Volcanology / Petrology / Geochemistry
Current members of the VPG research group include volcanologists Thomas Giachetti and Paul Wallace, hydrothermal geochemist Mark Reed, isotope geochemist Ilya Bindeman, petrologist/ isotope geochemist Jim Watkins, biogeochemist Qusheng Jin, and experimental petrologist Dana Johnston. Their individual research interests are summarized below.
Thomas is a volcanologist interested in understanding how volcanic eruptions evolve through time, especially the most explosive ones. He is studying in particular magma degassing and how this degassing affects the dynamics of volcanic eruptions. Thomas uses a range of field, laboratory and numerical modeling approaches, and oversees a textural laboratory that houses a helium pycnometer, a capillary flow porometer, a particle size analyzer and optical microscopes. Thomas previously worked on Soufrière Hills Volcano at Montserrat but his recent work has taken him to our local Cascade volcanoes, including Medicine Lake and Newberry volcanoes.
Leif studies fluid movements in and around volcanoes, glaciers, and bedrock landscapes. His volcanic interests include the eruption cycle, crustal magma transport, transitions in eruption style, volcanic seismicity, and the multiphase rheology of magmas. His glacial interests are primarily in glacial hydrology, mostly supraglacial stream morphodynamics. His landscape interests are in volcanic landscapes and the interactions between landscape construction through volcanism (both effusive and explosive), fluvial and glacial erosion. Leif’s group develops analytic and numerical mathematical models for these processes, in combination with field measurements and laboratory experiments using analog materials.
Paul is primarily interested in volcanology and is an expert on volatiles in magmatic and volcanic systems. His lab houses a Fourier transform infrared spectrometer which he and his students use to measure pre-eruptive H2O and CO2 contents in trapped melt (now glass) inclusions in phenocrysts. They also use the electron microprobe, ion probe, and laser ablation ICP-MS to measure the concentrations of other volatiles (e.g., Cl, S) and trace elements. A major focus of Paul’s group is in understanding the origins and role of fluids in subduction-related volcanism. Paul’s field-based studies take him and his students primarily to the volcanoes of Mexico and the Cascades.
A primary interest of Mark’s is computer modeling of fluid/gas/mineral equilibria in high-temperature magmatic, volcanic, and fumarolic systems, using software of his own creation. His work is driven by field investigations and fluid inclusion measurements in systems ranging from ore deposits now hosted in old plutonic rocks, to encrustations forming today in modern geothermal systems. Recent work has taken him to a variety of field locales, including the giant porphyry copper deposit in Butte, Montana and the active geothermal systems of Kamchatka and Iceland.
Ilya also has as his principle focus understanding volcanic systems and his approach relies primarily on measurements of the stable isotopic (e.g., 16O/18O; D/H) compositions of phenocrysts and glasses in erupted products, both current and ancient. This work is done in his state-of-the-art laboratory which houses a MAT 253 multicollector stable isotope mass spectrometer, a laser fluorination extraction line, a high-temperature pyrolysis system, and an automated system for analysis of carbonates and waters. He is also a regular user of he Cameca IMS1280 ion probes at UCLA and University of Wisconsin which he uses to gather geochronological measurements and in situ isotope measurements. Much of Ilya’s work centers on past supereruptions, including Yellowstone and Long Valley, but he also has studies underway on the products of recent and even current eruptions in Iceland and Kamchatka, and collaborative projects with others.
Jim studies geological processes in high temperature systems (magmas) as well as low temperature systems (aqueous solutions). His group uses a combination of laboratory experiments, isotope measurements, and theory to understand how environmental variables (such as temperature, pressure, and chemistry) influence the shape and composition of crystals and bubbles. This information in turn helps geochemists, volcanologists, and oceanographers decode the information that is recorded the geologic record. Jim oversees the Experimental Petrology Lab as well as the new Isotope Geochemistry Clean Room Facility.
Jin’s research focuses on how fast microbially-driven geochemical processes proceed in natural environments and how the rates of these processes affect environmental chemistry. Current research topics include: (1) natural arsenic contamination in groundwater of the Willamette Basin, Oregon; and (2) abnormal redox chemistry in Upper Klamath Lake, one of the largest lakes in western US. The groundwater project is to investigate how the close interactions between geochemical and microbial processes control the occurrence and attenuation of arsenic in groundwater; the lake project is to develop a new theory of geomicrobial kinetics to account for the impact of microbial diversity on the rates of biogeochemical processes. Both projects take a suite of multidisciplinary approaches, including field sampling and analysis, laboratory experiment, and numerical modeling.
Dana’s focus is primarily experimental in nature, providing laboratory support to the others in the group, in addition to his own work. The capabilities of his lab permit simulation of a wide range of high temperature geological processes at pressures to 35 kbar (~500,000 psi, or 100 km depth in the Earth). Current work includes high pressure studies of the near-liquidus phase equilibria of primitive lavas from the Trans-Mexican Volcanic Belt (together with Paul) and studies of the effect of decompression on vesiculation and crystallization in volcanic systems (together with Kathy and Paul) and mineral precipitation in hydrothermal systems (together with Mark).