Research Goals

One of the fundamental questions which drives our motivation for understanding the evolution of our Solar System is when and how did the rocky objects form and differentiate? From this, which geological processes operate(d) to establish the differentiated planets and moons we observe today, and over what timescales did these occur?

My research agenda focusses on investigating these questions by evaluating the processes integral to the geological and chemical evolution of rocky objects, and how what we learn from these has the potential to inform our future exploration of the inner Solar System and beyond. Specific locations and sample types are being investigated to address these questions.

On Earth, tectonic and magmatic processes have led to the generation of our planet’s core, mantle, and crust. The crust is the most accessible layer and the process of continental crust formation has long been recognized as a fundamental component of planetary evolution. The existence of plate tectonics Earth is one of the many reasons our planet is unique with the process of subduction playing a crucial role in element cycling, crustal formation, differentiation (and recycling), and planet habitability.

Through study of magmatic and crustal rocks associated with present-day and ancient geological systems, I aim to provide new insights into Earth's geological past and the processes which govern its evolution. This is achieved through a combination of field work and lab-based approaches where samples are characterized over a range of scales and a variety of microanlaytical techniques are utilized.

Investigating the components of trans crustal magmatic systems and the architecture of active continental margins

Field Area: Eastern Altiplano, Central Andes, Bolivia

Plio-Pleistocene monogenetic volcanic centers extend ~180km from arc front to the Eastern Altiplano in the Bolivian Andes. The easternmost centers of Quillacas and Pampas Aullagas are andesitic to dacitic in bulk composition and are hosts to lithologically diverse suite of hornblendites and crustal xenoliths (e.g., schists, gneisses, quartzites). Prior and current work focusses on the role of hornblendite formation in arc systems, crustal evolution of the South American margin, and the petrogenesis of host lavas. Future work will involve the investigation of the monogenetic volcanic centers to the west and will aim to provide an across arc transect of the lithosphere beneath the present day Central Andean margin.

Analytical techniques used: Polarized Light Microscopy; Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy; Electron Probe MicroAnalysis; (Multi Collector) (Laser Ablation) Inductively Couple Plasma Mass Spectrometry.

Evaluating the influence of slab rollback processes on the petrologic, geochemical, and geodynamic evolution of the lithosphere

Field Area: Absaroka Mountain Range, Wyoming, USA; Adel Volcanic Field, Montana, USA

Slab rollback, the processes through which a descending oceanic lithospheric plate steepens and starts to "roll back" into the mantle, plays an important role in understanding the geological evolution of convergent margins. From the Eocene (~55Ma) to the Miocene (~25Ma) rollback of the Farallon slab beneath western North America resulted in a suite of volcanism which traces a switch from a subduction-dominated regime to an extension-dominated regime. Study of recently sampled Eocene-age Absaroka units in Yellowstone National Park aims to evaluate the state of the lithosphere during the initial stages of slab rollback.

Earlier Mesozoic magmatism preserved in Central Montana provides an insight into the state of the lithosphere prior to slab rollback. Rocks within the Adel Volcanic Field, including the rare rock type shonkinite, were emplaced ~76Ma to ~73Ma and are syndeformational (contractional deformation associated with the Sevier-Laramide fold and thrust belt). Study of recently collected shonkinites aims to evaluate the origin of magmatism during this timeframe and the processes responsible for the petrogenesis of rare shonkinites.

Analytical techniques used: Polarized Light Microscopy; Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy; Electron Probe MicroAnalysis; Laser Ablation Inductively Couple Plasma Mass Spectrometry.

Understanding the processes and timescales associated with Earth's (early) Continental Crustal formation

Field Area: Torrey Canyon and South Pass, Western Wyoming, USA

Surface exposures of Earth's ancient continental crust provide an opportunity to investigate the process of crustal formation relatively early in a planets history. This includes investigating the mechanisms through which crustal formation occurs (e.g., juvenile production vs. recycling), and the timescales over which it occurs.

In this work, samples of Earth's Archean and early Proterozoic crust from the northwest and central Wyoming are being investigated with a focus on petrology and geochronology. Sample types include gneisses, schists, amphibolites, and granites, with a variety of isotopic systems being employed as tracers of crustal evolution (e.g., U-Pb and Hf in zircon).

Analytical techniques used: Polarized Light Microscopy; Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy; Laser Ablation Inductively Couple Plasma Mass Spectrometry.

While Earth’s geological record offers direct insights into our planet’s formation history, the record is punctuated due to the operation of plate tectonics which ultimately works to resurface our planet and return materials from the surface to the mantle. Our record of Earth’s earliest history (first ~500 million years), and thus insights into early planetary formation processes, is particularly incomplete, hence I look elsewhere in the Solar System to investigate the origins of the rocky bodies. The Moon is our nearest neighbor in space and one of the few objects from which samples which are spatially constrained have been returned from.

Through the study of returned Apollo samples and lunar meteorites, insights into the geological processes which operate on rocky objects have been, and continue to be, investigated.

Interrogating the compositional evolution of planetary interiors and the construction of basaltic crusts

Selected samples: Apollo basalts from missions 11, 12, 15, 17

The emplacement of basaltic materials on the surface of the Moon represents two processes integral to the differentiation of a rocky object: partial melting of an interior and the establishment (in part) of a planetary crust.

This work aims to quantify the petrochemical and petrophysical characteristics of the Apollo basalts through a combined microgeochemical, and structural (2-D, and 3-D) study of mineral phases within Apollo basalt suites. Through this approach, the magma dynamics associated with the ascent and emplacement of igneous rocks on the Moon will be investigated. Broadly, this will also advance our understanding of the processes associated with magma emplacement, and the rheological characteristics of magma, on extraterrestrial bodies.

This is being primarily achieved through 1) the identification of distinct crystal populations via elemental mapping and the analysis of major rock forming silicate minerals (pyroxene, plagioclase, olivine) for their major and trace element concentrations; and 2) investigation of the internal, 3D, structure of different basaltic products through computed tomography (e.g., vesicle orientations, mineral fabrics).

Through this combined approach, autocrystic and antecrystic populations are being characterized, the potential for transfer of lunar magma crystal cargoes identified, and the emplacement histories of basaltic lava flows on the lunar surface investigated.

Analytical techniques used: Polarized Light Microscopy; Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy; Laser Ablation Inductively Couple Plasma Mass Spectrometry, Computed Tomography.

Advancing our understanding of meteoritic breccia petrogenesis and impacts as a planetary resurfacing process

Selected samples: Feldspathic and basaltic lunar breccias

While the returned Apollo samples are spatially constrained, they do represent a limited sampling of the lunar surface. The study of lunar meteorites therefore expands our understanding of the Moon’s history as they represent a random sampling of the lunar surface. Lunar breccias, while lithologically and texturally complex, often contain a diverse array of lithologies and therefore have the potential to capture a broader picture of the Moon's geological history.

In this work both feldspathic and basaltic breccias are being studied. Distinct clasts, mineral grains, and melt (glass) spherules are being identified and their geochemical signatures used to evaluate potential sites of origin on the lunar surface (as informed by Apollo and remote sensing datasets).

Phases which have the potential to be dated (e.g., U-Pb dating in zircon, apatite) are of particular interest as results have the potential to contribute to our growing understanding the timing lunar differentiation events and the rate and timing of impact events in the inner Solar System.

Lunar meteorites which form the basis of this work include the Allan Hills (ALHA) 81005 feldspathic breccia and 2018-2019 Dominion Range (DOM) basaltic breccias.