Automated Petrography

Petrography of sectioned drill cutting as seen under optical microscope, Scanning Electron Microscope, and QEMSCAN
(the image is not part of the conference paper below) 

While compiling the 2011 publications relevant to Automated Mineralogy and Petrography for the Zotero Automated Mineralogy Library, I came across an abstract presented by Dirk van der Wal and Hans Kruseman at the VIII Congress of CIS Dressers (Ore Mining & Dressing Plants), held in Moscow during February 28 to March 2 at the at Congress Centre of the World Trade Center and organised by the Department of Enrichment of Ores NITU "MISIS", University of Moscow. This abstract presents an excellent introduction into how Automated Petrography fits into the bigger picture of Petrology and Petrograpy and is re-posted here:


Examples of Automated Petrography systems (MLA/QEMSCAN) used in the Minerals Industry

Dirk van der Wal, Hans Kruesemann
FEI Company , PO Box 80066, 5600 KA  Eindhoven, The Netherlands

Petrology is a Geoscience involved with understanding the provenance of rocks, such as depositional environment in the case of hydrocarbon reservoir rocks, or metamorphism in the case of “hard rocks”. Petrography is a branch of Petrology that involves microscopic description of mineral content and texture (microstructure) to aid interpretation of provenance.

The predominant petrographic system is a polarized optical microscope, used to identify minerals from their optical properties in crossed polarized light such as birefringes. Due to the manual and laborious nature of the technique, the Minerals Industry has struggled to deploy petrography in industrial use cases such as Geometallurgy or Mineral Processing.

Scanning Electron Microscopy (SEM) based Automated Petrography systems have been developed since the late 1980’s, predominantly in Australia (CSIRO, Univ. of Queensland), known as QEMSCAN® and Mineral Liberation Analyzer (MLA) respectively. Mineral classification technology based on backscattered electron intensity and elemental composition from energy dispersive spectroscopy has been developed over decades and provides a robust solution of automated fast mineral classification with the superior spatial resolution obtained from electron microscopy.

There are currently more than 150 Automated Petrography systems in use worldwide, predominantly in the precious and base metal mining industries. They are used to measure ore properties such as ore typing, precious metal host mineralogy, mineral associations (e.g. mineral liberation) or phase purity from core samples or grinded material.

Recent developments include advances in sample preparation and speed of analysis, aiming at reducing sample turn-around time to a point where data can be used near real-time to optimize the grinding and flotation circuit.

In this contribution, the Automated Petrography technology will be introduced and use cases illustrated from the precious metal (e.g. Pt, Au, U) and base metal mining industries (e.g. Cu, Fe).

Automated petrography applications in Quaternary Science

Cover of Quaternary Australasia Volume 28/2 December 2011 issue featuring QEMSCAN images of 2010 Brisbane Flood sediments 

While there is a strong industry focus on applying automated mineralogy and petrography analysis to petroleum exploration, mining and mineral processing, expert solutions such as QEMSCAN also provide exciting opportunities in other areas of Geoscience such as Quaternary Research. The December 2011 issue of Quaternary Australasia features a review article on "Automated petrography applications in Quaternary Science" by David Haberlah, Craig Strong, Duncan Pirrie, Gavyn K. Rollinson, Paul Gottlieb, Pieter W.S.K. Botha and Alan R. Butcher. The paper includes three compelling case studies on aeolian, fluvial and coastal sediments based on samples from the "red dawn" dust event in eastern Australia on September 23, 2009, the Icelandic Eyjafjallajökull volcanic eruptions in April 2010, the Brisbane floods in January 2011, and medieval mining impact on estuary systems along the coast of Cornwall, UK.

Abstract:
Automated petrography analysis integrates scanning electron microscopy and energy-dispersive x-ray spectroscopy (SEM-EDS) hardware with expert software to generate micron-scale compositional maps of rocks and sediments. While automated petrography solutions such as QEMSCAN® and MLA are widely used in the mining, mineral processing, and petroleum industries to characterise ore deposits and subsurface rock formations, only few Quaternary scientists have applied SEM-EDS compositional mapping to palaeo-environmental research. This paper explains the fundamentals behind the analytical method, describes the type of data that can be generated, and presents the latest advances. Potential applications in Quaternary Science are discussed, including the study of: 1) depositional and formation environments; 2) weathering and diagenetic history; 3) sediment provenancing and pathways; and, 4) the provision of complimentary data in chronostratigraphic studies. Three case studies illustrate potential applications in fluvial, aeolian and coastal research. The first case study applies automated petrography analysis to dust fingerprinting on samples collected from the ‘red dawn’ dust event that swept across eastern Australia on the 23 September 2009, and from the Icelandic Eyjafjallajökull volcanic eruptions that caused enormous disruption to air travel across Europe in April 2010. The second case study investigates flood deposits collected across Brisbane in the aftermath of the January 2011 floods. In the final case study we consider how automated petrography can aid the understanding of human impacts on the environment. Automated SEM-EDS technology was first developed by CSIRO in Australia, and made commercial by companies based in Brisbane. This proximity has proven an advantage to a wide range of researchers in Australasia pioneering innovative applications.

Reference:

Haberlah, D., C. Strong, D. Pirrie, G. K. Rollinson, P. Gottlieb, P.W.S.K. Botha, and A.R. Butcher. 2011. Automated petrography applications in Quaternary Science.Quaternary Australasia 28 (2): 3-12.