GEOLOGICAL SURVEY OF WESTERN AUSTRALIA
RECORD
I TITLE: EXPLANATORY NOTES ON THE ARCHAEAN ROCKS OF TH$ PERTH
1:250 000 GEOLOGICAL SHEET, WESTERN AUSTRALIA
by S. A. Wilde
Record No. 1974/15
CONTENTS Page GENERAL 1 GEOMORPHOLOGY 1 u CLIMATE 2
VEGETATION 2 PREVIOUS INVESTIGATIONS 2
PRECAMBRIAN ROCKS 3 REGIONAL SETTING 3 THE LAYERED SEQUENCES 4
THE JIMPERDSNG METAMORPHIC BELT 5 Gneisses 5 Schlsts 6 Other Rock Units 6
THE CHITTERING METAMORPHIC BELT 10
Gneis s e 6 10 Schists 11 Other Rock Units 12 M IGMAT ITE 12 GRANITIC ROCKS 14 DIORITIC AND SYENITIC ROCKS 17 MINOR INTRUSIVES 19 GRANITIC DYKES AND VEINS 19 DIORTTIC DYKES 19
DOLERITIC DYKES 19
QUARTZ DYKES AND VEINS 20
METAMORPWXSM 21 RELATIONS BETWEEN THE JIMPERDING AND CHITTERING METAMORPHIC BELTS 22
CAINOZOIC ROCKS 23 ii
GENERAL 23 TIERTIARYAND UNASSIGNED UNITS 24 QUATERNARY UNITS 5
STRUCTURE 26 FOLDING 26
FAULTING 29
ECONOMIC GEOLOGY 39
METALLIC MINERAjLS 31
GOLD 31
TUNGSTEN 3r MOLYBDENUM 31 IRON 32 VANADIUM 32 BAUXfiTE 32 . RUTILE 33 INDUSTRIAL ROCKS AND MINERALS 33
VERMICULITE 33 ASBESTOS 33 TALC 33
KYANITE AND SILLTMANITE 33 CtAY 34
KAOLIY 34 BUILDING STONE 35 AGGREGATF, BALLAST AND ROAD METAL 35
SAND 35 * WATER SUPPLIES 35
SURFACE WATER 35 GROUNDWATER 36 REFERENCES AND SELECTED BIBLIOGRAPHY 37
26th June, 1974. FIGURES
1, Structural Map of the Perth Sheet, shoving isograds (144
2. Cainozoic Rock Unit Relationships, East of the Darling
Scarp (14420)
3, Structural Interpretation of the Toodyay Area (14421)
PLATE
Perth 1:250 000 GeQlogical Sheet (PreliminBry Edition) GENERAE
of the Darling Fault, i,e,
ate3.y east of longitude 116°00'E. The geology of t
erth Basin are to the west of the Darling Fault has been previously described by Low (1971). The eastern portion of the sheet area, falls within the "Wheat Belt" natural region of Clqrke (1926) and is lar cleared for agriculture, The main town of Northam Ls linke bitumen roads to Perth and the other population centres at Pork, Toodyay, Bolgart, Calingiri and Goomalling. These, and other smaller settlements, are interconnected by numerous sealed and unsealed roads. The population in the western area is concentrated
along the main highways and in the Kalamunda area, an eastern suburb of the State capital, Perth, which is situated on the
coastal plain, 15 km to the west. The geological mapping was carried out during 1972
and 1973. 5h petrographic work was done by 3.D. Lewis and
Most of the sheet area falls within the Swanland Division of Yutson(1-950). It forms part of the Darling Plateau and has an average elevation of about 300 m. It is separated from the Swan Coastal Plain by the Darling Scarp (Saint-Smit 1912). The Darling Plateau represents an ancient erosion
surface that has been diss by streams that vary from youthful to mature. The principal river systems gre the Moore
and the Swan-Avon, 2
The northeast corner of the Sheet area, forms part of Jutson's Salinaland, with intermittent and internal drain- age toward a system of salt lakes.
CLIMATE
The Perth area has a dry-sunlmer subtropical
(Mediterranean) climate with an annual rainfall of about 890 mm. Most of the rain falls during the cooler winter months of May to September; the summer months of December to March ere hot and dry, whilst November and April are warm and changeable (Gentilli, 1969). Rainfall decreases rapidly east from the Darling Scarp, The annual rainfalls at Northam and Meckering are 434 mm and 384 mrn respectlvely.
VEGETATION
Rainfall and geology exert a strong control on the vegetation. The sclerophyllous forest of jarrah (Eucalyptus prginata) is characteristically developed on the laterite of the Darling Range (Gardner, 1944). Smaller associated trees and an undergrowth of sclerophyllous shrubs are also present. More sandy areas have prominent marri (E, calophylla). On the granitic and clayey soils of the Darling Range, wandoo (&. redunca var, elata) occurs, but is subordinate. East of the 385 mm isohyet it becomes dominant and, with its associates E. foecunda var, loxephleba and Acacia acuminata, formg an open, temperate savannah woodland, Ralophytic forms occur in Salinaland in the extreme northeast portion of the sheet. Species of Atriplex, Bassia and Kochia are most abundant (Gardner, 1944).
PREVIOUS XNVESTIGATIONS
There are numerous reports pertaining to the Archaean geology of the Perth Sheet, the most important; of which are 3
listed in the references, Most of the early accounts
to mineral occurrences and no eneral mapping was done
eo that of Fletcher and Bobson (11932) in t hider (1934 and 1944) mapped a sequence of m tamorphic roc in the Toodyay district; these rocks forming part of the Jimperding "Series" of Clarke (1930). Another metamorphic sequence in the lower Chittering Valley was described by Miles (1938) and name# the Chittering "Series". Zlater mapping by successive generations of university students under the direc- u tion of Professor R. T, Prider has extended the limit of both "Series", though mapped areas are small and rarely adjacent,
Simpson (1948, 1951 and 1952) gives details of mSneraL occurrences and some comments on the local geology, Lewis (1970) mapped the eastern portion of the Perth Sheet around Meckering. Preliminary Bouguer anomaly and total magnetic inten-
sity maps are available from the Bureau of Mineral Resources.
PRECAMBRIAN ROCKS
REGXONAL SETTING
area east of the Darling Fault Eorms part of the
lock. This rchaean nucleus, compo
granites an s en~lo~ing number of elongate ''
lts. The "greenstone" belts of the Eastern Goldfields region
consist of layered suc~e~sionsof felsic, mafic and
igneous rocks with varying, though minor, amounts of sedimentary material and are mainly of low mecamorphic grade. In aontrask,
the sequences exposed on the Perth Sheet are notable for the
complete lack of felsdc voZeanic rocks, tho subordinate amao
of mafic volcanic rocks and the high grade of regional mets-
~~~p~~sme The rocks occur in two distinct metamorphic belts
that extend northward on to the Moora 1:250 000 Sheet. 4
The more extensive eastern belt streec
northwest direction right across the Sheet extends beyond the Sheet area to the south and e rocks are essentially similar to those of the Jimperding
I1 Series", described by Prider (1934 and 1944) from the Toodyay area, and are grouped here as the Jimperding Metamorphic Belt.
The western belt occurs immediately east Qf the Darling Fault and extends from Upper Swan northward beyond Mogumber. This belt of rocks (the Chittering "Series" of Miles, 1938) is here referred to as the Chittering Metamorphic Belt.
These two belts are everywhere separated by granite or gneissic granite; the latter occurring north of Chittering.
The granitic rocks in the southwesteof the Sheet area are extensive and have only local developments of migmatite at their margins. 3n contrast, the granites occurring in the east and northeast portions of the Sheet area are less contin- uous and intimately admixed with broad zones of migmatite.
An age of 3 084 2 191 m.y. has been obtained by pooling certain gneisses of the Yilgarn Block, including samples from the Toodyay and Northam areas (Arriens, 1971). 4- A gneissic sample from the Pork area gave an age of 2 688 -
211 m.y. A pooled age of 2 661 $^ 51 m.y. was obtained from the granites of the "Wheat Belt" that intrude these gneisses -k (giving an isochron of 2 667 - 27 m,y. if further pooled with granites from the Eastern Goldfields).
THE LAYERED SEQUENCES
A wide range of lithologies are present in the Lay- ered sequences, The predominant rock types are granitic gneisses and schists, with locally abundant amphibplitcs and quartzites, together with thin units of ofher varieties of gneiss, banded iron formation (BIF) and mafic granulite.
Intrusive ultramafic rocks occur locally in the sequence,
Many of these have been deformed and they only occasionally transgress other rock boundaries.
6
The porphyri teneiss (Ang) is a co grained qua~tz-microcline-oligoclase-biotite(-ho~nblende) gneiss, It differs from the augen gneiss in containing ta megacrysts of picrocline and in having a less distinct biotite foliation. The rock approaches porphyritic granite in ap ance, but always retains a gneissic foliation. Its proximity
ranite and migmatite suggests that it was a gneiss that underwent metasomatism during emplacement of the granite.
Schists
Outcrop of the schist bands is poor and the rocks are usually overlain by a thick mantle of soil. Where exposedp they are mostly ferruginous or kaolinized. Quart?-mica schist
(Alb) is the predominant type, with biotite nprmally in excess of muscovite. Zt may be interbanded with guartz-mica-garnet schist (Alg~), though the latter also forms more extensive areas. The schist band extending from Jimperding Hill to
Clackline is andalusite.bearin&. (Ala) in the north; apparently devoid of alumino-silicates in the central portions, and
at Clackline. Many schist bands contain alumino-silicate minerals, but only those with abundant concentrations are distinguished on the map,
The See to have beep derived from other types by retrograde metamor- phism. At Smith's Mill Hill, large sericite flakes appear to have replaced original andalusite crystals,
wolite (Aa)".- occurs as thin, discrete bands within the gneissic scquerice and as broader u~jts intcr?anded with leucocratie quartzo-feldspathic gneiss, Typically, a: amphibolites are fine to medium grained and are composed of a xenomorphic grnnul :IT ncnrrcrate of horn51 ~ndrand nla~ioclnse
(andes-iric lIn'-radorite). 1E;'rtz ts narmally very miror, but ranges to 15 per cent in certain UlllfES, c 7
generally an accessory constituent, but may be locally almost as abundant as hornblende, Some bands contain cummingtonite and not hornblende. The broad amphibolite band, 6 km west of York, is chiefly a brown hornblende-diopside-labradorite gneissp and similar assemblages occur in the amphibolite units at Bolgart. Some thin bands consist almost entirely of hornblende and are thus hornblendites. In these, occasional cores of clinopyroxene appear to have altered piecemeal to hornblende,
Quartzite (Aqo) occurs in massive to flaggy bands that mostly form areas of high relief, owing to their resist- ance to erosion. They are metamorphosed orthoquartzites, consisting of interlocking grains of quartz with only minor amounts of muscovite, chyome-muscovite, feldspar, silli- manite or garnet. The green chrome-muscov$.te is characteris- tic, though variable in amount, Xt is most abundant in f3aggy units where it coats the foliation surfaces. The foliafion probably corresponds with original bedding, but it has certainly been emphasized during later structural deformation. A line- ation is common on the foliation planes,
Thin uaits of metamorphosed banded iron formation (BIF) are present throughout the sequence and are especially abundant east of Northam. The units are generally less than 30 m thick, and form good marker horizons. They may have local topographic expression, but in many places form only trains of rubble, The BIF is usually associated with map units An1 and Aqo, or with schist adjacent to quartzite,
Intense minor folding is a characteristic feature of the bands.
The banded magnetite-bearing quartzite (Aiq) is somewhat transitional to the metamorphosed orthoquartzite
(Aqo) but has centimetre-scale banding caused by concentra- tions of magnetite,
The unassigned BIF (Ai) includes the commoner assem- blages of quartz-magnetite-grunerite, quartz-hematite-grunerite and quartz-magnetite-hypersthene-grunerite as well as units e t r tJ g r a p h i -ally examined, Quartzose
erndrat wath a ale-rich and magnetite-rich bands, near ail’ooroloo indicate that the
inally much mor spread.
ongly magnetic BIFs occurs
east of ~~~~~~~~ Thes tite-hypersthene rocks
(@) are me iurn to eaarse grained and are not always well banded a
crops out; 20 km east of Mogumber. I ansists of an assemblage of quartz-ga nde-magnetite, It has
are a rather diverse group of rocks interban ed in the gneissic sequence, Some are well banded and appear similar to $IF, They differ from Aig in having con^^^^^^^^^ 1. nd quartz. Typical side-brown hornblende-
te and quartz), and hypersthene-garnet-
ocks of this type crop out
cdne~stof diopside-brown hornblende e-diopside-brown horn- They have affinities with re not usually banded.
re ~~~~~~ana~lypresent, as in the unit L krn common, The assembla
rid hypersthene-brown
el QCGUP in ~~~~~~~~~~nwith basic granulites rum, 1970). In a road
e-brown hornblende e,hypersthene-diopside- tite)assemblages, 9
These racks are well banded and occur in a sequence of amphi- bolites. At 2 km west-northwest o€ Grass Valley, a thin band of hypersthene-quartz rock occurs. Quartz is not abundant a the rock is essentially hyp~~stheni~e,though related to granulites. Ultramafic rocks (Au) are intrusive into the gneisqic sequence but are generally subconcordant and form part of the layered succession, They are generally foliated and thus pre- date the final deformation. No subdivision has been attempted on the map, owing to their variable mineralogy. The rocks are altered and occur chiefly as serpentinite and talcose rocks, and as serpentine-talc, serpentine-tremolite, tremolite- actinolite and tremolite-chlorite assemblages. Locally, silicified ultramafic rocks have developed, for example, at Mount Bakewell, A fresher peridotite occurs at Nunyle, 6 km east of Toodyay. Xt is mainly a bronzite peridotite with minor hornblende bronzitite, serpentinite and associated rhodingite (Elkington, 1963). In contrast, study of the margins o€ the talcose ultramafic, 9 km south-southwest of Bolgart, reveals that the original rock was a clinopyroxenite. Both peridotites and pyroxenites were therefore present in the Jimgerding Metamorphic Belt.
Thin units of cordierite-bearing gneiss (Ci) within the gneissic sequence are not extensive and are shown as mineral occurrences on the map. These include cordierite- anthophyllite, cordierite-quartz-biotite, cordierite-quartz- garnet-sillimanite-biotite and cordierite-hypersthene-quartz- biotite assemblages. Most of the cordierite-bear in6 rocks appear to be paragncisses, though Prj der (1940) suggests that the cordierite-anthophyllite racks near Noondeening Hill resulted from the intrusion of a hypersrhenite magma,
Small areas of calc-silicate Tock (Cs) occur in the layered succession and are similarly shown as mineral occur- rences on the map, These rocks comprise assemblages of
BiQgside-grossular-epidote-qu~r~~~ 10
There are also minor developments of many rock types, especially amphibolite, that are too small to indicate on the map.
THE CHITTERING METAMORPHIC BELT
A series of metamorphic rocks extends due north from
Bullsbrook East €or about 75 km to the northern limit of the
Perth Sheet, The average width of the belt is 10 km. The rocks have a northerly regional strike and dip steeply to east or west. The sequence consists of various gneisses and interbanded schists.
Gneisse s
The chief rock type is banded quartz-feldspar-biotite gneiss (Anb), essentially similar to the type occurring in the
Jimperding Metamorphic Belt. The biotite-rich layers are often extensive and increase in width toward interbanded schist units,
Two well marked bands of auaen gneiss (Ana) are present. They contain microcline megacrysts and ‘are petro- graphically similar to those described previously (p. 5 ).
The texture appears to be the result of cataclasis. This is also suggested by the fact that the southern unit is along the northern extension of the Swan Gorge mylonite zone (p.29), whilst the unit at Mogumber and Wannamal is associated with thin mylonite bands and is near a cataclastically-deformed granite (p.17).
Ln the northern part of: the belt, an interbanded sequence of melanocratic plagioclase gneiss and leucocratic quartz-feldsp-ar gneiss
(&) forms the most westerly unit of the metamorphic belt,
The melanocratic gneiss contains olive-brown biotite and dark green ferrohastingsite, T;t ranges to an amphibolite that consists entirely of a xenomorphic-granular aggregate of amphibole and plagioclase. The Leucocratic gneiss consists
Of Dotash feldnnar ntnoinrln~.nnnrf n.ro~t.., +..:&I.. ‘~d-~da- ra
netite, Zones f cataclasis, resulting in mylon~~ and blastomylonite, occur thro hout the sequence an
o increase n rthward to Mo umber. The eastern cont
Ana is sharp.
A thin band of melanocratic guartz-feldspar- hornblende-biotite gneiss and schist (And) occurs in the eastern part of the belt from Wannamal south to Bindoon, The gneissic bands contain megacrysts of microcline, oligoclase and biotite in a fine-grained matrix of quartz, feldspar, biotite and hornblende, The schists are richer in biotite and iack megacrysts.
There is an extensive development of quartz-feldspar- biotite granofels (Anf) in the Chittering area. The rock is a fine to medium-grained, blue, melanocratic gneiss that is poorly banded, but has a strong biotite lineation, It con- sists of a granoblastic aggregate of quartz, microcline and oligoclase with minor biotite. The relative proportions of microcline and oligoclase vary considerably. Biotite nor- mally forms individual crystals but may occur as cuspate wisps or, more rarelyS as distinct layers. The granofels is locally interbanded with thin units of Anb,
Schists
Numerous thin units of schist are intercalated with the gneisses. Many are discontinuous, partly as a result of poor outcrop and partly because of their lensoid form. Several more extensive bands crop out south of Bindoon, The rocks are chiefly e The relative amount o biotite and muscovite varies, whilst the biotite is co~m~~~y altered to chlorite, Interbanded units of Anb are ~ommo~~
The schist band 4 km east of Mo umber passes northward into a more gneissose rock with di continuous micaceous wisps defining a strong lineation. 12
and sillimanite schist (Als) respective
e schist (Aln) occurs 1 km east of
ere is a smaller outcrop (shown as
a mineral occurrence) at Lower Chittering.
Other Rock Units
is not abundant, bein to two main bands west of Bindoon. The northern band crops out at Mooliabeenee Hill where medium-grained hornblende- plagioclase amphibolite is interbanded with leucocratic quartz- feldspar gneiss, The southern unit is exposed in a roadway,
2 km further southwest where amphibolite, containing long needles of hornblende, occurs with buff, quartz-feldspar
ranofels and hornblende-~~arin~gneiss.
In the Chitterin Valley, shearing of the mar certain dolerite dykes has produced amphibolite (Mon
Quartzites have be recorded fro the Chitteri
hic Belt (G Jones, 1950
in megascopic app of the granofels (An€) sequence. However, th that feldspar is generally as abundant as quartz, Met orthoquartzite similar to that occurrirn in the Toodya has not been recorded.
The term ~ig~a~~teis used here to describe rocks intimately admixed with a granitic ~omponent~T granite may occur as veins subparallel to the foliation or more extensive aieas that cut irre ar$y across the gneis ra~iti~com
material has formed -in situ and appears to have developed first at the hinges of minor folds.
Migmatite (Am) occurs as a narrow, sporadically developed marginal zone to the granitic rocks in the southern part of the Perth Sheet. It also occurs within the granite area and is particularly extensive around Wooroloo and near the Darling Scarp, where it forms a number of subparallel north-northeast trending zones. In the northern part of the
Sheet area migmatite is more extensive and forms a broadp irregular zone between the layered succession and the granitic
rocks I
The migmatite of the Toodyay area is not directly related to intrusive granite but has resulted from mobiliza- rion of the gneisses, Migmatite and Anp are closely asso- ciated, the latter grading into migmatite with an increase in the amount of granitic neosome.
ortions of the migmatite containing abun- dant amphibole crystals, together with bands and "xenoliths" of ~mph~bo~i~eppear on the map as E, The zones near Por and Coondle are along strike extensions of amphibolite units and were probably derived from these by mobilization. The large area at CLaekli e is away from known am rences e locks of amp~ibo~iteare enc-l, granitic me ium. Discrete areas of ritic kor granite also occur within the migmat
ular to in icate separately on t to cut the rnigmatite, but were pra~~~ lower structural level. reas are associated
ve sharp or diffuse contact relations. The various t
ular areas of pegmatite are abundant and often associated with aplite. The rock has an allotriomorphic granular texture and consists of oli oclase, microcline and quartz, with mino
epidote, It is almost P
smaller plagioclase crys te is often present here,
Xenoliths of co near contacts with migmatite and the layere nowhere abundant. There may be a weak foLi y biotite and/or the felsic minerals wh i ch, c 3, o s cts, is generally subparallel to th c trend; but elsewhere is more random, Ne p, a strong shear folia- tion, defined by biotite an allels the mylonite zones (p. 30).
Grey forms a number of small irregularly shaped areas w1.thi.n the granite compl
Contacts with the ~ountr Age are generally sharp, Tabular mega ine microperthite average
1.5 cm in length and occ triomorphic granular aggregate of mierot nd quartz, with accessory biotite and ho~nb~en~e* crysts vary in abundance and are commonly aligned. T uth of Pork and at Bakers
Hill contains up to I lende. Mafic schlieren are abundant and the ho~nb~~~Probably resulted from con- tamination by am s. Thin veins and irregular areas of pegmati ~o~~~~r~ticgranite,
Near York, Ronno n Rock, vezns of fine to medium-grained a the granite, However, at
Walyormouring Lake v anite cut Age.
This suggests at leas sion for Age and/ or Agp,
Age and Agp are sharp, there are areas w s are intimately
p. Such areas of
is generally
usian, but scanty
e intrudes Agp,
(Agm) also have por- tions of Agg and an extensiv prnent of pegmatite and aplite, Gneissic xenoliths and rafts are abundant near migmatite contacts and it would appear that such areas arose from a
~omple~interaction between intrusive granite and the mlgma- titic gneisses.
Fine to medium-grained megacrysts of potash feldspar (ARP) are particularly extensive in the southern portion of the sheet area. They are areally associated with Age and Agp and appear to represent a transi- tional phase between these two varieties, The rocks are mesocratic and range from adamellite to granite. They are texturally and compositionally similar to Age except for the occurrence of microcline megacrysts. Only rarely are the megacrysts aligned and they are mostly ragged, with numerous inclusions of plagioclase, A few mafic schlieren and clotsaf biotite are present in rocks near the Avon River. The rocks grade into Agp with an increase in both size and abundance of the megacrysts, and into Age as these decline.
A large, discrete mass of foliated gneissic granite
(Agn) occurs in the Bolgart-Mogumber-Bindoon area. There is evidence of strong cataclasis, though the foliation and abun- dance of epidote shears decreases eastward. Indeed, the rock near Bolgart and Julimar Brook, although forming part of the same granitic mass, is a medium-grained granite with only a weak foliation and has been shown as Age on the map. Where least deformed, the granite consists of an allotriomorphic granular aggregate of microcline, orthoclase, albite/oligoclase and biotite, The orthoclase is perthitic and tends to enclose plagioclase, Further to the west, the granite is coarser grained and consists of perthitic orthoclase, albite, quartz and biotite, The perthite often forms elongate aggregates and has corroded plagioclase,
Quartz has slightly undulose extinction and occurs as stringers parallel to the perthite clusters. In the field, biotite most clearly defines the foliation. It occurs as cusplike aggregates 7
lsic areas. ~re~uent~~* these cusps have a consistent plunge on foliation surfaces.
ranite consists largely of pert
with minor albite and biotite. The quartz has strongly undulose extinction and is criss-crossed by thin
s of granulation, Zones of complete quartz granulation
ccur. Cuspate biotite is distinct in hand samples and is intergrown with chlorite. More advanced cataclasis results in the partial granulation of the perthite, together with
lete granulation of the quartz. The latter now occurs as
ar aggregate of subgrains with weakly undulose extinc- tion. There is a tendency €or areas of perthite enclosed in quartz to be rounded.
A distinctive variant of the granite crops out in a road-cutting, 5 km east of Mogumber. The rock is medium grained and contains rounded grains of quartz and feldspar,
In thin section, these crystals of undulose quartz and per- thitic orthoclase are sharply separated from a matrix of gra- phically intergrown potash feldspar, plagioclase and quartz.
Certain areas consist of a coarser intergrowth of orthoclase and quartz, whilst megacrysts of orthoclase up to 1 cm long are cut by parallel bonds of undulose quartz,
Around Bindoon and Chittering, the gneissic granite is commonly blue and much finer grained. It has a mortar texture of rounded grains of undulose quartz and potash feldspar in a matrix of graphically intergrown potash feldspar, plagioclase and quartz, Abundant biotite forms wispy aggre- gates that define a crude foliation, Locally, only the quartz megacrysts are distinct and the matrix is so fi the rock becomes a blastomylo ~~~~~T~~ AND SPENXTXC ROCKS
all outcrops of rock ranging in co sition from 9 to
occur scattered throug~Qut 18
are abundant and many are netoweined by the diorite. Appin veins are locally present,
The monzonites and syenites consist of microclin oligoclase, augite and hornblende, with minor quartz, sphene and apatite. Some of the rocks are even grained and occur as irregular patches in close proximity to amphibolite or hornblende- bearing gneiss. However, more gneissose syenitic rocks also occur, with a foliation marked by stringers of mafic minerals, blades of quartz and microcline, or differences in grain size,
ody at Katrine which is of this ty interbanded with leucocratic quartz-feldspar gneiss (Anl).
It entical to these gneisses (g.5) and there are no intrusive contacts. Streaks of amphibolite occ
h some of the dioritic and syenitic rocks are pre and some post- eformation their origin was probably sim-fl
Their associ matite, amphibolite and
ash me
Valley is tex 9
A number of fine or medium-grained, black and granitic dykes occur in the vicinity of York. They are only few metres wide and occur within the gneissic sequence. Biotit and/or hornblende are generally present.
Smaller dykes and veins of granite and adamellite a abundant around the plutonic intrusions. They are fine-grained and range to aplite. A notable feature is their grouping about an easterly strike direction. They is evident at Clackline, Meenar, Goomalling and Konnongorring. Some veins also occur within Agp and Agm, €or example, at Uberin Rock.
Veins of pegmatite and associated aplite are common in the gneisses and migmatite. They are subparallel to the metamorphic banding and, at Konnongorring, are at right angles to the fine-grained granitic veins,
DIORITIC DYKES A small number of fine to medium-grained dykes within the tonalite-diorite-monzonite compositional range occur in the Jimperding Metamorphic Belt and the nearby migmatite and
reas, The dykes are generally less than 10 m wide and are unfoliated. Their age is uncertain, though the dyke at Walyormouring Lake cuts Age.
DOLERTTIC DYKES -..“---I_ -..“---I_ - Tholeiitic, intrude all the A~c~~~a~rock type particular1 increase in generally around 2 to thickness. The smalle nocratic. Paaterial of art 0%” the area, show
~~SS~~it~%~ te, hornblen
rtz, with accessory epidote, sphene and chlorite.
Scarp, certain dykes have sheared margins, whilst, places in the Chittering Valley, they are compl
(Mong, 1964) e
Cross-cutting relations indicate several relative ages (Martin, Y961), though there may have been only one general period of dyke intrusion. The larger dykes have an overall north trend in the western part of the area whilst easterly and east-northeasterly trends are more prominent in the east, A
Rb-Sr age of 560 to 590 m.y. has been obtained from sheared and metasomatized dyke margins (Compston & Arriens, 1968).
A distinctive suite of fine-grained, melanocratic, plagioclase-phyric, basaltic dolerites occurs in the eastern portion of the Sheet area. These dykes have not been distinguished separately on the map. They consist of labradorite and augite phenocrysts in an aphanitic to fine- grained groundmass of plagioclase, augite, quartz, dendritic iron ores and occasional devitrified glass. Most of these dykes have a northeasterly trend.
A set of un is similarly restricted to the eastern part of the Sheet area,
The dykes trend northeast, with the exception of two north- northwest-trending dykes at Wongamine and Northam. They have
escribed by Lewis (1969, 1970), who attributes the abund- ance of granitic xenoliths to intrusion of dolerite alon shear-zones, The doleritic matrix to the xe to the plagioclase-phyric dolerites.
Innumerable small, pre and post-tectonic quartz vei are present in all Archaean rock types. A, number of quartz dykes also occur, the lar est extending for 30 km from Both ling south to the Salt River. Sev 21
ssociated with it r Burshndji
are present in the schis it east
ff, in the C~~~terinValley. Several other
nd veins throughout the Sheet area are associa with lines of faulting or shearing.
METAMORPHISM
The metamorphic mineral assemblages have been used to
roughly delineate regional metamorphic facies zones on the structural map (Fig.1). The Chittering and Jimperding Meta-
hic Belts have quite distinct mineral assemblages and there are also differences within each belt,
The abundance of kyanite and sillimanite, together with minor staurolite, in the schists of the Chittering Valley, the calcic plagioclase composition of the amphibolitic rocks and the scattered occurrence of garnet throughout the quartz- feldspar-biotite gneiss, indicates amphibolite facies conditions within the kyanite-sillimanite metamorphic facies series of
Miyashiro (1961). This facies series is characteristic of moderate to high pressure. However, the occurrence of chlori schists and rocks rich in epidote indicates lower temperatu and a range down into the greenschist facies, Such rocks are only developed locally and appear to have resulted from retro- grade metamor hism associated with shear zones parallel to the trend of the Darling Fault,
In contrast, the Jimperding Metamorphic Belt cont~in~
in andalusite and s~llimanite,and gener
rite Is a r re but widely clfstri
e The plagioclase in the amphi5
d often a~~o~iate~with c~~~fn onite, whils
~yroxe~eis comrno in the BIF and ma ranulite, These
rals indicate low pressur conditions of the andalusite- sillimanite facies series (Miyashiro, 1961) with a range from amphibolite to granulite facies metamorphism, The quartz- 22
~i~~~~~~~~-Q~~e> assembla e of the Eeu- neisses (Anl) is also characteristic of the facies, whilstthe rocks are texturally similar to the classic granulites of Saxony.
The metamorphic zones shown in Fig.1 have been extended and slightly modified from Stephenson (1970). Within the granulite facies zone there are areas that correspond more nearly to the amphibolite-granulite transitional facies
(Turner, 1968). These have not been separated, owing to the lack of detailed information. A larger area in this facies zone occurs west of York, between the granulite facies isograd and the migmatite zone surrounding the granitic rocks. It seems possible from the relict cores of pyroxene in many amphibolites and hornblendites (p. 6) that much of the Jimperding
Metamorphic Belt attained granulite facies conditions at some stage and that the present amphibolite facies zones could reflect later retrogressive effects. The later development of migmatite and intrusion of the granitic rocks could have been important in this respect.
The ultramafic rocks within the Jimperding Metamorphic
Belt only rarely retain their original mineralogy and are usually altered to greenschist facies assemblages.
RE~A~~~N§BETWEEN THE JIMPERDING AND
ITTERING METAMORPHIC BELTS
The various features described in previous sections suggest that there are fundamental differences between the
Jimperding and Chittering Metamorphic Belts and that they are not equivalent in age.
The important differences are listed below:-
1. Numerous bands of BIF, ortho- : No BIF or orthoquartzite; rare
quartzite and amphibolite amph ibo1 it e
2. Large areas of leucocratic : No quartz-feldspar-garnet gneiss
quartz-feldspar-garnet gneiss
3. No occurrence of orannfels : li'x+-enc:itm tinit nf crrannfelcr 23
ite : Within nite-sil~iman
8
e ~~~~~~~~ of ultramafic rocks : No ultramafic rocks.
There are no isotopic age dates on the Chittering Metamorphic rocks and data for the Jimperding Metamorphic Belt are sparse,
However, the lack of evidence for granulite facies rocks in the Chittering Valley, even allowing for the later, extensive retrograde effects, could imply a fundamental age difference between the belts, There is some evidence to suggest that, although only parts of the Jimperding Metamorphic Belt are now of granulite €acies, most of the rocks at some time appr or attained this grade of metamorphism and that present differ- ences may be due to a westward increase in retrograde effects.
Further, hypersthene-bearing BIF occurs less than 10 km from the Darling Fault north of Gillingara, on the Moora 1:250 000
Sheet (J.D. Carter, unpublished data). These rocks are of
Jimperding type and are apparently unaffected by northerly shear- ing in the area.
It is tentatively suggested that the rocks of the
Metamorphic Belt may be younger than those of th
Jimperding Metamorphic Belt, They occur close to the Darlin
Fault and thus have a similar distribution to the Middle or
Upper Proterozoic rocks of the Cardup and Moora Groups (Low,
1972a and 1972b, respectively), The position of these three dis- tinct groups of strata suggests possible marginal accretion onto the early Archaean nucleus of the Yilgarn Block, of which the
Jimperding Metamorphic Belt forms part, This gestisn was a
made by Wilson (s/958), althou h on somewhat di 'L
GEN~RA
The Cainozoic eposits have been mapped on the of their litho10 y and morphological features, Genesis is corn-
the distinction between Tertiary and Qu 24
s. is often do tful in the field. No subdivisio~of
ied by the second letter of a "Qtt unit
The relationships of the units are illustrated
Fig. 2.
TERTIARY AND UNASSIGNED UNITS
The most extensive deposit is Jaterite (Czl). In the west, it forms an extensive capping to the granitic rocks.
The surface is flat to undulating and is strongly dissected by streams, especially south of the Avon River. The deposit is generally pisolitic and may be massive or uncemented. It has
formed ,& situ from the weathering of underlying rocks and passes downward through a pallid zone into weathered bedxock.
Only local redistribution has occurred.
The eastern limit of the massive laterites is the
950 mm isohyet (Mulcahy, 1967). Further east, laterite is more sporadically developed. A number of deposits have developed on colluvial slopes above alluvium and are chiefly lateritized sands, It is not certain whether these deposits are coeval with the massive laterites.
A special type of siliceous duricrust (Czq) is developed over some of the larger quartzite units. It corresponds to the main laterite surface but is not ferrugin- ous. It consists of a pavement of white quartzite rubble and in situ quartzite, -7
Overlying the laterite, particularly in the eastern portion of the sheet, are deposits of yellow, grey or white sand (Czs) of variable thickness. There has been some redistribution of this material into eolian dunes. Where it overlies the massive laterite of the Darling Range the unit is much less extensive, is grey or white but not yellow, and is invariably associated with the drainage courses.
A unique deposit, shown on the map as , occurs
6 km south of Calingiri. It is a subhorizontal, 25
'' that con~a~ns1az uartz and kaolinized
dy matrix, an is associa
e The exact age of the unk~ownbut it has been lateritized in part. It oc drainage divide between the Moore, Avon and Mortlock systems and may represent the product of a pre-Pleistocene drainage system (Balleau, 1972).
A compact, partially lateritized gritty sandstone
(Czf) is associated with Czg and also occurs at the head of present drainage channels in the Calingiri area. It overlies
Czg 5 km east-southeast of Wyening Mission.
QUATERNARY UNITS
In the northeast portion of the Sheet, buff sand with distinct bands and lenses of ferruginous pisoliths (Qsp) forms a thin mantle over rock. The relief and photopattern are similar to soil-covered areas, and dykes can often be detected beneath the deposits. Areas of Qsp are particularly abundant around the Moore, ?Avon and Mortlock drainage divide and us~a~
rainage channels, giving way upslope or laterally laterite or rock outcrop, The deposits appear to be redi buted residual products whose position is closely related to
arly Quaternary drainage system.
Hummocky deposits of bright yellow sand (Qs) occur marginal to alluvial areas in Salinaland, They are of eolian origin, Similar yellow sand also overlies in much of this area. Older sandy alluvium (Qaf) an sand (Qas) associated with old stream channels are extensive upstream of the more recent alluvium of the Mortlock d system and near the drainage divides. The 01 a flak surface and is dissected, whereas Qas has an un surface and is often traversed by dunes, The more recent alluvium (Qra) has a fairly flat surface and lies above t normal level of the present streams. The deposits associ 26
h the Mortlock River (North Branch) and the salt lakes of
SaYEnaland are particularly extensive.
Salt lake deposits (Qws) occur in the broad alluvia
areas of Salinaland and with Qas in the eastern portion of the
Mortlock drainage system, Minor salt lakes have also developed
in sand over laterite north of Meckering,
Swamp and lacustrine deposits (Qrw) are generally
associated with Qas to the west of the Mortlock River (North
nch). They also occur with thin bands of alluvium and
colluvium (Qa) that have developed on the laterite of the
Darling Ran e. The deposits form rounded clay pans and swamp
Lacustrine deposits a so occur in the Brockman River between
Chittering and Mogumber.
In the east, colluvium (Qrc) consists of shallow
dipping sheets of sand on valley sides upslope from alluvium
and below rock or laterite outcrops, In the western area of
more active erosion, colluvium occurs between valley alluvium
and rock outcrop (separated from both by a marked change of
slope) and also occurs as scree deposits in valleys that are
y incising the laterite surface ofthe Darling Range.
In the eastern part of the Sheet area, bed-rock is
often largely or almost completely obscured by soil. However,
occasional outcrops and rock fragments enable the underlying
rock type to be determined. Such areas are denoted by an
overprint on the map.
STRUCTURE
~O~~~NG
The structure of the is
complex and difficult to interp
Pork and Northam and its northward extension through Bolgart
and Calingiri, the structure is superficially simple: a zon
of gneisses with abundant BLP and quartzite trends north-
northwest and has a regional dip to the east, A stro 27
generally plunges at moderate angles to the s
a However, paucity of outcrop, the le
of many units and the complexity of minor structures mean
that individual horizons cannot be traced over large distances,
At Jennapullin, a mafic granulite band is isoclinally folded
about north-trending axes with the minor fold closures plungin
steeply (70-85°) to the north. Shearing-out of limbs parallel
to the axial trend and transposition of structures occurs.
Similar features are evident south of Bolgart, where occasional
transposed fold cores in quartzite and amphibolite plunge
steeply to the north or south, The distribution of st
in the Bolgart-Wattening area also suggests that local varia-
tions in plunge occur.
It would appear from the minor structures that,
=_l;:hough there is a continuity of broad lithological zones in
the eastern part of the belt, the rocks have undergone intense
isoclinal folding, accompanied by shearing-out of limbs and
transposition. A series of later east-trending cross-folds
y accounts for variations in plunge,
In the Toodyay and York areas, the metasediments
nd east and t us strike almost at right angles to their
trend in the of the belt. Quartzite is domina
in both are s and its foliation is subhorizontal over much
the outcrop. The major folding varies from open to isoclinal,
with evidence of overturning (Prider, 1944; Stephenso
The earliest ase (P 3. 1 is now represented only by rootless isoclines. At least three, and possibly four, phases of fol
have affected the rocks and several interpretations are poss
on the available data, A structural interpretation of the
Toodyay area is presented in Pi e relation b
ng rocks and -~o~t~w~st-tre~d~n~locks to
the east is not clear, but there is evidence of stron
out of structures east of Toodyay, 2
A further complic ting factor is the regional
ment of migmatite and local mobilization of th gneisses, Ln general, the regional north-northwest t the metamorphic rocks tends to swing approximately easterly in the migmatite zones, especially where marginal to intrusive granites. The predominant foliation in these granites is also easterly. Although the intrusion of the granites is post- metamorphic, there is a marked parallelism of the granite con- tact and the metamorphic units between Clackline and the Malkup area. It is possible that the emplacement of granite had some effect on the structural style of neighbouring areas,
In the Chittering Metamorphic Belt, the metamorphic foliation is subparallel to the lithological banding. The predominant trend is north with steep dips to east or west,
Minor folding is complex within the schist units and the bedding in some places is at an angle to the schistosity. A strain-slip cleavage (S2) is locally developed, but its regional significance is not known.
The earliest and main phase of folding (P,) produced
es of north-trending tight to isoclinal folds. A number of fold axes are present in the Lower and middle Chittering
Valley but o the north, only one major anticlinal fold has
ized. Congruent minor folds suggest some QV to both east and west. It is not possible to match lit either side of the fold axes and it seems likely that a lot more isoclinal fol s remain un
A series of easterly trending cross-folds (F,), as recognized by Geary (1950) at Watt e Plat, occur th~~ughou the belt. They generally have little effect on the isocli folds, except fo an open-style foldin lineation, An exce tion occurs 5 krn s west of Bindoon, where an anticlinal cross-fold appears to aused a local wes deflection of the lithologies and F any mote cross- folds than are shown in Fig.1 are probably ~r~s~nt~ 29
An important feature is the development of both F 1 nd F2 folds in the cataclastic gneissic ranite (Agnjl Th F2 folds cause variations in the plunge of the distinctive biotite lineation (p.16). That the granite intrusion was pre or syn-F 1 is further suggested by the subparallelism of s contacts with the trend of the metasedimentary units, A ositive Bouguer anomaly over the granite is also diffi- cult to explain unless it forms a shallow, high level intrusion with much denser material at depth.
FAULTING
Few definite faults were recognized in the Sheet area, but it is likely that many more exist. Most of the faults have a northeast to northwest trend,but directions of displacement were hard to determine, Many of the larger quartz dykes appear to follow faults or crush and shear zones, as in the Malkug area (Cole and Gloe, 1940) and southeast of Nogumber, In the latter area, broad zones of intense quartz- veining occur withi cide with its of Age west of Bol
~e~m~~~t:~don its northern side by a quartz-veined fault. A e between the Swan Riv
60' or 920: have redu d the granfte to quartz-sericite schist (Whincup, 1970).
shear zone into the Chittering Metamo phic Belt: is represented by the mylonitic "€elds~~t~~~~uart~it~" of Miles (193$), 30
Bands of mylonite, blastomylonite and sheare
r in the western portion of the Chittering Metamor
elt, parallel to the Darling Fault, Near Mogumber, t morphic grade in the mylonite bands is similar to that adjacent gneisses, indicating that the shearing was pre or syn- metamorphic. At Bullsbrook, the deformation postdates the granite intrusion, whilst in the Chittering Valley, some of the dolerite dykes have been extensively sheared (p.19 ).
It seems likely that the present Darling Fault runs subparal to an ancient zone of north to north-northeast shearing that
een re-activated at various times.
A marked aeromagnetic anomaly trending 035 0 extends northeasterly from South Chittering to about 16 km west of
Bolgart. Exposure is poor, but the surface rocks are chiefly migmatite and gneissic granite (Agn). The lineament is s parallel to shear foliations in the adjacent rocks and to fauSt postulated by Wilson (1958) in this area. The lineament is also approximately coincident with the southeastern limit of the cataclastically deformed granite.
Recent fault scarps in the area were produced at
Me~k~~ing(1968) and Calingiri (1970) as a result of ~ar~~q~a~
h little surface trace of the later fault is evid
(Everingham and Parkes, 1971), The arcuate fault sc
Meckering (Everingham, 1968; Gordon, 1971) is still a marke feature in the area and was probably the result of east-w compression. The fault dips 45'E, Both these faults lie
hin a seismically active zone termed the Yandanooka-Cape
Rlche Lineament (Everingham, 1966). Epicentres of num~ro~~ earthquake shocks are spread over a fairly d Zone Some 5 km in width, mostly wit
However, if the events at Meckering and Ca the more intense seismic activity is pos ibly associated with the contact zone between the Jimperding Metamorphic Belt and the migmatite and granite complex to the north 31
ECONOMXC GEOLOGY
METALLIC MINERALS
Mineral production has been negligible, except for industrial products such as clay and aggregate. A little go1 and lateritic iron ore has been produced and minor occurrences of other minerals have been recorded.
GOLD (Au)
Shasts and adits were sunk for gold at Chittering,
Bolgart, Wongamine, Grass Valley and Jimperding Hill. Total recorded production amounted to 327 ounces of lode gold from
Jimperding Hill, together with 237 ounces of alluvial gold from Jimperding Hill and Wongamine. The lode gold was extrac- ted from quartz-veined aluminous schist and appears to have been concentrated at the base of the laterite profile. The alluvial workings at Bolgart, Wongamine and Grass Valley were in eluvial and colluvial deposits in close proximity to BIF.
The shaft at Chittering was sunk through quartz-veined schist.
TUNGSTEN (W)
Scattered boulders of wolfram occur 6 km north- northwest of Grass Valley (Blatchford, 1918). The country ro is leucocratic granitic gneiss (&) and quartzite (&), together with tourmaline-bearing ?vein quartz, Traces o ite (ferrous tun state) have been found associ at Jimperding Bill (Simpson, 1950). The deposits are not economic.
MOLYBDENUM (Mo)
The first discovery of molybdenite in Western was at Swan View, It occurs with pyrite and epidote in shear zones through &, There are also several small occurrences in the Spencers Brook area, Simpson (1952) records mining of the deposit in the Mokine railway cutting, though no pr~~~~~~o~ fllgures are available. 32
The first production of iron ore in the State was
rom lateritized BTF at Clackline. Between 1899 and li recorded production was 18 545 tonnes, though Hobson (1946) Scates that larger quantities were mined. The ore is h-grade limonite and was treated at the Fremantle Smelting Works. Some ore from the Wundowie-Coates Siding area was also treated at Fremantle, though most of the 82 273 tonnes produced from this area was smelted at Wundowie between 19
Several of the larger quartz-magnetite-hypersthene
BIF bands east of Northam have been drilled and tested, but not mined.
VANADIUM (VI A lateritized gabbroic intrusion at Coates Sidkla contains vanadium-bearing titaniferous magnetite. The intru- sion trends west-northwest but has little surface expression except for some relict textures in the laterite. Drilling has revealed cumulate textures and a compositionaL range from gabbro to anorthosite. This gabbro intrusion is the only one of its type known in the Perth Sheet area. The fresh rock contains an average of 0.54 per cent V205 and published ore reserves for the prospect amount to more than 227 000 tonnes of V205*
BAUXITE (Bx)
Bauxitic laterite is extenstve on the Darling Plateau.
Portions of the Alcoa mineral lease MLl SA and the Alwest
Agreement area extend northward onto the Perth Sheet, The
Pacminex deposits are centred on the area east of the lower Chittering Valley. A bulk sample from here has been tested and over 900 million tonnes of bauxite at around 32 per cent available alumina has been proved in the area. 33
RUTILE (R)
At Yulgering Well, 8 km northeast of Calingiri,a
small concentration of rutile was discovered in colluvium overlying migmatite (Jutson, 1912). Individual crystals reach
40 mm in length, but the amount of material is small.
INDUSTRXAL ROCKS AND MINERALS
VERMICULITE (Ve)
Vermiculite o€ varying quality is present in minor hroughout the area. Small lenses occur in the broad
schist unit, 8 km northeast of Bullsbrook East. It is also recorded from a serpentinite at Goomalling (Simpson, 1950).
ASBESTOS (Aa) At Goomalling, asbestiform anthophyllite is associated
with a talc-serpentine band within migmatite. Two prospecting
areas were worked in 1922, but no production was recorded.
-TALC (a) Both talc and asbestos occur in minor amounts in
certain altered ultramafic intrusions. The only talc deposit
worked is situated 9 km south-southwest of Bolgart. The
recorded production is 275 tonnes between 1946 and 1952, although the deposit is still worked sporadically.
AXD ___"l-._ll_.I1__"C__-~KYANTTE SILLIMANITE-- Concentrations of almost pure kyanite and sillimanite occur as lenses in the schists and gneisses of the Chitterin
Metamorphic Belt, Large quantities of kyanite are availabl
at Wattle Plat and sillimanite at Goyamin Pool, but would
quire crushing and special beneficlation, Sillimanite is
also a constituent of many schists in the Jimperding Metamorphic Belt. The only recorded production is 2 tonnes of sidlimanite from Clackline in 1948. 34
CLAY (C1) 3___
Large quantities of clay have been obtained from the
area and abundant supplies are available. Structural clay is
obtained from the pallid zone, formed during lateritic weatherin
of the granitic rocks, Most quarries are close to the Darling
Scarp. Recorded production of structural clay is 117 161 e8 to the end of 1972. Fireclay is obtained from the pallid zone
and from weathered aluminous schists. Production of fireclay
from weathered granitic rocks in the Glen Forest-Mahogany Creek
area amounted to 236 04." tonnes to the end of 1972. A small
quantity of fireclay (1 670 tonnes to 1972) has also been
produced from the pallid zone overlying porphyritic granite,
2 km south-southeast of Clackline. To the end of 1972, 108 486
tonnes of fireclay was ~oducedfrom weathered sillimanite- bearing schists at Clackline. Smaller amounts of clay have been obtained further north along this schist belt, but the material is generally less aluminous than at Clackline.
Total production of clay from the Perth Sheet area has been much greater, but no exact figures are available.
KAOLIN (Ck)
ount of residu material has been obtained from the pallid zone of th profile at Glen Forest Recorded production prior to 1952,
A flooded claypan (w),17 km west of Goomalling
lded 29 176 tqzne f good quality ceramic clay up to
1972. Four clay horizons up to 2 m thick are interstratifie with unconsolidat of lacustrine ori 35
BUXLDING STONE (Bs)
Local stone, especially cemented laterite rock, has been used for home construction in past dec to a lesser extent is employed at the present time. granite 6 km south of York has been quarried for facing stone.
Extensive use is made of laterite and granite in landscape gardening.
The quartzite band extending southward from Jimperding
Hill to Clackline is quarried sporadically along its length for building and facing stone ("Toodyay Stone"). Portions of this unit are fissile along planes crowded with green chrome mica,
The best quality facing stone has extremely smooth partings devoid of crenulations, The main quarry is situated 9 km south-southwest of Toodyay.
AGGREGATE, BALLAST AND ROAD METAL
There are abundant supplies of rock suitable for cruqhed aggregate (Rc)- and large quarries have been opened up
he Darling Scarp close to the metropolitan area. Railway
st has been provided by quarries in close proximity to
ailway lines. Innumerable small workin
ed pisolitic late
e1 for road making.
-SAND (Sa) antiti ties of sand. ate available, especially
art ~f the area. The most homogeneous material averlies laterite, San from the more recent alluvium ( used locally.
With the ex ion of the ~w~n-~von
rook, all strea 36
The Swan-Avon River flows at a greatly reduced rate during the dry season and is too saline for town water supply. East of the Darling Scarp, innumerable small dams have been cons along minor watercourses for stock use. There is a limited and local potential for further impounding of streams in this area and in the Piedmont Zone, at the foot of the Darling Scar
Perth's main water supply comes from dams on the
Canning and Serpentine Rivers, south of the Sheet area. The
Helena Reservoir lies partly within the mapped area and water from here is pumped along a pipeline to the Eastern Goldfields.
The main pipeline extends eastward through Northam and Meckering and, through a network of smaller subsidiary pipes, supplies water to these and other towns of the "Wheat Belt".
GROUNDWATER
Groundwater distribution varies with the following geological and geomorphological environments:
1, Piedmont Zone - alluvial-fan material consisting of
lenticular conglomerate, gravel, sand and clay bands
yields local supplies of potable water. Many bores
have silt problems and yield less than 450 litres
Scarp and Plateau - favourably site
s yield limited supplies
0th fresh and weathered granitic rock.
Supp l-ier; n:w 5cl o5~aitieci from the I atori i e i>a1 L i i:
ZOT~Pizlcrface, t IIP weathered rock below the pallid
zone and from joints and fissures within fresh
granitic rock, However, unsucce 1 bares are not 37
orten accompanied by soaks (u).The Bolgart township water supply is obtained from saturated sands of this type and
those at Yenart Soak have been tested (Balleau, 1972).
Other residual sand reservoirs are probably present near
permanent soaks along the upper portions of the Avon, Mortlock
and Moore drainage systems.
- REFERENCES AND SELECTED BIBLIOGRAPHY
f Arriens, P.A., 1971, The Archaean geochronology of Australia:
Geol. SOC. Australia Symposium, The Archaean Rocks, Perth,
May 1970, Abs. v.
Balleau, W.P., 1972, Saturated sands at Yenart Soak: West.
Australia Geol. Survey Ann. Rept. 1971, p.13-15.
Berliat, K., 1955, Notes on a talc deposit near Bolgart:
West. Australia Geol. Survey Ann. Rept. 1952, p.30-31.
Blatchford, T., 1918, Discovery of wolfram at Grass Valley, near
Northamp, South-West Division: West. Australia Geol.
Survey Ann. Rept. 1917, p.7-8.
1932, Report on an alluvial gold find on Yiniding Creek
eight miles south-west of Toodyay: West. Australia GeoL,
Survey Ann. Rept. 1931, p.9-10,
Brophy, F.J., 1963, Teh geology of the Whitfields Hill area,
near Toodyay, Western Australia: Univ. Vest, Australia
Eons. thesis (unpublished).
Campbell, W.D., 1907, Clay deposits of the Clackline district:
West. Australia Geol. Survey Ann. Rept. 1906, p.24-25.
Clarke, E. de C., 1927, Natural Regions in Western Australia:
Royal SOC. West. Austvtilia Jour., v.12, p.117-132.
1930, The Pre-Cambrian succession in some parts of
Western Australia: Australian New Zealand Assoc. Adv.
Sci. 1930, v.20, p. 155-192.
Cole, W.F. and Gloe, C.S., 1940, The geology and physiography
of the Malkup area: Royal SOC. West. Australia Jour,,
v.26, p.139-171. 38
Danielson, M.J., 1963, The high grade metamorphic and associated
rocks of the western part of the Needling Hills near York,
Western Australia: Univ. West. Australia Hons. thesis (unpublished). Compston, W., and Arriens, P.A., 1968, The Precambrian geo- chronology of Australia: Canadian Jour. of Earth Sciences, v.5, ~~561-583. Elkington, C.R., 1963, Bronzite peridotite and associated metamorphic rocks at Nunyle, Western Australia: Royal SOC. West. Australia Jour., v.46, p.13-27. Esson, A.G.D., 1927, The fireclay deposit on Mineral Claim
SOH, Clackline: West. Australia Geol. Survey Ann. Rept. 1926, p.32-15. Everingham, I.B., 1966, Seismicity of Western Australia:
Australia Bur, Mineral Resources Rec,1966/127 (unpublished), 1968, Preliminary report on the 14 October 1968 earth- quake at Meckering, Western Australia: Australia Bur. Mineral Resources Rec.1968/142 (unpublished). Everingham, l.B., and Parkes, A., 1971, Intensity data for
earthquakes at Landor (17 June 1969) and Calingiri (10 March 1970) and their relationship to previous Western Australian observations: Australia Bur. Mineral Resources Rec.1971/80 (unpublished).
Feldtman, F.R., 1920a, The clay deposits at Bolgart, South-West Division: West. Australia Geol. Survey Ann, Rept.1919,
p. 27-29.
1920b, The Clackline and Baker's Hill clay deposits,
South-West Division: West. Australia Geol. Survey Ann. Rept. 1919, p.29-30,
Fletcher, R.W., and Hobson, R.A., 1932, The physiography and
geology of the Upper Swan area: Royal SOC. West. Australia Jour., v.18, p.23-37. Forman, F.G., 1935, Lode mining at Yinniding Creek, Toodyay District: West Australia Geol, Survey Ann. Rept. 1934, p.12-13. 1937, A contribution to our knowledge of the Pre-Cambrian succession in some parts of Western Australia: Royal SOC. West, Australia Jour., v.23, p.xvii-xviii. 39
Frost, M.J., 1960, Complex -Jointing in the Shield Margin near Darlington, Western Australia: Royal Soc. West. Australia
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