Tue
24 SepMicroanalytical Centre (MAC) Update
The Microanalytical Centre (MAC), located on the fifth floor in the Willet Green Miller Centre (WGMC), has been busy this past summer adding, creating, innovating with instrumentation designed to enhance research capacity at the Harquail School of Earth Sciences, Laurentian University. Dr. Andrew McDonald , MAC Director and Rémy Poulin, Research Scientist listed significant updates below to keep students and researchers informed.
1. Addition of new SEM software, AZTEC (Oxford).
Through a generous contribution from the Harquail School of Earth Sciences, along with partial funding from the Dean’s office, MAC purchased AZTEC, the new SEM-EDS software package that builds upon the previous version, INCA, but with important additions and modifications including: a. Ability to capture higher-resolution images (up to 8192 dpi); b. Capacity to produce fully quantitative X-ray maps; c. Complete imaging stitching, meaning full PTS images, collected as X-ray maps, backscattered electron images, etc. can be assembled into publication-ready montages; d. Full mineral-liberation analysis (MLA) capabilities (useful in the analysis of trace minerals such as zircon, gold, PGM, etc.) and e. Quick, full-quant mineral analyses. The software is backwards compatible with INCA, so if you have a pre-existing copy of this on your work station, you can access your data in the same way as previously. The new software, AZTEC, is dongle-driven; we have obtained three additional licences, two of which will be available on dedicated computers on B5 and B8.
|
Figure 1: Rémy Poulin operating the cold cathode CL. |
Figure 2: Zonation in carbonates as revealed by CL. |
2. Enhancement of CL instrumentation.
Rémy Poulin has been working hard to improve our cold cathode CL instrument (Fig. 1), which is ideal for differentiating between generations of similar minerals (carbonates, feldspars, apatite, zircon, etc.; Fig. 2) in a very fast, simple way. The system is now housed on a newer Olympus binocular microscope with zoom magnification up to 45x, so the CL response in grains as small as 50 um can be visualized. The system routinely accepts standard PTS, but can also accept large-scale PTS and cut core up to ~ 10 cm in length. A new Basler digital camera has been added, so high-quality images can be collected. As well, important, subtle details regarding the peaks in a CL spectrum can now be obtained with a Ocean Optics spectrometer and related software. This means quantitative, not just qualitative, CL spectra can be obtained. Lastly, full images of entire PTS may be collected and stitched together with either Adobe or with the new imaging software, QuickPhoto (Fig. 3). The spectrometer is ideally suited for CL responses in the mid- to long-range portion of the visible spectrum and Rémy is working on adapting it to the shorter wavelength and UV portion of the visible spectrum.
Figure 3: Full PTS CL imaging.
3. Addition of new imaging software for opaque-dominated PTS.
With combined contributions from HES and Prof. McDonald, a new software package, QuickPhoto has been purchased. The HES unit has a long tradition in analyzing opaque minerals in relation to studying ore deposits; while there are numerous ways to obtain PTS images for transparent minerals, none suitable for opaque minerals has been available until now. We have investigated and worked with a small Czech company, Promicra, to obtain and refine a new software package, QuickPhoto, to solve this dilemma. A series of images, collected under polarized (or cross-polarized) reflected light conditions on standard (or larger) PTS are obtained using a manual X-Y stage. The images are stitched together in real time to create a montage of the complete PTS. The strengths of this software and the approach used include the ability to continually adjust the focus (eliminating issues related to variations in thickness of the PTS), an image that can be digitally zoomed (Fig. 8) so small grains (>25 um) are resolvable. The software is easy to use and fast, with complete PTS being imaged in 5 to 10 minutes. Higher-power objectives can be also be used to collect high-mag images on smaller areas. The setup is ideally suited for samples where opaques constitute a high proportion of the sample (>50%), but even PTS with lesser amounts (10- 15 modal %) opaques can be imaged.
|
Figure 5: Chromite & sperpentine, Ring of Fire. |
Figure 6: Bornite & chalcopyrite, McCreedy East mine. |
|
Figure 7: Galena & sphalerite in dolomite (MVT deposit). |
Figure 8: 50% digital enlargement of Figure 7. |
4. Addition of new(er) X-ray diffractometers (Bruker D8 systems).
The MAC received a used D8 microdiffractometer as a donation from the Canadian Museum of Nature, along with a gently-used instrument purchased by Prof. McDonald, to enhance the capacity in the area of solid-material and mineral analysis. The microdiffractometer can analyze microquantities of material (e.g., alteration rinds on sulfide minerals), effectively a sufficient amount to coat a glass fibre 100 um in diameter. No special preparation of the material is required and scans can be collected in ~ 1 hour. The second D8 (‘Leonard’) is also operational and will be used to analyze rock powders as well as to provide in-situ analyses of mineral in PTS, grain mounts, etc. Both instruments will augment our existing XDS Scintag instrument that continues to perform perfectly, despite its advanced age (> 20 yrs).
|
Figure 9: Inside the Bruker D8 Microdiffractometer showing the detector (left side) and sample (centre). |
Figure 10: Diffraction frames collected on <1 mg of a pink carbonate with the microdiffroctometer. |
Figure 11: Pink carbonate from Rundle deposit positively identified as near end-member calcite.
5. Demise of the SX-50.
Approximately two years ago, we received a Cameca SX-50 electron microprobe that used to be the primary workhorse of the OGL (until they purchased a new instrument). The instrument took enormous time and effort (provided by Dr. Kirk Ross and Rémy) to get operational, but unfortunately, now inoperable. This leaves an enormous hole in our microanalytical capacity and one that cannot be easily filled without obtaining a new instrument. During its limited lifespan, the SX-50 produced eight data sets that were used in support of publications, but it was turned off completely in March. Rémy continues to work on development of a new standard block that will be of great use both in quantitative analyses on the JEOL 6400 SEM and for a new probe, should one be obtained.
