NEWS (12/28/2016): I've recently learned that I will have the honor of receiving the 2017 Early Career Award from GSA's Mineralogy Geochemistry Petrology Volcanology division (MGPV). Thanks to Mike Garcia for the nomination and to the MGPV committee and Wendy Bohrson for the surprise announcement.

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Analytical tools

1- Electron microprobe analysis: the sample is hit with an electron beam and emits x-rays with wavelengths that fingerprint the elements present in the material analyzed. I use EPMA for chemical analysis of major, minor and sometimes trace elements in various phases (dominantly glasses and minerals) that constitute typical volcanic rocks, as well as different types of materials generated in the experimental petrology lab (e.g. alloys).

These days, I use the Field Emission Gun JEOL Hyperprobe JXA-8500F housed at the Geology and Geophysics department, managed by Eric Hellebrand and Michael Garcia. Check out some of the things I've been using the probe for lately here!


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Image from JEOL Usa


2- microRaman spectroscopy: the sample is hit with a laser (green or red light) and photons are being scattered inelastically after interacting with molecules composing the sample. The intensity of scattering depends on the molecular structure and the way in which the bonded molecules vibrate, bend/rotate, or stretch.

I currently use this technique primarily to quantify and map water hetergoeneity in glasses but also am interested in glass structure and how it changes right before/during crystallization. I use the WiteC Alpha300R Raman housed in the HIGP department at UH Manoa. Check out some of the things I've been using Raman for lately here!


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The confocal Raman microscope at UH


3-Scanning Electron Microscope: like for the microprobe, a focused beam of electron hits the sample and various interactions including secondary electrons, backscattered electrons, and light all can be detected and are used primarily for imaging specimens or semi-quantitative analysis (EDS). A neat little accessory detector allows most SEMs to measure crystallographic orientation using electron backscatter diffraction (EBSD).

I use the JEOL 5900LV SEM housed in the HIGP W.M. Keck lab for imaging samples and texture analyses, and, lately, more often to measure crystallographic orientation of olivine and other minerals.



4-Fourier-transform Infrared Spectroscopy: the sample is hit by an infrared broadband light source (multiple frequencies of light, unlike Raman), and the amount of the beam that is absorbed or reflected can be measured and used to assess the structure of materials and quantify volatile species.

I currently use the new Bruker FTIR recently purchased at the Hawaii Institute of Geophysics and Planetology (HIGP) to analyze H2O and CO2 in volcanic glasses (e.g. interstitial glass, melt inclusions). More to come in this section soon...!


5-He-pycnometer/permeametry: To quantify the capacity for gases to percolate through volcanic pyroclasts, I use He-pycnometry and permeametry. A He-pycnometer measures the volume of a sample (including interconnected bubbles), which can then be compared with bulk porosity (as measured by archimedes principle) to obtain estimates of connected and isolated porosity. The permeameter provides a measurement of how efficiently gases can circulate through the connected vesicle framework.

Lately, I have used the AccuPyc 1340 Helium Pycnometer at the Laboratoire Magmas et Volcans at the textural characterization lab. I also built two permeameters based on the design of Takeuchi et al. (2008), which are housed both at the Laboratoire Magmas et Volcans (Clermont-Ferrand, France) and at the experimental petrology lab at UH Manoa.


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Permeameter holder with sample enbedded in resin within the cylinder


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Sample preparation for permeability measurements