Using Zoned Minerals to Determine Timescales of Eruption Initiation
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Understanding the storage conditions and processes that occur within the magma reservoirs beneath volcanoes prior to their eruption is crucial to our ability to monitor such systems and develop effective hazard mitigation plans. My research exploits the magmatic histories recorded in erupted zoned minerals (akin to the rings in a tree) by use of in-situ geochemistry and diffusion chronometry to unravel the life stories and eruption triggers of individual magma bodies prior to their eruption.
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Case study: Lava Creek Tuff Supereruption, Yellowstone Caldera
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Yellowstone is a well-known volcano due to its catastrophic history and present-day hydrothermal and seismic activity. Our research suggests eruption initiation by magmatic recharge can occur on the scale of a human life (weeks to decades at most) in the case of the Lava Creek Tuff Supereruption (Shamloo and Till 2019; Shamloo et al. 2021). This work received press coverage in the New York Times and is featured in National Geographic. |
Ash distribution of three Yellowstone supereruptions, the most recent of which covered the majority of the USA (USGS.gov).
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Shamloo H. I., Till., C.B., (2019) Decadal Transition from Quiescence to Supereruption: Petrologic Investigation fo the Lava Creek Tuff, Yellowstone Caldera, WY. Contributions to Mineralogy and Petrology, 174(4), 32.
Till C.B., Vazquez J.A., Stelten M., Shamloo H. I., Shaffer J., (2019) Co-existing Discrete Bodies of Rhyolite and Punctuated Volcanism Characterize Yellowstone’s Post-Lava Creek Tuff Caldera Evolution. Geochemistry, Geophysics, Geosystems.
Till C.B., Vazquez J.A., Stelten M., Shamloo H. I., Shaffer J., (2019) Co-existing Discrete Bodies of Rhyolite and Punctuated Volcanism Characterize Yellowstone’s Post-Lava Creek Tuff Caldera Evolution. Geochemistry, Geophysics, Geosystems.
Using Experimental Petrology to Simulate Magmatic Processes
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Conducting high-temperature and pressure experiments allows us to simulate the conditions and processes that occur in a magma chamber. I use experimental petrology in my research to recreate tiny magma chambers in order to examine how specific atoms behave at magmatic conditions and leave chemical fingerprints on the crystal record.
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Developing a New Geospeedometer
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Diffusion chronometry (also known as geospeedometry) has become a popular tool for determining the tempo of magmatic processes. It is especially important to use multiple chronometers in a single phase for differentiating magmatic processes from one another (e.g., Shamloo and Till 2019). Current research uses a 1-atm vertical furnace to determine how and how fast magnesium diffuses in alkali-feldspar, a ubiquitous phase in silicic volcanic rocks. Results suggest Mg diffuses simultaneously by both a fast- and slow-mode, suggesting diffusion in feldspar is more complex than previously understood (Shamloo et al. 2021).
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Simple schematic of the experimental design for diffusion experiments (Shamloo et al. 2021).
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Shamloo, H., Till C. B., Hervig, R. L., (2021) Multi-Mode Magnesium Diffusion in Sanidine: Applications for Geospeedometry in Magmatic Systems. Geochimica et Cosmochimica Acta. https://doi.org/10.1016/j.gca.2021.01.044
Testing the Controls on Ba Zoning in Sanidine
Cold-seal pressure vessel apparatus in Jim Watkins Experimental Lab at University of Oregon.
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Ba zoning in sanidine is commonly observed and is used to make interpretations on the processes and timescales associated with magma storage and eruption. However, little is known on what actually controls Ba (and other trace element) zoning in sanidine, leaving it unclear on what Ba zoning in sanidine is really recording. My work explores these controls by conducting cold-seal pressure vessel experiments as well as Laser ICP-MS analysis of both natural and experimental sanidine and rhyolites. Pictured on the top right is a precious metal capsule with a crystallized magma chamber made at temperature and pressures relevant to shallow magma systems. The bottom right is a BSE image of the same experimental product featuring crystallized sanidine crystals (light grey) and rhyolite glass (dark grey). |
Shamloo et al., in prep; NSF EAR Postdoctoral Fellowship Award
Applying Computational Modeling to Datasets from Natural Systems
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Volcanic Repose Time & Evaluating Sampling Bias in Eruption Records Repose time (the timing between successive eruptions at a given volcano) is an important factor when assigning a volcano a specific threat level which informs scientists and the public of its potential hazard (Ewert et al. 2018). However, little work has focused on long-term patterns of eruptions at a given volcano and to what degree these records are influenced by sampling bias. My work examines these effects through statistical modeling of geochronological datasets (Shamloo et al. in prep; Shamloo et al., AGU Abstracts, 2019).
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