White Mica Chemistry from the Vulcan IOCG Prospect, South Australia

Gordon, Georgina1, Dmitrijeva, Marija2, Berthiaume, Jonathon2

1Geological Survey of South Australia, Adelaide, Australia.2Fortescue Metals Group Ltd., Keswick, Australia.

The Vulcan iron-oxide copper gold (IOCG) deposit in South Australia lies 30 km northeast of the world class Olympic Dam deposit. Three drill holes (VUD009, VUD015, VUD017), were chosen to examine the prospect scale alteration of white micas, across differing geophysical domains of the Vulcan IOCG prospect. A variety of breccias host mineralisation, including massive hematite and hematite-sericite-chlorite. The breccias are hosted within altered quartz-feldspar rock varying granitic to gneissic in texture. Dating of the host rock (VUD007) using zircon U-Pb geochronology showed that hematite-sericite-chlorite altered and brecciated granite was dated to 1.743+-Ma.

A spectral index for the AlOH – 2200nm white mica wavelength was plotted for the three drill cores (VUD009, VUD015, VUD017) showing excellent correlation with the aluminium assay values and iron oxide content. Sericite present in less altered, barren rocks was found to have longer wavelengths (2214-2218 nm), and transgressed to shorter wavelengths (2208-2212nm) – approaching iron enriched intervals. High aluminium content corresponded to longer wavelength sericite, opposite to iron content and differing from sericite wavelengths in the Olympic Dam deposit. A direct correlation between elevated copper and white micas was not observed.


Biography

Georgina began her spectral career at the Australian Mineral Foundation working on SWIR spectroscopy of the Data Metallogenica ore deposit sample collection. With the advent of the HyLogger instrumentation she began with the Geological Survey of South Australia 2001 and continues to work with spectral interpretation of mineral systems.

Tracing mineralogy and alteration intensity using the spectral alteration index and depth ratios at the Northwest Zone of the Lemarchant VMS deposit, Newfoundland, Canada

Jonathan Cloutier1,2,3 and Stephen J. Piercey1

1 Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador, Canada, A1B 3X5. 2 School of Earth and Environmental Sciences, University of St Andrews, Scotland, United Kingdom 3 Centre for Ore Deposit and Earth Sciences, University of Tasmania, Hobart, Tasmania, Australia

The use of hyperspectral reflectance in mineral exploration has been steadily increasing in recent decades. This study presents a novel approach that integrates geochemical and spectral proxies to delineate ore formation and alteration processes, which provide new spectral-based exploration parameters that can be used in real time. The precious metal-bearing, bimodal-felsic Northwest Zone of the Lemarchant VMS deposits, Newfoundland, Canada is used as a case study.

Alteration associated with the Northwest Zone includes intense and localized sulfide (pyrite, chalcopyrite, sphalerite and galena) and barite enrichment, and quartz, white mica and chlorite alteration. Zones of elevated Zn (>5000ppm) are associated with high chlorite carbonate pyrite index (CCPI), Ishikawa alteration index (AI), Ba/Sr, and low Na2O values and elevated SiO2 and K2O, Fe2O3, Na2O, and BaO contents, similar to global alteration signatures in VMS deposits. Mineralized areas contain phengitic white micas with 2200 nm absorption features longer than 2215nm and Mg-rich chlorites with 2250 nm absorption features shorter than 2252nm. Together, these data are consistent with the Northwest Zone having experienced intense hydrothermal alteration during the mineralization event.

A new lithology normalized spectral alteration index (SAI) for white mica and chlorite was developed in order to map and characterize the alteration intensity surrounding the deposit. In addition, depth ratio parameters (2200D/2340D vs 2250D/2340D) were used to characterize mineralogical changes and zonation. Together, these features document a paleo-fluid pathway with Mg-chlorite alteration extending to at least 300 m away from the mineralization, outside the study area, within the andesitic and dacitic units.

This study demonstrates that the use of VSWIR spectral reflectance data coupled with geochemical alteration proxies (i.e., AI, CCPI, Ba/Sr, Na2O) and lithogeochemical mass balance changes can identify and characterize alteration haloes and paleo-fluid pathways in the vicinity of VMS deposits. More specifically, hyperspectral reflectance can identify and quantify areas of intense alteration using spectral alteration indexes (SAI), estimate the relative abundances of white mica and chlorite using depth ratios, and characterize the chemical composition of the mineral phases, and relate them to specific alteration processes, which is not possible using only geochemistry. One of the main advantages of this method is that hyperspectral reflectance can be rapidly achieved on drill core at a high resolution for a relatively low cost, minimal sample preparation and results are available instantly, compared to a longer wait time for geochemical results, greatly enhancing decision making processes during drilling exploration programs, allowing vectoring and rapid decisions making during exploration programs.


Biography

Jonathan Cloutier obtained a Ph.D. from Queen’s University, Canada. Since graduating, he has worked as an exploration geologist, an embedded researcher at CSIRO, a postdoctoral research fellow at the Memorial University of Newfoundland as a lecturer at the University of St Andrews and is currently a research fellow at CODES.

Alteration signatures and footprints of the Ernest Henry deposit and camp: Spectral mineralogy and geochemistry

Courteney Dhnaram1, Vladimir Lisitsin1, Suraj Gopalakrishnan1, Daniel Killen1

1Geological Survey of Queensland, Brisbane, Australia

The Ernest Henry Cu-Au deposit is the best-known – and the most economically significant to date – example of Iron-oxide copper-gold (IOCG) deposits in the Cloncurry district of the eastern Mount Isa Province in Queensland, Australia. Geological Survey of Queensland (GSQ) has undertaken systematic sampling and mineralogical and geochemical analyses of drill core samples to characterise geochemical and mineralogical zonation of hydrothermal alteration associated with the Ernest Henry deposit, at a scale of hundreds to thousands of metres.

Short-wave infrared (SWIR) and thermal infrared data was collected using the GSQ’s HyLogger-3 machine across 19 drill holes (9 continuous drill holes and 10 sub-sampled drill cores), with >200 samples collected across these drill holes analysed for multi-element geochemistry (four-acid digestion – ICP-MS / OES; lithium metaborate fusion; fire assay – Au,Pt, Pd; Leco furnace – C, S; KOH fusion – ion chromatography – F; and Aqua regia – ICP-MS, Hg, Se, Te; 48-67 elements). 

Multi-element geochemistry from samples within the orebody identified a Cu-Ag-S-Te-As-Bi-Mo-W-Co-Se-Re (Pb-In-U-Sb-Sn) signature of the main phase of copper mineralisation. This signature is mostly seen within and near the orebody (up to 100m) and shows a strong association with potassic alteration.

Chlorite composition within both SWIR and TIR spectra varied from Mg-rich chlorite to Fe-rich chlorite with increasing distance to Ernest Henry orebody.  This trend was seen both along the NE and NW trending drill holes up to a distance of ~1km. Both SWIR and TIR spectra were used to discriminate early regional Phlogopite from pre-ore Biotite within the Dark Mica mineral group, with Biotite alteration extending to ~2km NE of the deposit and only 500m to the NW.

Potassic alteration from both geochemistry and mineralogy was identified ~1 km outwards of the deposit (within the proximal zone).  K-feldspar group compositional variations were identified using TIR, with potassic alteration consisting of microcline within the proximal to ore zone and orthoclase associated with copper mineralisation.

Multiple phases of the same mineral was identified in the hyperspectral data across the study area, specifically minerals previously thought to be only associated with early regional alteration (actinolite, albite, epidote etc).  Understanding which phases of these minerals are associated with pre-ore and ore mineralisation for similar Cu-Au systems will hopefully aid exploration in the future.


Biography

Courteney Dhnaram is a Senior Geoscientist within the Mineral Geoscience group at the Geological Survey of Queensland. Cpurteney has experience working across the state working on regional-camp scale projects, recently focusing on copper-gold mineral systems within North-West Queensland.

From proximal to remote sensing: analysing the pyrophyllite-muscovite association in the Buckskin range , Yerington district, Nevada (USA)

Portela, Bruno1; Sepp, Michael D.2; van Ruitenbeek, Frank J.A.1; Hecker, Christoph1; Dilles, John H.2

1Department of Earth Systems Analysis, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, 7514 AE Enschede, The Netherlands. 2College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 104 CEOAS Admin. Bldg., Corvallis, Oregon 97331, United States of America.

Hydrothermal mineral deposits such as skarns, porphyry, epithermal and SEDEX systems, are the primary source of mineral commodities of global importance, such as copper, gold, and silver. These types of mineral deposits have been subject to numerous studies over the years, using different approaches, including hyperspectral proximal and remote sensing. Since hydrothermal alteration minerals are active in, amongst others, the visible and infrared range, the analysis of spectral absorption features can be used to identify the mineralogy associated with different alteration events. Some alteration events are responsible for mineralisation, while other events do not generate any economic concentrations of precious elements. Therefore, it is important to develop a strategy to rapidly identify and map the indicator minerals linked to a mineralising event.

This research combined shortwave infrared (SWIR) proximal (SisuCHEMA hyperspectral imager) and remote (ProSpecTIR-VS sensor) sensing imagery to study how to discriminate intimate intergrowths of pyrophyllite and muscovite that are linked to different alteration events in epithermal gold systems. The main objective of this study was to characterise the occurrence of replacement textures by combining wavelength maps and a spectral index. The test area selected was the Buckskin range at the Yerington district, Nevada (USA), a high-sulphidation epithermal system.

Airborne data results showed outward zoning patterns from an inner zone of alunite ± pyrophyllite towards the surrounding area dominated by muscovite of varied wavelength position of its Al-OH absorption feature. Laboratory data improved the characterisation of the hydrothermal alteration mineralogy, which included alunite, pyrophyllite, muscovite, dickite, chlorite, topaz and zunyite. Spatial distribution of the pyrophyllite-muscovite association and, consequently, the textural relationship of the two minerals was addressed through the development of a novel spectral index, the pyrophyllite-muscovite index (PMI). Pervasive and veinlet-controlled textures were characterised, and a subtle shift in the wavelength position of the Al-OH absorption feature of muscovite from 2189 to 2195 nm was detected. Although the shift was not a direct indication of replacement, an intergrowth of pyrophyllite and muscovite sheets was suggested. The temporal relationship of the two minerals was then addressed: first through the interpretation of the alteration texture; second, through the backscattered electron images (BSE), confirming the muscovite replacement of pyrophyllite.

The association of the spatial distribution with the textural relationship of the pyrophyllite-muscovite association allowed the reconstruction of the fluid chemistry and fluid pathway linked to this scenario. An early-stage low pH high-temperature magmatic-hydrothermally derived fluid characterised by the presence of alunite ± pyrophyllite, responsible for an intense acid leaching and, consequently, the generation of permeable zones in the lithocap. These permeable zones worked as channels (feeders) for the emplacement of a late-stage fluid of near-neutral pH and lower salinity, characterised by the occurrence of muscovite of short to long-wavelength range. Therefore, this study clearly demonstrates the importance of characterising and mapping replacement textures at different scales to assist in the reconstruction of fluid emplacement and composition. Therefore, contributing to an improved understanding of a high sulphidation epithermal system and a better definition of target areas for follow-up mineral exploration studies.


Biography

Bruno Portela has a BSc degree in Geology from the University of Sao Paulo (Brazil) and an MSc degree in Applied Remote Sensing for Earth Sciences from the University of Twente, The Netherlands. Before his MSc, he worked for four years in different roles for BHP at Escondida Mine (Chile).

Characterising the hyperspectral SWIR features of tourmaline from two western Tasmanian granites

Cassady L. Harraden1, Wei Hong2,3, Cari Deyell-Wurst1

1Corescan Pty Ltd, Vancouver, BC, Canada, V6E 2E9 2Centre for Ore deposit and Earth Sciences (CODES), University of Tasmania, Hobart, TAS, Australia, 7001 3Department of Earth Sciences, School of Physical Sciences, The University of Adelaide, Adelaide, SA, Australia, 5005

Western Tasmania is one of the most important resource suppliers for Sn and W production in Australia and is host to numerous world-class high-grade deposits. The Heemskirk Granite, a highly productive batholith in this terrane, is associated with numerous skarns and greisens, which together have yielded a total of more than 104,000 tons of Sn. The nearby Pieman Heads Granite is of similar age (365-360 Ma; Hong et al., 2017) and has similar geochemical and mineralogical characteristics, but has not been associated with any known mineralisation. Both plutons contain abundant tourmaline in a variety of forms including magmatic hydrothermal veins, cavities, orbicules. This study compares the geochemical and spectral features of the tourmaline in both plutons to identify potential indicators of fertile magmatic systems.

Tourmaline samples were previously analysed by Hong et al. (2017) using Electron Microprobe (EMPA) and Laser-Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) to quantify the major and minor element compositions. Results showed that tourmalines are dominated by schorl varieties with a narrow range of chemical compositions (enriched in Fe and Al, moderately enriched in Mg, and poor in Ti, Li and Zn). Some systematic increases in Fe, Al and Li, and decreases in Mg and Ti are recognised from early- to late-stage tourmaline occurrences.

These analysed samples were also scanned using the Corescan Hyperspectral Core Imaging (HCI-3) system to obtain high resolution hyperspectral imaging data between 450nm and 2500nm (representing the visible to near-infrared (VNIR) and short-wave infrared (SWIR) regions). Characteristic absorption features in the SWIR are attributed to BOH, AlOH, and MgOH stretching vibrations: ~2200nm (AlOH), ~2250nm (BOH), ~2320nm (MgOH), and ~2360nm (BOH) (Hunt et al., 1973; Clarke et al., 1990; Bierwirth, 2004). Results show very little variation in individual wavelength values across samples for all four major SWIR absorptions. However, using combination of spectral features and specialised imaging capabilities, differences in tourmaline spectra between the two plutons are apparent. Tourmaline from the Pieman Heads Granite has relatively high ~2375nm wavelength positions while the ~2200nm and ~2250nm wavelengths are shifted to lower wavelengths. The Heemskirk Granite tourmalines display mid-range wavelength positions for all three absorption features. Additionally, variations in specific reflectance ratios in the SWIR region highlight zoning patterns that could reflect small-scale Fe variations.

Distinguishing between the barren Pieman Heads and fertile Heemskirk Granites has implications for Sn exploration activities in Western Tasmania. The major-element compositions of the tourmalines in these two granites are very similar but discrete variations in key SWIR absorption feature relationships are apparent using high resolution hyperspectral imaging. This demonstrates the potential to apply hyperspectral imaging techniques to differentiating compositionally similar intrusive bodies with different mineral potential for mapping and exploration activities in the region and beyond. 


Biography

Cassady’ current work with Corescan is focused on developing new geometallurgical and geotechnical applications using data collected from hyperspectral imaging technology. This was also the focus of her PhD research. Before completing her PhD she worked as an exploration geologist in Alaska, Colorado, Nevada, Utah, and Arizona.

Deriving Quantitative Alteration Mineralogy from TIR Hyperspectral Data in IOCG Systems

1Stromberg, Jessica, 1Schlegel, Tobias, 1Pejcic, Bobby, 1Birchall, Renee, 1Shelton, Tina

1CSIRO Mineral Resources, Kensington, Australia

Identifying alteration mineral zonation around hydrothermal ore systems is critical to the mineral exploration process. Hyperspectral methods are commonly used to map alteration because they are fast, inexpensive, and require little to no sample preparation compared to other mineralogical techniques such as scanning electron microscope (SEM) based mineral mapping, for example. The visible-near and shortwave infrared (VN-SWIR, 350-2500 nm) spectral regions are most used as they are sensitive to hydrated mineral phases including chlorite and white micas. However, in mineral systems which are iron oxide-rich or where key alteration assemblages include abundant anhydrous phases, such as in iron oxide-alkali-calcic alteration systems, using this spectral range can be problematic. In this case, the thermal-infrared (TIR) spectral range (6000-14500 nm) may be more appropriate as it is sensitive to anhydrous silicates such as quartz and feldspars. However, there are inherent challenges in unmixing hyperspectral data for deriving quantitative mineral abundances. In particular, when the quantification of minor or spectrally similar phases are key to the alteration assemblages, such as in the quantification of different feldspars. This can be overcome with the use of a calibration dataset such as quantitative X-ray diffraction or SEM-based quantitative mineralogy in combination with Partial-Least Square (PLS) regression methods. In developing such models, scale is of critical importance. Variability in the sampling area and volume between datasets is one of the greatest challenges in validating hyperspectral data with quantitative mineralogy, and in integrating any geoscience datasets. In this work, we used several hyperspectral and spectroscopic instruments (HyLogger, Agilent 4300 FTIR, Bruker Vertex FTIR, ASD Fieldspec Pro) to evaluate the impact of scale on hyperspectral data validation in IOCG systems. In this process we developed a methodology for creating the first scale-consistent dataset of VNIR-SWIR, TIR, and SEM-based quantitative mineralogy data on drill core samples. This dataset comprises 250 samples from a world-class IOCG deposit in which the key mineral phases, assemblages, and alteration patterns were identified using the SEM-based quantitative mineralogy. Hyperspectral data was processed using The Spectral Geologist Software (TSGTM) software and even with a scale consistent dataset, and a constrained mineral library based on the SEM-based mineralogy, conventional unmixing methods such as the The Spectral Assistant (TSATM) were unable to reproduce key alteration patterns for vectoring towards ore. Using the SEM-based mineralogy data, PLS modelling was applied to derive predictive models for key mineral phases from the TIR hyperspectral data. The resulting models produced quantitative mineralogy with r2 > 0.94 for key phases including quartz, K-feldspar, albite, calcite, and >0.80 for magnetite, biotite, and plagioclase. More importantly, the key mineral assemblages change with distance to ore and the relative abundance feldspar species (albite, K-feldspar, plagioclase) identified by the SEM-based mineral mapping were reproduced using PLS-derived mineral abundances in a validation drill core. This method and the models generated will provide a framework for improving the application of hyperspectral data for mapping alteration in IOGC systems.


Biography

Jessica is a Research Scientist in the Mineral Footprints team at CSIRO Mineral Resources where she leads Activity 5 of the NVCL and works on projects across multiple commodities applying the combined use of lab and field-based spectroscopic and geochemical techniques to address industry-specific challenges.

Modelling of petrophysical from hyperspectral drill core data collected from the Osborne Cu-Au deposit, Mount Isa Inlier, Queensland

Laukamp, Dr Carsten1, Francis, Neil1, Hauser, Dr Juerg1, Gopalakrishnan, Dr Suraj2, Mule, Shane1

1CSIRO, Perth, Australia, 2Geologial Survey of Queensland, Brisbane, Australia

The combination of magnetic susceptibility and density allows identification of iron oxide copper-gold (IOCG) mineralisation by estimating proportions of magnetite, sulphide and hematite alteration which can be indicative of IOCGs. In the frame of the National Virtual Core Library project, hyperspectral reflectance spectra acquired from drill core of the Osborne Cu-Au deposit, Mount Isa Inlier, Queensland using a HyLogger3 at GSQ’s Exploration Data Centre were compared with magnetic susceptibility and density measurements. In this study we explore the feasibility of inferring the petrophysical data from the 1) visible-near (VNIR), shortwave (SWIR) and 2) thermal (TIR) infrared wavelength regions. Specifically, we seek to predict magnetic susceptibility and density values in drill core sections where petrophysical data are not available and potentially extrapolate these to other hyperspectral data sets, such as those acquired by field or Earth Observation instruments.

Using The Spectral Geologist (TSGTM) software, partial least squares (PLS) was employed to derive predictive models using 23 unique magnetic susceptibility and density measurements, that were assigned to all nearby spectral measurements (+/- ~10cm). The values of the input magnetic sustainability and density values ranged from 0 to 2.3 K (Si) and 2.7 to 4.9 g/cm3, respectively. The hyperspectral data were not spatially re-sampled to fit with the drill core interval measured for petrophysical data. Instead, the original 1 cm spatial resolution was used to evaluate the variability of hyperspectral data within the petrophysical sample intervals. The correlation between the 23 measured and corresponding modelled magnetic susceptibility (n = 157) for the same 23 depth intervals was high for the VNIR-SWIR (r2 = 0.95) and the TIR (r2 = 0.969), but the PLS-modelled magnetic susceptibility values showed a large variance (± 0.8 and ± 0.5, respectively). Similarly, the correlation between the measured and modelled density was high for the VNIR-SWIR (r2 = 0.958) and the TIR (r2 = 0.989), with the PLS-modelled density values showing a large variance (± 0.4 g/cm3 for both wavelength ranges). However, HyLogger3 high-resolution RGB imagery showed that the predicted value ranges were sufficiently different to discriminate drill core intervals dominated by magnetite-rich rocks, from magnetite-rich breccia and least-altered (non-mineralised) rocks. PLS models based on the VNIR-SWIR wavelength ranges were mainly driven by depth changes of electronic transition absorption features related to iron and copper in the VNIR, which are most intense in the highly altered, magnetite- and/or sulphide rich rocks. PLS models based on the TIR wavelength ranges were highly influenced by the thermal background typically associated with iron oxides and sulphides. Density values modelled from VNIR-SWIR compared to those modelled from TIR showed a good correlation (r2 = 0.729), whereas the correlation between magnetic susceptibility modelled from VNIR-SWIR and TIR was comparably low (r2 = 0.518). While the small amount of data used to infer the models discussed here means that their predictive power needs to be assessed comprehensively, our results nevertheless indicate a high potential for successfully inferring petrophysical from hyperspectral data and cost-effective mapping of IOCG-related alteration. 


Biography

Carsten Laukamp is a senior research geoscientist at CSIRO Mineral Resources, based in Perth, Australia and is project leader of the National Virtual Core Library. Carsten explores the potential for combined use of reflectance spectroscopy, geochemistry and geophysics for tracing hydrothermal alteration signatures through cover and advancing ore body knowledge.

HIGH RESOLUTION VS. STANDARD RESOLUTION: How an increase in spectral resolution using a field portable spectrometer affects quality of data – a case study on Nickel exploration

Shelton Pieniazek, Lori1

1Spectral Evolution, United States

Standard resolution of a field portable spectrometer at 3nm (UV), 8nm (VIS) and 6nm(NIR) has been used successfully in the geological remote sensing and mining industry for a variety of applications. Alteration mapping has been key for finding different mineral assemblages that indicate an area of interest. Using a higher resolution field spectrometer has proven to be beneficial in understanding and identifying new features in a variety of different mineral groups and subgroups.

A study was conducted using three different field spectrometers, each with different resolutions. As you increase resolution, features that are not visible with a standard resolution spectrometer appear in all three ranges (UV,VIS,NIR) thus yielding a better understanding of alteration changes and geochemical conditions


Biography

Mrs. Lori Shelton Pieniazek is the Geologist for Spectral Evolution. She received her degree in Geosciences from Tennessee Technological University. Her main focus is on applying spectral geology applications to the mining and geological remote sensing industries.

HyLoggerTM mineralogy from chips: A RoXplorer pilot study

Moltzen, Jake1

1Geological Survey Of New South Wales, Londonderry, Australia

The RoXplorer® coiled tube drilling system is scheduled to be used for MinEx CRC drilling activities in New South Wales (NSW) from 2022 for National Drilling Initiative (NDI) areas South Cobar, North Cobar, Mundi, Forbes and Dubbo. This recently developed system provides a faster and more cost-effective alternative to conventional diamond and reverse circulation drilling, while also offering safety advantages and reduced environmental impacts (Hillis et al. 2014). Ongoing technology development within MinEx CRC will maximise RoXplorer® production during MinEx CRC drilling campaigns, with 5 km spaced holes planned throughout NDI areas to better understand basement and cover sequence geology and the potential for undiscovered ore deposits buried beneath cover.

In this pilot study, two trial drillholes from the RoXplorer® system were scanned using the HyLogger-3TM instrument to determine the best method for scanning RoXplorer® chips and to assess the quality of visible-near infrared to shortwave infrared (VNIR-SWIR) and thermal infrared (TIR) spectra for routine interpretation. Downhole chip samples produced by the RoXplorer® range in size from ~10 µm to ~4 mm (Tiddy et al. 2019), however a separated coarse fraction with sizes ranging from ~1 mm to ~4 mm was used for both drillholes. Outcomes from this study included:

  • VNIR‒SWIR and TIR spectra were found to be reliable for routine mineral identification, tracking mineral chemistry and identifying lithological variations downhole.
  • Black plastic chip trays produced better spectral results than clear or white trays.
  • Larger 50 mm x 50 mm chip compartments produced better spectral results than standard 25 mm x 50 mm chip compartments.
  • Regular linescan mode produced spectra with higher reflectance and therefore better sensitivity, than chip scanning mode.
  • Rinsing chips with water to remove clinging fines increased TIR reflectance by up to 40% and reduced volume scattering effects.

The findings of this work will be used to help develop a consistent approach to scanning future RoXplorer® drillholes across the state and territory Geological Survey HyLoggerTM nodes.

References

Hillis R. R., Giles D., Van Der Wielen S. E., Baensch A., Cleverley J. S., Fabris A., Uvarova Y. (2014). Coiled tubing drilling and real time sensing – enabling prospecting drilling in the 21st Century? Society of Economic Geologists Special Publications, 18, 243–259.

Tiddy C. J., Hill S. M., Giles D., van der Hoek, B. G., Normington V. J., Anand R. R., Baudet E., Custance K., Hill R., Johnson A., McLennan S., Mitchell C., Zivak D., Salama W., Stoate K. Wolff K. (2019). Utilising geochemical data for the identification and characterisation of mineral exploration sample media within cover sequence materials, Australian Journal of Earth Sciences, DOI: 10.1080/08120099.2019.1673484


Biography\

Jake completed undergraduate studies at Curtin University and honours at the University of Tasmania before spending 4 years working for Mineral Resources Tasmania with the HyLoggerTM team. He is currently employed as a spectral geologist with the Geological Survey of NSW to oversee the delivery of the NVCL project.

Validation of spectral data: A critical step towards accurated prediction

Ramanaidou, Erick1

1Mineral Resources – Discovery | CSIRO, Kensington, WA, Australia

The last three decades have seen the emergence of spectral mineralogy as a valued tool for the exploration and mining companies. From the past luggable GER IRIS and portable PIMA we now have access to an extended suite of small, fast, light and accurate field spectrometers such as the ASD and Spectral Evolution spectrometers covering the visible, near infrared and short-wave infrared – VNIR-SWIR 380 to 2500 nm range. In parallel, automated systems to scan diamond cores and drill chips have been developed such as the hyperspectral point analyser, the HyLogging System™, the hyperspectral imaging spectrometers, the Corescan™ Core Imager Mark III, SpecIm SisuROCK, Neo Hyspex and HCIS Terracore are commercially available for use by the exploration and mining companies. As well as VNIR-SWIR, the thermal infrared -TIR range (8 to 14 µm) is now available with the HyLogging System™ 3 providing the detection minerals such as quartz, felspar, olivine, pyroxene and garnet. Large volumes of diamond cores and drill chips have been measured by the exploration and mining companies and the spectral geologist research community has responded by providing automated ways of processing large number of spectra. The CSIRO- developed the spectral geologist or TSG™ offers two ways of processing the spectra (1) through the automated spectral analysis program or The Spectral Assistant (TSA) or through customised scripts, algorithms that use depth and minimum wavelength of absorptions to uniquely identify specific minerals. The TSA is applied for HyLogging System™ spectra on measured areas on around a few cm2 where mineral mixture is likely. On the other hand, the hyperspectral imaging Corescan™ Core Imager Mark III captures many pure pixels at a resolution of 500 µm and the mineral mapping processing is performed using a dedicated expert system program.

Reflectance spectra acquired using these systems are often the complex results of many absorptions embedding not only mineralogical but also particle size information. Although quite powerful, the processing methods previously mentioned require validation by more classical methods such as x-ray diffraction, Raman spectroscopy, X-ray fluorescence (XRF) and µXRF mapping to improve prediction.

Through examples selected from the iron ore and nickel laterite industries, it will be demonstrated that complementary and cross validated methods are essential to ensure that validation of spectral data is undertaken as a critical step towards accurate mineralogical prediction and that it is good to have redundant information.


Biography

Dr. Erick Ramanaidou is the Commodity Research Leader for iron ore and nickel laterite. He has been involved in spectral research for the last 25 years and has concentrated his effort to the understanding of the spectral properties of iron oxides and gangue minerals in iron ores.

About the GSA

The Geological Society of Australia was established as a non-profit organisation in 1952 to promote, advance and support Earth sciences in Australia.

As a broadly based professional society that aims to represent all Earth Science disciplines, the GSA attracts a wide diversity of members working in a similarly broad range of industries.

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