bruce f schaefer, program coordinator · 2020. 7. 17. · bruce f schaefer, program coordinator....

pmd CRC

Mineral Systems History Mineral Systems History Program: A Review Program: A Review

Bruce F Schaefer, Program Coordinator

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pmd CRCHistory Program OverviewHistory Program Overview•• Investigate dating of Investigate dating of mineralisationmineralisation, ,

deformation and metamorphismdeformation and metamorphism•• Three active technique development Three active technique development

approaches:approaches:–– ReRe--Os isotope Os isotope –– PbPb--PbPb step leachingstep leaching–– ArAr--ArAr geochronologygeochronology

•• Apply new analytical processes and Apply new analytical processes and capabilities to capabilities to mineralisationmineralisation and terrain and terrain evolutionevolution


pmd CRCH1: ReH1: Re--Os isotopes in geochronology, Os isotopes in geochronology, ore forming and exploration modelsore forming and exploration models

•• Work centered upon technique Work centered upon technique development, using material from Mt development, using material from Mt IsaIsa (I2 (I2 and I4) projects regarding the Mt and I4) projects regarding the Mt IsaIsa and and George Fisher ore bodiesGeorge Fisher ore bodies

•• Current work regarding the Ernest Henry Current work regarding the Ernest Henry system in progresssystem in progress–– Emphasis on feeding results back to the Emphasis on feeding results back to the

TerraneTerrane ProjectsProjects


pmd CRCH1: Recent ResultsH1: Recent Results•• ““Young” ages from both Mt Young” ages from both Mt IsaIsa and and

George Fisher George Fisher -- suggest the suggest the mineralisingmineralising event was widespreadevent was widespread

•• Possibly not Possibly not simply simply overprinting or overprinting or resetting…resetting…

•• See posters for See posters for more detail!!!more detail!!!


pmd CRCH2: H2: PbPb--PbPb step leaching as a possible step leaching as a possible means of dating mineralisation, means of dating mineralisation, metamorphism and deformationmetamorphism and deformation

• Commenced final stages of garnet geochronology associated with Broken Hill, building on the success of the work conducted by Maurizio Tonelli (PhD)– involve others in providing samples for the development work associated with

Pb-Pb step leaching of sulfides and magnetite

• Commencement of a new PhD (Kate Bassano) student to extend the technique to ore forming minerals, such as chalcopyrite and galena– Mixed initial results; poor spread from Mt Isa, however a wide range of Pb

isotopic ratios measured for Broken Hill

• Look for opportunities for wider application and development of networks to other potential projects– the commencement of Kate’s PhD project has improved networking between H2

and other projects


pmd CRCH2: Looking to the futureH2: Looking to the future

• Need to further test the garnet work– While we have sense of what will/won’t work well, the proof will be in rolling

out this technology to other projects. Is there funding to support such high risk work?

• Careful selection of chalcopyrite, pyrite and magnetite samples– Rather than focus on minerals from a specific setting (as in the garnet

project) we are keen to acquire (pure?) separates of these three minerals from a spectrum of different ore deposit types/styles. We would be delighted to receive such samples from any member of the pmd*CRC; indeed crosslinks with H1 have been initiated


pmd CRCH4: H4: ArAr--ArAr dating of dating of mineralisationmineralisation, , metamorphism and deformationmetamorphism and deformation• 40Ar/39Ar dating of white micas - W. Victoria (~95%).

– Timing of gold, deformation & alteration.– New regional tectonic model for W. Vic. - hybrid orogenic zone

(Delamarian + Lachlan orogens).• 40Ar/39Ar dating of pyrite (~70%).

– Stawell mine: Single grains; preserve correct age despite younger major intrusion-related overprint of the matrix!!

• 40Ar/39Ar dating and geochem of fluid inclusions (~30%).– Lenard Shelf; W. Vic. - ~95% meteoric fluid!– New ore deposition models; Re-evaluate analytical protocols.

• Extension of methods to other terranes (20%):– Mt Isa (e.g. Osborne, Cannington, Eloise); Yilgarn (Kanona Bell, Mt

Charlotte).– Ar-Ar (Py + magnetite), noble gas & Cl analyses in progress.– New post-doc - Mark Kendrick (Feb, 2004)!


pmd CRC

Pyrites preserve correct age (ca 440 Ma) despite major 400 Ma intrusion-related overprint of the matrix!!

Matrix age(ca400 Ma)

ca. 400 Ma Matrix sericite age(intrusion-related overprint)

40Ar/39Ar Dating of Single Pyrite

Grains


pmd CRC

440 Ma 440 Ma MagdalaMagdala Orogenic AuOrogenic Au(Lachlan(Lachlan--age deposit)age deposit)

ca. 400 Ma ca. 400 Ma WongaWongaintrusionintrusion--related Aurelated Au

REVISED TECTONICREVISED TECTONIC MODELMODEL

Stawell is in the Delamerian Fold BeltStawell is in the Delamerian Fold Belt

440 Ma

400 Ma

500 Ma cooling ages500 Ma cooling agesDELAMERIAN METAMORPHISMDELAMERIAN METAMORPHISM


pmd CRCH4: Future workH4: Future work

• Extension of geochron & geochem methods:– Yilgarn, Mt Isa, (Curnamona?) terranes.

• Team-based, deposit-scale approach essential!!– Critical to success of W. Vic. project + modelling.– Integration with structural + FI studies crucial– Potential to determine origin of ore fluids.

• Independent Structural work - John Miller(?)• Close liaison with terrane projects.

– Priority - Yilgarn; • Improved integration and communication

– Modelling projects, GA, CSIRO, Terrane and Fluid projects:– Attend terrane meetings + field/mine visits.

• Budgetary constraints!


pmd CRCHistory SummaryHistory Summary•• All projects have performed well in technical All projects have performed well in technical

development aspectsdevelopment aspects•• Transferring of data back to other programs of Transferring of data back to other programs of

the the pmdpmd*CRC*CRC is accelerating, and new links is accelerating, and new links emergingemerging

•• However, there are still many exciting things However, there are still many exciting things to do, with many developments coming from to do, with many developments coming from outside the original project scopesoutside the original project scopes

•• Need to plan and integrate next Need to plan and integrate next stage(sstage(s))

bruce f schaefer, program coordinator · 2020. 7. 17. · bruce f schaefer, program coordinator....

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