Regional alteration mapping using spectral mineralogy Gawler Craton Dr A J Mauger NVCL, PIRSA Node Dr A J Mauger NVCL, PIRSA Node

AuScope NVCL NCRIS Funded National Virtual Core Library Web access to Australian State core libraries Demonstrator web site at:

National Virtual Core Library – PIRSA Node HyLogger™ –1cm resolution contiguous spectra –0.1mm resolution linescan image –Laser height profiler – m per day –3 GBytes data per day –Fully interactively integrated spectra, mineral interpretation, core image, ancillary data –Over 300 open file holes on SARIG

TSG – Core Interface

One way to map alteration Scans entire hole Metres of mineral/hole e.g. if each hole 255 m ore

What we actually have to work with Holes start in altn Hole finish in altn Angle holes Stratigraphy Faulting Uneven distribution

Four Mineral Systems White Mica –Muscovite –Phengite Chlorite –Mg Chlorite –Fe Chlorite Carbonate –Dolomite –Siderite Iron Oxide –Fe 3 + Goethite –Fe 2 + Goethite –Hematite

Al(OH) Muscovite to Celadonite solid solution involves the depletion of Al and substitution of Fe and Mg Phengite is the general term for Al – poor, Fe - rich Muscovite approaching the Celadonite end-member chemistry Transition can be measured by wavelength of ~2200 nm absorption feature

Chlorite Fe – Mg substitution in Chlorite Measured by the wavelength position of the ~2350 nm absorption feature

Carbonate Fe – Mg substitution in carbonate Measured by wavelength position of ~2350 nm absorption feature

Iron Oxide Hematite and Goethite spectral signatures distinctive in VNIR Goethite empirically has two spectral signatures Interpreted as: Fe 2 + Goethite vs Fe 3 + Goethite Fe 3 + Goethite – derived from hematite Fe 2 + Goethite – derived from sulphide

White Mica Red – phengite Cyan – muscovite White – both Black – neither Olympic Dam – both Olympic Domain - more phengite southwards Olympic Dam Tunkillia Pernatty Moonta Barns Challenger

Chlorite Red – Fe Chlorite Cyan – Mg Chlorite Fe Chlorite proximal to ore Strong boundary to south of Olympic Dam Tunkillia Pernatty Moonta Barns ChallengerOlympic Dam

Carbonate Red – Fe Carbonate Cyan – Mg Carbonate High pH associated with abundant CO 3 pH increasing south and south-eastwards Tunkillia Pernatty Moonta Barns ChallengerOlympic Dam

Iron Oxide Red – Oxidised Cyan – Reduced Redox boundary south of Olympic Dam Tunkillia Pernatty Moonta Barns ChallengerOlympic Dam

Is it another Olympic Dam? –A complex redox environment –low pH, –Fe-Chlorite, –low Al white mica and –low Kaolin This study not filtered by geology, stratigraphy or depth District scale studies provide more complete story Requires more drillholes be scanned

Epilogue Large alteration systems Insufficient knowledge of background Need more drilling and scanning to fill the gaps Model will improve with data

Future Directions… Correlation with other alteration studies –Skirrow, GA –Katona, PIRSA Refine analysis to link in geological constraints Scan more IOCG holes Scan PACE holes Scan GA Transect holes Scan Company holes Results loaded into public access NVCL

Acknowledgements HyLogger TM is a trade mark of CSIRO South Australian Department of Further Education, Employment, Science and Technology (DFEEST) provides co-funding for South Australian node of NVCLwww.innovation.sa.gov.au AuScope Ltd is funded under the National Collaborative Research Infrastructure Strategy (NCRIS) an Australian Commonwealth Government Programmewww.auscope.org.au