Research | Sheree Armistead

A few examples of ongoing and recent research projects are outlined below. See my list of publications for further information on my research.

Pb isotopes to understand tectonics and mineralisation in the early Earth

My current research is focused on using a global compilation of Pb isotope data (along with complementary isotopes such as Nd and Hf) to understand isotopic heterogeneity in ore forming regions throughout Earth’s history. This research is in partnership with Laurentian University’s Metal Earth Project and the Geological Survey of Canada.

Click here to see a presentation I gave at the Metal Earth partner advisory meeting in October 2019 (shortly after beginning my postdoc), where I outlined the aims and scope of this project.

I am particularly interested in:

What the isotopic signatures mean for early Earth differentiation and geodynamic processes;
How regional to craton scale Pb isotope signatures can be used for mineral prospectivity;
The relationship with other isotopic systems (e.g. Nd, Sr, Hf);
How we can use these features to understand the tectonic and metallogenic evolution of the Superior Province in Canada

Collaborators: Sally Pehrsson (GSC), Bruce Eglington (USask), David Huston (Geoscience Australia), David Mole (Laurentian University)

Neoproterozoic evolution of circum-Antarctic terranes

Since March 2021 I have been based at the University of Tasmania as an Adjunct Researcher, due to the COVID-19 situation in Canada. In addition to my ongoing postdoc research, I am working with Dr. Jacqueline Halpin to decipher some of the cryptic orogenic events in terranes that were adjacent to Antarctica during the evolution of supercontinents Rodinia and Gondwana. These include the complex relationship between the East African Orogen (where my PhD was focussed) and the Kuunga Orogen. Due to the proximity in space and time of these two orogenic events, it can be difficult to unravel the timing of arc magmatism and metamorphism that led to the final amalgamation of these terranes, and the subsequent events that led to their breakup. Another key area for understanding the Neoproterozoic evolution of Antarctica is the Laurentia-Australia relationship in Rodinia. We propose undertaking studies on key areas including Tasmania that will help to constrain these models.

Detrital zircon geochronology

A big focus of my PhD research was using detrital zircon geochronology to unravel the paleogeographic history of Madagascar, Africa and India from the Archean to Cambrian.

I am especially interested in various statistical techniques to understand the complexity of large datasets of detrital zircon data. For an example of some of the R code I’ve developed for detrital zircon geochronology, check out my Detrital-geochron Github repository.

Using detrital zircon data, we showed that Archean sedimentary rocks in the Antongil-Masora domains of eastern Madagascar are indistinguishable from the western Dharwar Craton of India. See: A re-evaluation of the Kumta Suture in western peninsular India and its extension into Madagascar

More recently, I have been using detrital geochronology to understand the extent of the Paleoproterozoic Itremo Group in central Madagascar, and whether it extends into Africa and/or India as others have suggested. See: Proterozoic basin evolution and tectonic geography of Madagascar: implications for an East Africa connection during the Paleoproterozoic

Thermochronology

Minerals such as apatite, muscovite and biotite form and reset at lower temperatures (~250-500°C) than the more commonly used mineral zircon. We can use these minerals to understand the evolution of rocks and regions that underwent medium-temperature events.

We used novel laser ablation triple quadrupole inductively coupled plasma mass spectrometry (LA-QQQ-ICP-MS) to analyse Rb-Sr in muscovite and biotite. This forms part of a broader method development initiative at the University of Adelaide for this technique. Additionally, we analysed U-Pb in Apatite, which records temperatures of ~500°C. This method was developed at the University of Adelaide as part of a broader Apatite Fission Track setup lead by Gilby Jepson and Jack Gillespie.