The Willyama The Willyama ComplexComplex

Setting the sceneSetting the scene

3 main c. 1820 Ma cratonsSeparated by central Australian orogens

Curnamona ProvinceCurnamona Province

Palaeoproterozoic metamorphic Palaeoproterozoic metamorphic basementbasement

AdelaideanAdelaidean sedimentary sedimentary rocks rocks

Mesozoic &Mesozoic &Cenozoic Cenozoic

Willyama ComplexWillyama Complex

Focus of an enormous amountFocus of an enormous amount of work of work Ag-Pb-Zn orebody Ag-Pb-Zn orebody

Greenschist to granulite Greenschist to granulite facies inliers -fault contact facies inliers -fault contact or unconformably overlain or unconformably overlain by Adelaidean rocksby Adelaidean rocks

Metasediments, orthogneiss, Metasediments, orthogneiss, granite and amphibolite bodiesgranite and amphibolite bodies

All multiply deformedAll multiply deformed

Basement rocksBasement rocks Detailed mapping revealed a stratigraphyDetailed mapping revealed a stratigraphy

within the Willyama Complex metaseds within the Willyama Complex metaseds Can see sedimentary features preserved Can see sedimentary features preserved

through effects of metamorphism - give through effects of metamorphism - give way up features - use marker horizonsway up features - use marker horizons

Need to establish timing and nature of rock bodies - sedimentary or igneous?

Oldest rocks - 1700 - 1650 MaOldest rocks - 1700 - 1650 Ma Deformed and metamorphosed at c. 1580 Deformed and metamorphosed at c. 1580

MaMa

General General progressionprogression

Upper units -Upper units - turbidites and turbidites and other clastic other clastic sedimentssediments

chemical chemical sedimentssediments

Quartzofeldspathic Quartzofeldspathic gneiss with BIFgneiss with BIF

lower units of lower units of composite gneiss composite gneiss (migmatite, schist)(migmatite, schist)

Multiple deformation Multiple deformation eventsevents

See effects of 2 or three regionally See effects of 2 or three regionally penetrative deformation eventspenetrative deformation events

Early, bedding parallel foliation Early, bedding parallel foliation deformed by folds with a steeply-deformed by folds with a steeply-dipping axial planedipping axial plane

Retrograde shear zones - D3Retrograde shear zones - D3 Then effects of another two vents Then effects of another two vents

that deformed the Adelaidean seriesthat deformed the Adelaidean series

Metamorphic gradeMetamorphic grade

Greenschist to granulite faciesGreenschist to granulite faciesmeans overall block tiltmeans overall block tilt

Weekeroo - and-st-g-bi-mu q schistsWeekeroo - and-st-g-bi-mu q schistshonest amphibolite facies conditionshonest amphibolite facies conditions

Peak conditions earlyPeak conditions early S1, S2 cut by RSZS1, S2 cut by RSZ And -> sill -> kyAnd -> sill -> ky

AdelaideanAdelaidean Series of Neoproterozoic to Cambrian Series of Neoproterozoic to Cambrian

basins throughout Australia basins throughout Australia Willyama Complex acted as basement Willyama Complex acted as basement

and source - see distinctive cobbles in and source - see distinctive cobbles in the Adelaidean rocksthe Adelaidean rocks

Quartzites±magnetite, dolomites, Quartzites±magnetite, dolomites, siltstones are the main lithologiessiltstones are the main lithologies

seriesseries 5 main lithostratigraphic units5 main lithostratigraphic units Hawker Group - Hawker Group -

Cambrian limestone and shaleCambrian limestone and shale Wilpena GroupWilpena Group- -

shale, silstone,sandstoneshale, silstone,sandstone Umberatana GroupUmberatana Group- - massive tillites, sandstone massive tillites, sandstone

and arkoses; laminated silts, shales, carbonates; and arkoses; laminated silts, shales, carbonates; marine glacials, red sandstone and siltstonemarine glacials, red sandstone and siltstone

Burra GroupBurra Group - - basal sandstone - conglomerate basal sandstone - conglomerate passes into argillite-carbonate sequencepasses into argillite-carbonate sequence

Callana BedsCallana Beds - - volcanics, conglomerates, volcanics, conglomerates, limestone and sandstone unconformable on Mt limestone and sandstone unconformable on Mt PainterPainter

Mesozoic and TertiaryMesozoic and Tertiary Mesozoic - eastern Australia flooded Mesozoic - eastern Australia flooded

by shallow seas - GAB and dinosaur by shallow seas - GAB and dinosaur fossilsfossils

Tertiary - developed laterites, break-Tertiary - developed laterites, break-aways, opalsaways, opals

And the job to doAnd the job to do

Information Research ProcessInformation Research Process Define the taskDefine the task Locate the informationLocate the information Selection - Selection - what information is relevant what information is relevant

to the defining stageto the defining stage Organizing - Organizing - how to use the informationhow to use the information Presentation - Presentation - how to communicate the how to communicate the

information to the target audienceinformation to the target audience Assessing/reflection - Assessing/reflection - how well did I how well did I

answer the question; what did I learnanswer the question; what did I learn

20 minute task20 minute task

Group 1&2Group 1&2Flow diagram to identify igneous Flow diagram to identify igneous rocksrocksGroup 3 - 10 min review - 2 good Group 3 - 10 min review - 2 good points, 2 ways to improvepoints, 2 ways to improve

Group 4 & 5 - sedimentary (Group 6)Group 4 & 5 - sedimentary (Group 6) Group 7 &8 - metamorphic rocks Group 7 &8 - metamorphic rocks

(Group 9)(Group 9)