Photo: Koma Kulshan/Mount Baker, Yamakiasham Yaina/Cascades, USA

Peer-Reviewed Publications

Downs, D.T., Sas, M., Hazlett, R.W., (2023) Chemistry and petrography of early 19th century basaltic andesites and basalts from the Kamakai'a Hills in the Southwest Rift Zone of Kīlauea volcano, Journal of Volcanology and Geothermal Research, v. 444, p.107167
Read article here

Sas, M., Shane, P., Kawasaki, N., Sakamoto, N., Zellmer, G.F., Yurimoto, H. (2022) Inter- and intra-crystal quartz δ18O homogeneity at Okataina volcano, Aotearoa New Zealand: Implications for rhyolite genesis, Journal of Volcanology and Geothermal Research, v. 421, p. 107430
Read article here

Sas, M., Shane, P., Kuritani, T., Zellmer, G.F., Kent, A.J.R., Nakagawa, M. (2021) Mush, melts and metasediments: A history of rhyolites from the Okataina Volcanic Centre, New Zealand, as captured in plagioclase, Journal of Petrology, v. 62, p. 1-26
Read article here

Sas, M., Kawasaki, N., Sakamoto, N., Shane, P., Zellmer, G.F., Kent, A.J.R., Yurimoto, H. (2019) The ion microprobe as a tool for obtaining strontium isotopes in magmatic plagioclase: A case study at Okataina Volcanic Centre, New Zealand, Chemical Geology, v. 513, p. 153-166
Read article here

Zellmer, G.F., Kimura, J.-I., Chang, Q., Shellnutt, J. G., Sas, M., Shane, P. (2018) Rapid determination of initial 87Sr/86Sr and estimation of the Rb-Sr age of plutonic rocks by LA-ICPMS of variably altered feldspars: An example from the 1.14 Ga Great Abitibi Dyke, Ontario, Canada, Lithos, v. 314-315, p. 52-58
Read article here 

Sas, M., DeBari, S. M., Clynne, M. A., and Rusk, B. G. (2017) Using mineral geochemistry to decipher slab, mantle, and crustal input in the generation of high-Mg andesites and basaltic andesites from the northern Cascade Arc, American Mineralogist, v. 102, p. 948-965
Read article here

Cortés, J. A., Smith, E. I., Valentine, G. A., Johnsen, R., Rasoazanamparany, C., Widom, E., Sas, M., and Ruth, D. (2015) Intrinsic conditions of magma genesis at the Lunar Crater Volcanic Field (Nevada), and implications for internal plumbing and magma ascent, American Mineralogist, v. 100, p. 396–413 
Read article here

Interested in an article but don't have access? Contact me!

Current Research

Understanding magma connectivity between adjacent, contemporaneous volcanoes, central Oregon

Klah Klahnee/Three Sisters are located in the ancestral homelands of the Confederated Tribes of Warm Springs.

The Three Sisters (or Klah Klahnee, "Three Points") Volcanic Complex (TSVC) is a compositionally diverse volcanic complex in central Oregon. While North Sister and ample periphery vents erupt lavas of mafic composition, the coeval and relatively young (<50 ka) Middle Sister and South Sister volcanoes are mafic-intermediate in composition (having largely erupted basaltic andesites to dacites) and intermediate-silicic in composition (having largely erupted andesites to rhyolites), respectively. Our ongoing work aims to decipher origins, crustal storage conditions, and interactions between Middle Sister and South Sister magmas in order to understand the transcrustal TSVC magmatic system as well as possible causes for eruption.

This work is in collaboration with Dr. Nathan Andersen at the USGS.

Photo: Camp Lake, OR with views of South Sister, one of Klah Klahnee/Three Sisters volcanoes.

Generation, storage, and interactions of evolved magmas in the Kīlauea SWRZ, Hawai'i

Kīlauea is located in the ancestral homelands of Native Hawai'ian peoples.

The Southwest Rift Zone (SWRZ) of Kīlauea volcano is a frequently active volcanic zone that last erupted in 1974. Interestingly, the SWRZ has erupted numerous evolved lavas (basaltic andesites) relative to typical summit and East Rift Zone lavas (basalts). This project aims understand the origins, storage, and relations of these lavas, and to refine our knowledge of the Kīlauea magma reservoir. To read more about our work, go here.

This project is in collaboration with Dr. Drew Downs at the USGS.

Image: Photomicrograph of a pyroxene-plagioclase cluster from a SWRZ basaltic andesite. Image courtesy of Dr. Drew Downs, USGS.

Interested in working together? Looking to get a M.Sc. degree in igneous petrology/geochemistry? WWU undergrad looking to do independent study or a senior thesis? Shoot me an email!

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Past Research

Isotopic ratios of minerals and their implications for rhyolite genesis in a subduction-extension setting, Okataina, Aotearoa New Zealand

Okataina volcano is located in the homelands of the Te Arawa waka.

Mineral compositions and textures are vital to understanding how magmas are produced and erupted in volcanic centers. Isotopic compositions of minerals in volcanic materials help us decipher magma sources (i.e., mantle, crust) as well as understand how contributions of mass from those different sources have changed over time. When combined, mineral geochemistry, textures, and isotopic compositions can significantly change our understanding of magmatic systems and their evolutionary paths.

The purpose of this project was to understand how crustal and mantle inputs into the magmatic system of the Okataina Volcanic Centre have varied across space and time. The Okataina Volcanic Centre is one of only two dormant, caldera-forming silicic centres in the world’s most recurrently active silicic volcanic region - the Taupo Volcanic Zone of North Island, Aotearoa New Zealand. Okataina has been periodically active for at least 0.6 Ma, including three known caldera-forming events and tens of intra-caldera events that range from silicic dome-building events to mafic fissure eruptions. To understand fluctuations in the Okataina magmatic system, we investigated isotopic compositions of silicic minerals. Specifically, we looked at oxygen isotopic ratios of quartz, and Sr and Pb isotopic composition of plagioclase, from several Okataina high-SiO2 rhyolitic deposits. Our results show that relative mantle and crustal mass contributions to the Okataina magmatic system have been consistent over time, and that crustal assimilation occurs prior to rhyolite formation and segregation.

Plagioclase textures, compositions and Sr-Pb isotopes
Project supervision: Dr. Phil Shane, UOA, Dr. Georg Zellmer, MU, with invaluable help from Dr. Takeshi Kuritani, HU
Article can be found here

Quartz textures and δ18O
​Project supervision: Dr. Phil Shane, UOA, Dr. Georg Zellmer, MU, with
invaluable help from Dr. Noriyuki Kawasaki, HU, Dr. Naoya Sakamoto, HU, and Dr. Hisayoshi Yurimoto, HU 
Article can be found here

High-spatial resolution Sr isotopic analyses of plagioclase

Strontium isotopic ratios of rocks and minerals are helpful in determining magma sources and can be particularly helpful when determined for different compositional zones of minerals. Compositional zones in minerals are important because each zone represents a "snapshot" of the magma from which it crystallized. Consequentially, compositional changes within minerals, such as major and trace element changes and/or changes in isotopic ratios, indicate changes to the magma reservoir in which the crystal grew.

Plagioclase, an abundant magmatic mineral, is an ideal recorder of magmatic processes because it is stable across a wide range of conditions (different pressures, temperatures, oxygen fugacity conditions, H2O contents) and responds readily to fluctuations in these conditions through compositional and textural changes. It also readily incorporates Sr into the crystal structure as Sr replaces Ca, a major constituent of plagioclase. Therefore, the ability to obtain Sr isotopes in plagioclase using a smaller analysis diameter than currently available will improve our understanding of magmatic processes and the rates at which they occur (smaller scale = shorter time "snapshot"). Thus, the focus of this project was to develop a high-resolution multi-collector secondary ionization mass spectrometry (MC-SIMS) method for obtaining Sr isotopic compositions in plagioclase. We tested the applicability of this method using plagioclase extracted from high-SiO2 rhyolites. Our results show that this method is ideal for systems with large fluctuations in Sr isotopic compositions. To read about our results, go here.

Project supervision: Dr. Phil Shane, UOA, Dr. Georg Zellmer, MU, with invaluable help from Dr. Noriyuki Kawasaki, HU, Dr. Naoya Sakamoto, HU,  Dr. Hisayoshi Yurimoto, HU, and Dr. Adam Kent, OSU

Photo: plagioclase crystal analyzed using MC-SIMS (small spots) and LA-MC-ICP-MS (large ablation tracks), showing the differences in spatial resolution between the two methods. 

Origins of high-Mg basaltic andesites to andesites, Northern Cascade Arc, Washington, USA

Kulshan/Mount Baker is located in the ancestral homelands of the Nooksack Tribe. Dahkobed/Glacier Peak is located in the ancestral homelands of the Sauk Suiattle Tribe.

A fundamental question in geology is whether the crust of subducting oceanic plates (slabs) gets hot enough to melt and generate magma in volcanic arcs. Slab melt generation is considered feasible underneath the Cascade Arc because the Juan de Fuca Plate, which is subducting beneath the North American Plate, is relatively young in age and is considered “hotter” than older subducting plates. This study examined the plausibility of slab melting beneath North Cascades volcanoes, specifically Kuma-Kulshan (the Mount Baker Volcanic Field) and Dahkobed (Glacier Peak), where rare lava flows that are classified as high-magnesium andesites and basaltic andesites have been previously identified. These rocks types were selected because they have been associated with slab melt generation in arcs worldwide, although numerous petrogenetic hypotheses exist.

We combined major, minor and trace element geochemistry of minerals and whole rock to test these origin hypotheses, and determine which, if any, are applicable to these North Cascades high-magnesium andesites and basaltic andesites. The most powerful method utilized to test most aforementioned hypotheses is mineral chemistry. Specifically, correlation between Mg contents and trace element (e.g., Nd, Yb, Sr) contents in the mineral clinopyroxene, acquired via laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS), proved particularly enlightening. Our results show that slab melt is feasible below the northern Cascade Arc. To find out more you can read the article here. 

Project supervision: Dr. Susan M. Debari, WWU, Dr. Michael A. Clynne, USGS, and Dr. Brian G. Rusk

Photo: columnar jointed outcrop of the Lightning Creek lava flow, Dahkobed/Glacier Peak.

Basaltic magmatism at the Lunar Crater Natural National Landmark, Nevada, USA

Lunar Crater is located in the ancestral homelands of the Western Shoshone people.

Lunar Crater National Mark is a monogenetic volcanic field where over 100 cinder cones and associated lava flows, ranging in age from over 2.5 Ma to about 20 ka, are exposed. We applied crystal-size distribution (CSD) to three basalt flows in the extreme northern part of the Lunar Crater Volcanic Field.

CSD is a technique that applies both mathematical and theoretical relationships in order to correlate textures of igneous rocks to their eruptive history by providing information on crystal populations. It is an important tool used to relate lava flows and determine the lavas' cooling history and rate of ascent. CSD was one component of this multi-component, collaborative study. To read about this study go here.

Project supervision: Dr. Gene Smith, UNLV
Thanks for everything, Gene. You will be missed.

Photo: Lunar Crater volcanic crater, a maar crater

Quartz deformation

Deformation is a rock’s mechanical response to external parameters such as temperature and pressure. Knowledge of deformation is necessary to understand geodynamic processes. The behavior of rocks and minerals during deformation depends on the behavior of individual mineral grains within the rock and how they interact. The purpose of this study was to better understand such grain-to-grain interactions when dealing with polycrystalline quartz, a common rock-forming mineral.  

To do this, we used the D-DIA apparatus located at the X17B2 beamline
at the National Synchrotron Light Source (NSLS) to conduct deformation experiments. The D-DIA module is installed in a large volume hydraulic press.  It consists of 6 WC anvils, the top and bottom of which move independently, and compress a cube-shaped sample assembly and induce deformation at a controlled rate.  

Our results showed that (1) the elastic slope can be reproduced in each independent experiment, (2) the yield strength, the point where the sample begins to deform plastically, is temperature-dependent, (3) all three quartz lattice planes display a similar behavior and temperature-dependency. To read more about deformation research visit here.


Project supervision: Dr. Pamela Burnley, UNLV

Photo: deformation of quartz sample