, Volume 1 edited by F. E. HUGHES: The Australasian LIPPLE, S. L., 1975, Defi nitions of new and revised stratigraphic units Institute of Mining and Metallurgy, Monograph 14, p. 155–158. of the eastern Pilbara region: Western Australia Geological Survey, GLIKSON, A. Y., DAVY, R., and HICKMAN, A. H., 1986, Geochemical Annual Report 1974, p. 58–63. data files of Archaean volcanic rocks, Pilbara Block, Western MacLEOD, W. N., and de la HUNTY, L. E., 1966, Roy Hill, W.A.: Australia: Australia Bureau of Mineral Resources, Geology and Western Australia Geological Survey, 1:250 000 Geological Series Geophysics, Record 1986/14. Explanatory Notes, 27p. HICKMAN, A. H., 1975, Precambrian structural geology of part of the MacLEOD, W. N., de la HUNTY, L. E., JONES, W. R., and HALLIGAN, Pilbara region: Western Australia Geological Survey, Annual Report R., 1963, A preliminary report on the Hamersley Iron province, 1974, p. 68–73. North–West Division: Western Australia Geological Survey, Record HICKMAN, A. H., 1977, New and revised defi nitions of rock units in 1963/11, 45p. the Warrawoona Group, Pilbara Block: Western Australia Geological McNAUGHTON, N. J., GREEN, M. D., COMPSTON, W., and Survey, Annual Report 1976, p. 53. WILLIAMS, I. S., 1988, Are anorthositic rocks basement to the HICKMAN, A. 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VAN KRANENDONK, M., PHILLIPS, D., BAKER, D., and NELSON, D. R., 1998, 144993: dacite, Booloomba Pool, in Compilation BRAUHART, C., 2002, The timing of mineralization in the Archaean of geochronology data, June 2005 update: Western Australia North Pilbara terrain, Western Australia: Economic Geology, v. 97, Geological Survey. p. 733–755. NELSON, D. R., 2002a, 160220: tuffaceous rhyolite, Fieldings Gully JAHN, B., and SIMONSON, B. M., 1995, Carbonate Pb–Pb ages of the Well, in Compilation of geochronology data, June 2005 update: Wittenoom Formation and Carawine Dolomite, Hamersley Basin, Western Australia Geological Survey. Western Australia (with implications for their correlation with the Transvaal Dolomite of South Africa): Precambrian Research, v. 72, NELSON, D. R., 2002b, 144681: agglomeratic rhyolite, Baroona Hill, p. 247–261. in Compilation of geochronology data, June 2005 update: Western Australia Geological Survey. JIANG, W.–T., and PEACOR, D. R., 1994, Formation of corrensite, chlorite and chlorite–mica stacks by replacement of detrital biotite NELSON, D. R., 2002c, 169030: hornblende–biotite quartz monzodiorite, in low-grade pelitic rocks: Journal of Metamorphic Geology, v. 12, Granite Hill Well, in Compilation of geochronology data, June 2005 p. 867–884. update: Western Australia Geological Survey. KLOPPENBURG, A., WHITE, S. H., and ZEGERS, T. E., 2001, NELSON, D. R., 2004a, 169044: muscovite–biotite monzogranite, Structural evolution of the Warrawoona greenstone belt and adjoining Ripon Hills Road – Yandicoogina Creek Crossing, in Compilation of granitoid complexes, Pilbara Craton, Australia: implications for geochronology data, June 2005 update: Western Australia Geological Archaean tectonic processes: Precambrian Research, v. 112, Survey. p. 107–148. NELSON, D. R., 2004b, 169187: coarse lithic–quartz sandstone, Blue KOJAN, C. J., and HICKMAN, A. H., 1998, Late Archaean volcanism in Spec mine, in Compilation of geochronology data, June 2005 update: the Kylena and Maddina Formations, Fortescue Group, west Pilbara: Western Australia Geological Survey. Western Australia Geological Survey, Annual Review 1997–98, NELSON, D. R., 2004c, 169194: coarse lithic–quartz sandstone, Blue p. 43–53. Spec mine, in Compilation of geochronology data, June 2005 update: Western Australia Geological Survey. KRAPEZ, B., 1984, Sedimentation in a small, fault-bounded basin: the Lalla Rookh sandstone, east Pilbara Block, in Archaean and NELSON, D. R., 2004d, 169199: coarse lithic–quartz sandstone, Proterozoic basins of the Pilbara, Western Australia: evolution Branchies Well, in Compilation of geochronology data, June 2005 and mineralization potential edited by J. R. MUHLING, update: Western Australia Geological Survey. D. I. GROVES, and T. S. BLAKE: The University of Western NELSON, D. R., 2004e, 169200: coarse lithic–quartz sandstone, Australia, Geology Department and University Extension, Publication Branchies Well, in Compilation of geochronology data, June 2005 no. 9, p. 89–110. update: Western Australia Geological Survey. KRAPEZ, B., 1989, Depositional styles and geotectonic settings of NELSON, D. R., 2004f, 177131: coarse-grained metasandstone, Lionel Archaean metasedimentary sequences: Evidence from the Lalla Well, in Compilation of geochronology data, June 2005 update: Rookh Basin, Pilbara Block, Western Australia: The University of Western Australia Geological Survey. Western Australia, PhD thesis (unpublished). NELSON, D. R., 2004g, 178005: porphyritic hornblende–quartz KRAPEZ, B., 1993, Sequence stratigraphy of the Archaean supracrustal micromonzodiorite, Eastern Creek Well, in Compilation of belts of the Pilbara Block, Western Australia: Precambrian Research, geochronology data, June 2005 update: Western Australia Geological v. 60, p. 1–45. Survey. 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R., 2005e, 178008: biotite–muscovite tonalite gneiss, for the Marble Bar Region, Pilbara Craton, Western Australia: The Mount Elsie, in Compilation of geochronology data, June 2005 University of Western Australia, Geology Department and University update: Western Australia Geological Survey. Extension, Publication no. 22, p. 395–407. NELSON, D. R., 2005f, 169260: foliated biotite tonalite, Bullyarrie Well, TRENDALL, A. F., 1979, A revision of the Mount Bruce Supergroup: in Compilation of geochronology data, June 2005 update: Western Western Australia Geological Survey, Annual Report 1978, Australia Geological Survey. p. 63–71. NELSON, D. R., 2005g, 169263: tonalite gneiss, Bullyarrie Well, in TRENDALL, A. F., 1983, The Hamersley Basin, in Iron formations — Compilation of geochronology data, June 2005 update: Western facts and problems edited by A. F. TRENDALL and R. C. MORRIS: Australia Geological Survey. Amsterdam, Elsevier, p. 69–129. NELSON, D. 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Granite–Greenstone Terrane, Western Australia — a fi eld guide: Western Australia Geological Survey, Record 2001/9, 134p. OSTWALD, J., 1993, Manganese oxide mineralogy, petrography and genesis, Pilbara Manganese Group, Western Australia: Mineralium VAN KRANENDONK, M. J., HICKMAN, A. H., SMITHIES, R. H., Deposita, v. 28, p. 198–209. NELSON, D. R., and PIKE, G., 2002, Geology and tectonic evolution of the Archaean North Pilbara Inlier, Pilbara Craton, Western PASSCHIER, C. W., and TROUW, R. A. J., 1996, Microtectonics: Berlin, Australia: Economic Geology, v. 97, p. 695–732. Springer–Verlag, 289p. VAN KRANENDONK, M. J., SMITHIES, R. H., HICKMAN, PETTIJOHN, F. J., POTTER, P. E., and SIEVER, R., 1987, Sand and A. H., BAGAS, L., WILLIAMS, I. R., and FARRELL, T. R., 2004, sandstone: New York, Springer–Verlag, 553p. Archaean supergroups and supersuites in the northern Pilbara PIDGEON, R. T., 1984, Geochronological constraints on early volcanic Craton: the application of event stratigraphy to 1 Ga of crustal and evolution of the Pilbara Block, Western Australia: Australian Journal metallogenic evolution: Western Australia Geological Survey, Record of Earth Sciences, v. 31, p. 237–242. 2004/5, p. 5–7. SMITHIES, R. H., HICKMAN, A. H., and NELSON, D. R., 1999, WIJBRANS, J. R., WHITE, S. H., NELSON, D. R., KLOPPENBURG, New constraints on the evolution of the Mallina Basin, and their A., and ZEGERS, T. E., 2000, The age of metamorphism of Archean bearing on relationships between the contrasting eastern and western Mid and Upper Crustal rocks of the eastern Pilbara Craton, Western granite–greenstone terrains of the Archaean Pilbara Craton, Western Australia: 2000 Canadian Society of Exploration Geophysicists Australia: Precambrian Research, v. 94, p. 11–28. Conference, 2000, Abstract, 29 Farrell Appendix 1 Gazetteer of localities on EASTERN CREEK Place name MGA coordinates Easting Northing Coondamar Horse Creek base metal prospect 259150 7572200 Coondamar Creek Mogul base metal prospect 256745 7576761 Donkey manganese prospect 284935 7575761 Eastern Creek Well 253900 7598600 Federal gold mine (abd) 241815 7583930 Hallcomes Peak 257100 7577030 Mount Elsie 250370 7609100 Mount Hays 270000 7580300 Mount Olive 254600 7599600 Parnell gold mine (abd) 241605 7583961 Redmond manganese prospect 286635 7576161 Snake Hill manganese prospect 293135 7587361 Steel Well (abd) 248100 7617900 Sunset Hill manganese prospect 291235 7581311 NOTE: abd = abandoned 30 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet REEK C ASTERN p p -gmh p p c-kds Mount Bruce Supergroup Group Hamersley Dolomite Carawine q-mh q-mx Supergroup De Grey Supergroup De Grey Nullagine Group Nullagine Group Mosquito Creek Formation Mosquito Creek Formation j-cl m-bd m-cc m-bng mk-bntt m-bk Mount Bruce Supergroup Mount Bruce Supergroup t-bntt k-bng Group Fortescue Mount Bruce Supergroup Group Fortescue Mount Bruce Supergroup km-kts Mount Bruce Supergroup Group Fortescue Group Fortescue k-xbk-bb Group Fortescue Jeerinah Formation Mount Bruce Supergroup h-xs-f Maddina Formation Mount Bruce Supergroup hb-fr Maddina Formation Group Fortescue Maddina Formation Mount Bruce Supergroup Member Kuruna Maddina Formation: Group Fortescue Mount Bruce Supergroup Mount Bruce Supergroup r-bbg Group Fortescue Group Fortescue r-scp Maddina Formation Group Fortescue Mount Bruce Supergroup Formation Tumbiana r-sl Formation Kylena r-st Mount Bruce Supergroup Group Fortescue Formation Kylena Formation Kylena Group Fortescue Mount Bruce Supergroup Formation Hardey Mount Bruce Supergroup Group Fortescue Bamboo Creek Member Formation: Hardey Group Fortescue Mount Bruce Supergroup Mount Bruce Supergroup Mount Roe Basalt Group Fortescue Group Fortescue Mount Roe Basalt Mount Roe Basalt Mount Roe Basalt bo-gm Split Rock Supersuite Granite Downs Bonney p z c f r bg ha fo fo fo fo fo fo fo fo fo fo fo fo fo fo fo fo sr nu nu W1 W1f C1 C1f C2 R2 A1 R2k R3f A1 Appendix 2 Correlation of rock codes and stratigraphic names on E Correlation of rock with rock codes and stratigraphic names used in the GSWA databases codes and stratigraphic names used in the GSWA with rock mh P_ bd Granitic Complex Kurrana Granite Downs Bonney A b c Mount Bruce Supergroup Group Hamersley Dolomite Carawine A qs qsc Pilbara Supergroup Pilbara Supergroup Group De Grey Group De Grey Mosquito Creek Formation Mosquito Creek Formation A A k j mbi mcc Mount Bruce Supergroup Mount Bruce Supergroup m Mount Bruce Supergroup mk Group Fortescue Group Fortescue mbk Group Fortescue Mount Bruce Supergroup Mount Bruce Supergroup t Mount Bruce Supergroup Group Fortescue kbi Group Fortescue Group Fortescue kkl Mount Bruce Supergroup Mount Bruce Supergroup kbk Maddina Formation Jeerinah Formation Mount Bruce Supergroup h Group Fortescue Maddina Formation Group Fortescue Mount Bruce Supergroup hb Group Fortescue Maddina Formation Group Fortescue Member Kuruna Maddina Formation: Mount Bruce Supergroup r Maddina Formation Mount Bruce Supergroup Group rsc Fortescue Group Fortescue rsl Formation Tumbiana Formation Kylena Mount Bruce Supergroup A rst Mount Bruce Supergroup Formation Kylena Group Fortescue Mount Bruce Supergroup Formation Kylena Group Fortescue Mount Bruce Supergroup A Group Fortescue A Formation Hardey A Group Fortescue Bamboo Creek Member Formation: Hardey A A A Mount Roe Basalt Mount Roe Basalt Mount Roe Basalt A Mount Roe Basalt A A A A A A A A g cb Pinjian Chert Breccia AP_pj-ccx Pinjian Chert Breccia h f f f f f f f f f f f f f f f f d d Qw Qwf Qc Qcf Czc Czrz Czrk Czrf Czoc Pa ! unit Lower Formation: Oakover Formation Paterson Noa-ktpl CPpa-sgpg unit Lower Formation: Oakover Formation Paterson Map code Supergroup Qaa Old Group/Complex Member Old Formation: code New Supergroup/Supersuite New Group New Member Formation: New Qao d AP_o q Ad A AP_zq Aod ! A A A Ag A A A A A A A A A A A A Agd A A A Agh Agkh Agnh 31 Farrell ge-mgtn Mount Billroth Supersuite Golden Eagle Orthogneiss el-mgtss el-mr Emu Pool Supersuite Emu Pool Supersuite Tonalite Elsie Creek Tonalite Elsie Creek q-ml q-xml-mt q-mt c-xmd-mwa Supergroup De Grey c-xmd-mgn Supergroup De Grey Supergroup De Grey c-mcj Supergroup De Grey c-xmh-mwa Supergroup De Grey Nullagine Group c-mhc Nullagine Group Nullagine Group Supergroup De Grey c-mt Nullagine Group Supergroup De Grey c-mtw Nullagine Group c-mtwk Supergroup De Grey Nullagine Group Mosquito Creek Formation c-mf Mosquito Creek Formation Nullagine Group c-mog Coondamar Formation Supergroup De Grey Supergroup De Grey c-mbb Coondamar Formation Supergroup De Grey Mosquito Creek Formation Nullagine Group c-mws c-mbm Coondamar Formation Supergroup De Grey Nullagine Group Nullagine Group Supergroup De Grey c-ma Coondamar Formation Nullagine Group Supergroup De Grey c-mapt Supergroup De Grey Coondamar Formation c-mwrc Nullagine Group Supergroup De Grey Nullagine Group c-max Coondamar Formation Nullagine Group Coondamar Formation Supergroup De Grey Supergroup De Grey Coondamar Formation Nullagine Group Supergroup De Grey Nullagine Group Coondamar Formation Supergroup De Grey Coondamar Formation Nullagine Group Nullagine Group Coondamar Formation Nullagine Group Coondamar Formation Nullagine Group Coondamar Formation Coondamar Formation Coondamar Formation Coondamar Formation Coondamar Formation w-bb w-cc w-mdq w-o e-bbo Pilbara Supergroup e-bk Pilbara Supergroup Pilbara Supergroup e-mbmk e-mbmz Pilbara Supergroup Group Kelly Pilbara Supergroup e-xmws-mlv Group Kelly Group Kelly e-bbvt Pilbara Supergroup Pilbara Supergroup Pilbara Supergroup e-o Pilbara Supergroup Group e-mu Kelly Group Kelly e-muk Group Kelly Pilbara Supergroup Group Kelly e-mapt Group Kelly Formation Wyman Group Kelly e-max Formation Wyman Formation Wyman Pilbara Supergroup e-ccb Pilbara Supergroup Pilbara Supergroup e-sl Group Kelly Pilbara Supergroup Formation Wyman e-fnv Euro Basalt Pilbara Supergroup Group Kelly Euro Basalt Euro Basalt Group Kelly Euro Basalt Pilbara Supergroup Group Kelly Euro Basalt Group Kelly Pilbara Supergroup Pilbara Supergroup Group Kelly Euro Basalt Group Kelly Euro Basalt Group Kelly Euro Basalt Group Kelly Euro Basalt Euro Basalt Euro Basalt Euro Basalt Euro Basalt Euro Basalt a-cc a-bk Pilbara Supergroup Pilbara Supergroup Group Kelly Group Kelly undivided undivided nu nu nu nu nu nu nu nu nu nu nu nu nu nu nu nu nu nu nu nu mb em em w w ke ke ke ke ke ke ke ke ke ke ke ke ke ke ke ke ke ke (continued) Appendix 2 ge m pf Granitic Complex Kurrana Granitic Complex Yilgalong Golden Eagle Orthogneiss Granitic Complex Yilgalong A A A (cc) (bk) Pilbara Supergroup wb Pilbara Supergroup wcc Pilbara Supergroup wssz Pilbara Supergroup Group Warrawoona wd Pilbara Supergroup Group Warrawoona eb Pilbara Supergroup ebk Group Warrawoona Group Warrawoona Pilbara Supergroup ebkc Group Pilbara Supergroup Warrawoona ebkz Pilbara Supergroup ebs Group Pilbara Supergroup Warrawoona ebx Formation Wyman Group Warrawoona Pilbara Supergroup Group Formation Wyman ed Warrawoona Pilbara Supergroup Group Warrawoona Formation Wyman eu Group Warrawoona Pilbara Supergroup euk Formation Wyman Pilbara Supergroup eup Group Warrawoona Euro Basalt Pilbara Supergroup Group eux Warrawoona Euro Basalt Pilbara Supergroup Euro Basalt eccw Group Warrawoona Pilbara Supergroup Euro Basalt esl Pilbara Supergroup Group Warrawoona Group efv Warrawoona Euro Basalt Pilbara Supergroup Group Warrawoona Euro Basalt Pilbara Supergroup Group Warrawoona Group Warrawoona Euro Basalt A A Euro Basalt A Euro Basalt Group Warrawoona Group Euro Basalt Warrawoona A Euro Basalt Euro Basalt A A Euro Basalt Euro Basalt A A A A A A A A A A A A A A qsl qss Pilbara Supergroup qst Pilbara Supergroup nlb Pilbara Supergroup nlbn Pilbara Supergroup ncc Group De Grey Pilbara Supergroup nsl Group De Grey Pilbara Supergroup nss Group De Grey Pilbara Supergroup nst Group De Grey Pilbara Supergroup Group De Grey nstb Pilbara Supergroup nstbc Group De Grey Pilbara Supergroup Mosquito Creek Formation nfv Pilbara Supergroup Group De Grey Mosquito Creek Formation nog Group De Grey Pilbara Supergroup Mosquito Creek Formation nb Group De Grey Pilbara Supergroup Coondamar Formation Group De Grey nba Coondamar Formation Group De Grey nbk Pilbara Supergroup Pilbara Supergroup Coondamar Formation nu Group De Grey Pilbara Supergroup Coondamar Formation nup Group De Grey Coondamar Formation nur Pilbara Supergroup Group De Grey A Pilbara Supergroup Coondamar Formation nux Group De Grey A Coondamar Formation Pilbara Supergroup Group De Grey Coondamar Formation A Pilbara Supergroup Group De Grey Coondamar Formation Group De Grey Coondamar Formation A Group De Grey A Group Coondamar Formation De Grey Coondamar Formation A Coondamar Formation A A Coondamar Formation Coondamar Formation A A Coondamar Formation A Coondamar Formation A A A A A A A A A k a a d d d d d d d d d d d d d d d d d d d d w w w w w w w w w w w w w w w w w w w w Map code Supergroup A Old Group/Complex Member Old Formation: code New Supergroup/Supersuite New Group New Member Formation: New A A A A A A A A A A A A A A A A A Ag A A A A A A A A A A A A A A A A A A A Ag Ag A A A 32 GSWA Explanatory Notes Geology of the Eastern Creek 1:100 000 sheet Appendix 3 Defi nition of stratigraphic names on EASTERN CREEK Coondamar Formation Remarks: Previously included in the Mosquito Creek Formation (Hickman, 1978). Synonymy: informally Derivation of name: Coondamar Creek in the southern part referred to as the Middle Creek Formation (Blewett et al., of EASTERN CREEK. 2002). Distribution: Southern margin of Mosquito Creek Basin, in the southwest of EASTERN CREEK and southern part of References NULLAGINE, and the northern margin of the basin, to the west and south of Eastern Creek Well on EASTERN CREEK. BAGAS, L., FARRELL, T. R., and NELSON, D. R., 2004, Age and Interpreted to underlie the 1800 km2 outcrop extent of the provenance of the Mosquito Creek Formation: Western Australia Mosquito Creek Basin. Geological Survey, Annual Review 2003–04, p. 62–70. BLEWETT, R. S., HUSTON, D. L., MERNAGH, T. P., and KAMPRAD, Type area: Southwest of Hallcomes Peak, from MGA J., 2002, The diverse structure of Archaean lode gold deposits of 250000E 7569000N to MGA 250000E 7575200N. the southwest Mosquito Creek belt, east Pilbara Craton, Western Australia: Economic Geology, v. 97, p. 787–800. Lithology: Metamorphosed and multiply deformed sandstone and siltstone (typically chloritic), with minor HICKMAN, A. H., 1978, Nullagine, W.A.: Western Australia Geological Survey, 1:250 000 Geological Series Explanatory Notes, 22p. chert, basalt, gabbro, ultramafi c rock, and felsic rock. Metamorphosed to amphibolite, chlorite–actinolite schist, McNAUGHTON, N. J., COMPSTON, W., and BARLEY, M. E., 1993, semipelitic schist, tremolite–actinolite schist, and quartz– Constraints on the age of the Warrawoona Group, eastern Pilbara muscovite schist in zones of higher metamorphic grade. Craton, Western Australia: Precambrian Research, v. 60, p. 69–98. Estimated thickness 1–2 km. NELSON, D. R., 2002a, 160220: tuffaceous rhyolite, Fieldings Gully Well, in Compilation of geochronology data, June 2005 update: Relationships: Tectonic contact with the Kurrana Western Australia Geological Survey. Terrane to the south. Tectonized contact with the Wyman NELSON, D. R., 2002b, 144681: agglomeratic rhyolite, Baroona Hill, Formation in East Pilbara Granite–Greenstone Terrane to in Compilation of geochronology data, June 2005 update: Western the north. Probable faulted unconformity with overlying Australia Geological Survey. c. 2926–2905 Ma siliciclastic rocks of the Mosquito Creek NELSON, D. R., 2005a, 178013: quartz diorite gneiss, Quartz Hill, Formation. in Compilation of geochronology data, June 2005 update: Western Australia Geological Survey. Age: Between c. 3325 and 3315 Ma, the age of the Wyman Formation (Thorpe et al., 1992; McNaughton et al., 1993; THORPE, R. A., HICKMAN, A. H., DAVIS, D. W., MORTENSEN, Nelson, 2002a,b), and c. 2926 Ma, the likely maximum J. K., and TRENDALL, A. F., 1992, U–Pb zircon geochronology age of the Mosquito Creek Formation (Bagas, et al., 2004). of Archaean felsic units in the Marble Bar region, Pilbara Craton, Western Australia: Precambrian Research, v. 56, p. 169–189. A tentative age of c. 3035 Ma (Nelson, 2005a) for a single zircon from a deformed monzogranite intrusion in the Coondamar Formation indicates the possibility of an older minimum age. 33 PILBA 7196 6096 CRATON RA 7192 Zn Au Ag Pb Sb Cu Mn Ba e.g. sin e.g. e.g. Greenstone Te Greenstone rrane BA SIN Creek HAMER SLEY BA SLEY CA NNING SIN E ast Pilbara Pilbara ast Mosquito Mosquito GraniteÊ A I L Terrane A Terrane Kurrana R Kurrana E Y V T LE 3.0¾ R U S S U A ANG L A agnetic north agnetic C I MODITY GROUPS MODITY GRID / MAGNETIC N G 10 O R MN L DIRECTOR O E G E T TIM GRIFFIN etal W E S plex GN åa ñHc åa TN etal ðcb Kilometres agnetic north is correct for correct is north agnetic oves easterly by about 0.1^ in 0.1^ about by easterly oves CE ñFj ap. M ap. EN MINERAL AND ROCK COMMODITIES ROCK AND MINERAL MINERALIZATION STYLES * STYLES MINERALIZATION d Vein and hydrothermal and Vein Base metal Base Stratabound volcanic and sedimentary sedimentary and volcanic Stratabound Precious m Precious m industry Steel Regolith hosted Regolith RID 0.8¾ ñFm ðcb G also in the DoIR MINEDEX database MINEDEX DoIR the in also q 14 years. 14 2005 and m and 2005 of the m the of are shown diagrammatically for the centre the for diagrammatically shown are True north, grid north and m and north grid north, True associated with Proterozoic intrusions Proterozoic with associated Golden Eagle Orthogneiss Bonney Downs Granite INERAL AND ROCK COM ROCK AND INERAL Dept of Land Information Dept of Land Information 89 Dept of Land Information CONVERG MINERAL OCCURRENCES Zinc...... Silver...... Manganese...... Lead...... Gold...... Antimony...... Copper...... M Commodity is gold unless otherwise indicated on the map the on indicated otherwise unless gold is Commodity Kurrana Granitoid Com Yillgalong Granitoid Complex Kurrana Granitoid Complex Hornblende monzogranite Hornblende Approximate limit of contact metamorphism contact of limit Approximate *ÝLarger symbols represent non-gold mines or deposits or mines non-gold represent symbols *ÝLarger Dept of Industry and Resources Dept of Industry and Resources Dept of Industry and Resources Dept of Industry and Resources OPERATING STATUS AND SITE IDENTIFICATION NUMBER IDENTIFICATION SITE AND STATUS OPERATING Abandoned mine Abandoned Mineral deposit Mineral Mineral occurrence or prospect or occurrence Mineral Dolerite dyke; partly subsurface partly dyke; Dolerite vein Quartz ñFm d ñgA Mineral occurrences and numbers are from the GSWA WAMIN database. WAMIN GSWA the from are numbers and occurrences Mineral ñgKge ñgKbd ìgBmh Western Australia ñFj ñFk d q 0 Geological Survey of Bridget Suite Bridget 2005 ber ñgA Fault MAY 2005 MAY 2003 MAY 2003 MAY 2003 NOV 2004 1999ÝÊÝ2005 d q ñFk 52 Septem 1 q q d q ñFm 567 ñFt q ñFhb d ñFh d ñgA 0 1 ñFhb Version 2.0 _ 2.0 Version FIRST EDITION 2004 q Kilometres d d ond SCALE 1:Ý500Ý000 ñFr ñFh ñWe d ñDq SCALE 1:100Ý000 Redm GEOSCIENCE AGREEMENT PRODUCT OF THE NATIONAL d Western Australia 2005 d ñFj d DATA DIRECTORY 5 d 4 Well 42 8 0 4 5 24 45 27 178202 d WAMIN MAY 2005 WAROX GESMAR 70 ñFk MINEDEX 34 82 GEONOMA 8 ñFm d ñFhb 50 d 4 Z Yard (abd) d ñDnog d 360 Rockhole Spring d JIM LIMERICK 05 Bore Redmond Fault d ñWe ñgA VERTICAL DATUM: AUSTRALIAN HEIGHT DATUM ñFk ñDq INTERPRETED BEDROCK GEOLOGY Fault q EASTERN CREEK UNIVERSAL TRANSVERSE MERCATOR PROJECTION d GDA94 positions are compatible within one metre of the datum WGS84 DIRECTOR GENERAL d Grid lines indicate 1000 metre interval of the Map Australia Zone 51 ñDq ñgKge d ñFh d 2 d SHEET 3054 ñDns Fault ñDnlb The Map Grid Australia (MGA) is based on the Geocentric Datum of 1994 (GDA94) d ñWe Spec ation d d HORIZONTAL DATUM: GEOCENTRIC DATUM OF AUSTRALIA 1994 d d ñFr d d d d d d d d 1 ñgKge Reference points to align maps based on the previous datum, AGD84, have been placed near map corners ñFhb d ñDnlb GEOCENTRIC DATUM OF AUSTRALIA Blue ñWe Euro Basalt Euro Jeerinah Formation Jeerinah Paterson Formation Paterson Dolomite Carawine Formation Maddina Formation Kylena Basalt Roe Mount Formation Creek Mosquito Tumbiana Formation Tumbiana Komatiitic basalt; minor chert and gabbro and chert minor basalt; Komatiitic Form Wyman Pinjian Chert Breccia Chert Pinjian q d d q Bamboo Creek Member Creek Bamboo Mica schist and amphibolite and schist Mica undivided rocks, Metasedimentary Metagabbro ñWw ñDns d ñgKbd d Department of Industry and Resources Hardey Formation Hardey Coonamar Formation Coonamar d Coondamar 0 åa ðcb d ìgBmh ñFr ñFj ñHc ñFt ñDns ñFk ñFh ñDq ñDn ñFm ñWe ñWw d ñW(bk) ñFk Structural data ThemeGeologyMineral occurrences (non-confidential) Cadastre Data SourceHorizontal control GSWA Data Currency TENGRAPH Agency MAY 2003 Dept of Industry and Resources Topographic nomenclature Topography DLI and GSWA field survey For further details, refer to main reference main to refer details, further For ñFh ñFhb ñDnlb ñDns ñDnog ñDn ñDn ìgBmh ñWe Kelly Subgroup Kelly Unassigned Metres 1000 Warrawoona Group Warrawoona Fortescue Group Fortescue De Grey Group Grey De ALAN CARPENTER, M.L.A. MINISTER FOR STATE DEVELOPMENT Mount Bruce Supergroup Bruce Mount Pilbara Supergroup Pilbara 0Ê15°...... strike-slip, showing relative horizontal displacement...... horizontal relative showing strike-slip, exposed...... unspecified...... thrust or reverse fault; triangle on upthrown side...... upthrown on triangle fault; reverse or thrust vertical...... anticline...... inclined...... syncline...... igneous layering...... igneous exposed...... concealed...... Z-vergence...... photography aerial from estimated dip and strike structure...... sedimentary bedding...... graded texture...... spinifex foliation...... of trend inclined...... inclined...... syncline; exposed, concealed...... exposed, syncline; unspecified...... inclined...... trend of bedding...... of trend inclined...... inclined...... anticline; exposed, concealed...... exposed, anticline; inclined...... pillow structure...... pillow vertical...... Crenulation cleavage, showing strike and dip and strike showing cleavage, Crenulation Strongly foliated rock...... foliated Strongly Track...... Fault Abandoned mine, deposit, or occurrence...... or deposit, mine, Abandoned Geological boundary Geological direction plunge generalized and trace surface axial showing Fold, plunge and trend showing axis, fold Small-scale dip and strike showing joint, or Fracture lineament Airphoto unsealed...... road, Formed Building...... waterhole...... with Watercourse well...... Bore, centre...... Mining Contour line, 20 metre interval...... metre 20 line, Contour Axis of crenulation, showing trend and plunge plunge and trend showing crenulation, of Axis Rockhole...... Yard...... Mineral lineation, showing trend and plunge plunge and trend showing lineation, Mineral Spring...... Horizontal control; major, minor...... major, control; Horizontal Bedding, showing strike and dip and strike showing Bedding, BeddingÊcleavage intersection lineation, showing trend and plunge plunge and trend showing lineation, intersection BeddingÊcleavage Mineral field district boundary...... district field Mineral Way-up indicator Way-up Abandoned...... Metamorphic foliation, showing strike and dip and strike showing foliation, Metamorphic Isotopic age determination site with identification number..... identification with site determination age Isotopic A A GUN 3153 3152 BLE 3154 3155 EARAN P TALAWAN WO K E EE WNS G OOK C RN CR RN 51-9 3053 3052 3054 3055 GALON YIL SF SF 51-5 SF ALFOUR DO ALFOUR MOUNT CANNING BASIN CANNING EASTE PILBARA CRATON PILBARA B NULLAGINE R BRAESIDE EK BALFOUR DOWNS BALFOUR DGA 2 GINE E 2953 295 2954 2955 ULLA Kurrana Terrane Kurrana HAMERSLEY BASIN HAMERSLEY Terrane Kurrana Basin Creek Mosquito East Pilbara GraniteÊGreenstone Terrane GraniteÊGreenstone Pilbara East N OUNT ETHEL CRE ETHEL OREENA DOWNS OREENA M N AR OCK R Y HILL Y 2853 BLE B BLE 2852 2854 2855 WARRIE RO PLIT S MAR SHEET INDEX SHEET 1:100Ý000 maps shown in black in shown maps 1:100Ý000 1:250Ý000 maps shown in brown in shown maps 1:250Ý000 53 T MARSH T 27 2752 2754 TH SHAW TH 2755 yers; EELI WOLLI EELI OR W TAMBOURAH SF 50-8 SF N MOUN SF 50-12 SF ROY HILL ROY MARBLE BAR MARBLE ORGE GINA Search for current GSWA map products online www.doir.wa.gov.au/ebookshop online products map GSWA current for Search NJINA T GE T 2653 2652 2654 2655 E SPRINGS E OD N MU W ñDnfv HIT OU W M etamorphosed ñWwd ñWed small plugs and dykes orphosed ñDnux ñDnstbc MADDINA FORMATIONS HornblendeÊquartz monzodiorite and diorite; orphosed etam orphosed and (AgKge) f etam etam hist; m hist; JEERINAH ñgd ñDnur ñWefv ñDnstb inor chert; m chert; inor A.C.T. N.S.W. LE ORTHOGNEISS LE Tas. Qld Vic. orphosed orphosed orphosed etam ñDnup ñDnst GOLDEN EAG GOLDEN ñWebx ñWesl 2755 MaÝì c. S.A. N.T. cal chert and silicified rock of uncertain origin; metamorphosed origin; uncertain of rock silicified and chert cal orphosed ñDnu CARAWINE DOLOMITE ñDnss ñWeccw ñDqst ñWebs orphosed atiitic basalt atiitic inor fine-grained sandstone; m sandstone; fine-grained inor W.A. phibolite; includes minor andalusiteÊmuscovite schist and phyllite and schist andalusiteÊmuscovite minor includes phibolite; Óoc Ôcf osed ñWebkz ñDnsl ñDnbk ñFrst ñDqss ñWeux etamorphosed phibolite orphosed layered orthogneiss derived from monzogranite, granodiorite, tonalite, and pegmatite; alternating biotite- and feldspar-rich la etam monzogranite, medium grained, sparsely porphyritic; locally muscovite bearing; strongly foliated along Coondamar Fault Ôc chert breccia, locally bedded; overlies sandstone, siltstone, and mudstone; diamictite; fluvioglacial deposits ñWeup ñDncc tuffaceous siltstone and sandstone; commonly with accretionary lapilli ñDnba thin-bedded chert, silicified shale, and mudstone; minor sandstone uscovite schist, and am and schist, uscovite Órz orphosed ñDqsl ñFrsl ñWwssz grey-brown recrystallized dolomite with minor shale and chert monly with secondary carbonates; local zones of strong carbonate alteration; m alteration; carbonate strong of zones local carbonates; secondary with monly ñWebkc orphosed siltstone and tuffaceous siltstone with reworked accretionary lapilli etam orphosed only pillowed; local pyroxene-spinifex texture and zones of carbonate alteration includes some mafic schist; metamorphosed schist; mafic some includes alteration carbonate of zones and texture pyroxene-spinifex local pillowed; only inantly serpentinized; locally porphyritic locally serpentinized; inantly salt and associated quartz-vein breccia; metamorphosed breccia; quartz-vein associated and salt quartzÊfeldspar porphyry; commonly columnar jointed, locally layered inor tholeiitic basalt; massive and pillowed; metamorphosed pillowed; and massive basalt; tholeiitic inor etasandstone; chlorite bearing; includes thin layers of amphibolite and tremoliteÊchlorite schist tremoliteÊchlorite and amphibolite of layers thin includes bearing; chlorite etasandstone; redom q undivided, includes sandstone and siltstone; minor conglomerate massive and amygdaloidal basalt includes layers and lenses of amphibolite and ultramafic schist Chert; includes silicified siltstone ATION ATION inor m inor -bedded sandstone, siltstone, and shale; commonly with graded bedding, rare cross-bedding; probable turbidite deposits; m deposits; turbidite probable cross-bedding; rare bedding, graded with commonly shale; and siltstone, sandstone, -bedded ñW(bk) Ôao ñDnb Ôwf ñFhb ñFrsc Órk ñWwcc ñDnlbn ñDqsc ñgApf ñWebk GOLDEN EAGLE ORTHOGNEISS: ñWeuk Basaltic andesite and andesite; minor basalt BONNEY DOWNS GRANITE: Kuruna Member: Komatiitic basalt Massive and amygdaloidal basaltic andesite; minor basalt and andesite; rare basaltic fragmental rock Thin-bedded limestone and calcareous shale Massive and amygdaloidal komatiitic and tholeiitic basalt; minor basaltic fragmental rock atiite, typically with relict olivine-spinifex texture olivine-spinifex relict with typically atiite, Colluvium _ partly consolidated deposits of silt, sand, and gravel; dissected assive and pillowed; includes zones of silicified rock; metamorphosed rock; silicified of zones includes pillowed; and assive Hornblende monzogranite; medium grained, undeformed; in small plutons PINJIAN CHERT BRECCIA: PATERSON FORMATION: FORMATION: PATERSON Massive to amygdaloidal basalt, and basaltic andesite CARAWINE DOLOMITE: metamorphosed weakly sills; and dykes in dolerite; coarse-grained to Fine- JEERINAH FORMATION: MADDINA FORMATION KYLENA FORMATION KURRANA GRANITOID COMPLEX TUMBIANA FORMATION: KURRANA GRANITOID COMPLEX HornblendeÊplagioclase-phyric felsic intrusive rock; variously foliated; metamorphosed oliteÊchlorite schist; includes minor am minor includes schist; oliteÊchlorite etaperidotite; typically serpentinized typically etaperidotite; Komatitic basalt, comm basalt, Komatitic m basalt; komatiitic Carbonate-altered ba komatiitic Silicified Mafic schist, slate, and strongly foliated, metamorphosed kom metamorphosed foliated, strongly and slate, schist, Mafic metamorphosed rock; fragmental Basaltic Metakom p Metaperidotite; grained coarse locally Metapyroxenite; Komatiitic basalt; m basalt; Komatiitic Amphibolite and chloriteÊactinolite schist chloriteÊactinolite and Amphibolite metagabbro with associated commonly Metapyroxenite; Trem M Basaltic-lithic sandstone, com sandstone, Basaltic-lithic ChloriteÊactinolite schist, quartzÊmuscovite schist, and amphibolite locally interleaved with with interleaved locally amphibolite and schist, quartzÊmuscovite schist, ChloriteÊactinolite Sandstone; massive or cross-bedded; includes local siltstone; metam siltstone; local includes cross-bedded; or massive Sandstone; Pebble conglomerate, and minor cobble conglomerate and sandstone; locally channelized; metamorphosed channelized; locally sandstone; and conglomerate cobble minor and conglomerate, Pebble m includes bedding; parallel thin shale; and siltstone Siliceous m cross-bedded; and marked ripple locally thickening, upwards and coarsening upwards shale; and siltstone, Sandstone, etasiltstone; m etasiltstone; Siltstone, sandstone, and minor conglomerate, typically silicified; includes lo includes silicified; typically conglomerate, minor and sandstone, Siltstone, Basalt; m Basalt; metamorphosed origin; uncertain of rock silicified and chert Grey metamorphosed dolerite; and Gabbro m basalt; komatiitic minor pillowed; generally Basalt; metam gabbro; and Dolerite m undivided; rock, Ultramafic metam chert; layered Grey-white metamorphosed chert; grey local includes weathered; typically rock, sedimentary clastic Fine-grained metamorph foliated; strongly rock; volcaniclastic Felsic Metamorphosed ultramafic rock, undivided rock, ultramafic Metamorphosed M foliated locally metadiorite; minor includes Metagabbro; Tholeiitic basalt; generally pillowed; minor massive komatiitic basalt; metam basalt; komatiitic massive minor pillowed; generally basalt; Tholeiitic Felsic volcaniclastic rock; partly silicified; includes local feldsparÊquartz porphyry; metamorphosed porphyry; feldsparÊquartz local includes silicified; partly rock; volcaniclastic Felsic Basaltic-lithic sandstone and subordinate granulestone; metamorphosed granulestone; subordinate and sandstone Basaltic-lithic Foliated sandstone and siltstone; typically chloritic; includes chloriteÊactinolite schist and phyllite; metam phyllite; and schist chloriteÊactinolite includes chloritic; typically siltstone; and sandstone Foliated Layered chert; typically ferruginous; metamorphosed ferruginous; typically chert; Layered ChloriteÊactinolite schist, quartzÊm schist, ChloriteÊactinolite Sandstone; includes local siltstone; metamorphosed siltstone; local includes Sandstone; Ferruginous sheetwash deposits; silt, sand, and ferruginous nodules in distal outwash fans; locally derived from erosion of Czr Ferruginous colluvium; unconsolidated silt, sand, and rock debris; locally derived from erosion of Czrf and weathered Lower unit; limestone and calcareous sandstone Thin- to medium to Thin- Siliceous siltstone, commonly ferruginous; includes minor sandstone and pebbly sandstone Sandstone; contains local beds with accretionary lapilli Poorly sorted, polymictic pebble and cobble conglomerate; includes sandstone and local boulder conglomerate Bamboo Creek Member: 61. d COONDAMAR FORM COONDAMAR Grey chert and silicified rock of uncertain origin; metamorphosed origin; uncertain of rock silicified and chert Grey sc mafic some includes alteration; carbonate of zones and texture pyroxene-spinifex local pillowed; commonly basalt, Komatiitic WYMAN FORMATION EURO BASALT Alluvial clay, silt, sand, and gravel in rivers, creeks, and on floodplains Overbank deposits; alluvial clay, silt, and sand on floodplains Sheetwash deposits _ clay, silt, sand, and pebbles in distal outwash fans; no defined drainage Colluvium _ unconsolidated silt, sand, and rock debris; scree and talus Biotite monzogranite and granodiorite; foliated; metamorphosed Feldspar porphyry dyke; metamorphosed Residual ferruginous duricrust; locally includes massive laterite and deeply weathered, ferruginous rock Residual calcrete; massive, nodular, and cavernous limestone Residual silcrete and siliceous duricrust; includes local secondary chert breccia OAKOVER FORMATION Dolerite and gabbro dykes; dashed where interpreted from aeromagnetic data; partly subsurface; various generations Quartz vein MOSQUITO CREEK FORMATION CREEK MOSQUITO HARDEY FORMATION: MOUNT ROE BASALT: ñFmk ñFj åa Ôw ñFt ñd ñFr ñFmbi Óc ñFh Órf Ôaa ñFm ñFmcc ðcb ñDnog ñHc ñDnlb ñFkkl ñFmbk ñgh ñWeu ñFkbi ñgAm ñWeb ñDqs ñW(cc) ñWwb ñgKge ñgKbd ñFkbk ìgBmh . ebs Ôaa Ôao ñW(cc) ñWwb ñWwssz ñWwd ñWwcc ñW(bk) ñDnst ñDnsl ñDncc ñDnlbn ñDnstbc ñDnstb ñDnlb ñDnog ñDnup ñDnu ñDnbk ñDnss ñDnfv ñDnba ñDnux ñDnur ñDnb d Ôw Ôwf Ôc Ôcf q YILGALONG GRANITOID COMPLEX ñgAm ñgApf Órf Órk Órz Óoc ñDqsc ñDqst ñDqss ñDqs ñDqsl ñFh ñFhb ñFr ñFrsc ñFrsl ñFrst ñWeb ñWebk ñWebkc ñWebkz ñW ñWebx ñWed ñWeu ñWeuk ñWeup ñWeux ñWeccw ñWesl ñWefv 2Ê69. WA 178014. WA A 178005, 178008. 178005, A A 169030. A A 178012. A A 144993. A A 168935 A nces, v. 38, p. 261Ê281. p. 38, v. nces, Kelly Subgroup Kelly Unassigned cie SW SW SW SW S esearch, v. 72, p. 247Ê2 p. 72, v. esearch, set, G set, Bridget Suite Bridget Group Hamersley De Grey Group Grey De Fortescue Group Fortescue Warrawoona Group Warrawoona Earth f dataset, G dataset, brian R brian ology dataset, GS dataset, ology eview 2003Ê04, p. 6 p. 2003Ê04, eview Mount Bruce Supergroup Bruce Mount Pilbara Supergroup Supergroup Pilbara Pilbara Supergroup Supergroup Pilbara ology ology dataset, GSW dataset, ology ology dataset, G dataset, ology ology dataset, G dataset, ology recam Journal o Journal ochron QUATERNARY PERMIAN ge 1803 MaÝâ eochron eochronology data eochronology eochron A stralian g c. WA Annual R Annual WA A A g A A geochron A A geochron A A g A SW W ., G ., . Simonson, P Simonson, . CAINOZOIC PALEOZOIC PROTEROZOIC Au 991, 2541 MaÝä 2687 MaÝå 2717 MaÝè 3292 MaÝì 2719 MaÝê 2765 MaÝå 2838 MaÝî 3178 MaÝò . M . 2926Ê2905 MaÝð PALEO- c. c. c. c. c. c. c. c. d B d t al., 1 al., t 1:100Ý000 Geological Series. an PHANEROZOIC PROTEROZOIC ARCHEAN GSW 1998, lson, elson, 2005, GSW 2005, elson, elson, 2001, GSW 2001, elson, . Jahn . . Nelson, 2002, GSW 2002, Nelson, . . Nelson, in prep in Nelson, . R. N R. R. Ne R. R. N R. . . . R. Nelson, 2004, GS 2004, Nelson, R. . . . (1) D. R D. (1) (6) D (6) (7) D. R D. (7) (8) L. Bagas et al., 2004, GS 2004, al., et Bagas L. (8) (2) B. M B. (2) (4) D. D. (4) D (9) (3) N. T. Arndt e Arndt T. N. (3) (5) D (5) Edited by G. Hall, C. Strong, and Loan Cartography by P. Backhouse, G. Wright, and B. Williams Topography from the Department of Land Information Sheet SF 51-5, 3054, with modifications from geological field survey Published by the Geological Survey of Western Australia. Digital and hard copies of this map are available from the Information Centre, Department Industry and Resources, 100 Plain Street, East Perth, WA, 6004. Phone (08) 9222 3459, Fax 3444 WebÝ www.doir.wa.gov.au EmailÝ [email protected] Plotted by the Geological Survey of Western Australia The recommended reference for this map is: FARRELL, T. R., 2005, Eastern Creek, W.A. Sheet 3054 (Version 2.0): Western Australia Geological Survey, Geology by T. R. Farrell 1999Ê2001, 2004 by: Geochronology 50' 40' Woodie Woodie Mine 36 km 36 Mine Woodie Woodie 21^30' 22^00' îì20 îì10 18 08 16 14 06 îì00 04 02 12 98 96 94 92 88 îê90 îê80 82 74 86 84 76 72 78 îê70 68 66 åa 20 ðcb Ôaa ñHc 380 18 121^00' Ôaa ñd Óc ðcb ROAD Óoc Órz Mn c 121^00' 380 Óc 6099 Ôaa Ôw Ó 340 Óoc 360 300 Ôw ñHc ñFmbi Ôc 92 Snake Hill 400 WOODIE 380 Ôc 260 ðcb ñHc Ôaa WOODIE Óoc 340 Ôcf E Ôc IN SEA LEVEL 2 km 4 km 92 ñFj LLAG U N 6097 Sunset Hill Mn Ôc D 340 ñFkbi SHEET 3054 ðcb 360 Mn Ôaa 240 46 7192 ðcb 340 Ôw 30 400 0 ñFmk ñFj ñgKge ä90 Ôc ñDnlbn ñFmbi ðcb Skull Springs West 360 Ôaa 360 360 landing ground Creek 22 ä90 ñFj M 44 Ôao 422m Ôaa 11 Órk 340 380 340 360 Órz 360 Ôw ñFm 88 d 380 Creek 360 ñgKge Ôc ñFmbi Órf ñFj ñDnlbn Óc 12 88 Ôwf 380 ñFmbi q 6096 Redmond Mn t Ôw RIVER Coondamar Fault Ôc Órf Ôaa Depo 10 340 ñDnsl q 300 86 ñFmbi Ôcf 340 ñDnss 280 Creek 86 ðcb ñDnu Terrella 24 Ôw ñDnup ðcb ñDnlbn ñDnlb 380 7196 Donkey Mn 360 10 ñDnux Ôwf Ôw ñFj 260 Órf 15 84 ñFj 360 Ôc 380 ñDnst 22 340 Ôcf 280 84 Ôw ñDnur ñDnog ñgKbd 360 340 Yard d DAVIS Boodalyerri Ôw 380 d ñFmbi ñDnur 300 ñFm 82 360 16 420 ñDnlb 340 Ôc Ôaa Ôcf 9 82 ñDnsl ñDnss ñFj ñFmbi landing ground (abd) ñFm ñDnlb 300 Órf ñgKge Ôc Órf Ôw ðcb ä80 d 360 d Ôwf ä80 d ñFm Ôw Ôaa 360 Ôc ñFmbk Órf ñFmbk 400 Ôwf Ôaa 420 320 380 Ôwf 78 ñDqs Creek 300 ñFj 360 Ôw ñFt 78 d Ôc 360 Ôwf Ôcf Redmond Fault Ôaa 380 ñDnss allin Rockhole Ôw 76 340 Billin B q ñFmbi SKULL SPRINGS ROAD SPRINGS SKULL Ballin ñDnlb 380 50' 50' q ñFkbi 360 76 360 ñDnba ñgAm 400 34 Billin ñFkbk ñDnsl q Ôwf 360 ñFkkl Ôaa 17713 Boodalyerrie East Au Ôw ñFm 74 54 ñFkbi q 20 q 28 ñgKge ñDqs 42 380 ñFkbi 400 10 ñFkkl ñDnba q 74 q 380 q Ôc q ñFmbk ñFmbi Ôc ñFkbi 360 3 17712 Rockland Au 380 320 q q q 72 q Blue Spec Fault q q q q 45 d ñFkbk 420 72 q d ñFkkl q 420 14 17711 Bateman and Whites Reward Au,Ag 42 d d ñDnsl ñFkkl q 400 ñFt Cooke Creek Cooke q d d 400 d d d d 15 d 380 ä70 360 q q ñFkkl d ñFrsl MOUNT HAYS reek C q d 320 d ñgAm ñDnlb ä70 Cooke Creek Cooke 36 ñFkbi 0 7645 Golden Granite Au q Hays Creek 38 d 420 ñDnsl q 15 10 Ôc 52 Creek ñFhb 400 ñFt q q 68 ñFkbk 17714 Granite Proprietary Au 400 ñDqs ñDnss d 20 80 3 ñDnsl q ñWebk Little ñDnba ñgKge q Hays Spring ñFh q 68 ñFhb 48 9 d d 25 q Redmond ñFrsc d ñFm ñDnlb 300 q d d 9 340 q 440 55 ñDnsl 66 10 q ñFh 440 ñFkbi d ñDnba 80 18 d q q Ôc q DIAGRAMMATIC SECTIONS 420 66 8 ñFr d 24 Órf q 12 0 42 Ôc 45 Ôcf 420 52 12 10 d ñFkkl 320 8 420 ñW(cc) Órf 22 ñFkkl ñFkkl d 64 ñWebk landing ground d d ñDqsl ñFh 8 10 ñDnss d 12 ñFmbi 6 84 85 ñWeup Órf ñFkkl q ñFkbk 64 Au ñFkbk d 88 20 d 48 86 10864 6 420 70 ñWebk ñDqs ñFkkl 87 Ôcf 26 d d 26 400 ñW(cc) landing ground 460 ñDnss ñFh d 84 d ñFh d 76 Eastern Creek Eastern ñFj 460 Eastern Creek 12 ñFkkl 85 48 ñFkbi 5 ñDqs 62 Au 360 Creek 76 62 ñFrsl 70 ñW(cc) 17715 ñW(cc) ñW(bk) Órf Ôaa 76 15 ñFmbk Adele East 87 400 69 MARBLE BAR DISTRICT d ñDnstbc ñFkkl 62 64 ñFmcc 85 Ôc 84 82 Yilgalong ñDnog d ñDqs ñFm ñW(cc) 14 ñDqss 83 74 52 65 ñFh ñFkkl 82 d ñFkkl 77 NULLAGINE DISTRICT ñFt 82 Ôc d Ôaa 80 ñFrsc Creek 68 6767 78 Adele d Au ñDqsl 52 ñW(cc) 74 ñFrst PILBARA MINERAL FIELD 82 d ñFkkl ñW(cc) q d d ñFhb 69 14 ä60 d 88 ell (abd) 460 Ôaa 40 420 35 W q ñFkbk ñW(cc) Bore (abd) 78 ñFkbi ñW(cc) Órf ñgAm ñFkbk d d ñFhb d 72 80 ñFrsl d 77 400 ñDqsl 78 d 44 d ä60 400 q 38 d 420 ñFmbk 82 ROAD Órf d River Creek 78 ñFj 85 d 4614 Coondamar Creek Mogul Cu,Pb,Zn,Ag 5828 Coondamar Creek CEC Cu,Pb,Zn ñDnstb d d ñWwcc ñFkkl 76 70 q Little d d 14 q 13 ñDqst ñWebk d 5829 Coondamar Creek Grit Cu q 72 77 34 Ôcf 84 ñFkkl d ñFt Órf 40' 12 40' 76 Ôc ñFkkl d Coondamar ñDqsc ñDqst 5830 Coondamar Horse Creek Cu,Pb,Zn,Ag,Au 50 q ñDqs 58 320 d d d 87 76 landing ground ñDnss 380 q 400 q ñFrst ñWwssz Ôw 85 ñDnsl Ôaa q Ôw 380 72 ñFt ñFkkl 380 34 ñFt ñWwssz GEOLOGICAL SURVEY OF WESTERN AUSTRALIA 460 m 76 10 340 87 q ñWwcc 4 30 15 85 60 88 ñFkkl q 380 q Órf ñFrsl 58 q ñDnu q ñDnss 178202 60 18 ñWeup d Órf d 20 22 10 ñDnog Órf ñWwcc 40 7 HALLCOMES PEAK ñDnur 22 ñFt d 12 7 q q d 82 78 81 65 30 82 Z 68 38 85 d d 30 72 q ñFkkl 20 ñDnss 0 380 10830 Eastern Creek 3 Au 420 40 60 400 ñDnlbn 82 Au ñDnss 380 68 420 ñFkbi d 81 56 ñDnur 30 10844 40 ñDnss q 70 q 72 80 70 85 6 d q 83 Au 10839 Eastern Creek 5 q ñDnlbn c 25 q 2 D 28 68 ñDnfv 70 q Ó 2 76 d d q 68 46 d 78 Órf q q q q 42 38 q 80 d d ñDnog ñDnss 56 Eastern Creek 9 q q 78 q 70 ñDnur d ñDqsc ñFkbi 40 14 ñFkkl q 48 q Z 78 44 ñFkbk ñDnst d ñFh d 70 q q MOUNT OLIVE ñDqsc ñDnlbn BC q d 34 8 d 30 80 50 30 ell q q 77 q q ñDnfv reek W 76 54 16 82 d d 83 12 81 ñgAm SPRINGS 4440 q Creek 5704 ñDnog 78 4406 34 50 54 q 73 ñDnux ñDnu 17 58 4405 ñDnss q ñgAm d Nellie q 80 q 82 35 Eastern C ñDnss ñDnsl ñDqsc 340 ñFhb q 64 q ñDnsl ñFkbk 70 d d 18 d 178010 22 4404 12 d ñgAm ñFhb 4434 58 d 48 q 360 420 ñWeccw 85 54 q 88 22 d ñWeu EASTERN CREEK q 440 82 14 4403 ñWebs ñgAm 40 75 29 87 ñDnlbn 4414 Au 10831 Eastern Creek 4 ñFrsc 420 16 ñDqsl 65 B q d 79 32 78 60 d 42 ñDqsc 80 28 360 10 q 4407 q ñW(cc) 74 ñWebs 5701 420 72 74 5699 ñDnog q 30 5700 Au ñgAm ñgAm ñDnog d ñFr ñDnss 85 82 ñDqst q ñDqsc d d ñWebs 76 86 52 20 32 4401 WALSH PEAK 5703 ñWeccw ñDnsl 36 ñWeux ñWebk 83 q SKULL SKULL 69 60 ell (abd) d q ñDnsl 80 ñDnux 360 d ñgKge q 320 24 W q 67 ñDqsl 80 400 64 83 76 178007 4400 82 q ñWed 84 ñWebs ñWeccw Z ñDnog ñDqsc d d ñDqst ñWwcc Creek 22 20 q 52 ñgApf 80 ñWeccw d 400 ñWed 74 d q ñWwcc 32 ñDnss 87 ñWeccw q 70 ñWeccw 70 d 80 68 d 85 71 5824 Elsie Abd South Au d ñWeuk ñWwssz 26 88 ñDnba ñWeccw d ñWeccw 76 ñDnog 4 44 78 d 54 21 ñWeup ñWeccw 440 62 ñWebs q 10846 q 78 q Au 4458 ell ñWesl 36 d 5718 42 5712 ñWeccw 340 d W 82 Cooke ñWeccw 50 q d 76 d 78 71 72 44 10 ñWeccw ñDqsc ñWeccw 84 q d 49 12815 d Z ñWeup 460 42 ñDqsc 88 52 ñDnss 75 ñWeux ñWebkz ñWeccw 88 ä50 ñDqsc ñWesl Au ñDnstbc 10 ñWesl 28 q 78 Au ñWwcc 178008 20 38 12 80 75 74 ñWeccw d d 32 20 Óc 12620 22 30 ñDnup ñWebkz 440 61 d 28 32 10843 80 q C d ñWeccw d 44 Au 78 35 30 5717 d 80 Ôc ñgApf q 75 2 12621 5825 4457 82 q 82 ñDqs 85 502 m 10842 Eastern Creek 7 14 ñWed ELSIE 380 q 86 65 d ñWeccw d ä50 72 78 Elsie Creek Elsie ñWeccw ñWebkz d ñWeu 8 q 28 ñWed d 87 76 ñDqsc ñWeccw 82 ñWwcc ñWeccw ñWebk ñWeu 80 ñDnog Ôc 80 80 Eastern Ck Eastern 74 Eastern Creek 8 ñDqs 25 q d 23 ell (abd) 46 60 q d 380 82 q 74 12 ñWeccw ñDnlb 74 d 83 35 ñWeup 66 70 55 ñDqsc ñWwb ñWed ñWeup ñDnsl d Ôc q Óc ñWebs 82 78 ñWeccw 50 82 d ñDnstbc 62 MOUNT ELSIE ñWesl 30 q q 460 ñWed 82 44 6 d ñWed 24 ñWeccw 65 Steel W ñDqst ñWeccw Creek 54 86 ñWebs ñDnog 10 Au 0 q 75 74 80 ñWwcc 32 ñWeccw 48 86 ñWeccw 80 10600 q ñWwssz 70 48 d ñWeup ñWwcc 65 40 78 56 ñWeccw ñDqsl 78 q 35 q ñWwcc Elsie ñDnstb 12 ñWeccw 10602 Eastern Creek 2 Au 38 ñWwcc ñWeccw Ôw Au 10845 Eastern Creek 10 ñWeccw ñWesl 52 76 q Creek 73 ñgh 85 72 ñWeccw 78 ñWeccw 340 78 ñWeccw 17019 340 Meentheena lead Pb 64 34 75 ñWebx 35 Ôc 10841 Eastern Creek 6 Au ñWebx d ñWesl 25 80 400 60 ñgd 33 88 Eastern Creek 1 d 32 d ñDqsc 80 60 48 380 70 ñDnss 80 76 82 ñWebx ñWeccw 48 ñDnog 62 ñWesl 20 d 76 ñDnss ñWed 44 d ìgBmh 73 87 ñDqss 34 q ñWebs ñDnba ñWeccw ñDqst ñWeccw 12 ñWed ñWwssz 420 53 84 d ñgKbd landing ground ñWeccw Ôc ñWeccw 80 ñgh 70 56 84 88 30 ñWwcc 55 ñWwcc 76 q ñWwcc 12830 Trio MH Au q ñWesl ñWesl ñDqsl 440 82 d 16 380 82 ñDnstbc 84 26 72 87 ñWeccw 83 Windywindina 45 ñDqst d ñDnup q 75 ñWeccw d 440 74 88 ñWeccw ñWeccw ñDnstbc 46 12 ñWeccw 50 60 q ñWwssz ñWeccw 178005 52 q ñgd 58 ñgh ñWebs 360 d 80 70 ñDqs 28 77 ñWebk q ñFh ñWwcc 73 ñDnss 84 ñDnba 70 72 48 ñWebx ñWesl 42 30 48 ñDnlb 36 q 25 ñFr 80 ñDqsl 18 80 46 d ñWesl 50 ñWwssz 50 18 80 460 ñDnsl d 76 q d ñWebs ñgh ñWed 400 ñDnba ñWeccw 5276 87 Woods Creek 60 Au 64 70 340 q ñWebkc 8 d d ñDnss ñFr 13 d 53 24 ñFkbi 6 48 80 64 45 ñW(cc) 50 84 ñWwcc ñFhb ìgBmh Ôc 48 ñDnsl d 80 52 10 80 28 22 440 4 ñFhb ñWebk ñWwcc 16 ñWwb 70 84 84 80 70 ñWeccw 86 ñDnog ñWebk 85 d 20 ñWwcc 72 ñWwb 2 76 76 ñWeccw 400 q 44 11 85 82 10 75 77 ñWefv ñDnog Creek ñDnba ñDnba 52 ñFh q ñDqsc ñFr 78 70 80 d 70 77 Ôc 70 d d 70 460 ñFh d ñWeccw 36 360 d 420 56 ñWefv 420 ñDqsc 83 Óc 60 60 74 83 45 70 ñFkbi 82 44 28 ñDqsc 70 77 74 Coondoon ñWebk 82 ñWeccw d ñFr ñDqsc 68 ñWwd 77 13 75 ñDnba ñFkbi khole 52 70 ñWeccw 70 80 50 ñWeb 53 360 ìgBmh ñDnup ñWwssz ñWwcc ñDqsc 300 54 Hanns Roc A q 64 87 ñDnlb q 4376 Reward ñWwd 42 landing ground 10 F 626 40 50 76 80 ñDnba ìgBmh 25 480 84 q 70 87 ñWwssz 82 80 85 332 m 42 80 ñWefv 78 q 70 86 NM ñDncc 12420 Bannockburn Au ñWwssz Ôw 69 340 84 ñWeccw ñDqsc 2 km 4 km ñW(cc) 38 d ñW(cc) q 72 75 ñDnst 75 85 Au,Sb ñDnba 76 78 ñWwcc ñW(cc) 75 ñW(cc) ñWwssz d ñDnog d ä42 8 67 85 q ñWwcc 87 ñDncc ñDqsl d ñDqsl 460 ñDnst ñDnog Au 5695 54 ñWed 4377 7 ñW(cc) 88 SEA LEVEL ñWwd 22 460 ìgBmh 4381 ñDnb d 78 32 Ôc ñDncc 360 ìgBmh 70 80 ñWebk 70 ñW(cc) ñDnlb ñDnbk ñDnss ñW(cc) ñW(cc) Ôaa ñWeb 78 86 ñW(bk) ñWwcc d MOSQUITO CREEK ñW(cc) ñDqsc ñWeccw 5694 Ôaa 4380 ä42ôôôÜE Parnell MH Au,Sb ñWwd A ñW(cc) îê66ôôôÜN 68 74 72 84 82 88 78 86 76 94 92 04 02 96 98 08 12 06 16 14 18 120^30' îê70 îê80 îê90 120^30' îì00 AUSTRALIA 1Ý:Ý100Ý000 GEOLOGICAL SERIES îì10 îì20 Nullagine 33 km 33 Nullagine 50' 21^30' 22^00' 40' 04 Oct 2005 15:56:33 T:\CAMP\Projects\Current\Eastern_Creek\P3054-gda.dgn FARRELL The EASTERN C REEK 1:100 000 sheet in the eastern part of the Archean Pilbara Craton covers an area straddling the boundary between the granite– greenstone basement and the unconformablyoverlying volcano-sedimentary Hamersley Basin. T he granite – greenstone basement contains deformed and metamorphosed greenstones and granites of the East Pilbara Granite– Greenstone Terrane, metamorphosed mafic, ultramafic, felsic, and sedimentary rocks of the Mosquito Creek Basin, and granites and gneisses of the Kurrana Terrane.T he Hamersley Basin consists mainly of basalt, basaltic andesite, tuffaceous sedimentary, and felsic volcanic rocksof the Fortescue Group, and dolomitic rocks of the Hamersley Group. Gold is deposited in late shear zones along the margin of the Yilgalong Granitic Complex, in greenstones near Mount Elsie, and in metasedimentary rocks of the Mosquito Creek Basin. Base metal mineralization (copper– lead –iszinc) near the base of the Mosquito Creek Basin in the volcano-sedimentary Coondamar Formation. A chert breccia developed over intensely weathered dolomitic rocks of the Hamersley Group contains supergene manganese mineralization. Geology of the Eastern Creek 1:100 000 sheet These Explanatory Notes are published in digital format (PDF) and are available online at: www.doir.wa.gov.au/gswa/onlinepublications. 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 are available from: 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/onlinepublications