Microanalysis and Imaging

Automated Elemental Analysis with Oxford INCA Feature

Age Determination and Zoning!

If you are trying to determine the age of your rock and mineral specimens via Th/U dating, let us help you to quickly and efficiently locate all of your monazites. If you have a mountain to date, send us a 'polished' (coated or not) thin section or a slab that is smoothly sawed to dimensions: 95 x 95 (or less) x <10mm, and we will locate all of the exposed monazites on both exposed surfaces. Each monazite will be enumerated and characterized with respect to morphology and elemental composition. Thorium-containing monazites, classified separately, are characterized by x,y location and elements by weight percent. We also do garnet crystals as well as other inclusions for quantification and statistical characterization. If we can't do it, you won't be charged, and you will get your specimen returned in the same condition in which it was received.

Zoning is a phenomenon characterized by gradients of elemental concentrations in mineral and rock inclusions such as garnet crystals. As an example of how we can handle such things with our system, we have had several specimens laden with garnet crystals. In each case, analysis of those with zoning was desired. We used automation to test a large sample of those present to determine the most likely candidates for longer analysis. With that smaller group, we used the 'macro' utility in INCA ("Automate") to define areas and fields for which we wanted extended elemental mapping performed. Once finished with the setup of the macro, we pressed the 'Run' button and went home for the night. The file produced was ready for viewing in the morning. Such offline analysis is the hallmark of our system.

Petrographic Thin Sections

"Automate" has a sub-module called "Montage" which is the method we use to create images and elemental maps of large specimens. "Automate" provides a 'macro' environment in which pre-defined imaging and analytic tasks can be performed on a series of objects, fields or areas of the specimen(s) on the stage. Thus, one can predefine an automated sequence of 'Point & ID' and/or elemental 'Mapping' of objects and areas in the specimen(s) on the stage. The large garnet crystals in Slab-1, below, can only be mapped for elemental zoning by using a combination of the 'Montage' and 'Mapping' modules in the INCA armamentarium. Further, we have performed elemental mapping of large objects using 'Montage', 'Mapping' and higher magnifications to yield high-density elemental maps as montages. The profit of this approach is that a user who wishes to study elemental zoning in geologic inclusions by using the Electron Probe MicroAnalyzer (EPMA) saves time and money by pre-determining those inclusions that show evidence of zoning by using the surveying capabilities of automated EDS and SEM. The addition of variable pressure (VP) to our Environmental SEM (ESEM) simply reduces the need for carbon coating (to counter electron charging of the specimen) when searching out small inclusions such as monazites in a petrographic specimen. Automated surveys with the (E)SEM have permitted one of our geologists to instruct the operator of an EPMA at some distance as to the location of a series of monazites that had been previously located and analyzed by "Feature" automation.

Let us Pre-locate all of your monazites, zircons or garnet crystals while you collect more rocks from the field.

We provide a tabular data stream in Excel (or text) files as shown below. Pricing?

Backscattered Electron Montage Images

Montage Image of standard petrographic thin section.

Click on image at left to see larger montage with visible scale.

Rough-Sawed Rock Data

Large-Scale Automation using INCA Feature and Automate.

Slab-1 Images (Garnet Crystals)

Click on image to ZOOM!

NOTE: the left image was acquired with a flat-bed scanner, while the right is a montage of backscattered electron images.

Class distribution of Garnet Crystals (copied with slight changes from INCA)

Class	Rank	Features	% total features	Feature area (sq. µm)	% total area
Garnet<100	GS-1	169	9.1	620,000	0.02700
Garnet<150	GS-2	39	2.1	444,000	0.01900
Garnet<200	GS-3	9	0.5	217,000	0.00934
Garnet>200	GS-4	5	0.3	235,000	0.01000
Si-Al	Other	1,590	85.2	1,390,000,000	59.87000
Zr	Other	0	0	0	0.00000
F	Other	0	0	0	0.00000
P	Other	0	0	0	0.00000
Garnet-Small	Other	39	2.1	59,400,000	2.55500
Ti	Other	2	0.1	15,100	0.00065

The data in the table above illustrate some of the output from a completed automated "Feature" examination of Slab-1 for garnet crystals. Since the qualification for object identification is a grayscale signature in the backscattered image, objects other than garnet crystals can be identified and analyzed. This explains the inclusion of "Si_Al" and "Ti" objects in the list. Further, since each identified object is also analyzed for its morphology, the user can 'collect' a database using relatively general criteria and later refine the criteria to further characterize a subset of the object of interest. In the table below, the column heading, "ECD (mm)" stands for ' Effective Circular Diameter'. It is calculated from the 'area' subtended by a single pixel which is determined by knowledge of the real area represented by a pixel at any magnification.

Click to see: Larger Slab-1 Data Table in separate window.

Note that Data Table cannot shrink!

Pricing

Petrographic thin section:

Image Montage ($40/run): 25 x 37mm slide, low magnification, 512 pixel width, fast capture.
Image Montage ($100/run): 1 x 50 x 75mm slide, low magnification, 512 pixel width image, fast capture or 3 x 25 x 37mm slides.
Feature survey (High-Z elements): $60 for setup + $10/hr of runtime > 1hr. [Generally a petrographic thin section takes 30min to analyze 100 monazites.]
Elemental Map Montage: $40 (setup + 2hr beam time) + $10/hr >2hr (average zoning run for montage ~4-6hr) [For 6hr run, the cost would be = $80.00.]
Single Field Line Scans - Automated: $40 (setup + 2hr beam time + $10/hr >2hr)

Results are returned on easy-to-read Excel worksheets in an Excel workbook (or delimited text with headers).
An image montage is created from all surfaces analyzed and returned as a JPEG or TIFF image (2048 pixels horizontal resolution.) Montages are assumed - without further comment to be acquired from standard geological thin sections.

Microanalysis and Imaging

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