The 1997 program was organised as a joint venture between the Victorian Division of the GSA and the ASEG (Australian Society of Exploration Geophysicists) Victoria Branch. It was intended to reflect and build on the increasingly closer, complementary and symbiotic relationship that has been developing between geologists and geophysicists over recent decades. Some of the benefits of this growing relationship have been highlighted by the early outcomes and spin-offs from the integrated activities based on quality airborne regional surveys such as the VIMP programme and its Australia-wide equivalents.

These transcend the limiting aspects of tenement, state and ocean/continent boundaries. The high quality of the speakers made it almost impossible to pick favourites or winners in the presentation stakes. Both keynote and case-study speakers provided ideas and illustrations on alternative applications and directions of the integrated approach, new developments of technologies and thoughts on future trends. It was all a real eye-opener to the many undergraduate students in the audience! Following up on last year's successful innovation, a small, varied, theme-related exhibition added extra sparkle, and some nostalgia, to the proceedings.
 
1997 SELWYN LECTURE: Some new integrated air and space-borne mapping technologies from the CSIRO.
Dr Jonathan Huntington, CSIRO Division of Exploration and Mining
 
Introduction
Significant trends influencing the Australian minerals industry are driving the need for major changes in mapping technologies. Amongst these are the need for:
  • reduced cost of airborne surveys
  • new geological knowledge
  • deeper penetration
  • globalisation of Australian exploration
  • more sophisticated (and integrated) interpretation methods.
CSIRO's Division of Exploration and Mining (DEM) are involved in aspects of all these issues as we strive to support the industry with tools appropriate to exploration that must be progressively more competitive, run on narrower margins and be environmentally and socially responsible. This paper presents examples of some of the current work that addresses these changes mentioned above, viz.:
Trends
Examples
  • Reduced cost of airborne surveys
  • Project Cerberus
  • UAVs
  • New geological knowledge
  • Mineral mapping technologies
  • Regolith characterisation with geophysics
  • Deeper penetration methods
  • Improved electromagnetic methods
  • Gravity methods
  • Globalisation of Australian exploration
  • The ARIES-1 project
  • More sophisticated (and integrated) interpretation methods
  • Joint interpretation, forward modelling, residual analysis GIS, noise reduction methods in radiometrics
Improved Interpretation Methods
Airborne gamma-ray surveys (radiometrics) are now routinely collected in most airborne geophysical surveys and produced as highly informative image maps as part of regional multi-client and state exploration initiatives. Radiometrics may be regarded as a mature technology, but while regularly collected it is often interpreted only in rudimentary fashion and considerable scope exists for improvements in pre-processing and more intelligent interpretation. Radiometric surveys now commonly collect 256 channels of data allowing the application of improved noise reduction and modelling methods that can greatly improve the data's utility. Interestingly, many of these methods are based on techniques for the improvement of Landsat and remotely-sensed scanner data developed by the CSIRO in the 1980s (Green et al. 1988; Dickson 1997 pers. comm.). Some of the improvements gained from these methods (e.g. Hovgard 1997) are equivalent to increasing the size of the gamma-ray detecting crystal packs, which in turn could lead to reduced instrumentation/survey costs.
It remains to be seen if this transpires, or whether people will just prefer the increased detail permitted by both large crystal packs and improved processing software. Integrating geophysical data and vector-based geological maps in GIS systems has also demonstrated that one can quickly undertake residual analysis methods to highlight radioelement distributions not predicted by a model of the background lithologies or the regolith. In this way one can highlight areas that may have suffered increased amounts of, say, potassium metasomatism, relative to the background. Such residual analysis methods may, in fact, be applied to many types of surveys where one is looking for departures from a predicted background.
Mineralogical Mapping
Mineral mapping is the non-invasive identification and mapping of rock, regolith and alteration mineralogy using the principles of spectroscopy. It is that facet of remote sensing that has been specifically tailored to the needs of exploration and mining over twenty years of R & D, largely here in Australia (Huntington 1997). Its emphasis is less on spatial mapping of landform or structure or major litho-stratigraphic relationships, than on the specific identification of mineralogical composition indicative of specific formations, host rocks, alteration zones or components of the regolith. This can now be carried out in the field, from airborne platforms (Huntington & Boardman 1996) and, hopefully, soon from the global vantage point of space.
Mineralogical mapping is one example of the new geological knowledge that we are now seeing appear. The PIMA-11 hand-held technology has demonstrated the reality of mineralogical mapping and an understanding of relationships between mineralogy and ore systems. This has helped enormously the understanding of what might be achievable from air- and spaceborne platforms and why this new type of information might be valuable. From a better understanding of the science of mineralogical mapping we thus now need to move on to considering how best to deliver such information in a cost-effective manner. Setting up special-purpose companies, flying special-purpose instruments on surveys with a single objective is getting harder and harder to justify financially.
An alternative approach to mineralogical mapping is to integrate the collection of such data with routine airborne geophysical surveys. To this end CSIRO is developing the prototype for a new data product called "Airborne Mineralogy" derived from a low-flying, profiling (non-scanning) reflectance spectrometer called OARS. This new instrument will be flying by mid-1998 and, when refined, will lead to the manufacture of multiple airborne instruments called GIMMS (geophysically integrated mineral mapping spectrometer) for the airborne geophysical market. Simulations of this new product have demonstrated that two-dimensional maps can be made of many mineral species and that when interpolated in the same way radiometric data are gridded, can produce valuable image maps of the composition of host lithologies, alteration zones and regolith components. These might include maps of sulphate, phyllosilicate, clay, carbonate and iron oxide minerals.
Cerberus
As margins for airborne geophysical surveys decrease and new technologies come along for other airborne surveys, it makes enormous economic sense to try to integrate more instruments into the one survey mission. The Cerberus project, a joint venture between the Federal Government's R & D Start program, World Geoscience Corporation and the CSIRO, is planning to test and demonstrate that multiple instruments (which have traditionally been flown separately) when flown together, can bring significant reductions in data acquisition cost and benefits from synergistic interpretation. The project aims to develop modified instruments that can fly together without interfering with each other.
Specifically Cerberus will co-fly airborne magnetics, radiometrics, electromagnetics (AEM) and two mineral mapping spectrometers. Clearly some technical challenges need to be overcome, in particular with respect to the interference generated by AEM systems, but a successful project could mean exploration and mapping programs will get much more information for almost the same amount of money.
On the interpretation side we also anticipate learning to carry out joint-inversions of multiple data sets and joint interpretations using more than one input. For example, improved radiometric interpretations are foreseen from the ability to relate gamma-ray geochemistry (from radiometrics) with the surface distribution of specific minerals (derived from the mineral mapping spectrometers). Already analyses of selected samples showing PIMA-11 absorptions due to potassium substitution in micas have been confirmed with gamma-ray derived potassium measurements.
Cerberus will include two types of mineral mapping spectrometer: a version of GIMMS, tailored for the Cerberus environment, and a new mid-infrared sensor called TIPS (thermal infrared profiling spectrometer). GIMMS operates in the visible and shortwave infrared and is suited to mapping silicates with OH in their lattices. TIPS will concentrate on the thermal or mid-infrared region between 8 and 1 2 micrometres, where Si-O vibrations allow one to map many other non-OH bearing phases, such as quartz, feldspars, olivines, pyroxenes and garnets, as well as the carbonates. This ability has already been demonstrated with CSIRO's MIRACO2LAS mid-infrared, active spectrometer (Whitbourn et al. 1994).
ARIES-1
The globalisation of exploration and the dominant role by Australian companies in energetic exploration in many countries now opening their doors to foreign investment and new exploration strategies, brings great opportunities for us to consider tools to better map remote, logistically challenging regions overseas. A reduction in aircraft costs will certainly help this, but it will always be costly and challenging to move fleets of planes from country to country. The opportunity to learn to map mineral distributions from space, the objective of the ARIES-1 project, will bring further advantages in both the generation of new knowledge and reductions in data costs. Recent simulations of ARIES products have themselves brought to light new mineral distributions, not previously known about, as well as demonstrated that the ARIES-1 design should be able to deliver such new knowledge from anywhere on earth where sufficient exposure exists (say 50% ground cover).
Other trends
Three other trends that will certainly impact on mapping and improved integrated interpretation in the years ahead include, firstly, the potential use of UAVs (unmanned airborne vehicles) that will allow very long endurance airborne surveys at low altitudes eguipped with multiple instrument arrays (Green 1997). This should, in time, further reduce data acquisition costs. The second trend will be in the improved depth penetration afforded by the next generation of airborne electromagnetic sensors. Finally the long-term development of airborne gravity gradiometry will provide real insight into the depth structure of the earth.
CSIRO, the CRC for Australian Mineral Exploration Technologies, the exploration industry, AMIRA and the contracting industry are all combining in developing these new methods, which should continue to revolutionise the way we explore and map the world's geology. Over the next decade we can be assured of new methods, increased precision and new knowledge hopefully acquired at substantially reduced cost.
Acknowledgements
I am indebted to Dr Andy Gabell of World Geoscience Corporation for information and illustrations regarding the Cerberus project, to Dr Bruce Dickson for information on developments in airborne radiometrics and Dr Tim Munday for information on the application of airborne electromagnetics methods in the regolith mapping.
References
GREEN, A.A., BERMAN, M., SWITZER, P. & CRAIG, M.D., 1988. A transformation for ordering multi-spectral data in terms of image quality with implications for noise removal. IEEE Transactions on Geoscience and Remote Sensing 26, 65–74.
HOVGAARD, J., 1997. A new processing technique for airborne gamma-ray spectrometer data (NASVD). In: Proceedings of the American Nuclear Society Symposium on Emergency Preparedness and Response, San Francisco.
HUNTINGTON, J.F. & BOARDMAN, J.W., 1996. Semi-quantitative mineralogical and gealogical mapping with 1995 AVIRIS data. In: Proceedings of the 2nd International Symposium on Spectral Sensing Research '95 (ISSSR), 26 Nov – 1 Dec, 1995, Melbourne, Australian Government Publishing Service.
HUNTINGTON, J.F., 1997. Field, air and spaceborne mineral mapping for exploration. In: Proceedings of the 38th AM IRA Annual Technical Meeting, ISBN 0908039654, E3.1–E3.12, Australian Mineral Foundation, Adelaide, 11th September, 1997.
WHITBOURN, L.B., HAUSKNECHT, P., HUNTINGTON, J.F., CONNOR, P.M., CUDAHY, T.J. & PHILLIPS, R.N., 1994. Airborne CO2 laser remote sensing system. In: Proceedings of the 1st International Airborne Remote Sensing Conference and Exhibition: Applications, Technology and Science, Strasbourg, France, 12–15 September 1994, 11-94 – 11-103.