Case Study - 3D Mineral mapping of the St Ives Archean Au deposit

Aim | Geological Setting | Potential for Mineralisation | Project | People | References | Links

Aim

To evaluate and showcase the geoscience products created by the Centre of Excellence for 3D Mineral Mapping at CSIRO two public 3D Mineral Mapping case studies will be established. One case demonstration focuses on the Kambalda St Ives district, located in the Eastern Goldfields of the Yilgarn Craton (Australia). Remote (ASTER and HyMap), drill core and field spectral data will be assessed and compared with geophysical and geochemical data to create a 3 dimensional mineral systems analysis. A close collaboration with Gold Fields Limited and the Geological Survey of Western Australia (GSWA) is a key factor of the project.

Geological Setting

The Kambalda St Ives district is located about 80 km south of the mining town of Kalgoorlie, Western Australia, ca. 630km east of Perth (Fig. 1). The Kambalda St Ives district is part of the southern Norseman-Wiluna greenstone belt, which is allocated to a ca. 2.8 to 2.6 Ga old granite-greenstone terrain (Eastern Goldfields Superterrane) of the eastern Yilgarn Craton.

The Boulder-Lefroy Fault zone in the east and the Merougil/Speedway Fault zone in the west frame the Kambalda corridor containing the Archean Kalgoorlie Group (komatiitic and basaltic rocks), the Black Flag Group (clastic sedimentary rocks and felsic volcanic-volcanoclastic rocks) and the Merougil Formation (Terrigenous rudites, arenites and minor argilites) (Prendergast, 2007).

Fig. 1: Geological map of the Kambalda St Ives district showing the location of major gold deposits (from Neumayr et al., 2008).

Potential for Mineralisation

The Eastern Goldfields Superterrane in the eastern Yilgarn Craton in Australia is well endowed with metallogenic provinces of Ni, Fe, Cu-Zn and Au deposits (Barley et al., 1998; Groves & Barley, 1994). The Kambalda St Ives district contains significant concentrations of komatiite-associated Fe-Ni sulphide deposits and mesothermal gold deposits (Connors et al., 2005). Fe-Ni sulphide deposits are associated with the Lunnon Basalt and Kambalda Komatiites, which are part of the Kalgoorlie Group. Mesothermal gold is closely associated with brittle-ductile transgressive structures (D4a acc. to Blewett & Czarnotta, 2007; D3 acc. to Nguyen, 1997) and hosted by the Kalgoorlie Group. At St Ives operations ore is currently minded from three underground mines, four open pits and 10 stockpile sources (http://www.goldfields.co.za/ops_int_st_ives.php).

Project

Remote, drill core and field spectral techniques provide valuable data for mapping mineralogy and are therefore not only applicable to complement geological maps but also to map out various alteration patterns and compositional changes possibly related to mineralisation. Previous studies by Cudahy et al. (2009) showed how thermal infrared reflectance data from drill cores can be used to track alteration associated with Archean Gold mineralisation at Kambalda. Furthermore it has been shown by CSIRO researchers at the St Ives gold mine that large drill hole-derived SWIR spectra datasets can be used to spatially characterise mineralogical distribution and to identify the distribution of structurally-focussed hydrothermal fluids (Roache, 2008). This technique has been adopted by Gold Fields Limited staff as well as consulting geologists.

HyMap data over the Kambalda St Ives district were collected in 2 phases by the HyVista Corporation (2005 for CSIRO, GSWA and CRC Leme; 2008 for Gold Fields Limited). The application of the earlier acquired spatial data for mapping mineral and alteration assemblages was shown by Vitins (2009), who generated chlorite composition products. The chlorite composition is of particular importance for Archean Au exploration in the Eastern Yilgarn, as certain compositional changes of the chlorites are spatially related with well endowed sequences. Further research is currently undertaken by CSIRO workers to refine the possibilities for mapping the chlorite composition and other important alteration minerals with hyperspectral techniques (MERIWA, M400 Project).

The newly started Centre of Excellence for 3D Mineral Mapping will generate a suite of mineral products, similar to the ones previously made available on the NGMM webpage (www.em.csiro.au/NGMM). In a first step an atmospheric correction will be applied to the raw data, which will be then processed by using CSIRO’s C-HyperMAP software to create the various geoscience products. Additionally spectral drill core data will be collected with GSWA’s Auscope National Virtual Core Library HyLogger instrument. The new spectral data will be then compared with other existing spatial (magnetics, radiometrics, seismics) and drill core datasets (spectral, multi-element geochemistry and isotope composition) and combined in geo-information (ArcGisTM) and 3D modelling (LeapfrogTM, GoCadTM) software packages. The resulting 3D mineral-physicochemical maps are expected to show evidence of alteration patterns as potential vectors to Archean Au mineralisation.

People

Prime contact: Carsten Laukamp (Research Geoscientist, CSIRO, email)
Tom Cudahy (Spectral Geologist, CSIRO and CoE C3DMM Director)
Andrew Rodger (Physicist, calibration and algorithm development CSIRO)
Michael Caccetta (Software Engineer, CSIRO)
Rob Hewson (Geophysicist, TIR spectroscopy, CSIRO)
Klaus Gessner (3D Engineer, Geologist, UWA)
Matt Wyatt (Web delivery Engineer, CSIRO)
John Miller (Structural Geologist, CET, UWA)
Damien Keys (Research Geologist, Gold Fields Limited)
Ruth Murdie (Geophysicist, Gold Fields Limited)
Lena Hancock (Mineralogist, GSWA)

References

Barley, M.E., Krapež, B., Groves, D.I., Kerrich, R., 1998a. The Late Archaean bonanza: metallogenic and environmental consequences of the interaction between mantle plumes, lithospheric tectonics and global cyclicity. Precambrian Research, v. 91, p. 65 - 90.

Blewett, R. S., Czarnota, K., 2007, Tectonostratigraphic architecture and uplift history of the Eastern Yilgarn Craton, Geoscience Australia, Record 2007/15.

Cudahy, T., Hewson, R., Cacetta, M., Roache, A., Whitbourn, L., Connor, P., Coward, D., Mason, P., Yang, K., Huntington, J., Quigley, M., 2009, Drill Core Logging of Plagioclase Feldspar Composition and Other Minerals Associated with Archean Gold Mineralization at Kambalda, Western Australia, Using a Bidirectional Thermal Infrared Reflectance System: Reviews in Economic Geology, v. 16, p. 223 - 236.

Connors, K., Donaldson, J., Morrison, B., Davis, C., Neumayr, P., 2005, The Stratigraphy of the Kambalda St Ives District: Workshop Notes. Internal report, TNSIG0329. Gold Fields St Ives.

Groves, D.I., Barley, M.E., 1994. Archean mineralization. In: Condie, K.C. (Ed.), Archean Crustal Evolution. Elsevier, Amsterdam, pp. 451–493.

Neumayr, P., Walshe, J., Hagemann, S., Petersen, K., Roache, A., Frikken, P., Horn, L., Halley, S., 2008, Oxidized and reduced mineral assemblages in greenstone belt rocks of the St. Ives gold camp, Western Australia: vectors to high-grade ore bodies in Archaean gold deposits?: Mineralium Deposita, v. 43, p. 363 - 371.

Nguyen, T. P., 1997, Structural controls on gold mineralisation of the Revenge Deposit and its setting in the Lake Lefroy area, Kambalda, Western Australia: Unpub. PhD thesis, University of Western Australia.

Prendergast, K., 2007, Apllication of lithogeochemistry to gold exploration in the St Ives goldfield, Western Australia: Geochemistry: Exploration, Environment, Analysis, v. 7, p. 99 - 108.

Roache, T., 2008, Hyperspectral Modelling in Mining & Exploration: Advances in the Understanding of Structurally-Controlled Mineralisation: Australian Earth Science Convention, Perth, 20 July - 24 July 2008, 2008, p. 211.

Vitins, I., 2008, Airborne hyperspectral mapping of chlorites in the northern Kambalda Dome region: Unpub. MSc thesis, ETH Zurich, 86 p.

Links

Goldfields - http://www.goldfields.co.za/
© Copyright 2009 CSIRO. Last updated: 1st September 2009