I am pursuing research projects here in southern New Mexico and in the Cascade range of the pacific northwest. In general, my research is motivated by the following questions:
- Where and how do magmas evolve prior to eruption?
- What are the origins of and inputs to arc magmas?
- What processes (degassing, crystallization, assimilation, etc.) occur during magma storage, ascent and eruption?
- How and why does eruption style change during one eruption?
- How do volcanic fields evolve over time?
- What are the timescales of key magmatic processes (intrusion, rejuvenation) prior to eruption?
*I will likely be accepting an MS student to start in the Fall of 2020; please contact me if these projects, or others that we could develop, would be of interest!*
*My students and I will be presenting our resesearch at the upcoming GSA Annual Meeting in Phoenix – see project descriptions below for dates of talks/posters. Please stop by, or send an email, if you want to chat at GSA!*
1. Along-arc trends in mafic magma geochemistry and the role of sediment subduction in the southern Cascades
This project, submitted by myself and Dr. Frank Ramos, was awarded NSF funding (starting July, 2015) to investigate along-arc trends in the compositions of primitive mafic magmas of the Cascade arc as well as the importance of subducted seafloor sediments to the magmas that are formed and erupted in the southern Cascades. Along with two MS students, we have sampled and analyzed the major and trace element and isotopic (Sr-Nd-Hf-Pb-O) compositions of basalts erupted in south-central Oregon and from seafloor sediments of the Gorda Plate. Additionally, olivine-hosted melt inclusions from 5 localities have been analyzed to constrain the pre-eruptive volatile contents (H2O, CO2, S, Cl) of the magmas.
Using these data, combined with Ar-Ar geochronology, we are evaluating the temporal and spatial variations in mantle source beneath the arc and the additions of a “subduction component” (fluids/melts of altered oceanic crust +/- seafloor sediment) to that mantle.
- GSA presentation by MS student Jamie Shaffer: “Evaluating subduction contributions to the southern Cascade arc: Insights from the geochemistry of mafic arc lavas and Gorda plate sediments”, Tuesday, Session T35, Poster 184-5, 4:30-6:30 pm
2. Volatile contents and storage of rhyolitic magmas from the Organ Caldera, NM
The Organ Mountains, just east of Las Cruces, expose the plutonic and
volcanic portions of the Organ Caldera. Caldera collapse occurred during large volume, explosive eruptions ~35 million years ago. Several thick ignimbrites are preserved in the southern Organ Mountains. Through analysis of quartz-hosted melt inclusions, we are investigating the volatile contents of these explosive eruptions, and when they can tell us about magmatic storage conditions (pressures, and thus depths). Additionally, the melt inclusions track changes in the melt composition over time, revealing magma chamber processes (convection, stratification, influxes of new magma) prior to eruption.
MS student Jenna Lente (2017) completed her research on the first- and last-erupted tuffs from the caldera. She found high volatile contents (<6.5 wt%) in melt inclusions from the first-erupted tuff and determined that the magma chamber was stored at upper crustal depths of ~4-9 km. Additionally, the chamber was convecting and well-mixed prior to eruption. More research remains to be done on the later, more-voluminous tuffs of Organ caldera.
There are many other project options in and around Organ caldera – please contact me if you’re interested!
3. Spatial and temporal variations in rhyolitic volcanism in southern New Mexico ~36-30 Ma
Volcanism associated with the broader “ignimbrite flare-up” began in southern New Mexico ~36 Ma. Numerous calderas erupted between ~36 and ~30 Ma, depositing thick tuffs and rare pumice fall units. This research project, funded by an AGeS2 grant to a current MS student, evaluates the age progression of volcanism in southern New Mexico at this time using high-precision Ar-Ar geochronology of single sanidine crystals from the tuffs. We hope to determine whether or not caldera volcanism migrated westward over time coincident with westward rollback of the Farallon plate.This project will also investigate whether tuffs can be correlated using sanidine geochemistry (trace elements, Pb isotopes).
There are many other possible projects on the rhyolites of southern New Mexico (for example, detailed geochemical/stratigraphic studies of individual eruptions); please let me know if you are interested in developing an MS project in this area.
4. Blue Lake maar – a young phreatomagmatic eruption in the Oregon Cascades
I have been studying the deposits from a young mafic eruptive center in the Oregon High Cascades in order to understand the pre-eruptive magma storage and eruption processes of this volcano. I have found that the Blue Lake eruption began with a brief magmatic phase and then quickly transitioned to a phreatomagmatic eruption, producing small surge deposits and ejecting large lithic blocks. The eruption than transitioned back to voluminous magmatic phase, with abundant vesicular scoria deposited. I have mapped the deposits (isopach maps) and am using the deposit granulometry and componentry of the eruptive products in order to eruption style. Additionally, I used melt inclusion H2O and CO2 contents (reported in Ruscitto et al., 2010) to constrain the pre-eruptive storage pressures, and thus depths, of the magma. Finally, diffusion modeling of zoning in olivine crystals indicates that a new magma intruded into the system approximately 1 year prior-to eruption. Together, these results inform us about eruption processes and fluctuating eruption styles, and importantly, the potential hazards posed by future phreatomagmatic eruptions in the Cascades.
- Invited talk at GSA: “Combining physical volcanology and magma geochemistry to understand the complex history of a young, monogenetic volcano: Blue Lake crater, Oregon” Sunday, Session T17, 4:10-4:30 pm
5. Monogenetic volcanism in the Potrillo Volcanic Field, NM
The Potrillo Volcanic Field contains numerous monogenetic volcanoes (cinder cones, shields, tuff rings and maars) that are relatively young (~17,000-80,000 ybp). An MS student and I are using both field mapping and satellite imagery of the surge deposits from Kilbourne Hole maar crater to provide an estimate of the lateral extent and volume of these deposits. Additionally, we are using the locations of large blocks and bombs around the crater to estimate ejection velocities and explosion energies. Finally, detailed stratigraphy of the deposits will be used to determine how the eruption progressed.
There are many possible MS project options in the Potrillo Volcanic Field, so please get in touch if you are interested in young rift basalts!
- GSA presentation by MS student Daniela Vitarelli: “Eruptive volume and explosion energy estimates from Kilbourne Hole, southern axis of the Rio Grande Rift, southcentral New Mexico”, Sunday, Session T62, Poster 51-7, 3:30-5:30 pm