Welcome to the QEMSCAN Laboratory

A New View of Rocks

Frederick A. Sutton Building

University of Utah

Department of Geology and Geophysics

Room 322

QEMSCAN Technology combines the benefits of high-resolution electron microscopy with the exponentially growing power of data interpretation in one linked system.  The QEMSCAN approach to a problem is to rapidly obtain thousands of high-resolution mineralogical images and apply rigorous statistical evaluation of the data.  This means that very high confidence (95%+) level results are obtained for the problem being investigated.  Four high-speed, nitrogen-free energy dispersive detectors gather and merge element x-ray data to identify minerals.  The mineral images permit users to quantify abundances, morphology and mineral associations with unprecedented precision, accuracy and speed.  QEMSCAN Technology is having a major impact on the study of fine-grained materials (down to 1 micron) where quantitative mineralogical data are difficult to obtain.  QEMSCAN technology has seen applications in mining, metallurgy and mineral exploration, oil and gas exploration, coal, environmental geology, and forensic geoscience.  Applications to the geosciences are in their infancy.  This QEMSCAN Laboratory at the University of Utah is the first instrument of its kind housed entirely within an academic department in a U.S. university.  A sister facility at the University of Utah is located in Research Park in the Energy Geoscience Institute (EGI).  Our mission is to be the “go to” facility for the characterization of fine-grained materials.

How it Works

Mineralogical images are created by collecting 1000-count EDAX spectra on each analysis spot on the sample at the rate of ~700,000 cps.  Spectra are compared to a library of reference spectra to obtain a mineralogical match.  Each mineral is assigned a default color that can be changed by the user.  Analysis proceeds by collecting X-rays on spots arranged in a grid with a predetermined spacing within a small field of view.  Sequentially analyzing and stitching together 1-3 mm size square fields yields an image of a portion or the entire surface of the sample.  In the case of particles, a grid of analysis points is superimposed on each particle in the sample block.?The resolution of the image depends on the spacing of the analysis spots.  The total length of time for an analysis depends on the total number of spots analyzed.  A typical image using 10 ?m spacing consists of 3 million measured spectra over a 15 X 20 mm surface area.?Each spectra corresponds to a phase that has a pre-defined composition, and the task in the data reduction step is to group similar spectra together.  The final result is an image that highlights the mineralogical aspect that the user seeks to convey.  In a post analysis stage, these images are further processed to extract quantitative information such as grain size distribution and a host of other parameters, some of which are illustrated below.

Applications

Qemscan Technology is ideal for obtaining high-resolution mineral/chemical information on solid samples.  These data are used create detailed color-coded images of the phases in the client’s materials suitable for textural studies relevant to various applications.  The digital images can be processed to quantify any desired aspect of the sample (grain size distribution, mineral associations, grain morphology, etc.).  In addition, textural data bulk rock chemistry is obtained.  Recent examples:?    Shales (link)?    Sandstones (link)?    Carbonate rocks (link)?    Metamorphic rocks (link)?    Igneous rocks (link)?    Ores: head, concentrates, tails (link)?    Tailings and soils (link)

Accomplishing the project

Project design:

Carefully thought-out projects (“cradle to grave”) are likely to meet with much greater success than poorly designed projects.  What roll does QEMSCAN analysis meet in the proposed project?  Are other analytical tools more suitable?  Attention should focus on the desired results and the steps that are required to achieve this end.?Projects come in all sizes.  QEMSCAN is particularly suited to large projects where statistically sound data are required.  In such projects QEMSCAN data has the capacity to greatly reduce risk and increase the net present value of a program.  We encourage early discussion of how QEMSCAN analysis will benefit a client’s project.

Sample format:

QEMSCAN “ready” samples consist of a) polished-thin sections or b) rocks or loose particles (soil, chemical precipitates, crushed materials) mounted in 25 or 30 mm-round epoxy plugs.  Smooth cut rock surfaces can also be used provided the samples fit the sample holders.  One of the most important considerations is whether the prepared sample is a representative sample and captures the essence of what the investigator seeks to characterize.?At this time we do not prepare polished thin-sections, but we can refer you to organizations that prepare polished thins-section.  We can assist with the preparation of polished epoxy plugs of the required dimensions.?Samples are carbon-coated prior to analysis.

Analysis:

    Analysis of a sample involves instrument set-up and the creation of a sample naming and analysis protocol.  The analysis protocol involves the specification of type of sample to be analyzed (plugs, thin-sections), type of analysis (point count, field stitch, etc), portion of sample to be analyzed, sample location, spatial resolution, reference spectral library, and several other parameters.  Analyses run in automated fashion and runs on single sample may last a few minutes or many hours, depending on the experimental set-up to obtain the required data.

Data Reduction:

    After the analytical run is complete, the results are examined and assembled into reports that focus on the users need.  This involves the verification of the correct classification of spectra into relevant mineral grouping, color selection, generation of images and pertinent graphs and tables.  Depending on the complexity of the sample this step can represent a significant portion of the entire analytical sequence.  At a higher level, QEMSCAN data are iteratively incorporated in ongoing projects.

Wrap-up:

    A final report is produced that summarized the results.  Interim reports may also be prepared.

Cost

Users fees are on a per hour basis, and clients will be charged a fee on a per sample basis according to type of analysis (particles, field scans), the resolution desired, data reduction time, and origin of the requester.  We would be glad to discuss your project; please contact Dr. Erich Petersen for an appointment.

Contacts:

Dr. Erich U. Petersen

erich.petersen@utah.edu

801-581-7238 (office)

801-440-1069 (cell)

801-585-3604 (Lab)