I d EPMA f h l i TDI bi d EDS WDS MAN l i d d bl k Improved EPMA of tephra glasses using TDI, combined EDS+WDS, MAN, a multi‐standard blank Improved EPMA of tephra glasses using TDI, combined EDS+WDS, MAN, a multi standard blank correction and a multi‐standard normalization to facilitate smaller beams more elements correction, and a multi‐standard normalization to facilitate smaller beams, more elements, greater precision and better between session reproducibility greater precision, and better between‐session reproducibility g p , p y INQUA–INTAV International Q Field Conference and Workshop Stephen C Kuehn – Department of Physical Science Concord University USA Transylvania, Romania 24 29 J 2018 Stephen C. Kuehn Department of Physical Science, Concord University, USA 24‐29 June 2018 Rationale Abstract N d f S ffi i t P i i d C i t t Rationale Abstract: Analysis of natural and synthetic glasses is a common application of electron probe microanalysis Need for Sufficient Precision and Consistent (EPMA) Since the late 1960s EPMA has remained at the forefront of tephra glass analysis because of the Accuracy to Distinguish Similar Samples Need for Small Beam Sizes (EPMA). Since the late 1960s, EPMA has remained at the forefront of tephra glass analysis because of the technique’s high spatial resolution analytical sensitivity rapidity cost effectiveness and potential for high Accuracy to Distinguish Similar Samples Need for Small Beam Sizes technique s high spatial resolution, analytical sensitivity, rapidity, cost‐effectiveness, and potential for high i i Th tt ib t k it ibl t h i ll fi i t d th b id tif d l t th G precision. These attributes make it possible to chemically fingerprint and thereby identify and correlate the d f d d l l G 0.23 +/- 0.03 B deposits of individual volcanic eruptions. B 0.27 +/- 0.04 MgO in glass from Glacier In recent years there have been an increasing number of tephra studies which target trace deposits of volcanic ash MgO in glass from Glacier Peak G and B In recent years, there have been an increasing number of tephra studies which target trace deposits of volcanic ash known as cryptotephra This has greatly expanded the geographic range of tephra correlation to localities more Peak G and B ash/pumice (tephra) known as cryptotephra. This has greatly expanded the geographic range of tephra correlation to localities more than 5000 km from their volcanic sources However cryptotephra deposits often contain sparse small grains /p ( p ) deposits using two than 5000 km from their volcanic sources. However, cryptotephra deposits often contain sparse, small grains. Addi i ll i ibl h b d i i i h ll f l b b bbl G different procedures h d ff l l f Additionally, even visible tephra beds may contain grains with very narrow walls of glass between bubbles or an 0.24 +/- 0.01 B with different levels of precision abundance of microcrysts which also limit the size of target areas available for analysis. Thus, to maximize the 0.27 +/- 0.02 precision. amount of data that can be collected, it may be necessary to use smaller electron beam diameters. , y y In addition some volcanic centers tend to repeatedly erupt tephras with a very strong “family resemblance” in their Small narrow grains In addition, some volcanic centers tend to repeatedly erupt tephras with a very strong family resemblance in their h i t Alth h h l l l t d iti b h l f l i tt ib ti t h t ti l Small, narrow grains (4 6 and 10 micron beam damage) geochemistry. Although such closely‐clustered compositions may be helpful in attributing tephras to a particular (4, 6, and 10 micron beam damage) source volcano, distinguishing between individual eruptions becomes much more difficult. Increasing the precision and between‐session reproducibility of EPMA analysis can help increase confidence in tephra correlations . To enable routine precise and accurate EPMA of silicate glasses at smaller beam diameters using a broad range of To enable routine, precise, and accurat