Fieldwork in Egypt! An expedition to research an ancient subduction plate boundary

By: Benjamin Mayor, PhD Candidate

In December 2025 Dr. Alissa Kotowski and myself (Ben Mayor) embarked on an adventure, in collaboration with Cairo University and the Egyptian Geological Survey, to study a Precambrian ophiolite in the South Eastern Desert of Egypt! This was a very special opportunity to work together on an a major ophiolite sequence which has not has been studied in detail due to its extremely remote location. The expedition was specifically targeted to gather a new dataset from the metamorphic sole of the Wadi Haimur Ophiolite, as this is one of the oldest known examples of a sole in the world (~700 million years old in the Cryogenian Period). The fieldwork is a major focus of my PhD research on metamorphic soles, aiming to understand what they teach us about the creation of new subduction plate boundaries throughout geological time.

An amazing experience and a great challenge!

Egypt’s South Eastern Desert contains the Red Sea Hills, a mountainous region that exposes the Precambrian basement of East Africa (a tectonic mosaic of geological terranes that formed 900-550 million years ago). In the field, the scale of exposed outcrop was immense. A sharp contrast to Alissa’s previous field work on the Mont Albert ophiolite (Québec) where exposed sole outcrops are often challenging to access, heavily covered in trees, vegetation and moose. The temperature in the field was pleasant and luckily we did not encounter any deadly snakes or scorpions! The continuous exposure of the plate boundary was both incredible and overwhelming. We therefore had to strategize how to best use our limited 6 days of field work. We focused on our mission to collect several detailed transects of the metamorphic sole. Starting at the structural base of the sole we moved upwards towards the tectonic contact with the overlying mantle lithosphere and collected and measured the structure of around 100 rocks samples over several transects. We also collected duplicate samples for the Egyptian Geological Survey. We found lithologies such as mafic amphibolites, meta-sediments, meta-volcanics and a bizarre suite of metasomatic schists with huge garnet crystals intercalated with the mantle!

What are ophiolites and metamorphic soles? Why are we researching them?

Ophiolites are sequences of ancient oceanic lithosphere tectonically emplaced onto continental crust. They offer Earth scientists a rare window to directly study the rocks that record deep geological processes that occur during the evolution of ocean crust, from the birth of new crust at ocean spreading centres to the demise of ocean lithosphere at convergent plate boundaries. This ‘sinking’ of dense ocean lithosphere into the mantle is called subduction - a cyclical global tectonic process which drives plate motion and underpins many of the long-term geochemical cycles vital to sustaining climate and life on our planet. However, a poorly understood process within this cycle is how do new subduction zone begin? (subduction initiation). This is a fundamental problem in tectonics as geologists want to understand the primary mechanism responsible for the generation of new subduction zones throughout Earth’s long history of plate tectonics. This connects into the bigger picture mystery of how, why and when did plate tectonics emerge within Earth’s large-scale planetary evolution.

We cannot directly observe formation of new subduction zones today as the timescales are on the order of millions of years and the youngest subduction plate boundaries today are inaccessible deep in the lithosphere. Luckily ophiolites provide us with a

I research this topic of subduction initiation, with my supervisors Dr. Alissa Kotowski and Prof. Douwe van Hinsbergen, by directly studying ancient examples of exhumed subduction plate boundaries from ophiolites called metamorphic soles. Metamorphic soles are high pressure - high temperature slices of oceanic crust decoupled from the early hot subducting ocean plate which is accreted below the base of the overlying  mantle lithosphere belonging to the forearc of the subduction zone. This whole sequence of overlying ocean lithosphere is then later emplaced onto a continent during mountain building events, allowing us to study long extinct plate boundaries on the surface today!

Why is the Wadi Haimur Ophiolite a unique field locality to study metamorphic soles?

The exceptional exposure and old age, in comparison to other ophiolites in the rock record, motivated us to collaborate research on the Wadi Haimur ophiolite. It is a field location uniquely suited to begin testing the hypothesis that metamorphic sole and ophiolite formation has slowly evolved throughout geologic time in response to the gradual cooling of the mantle temperatures since Earth’s formation. This is a new and exciting puzzle piece within Alissa’s broader research ambitions to eventually understand and quantify how Earth’s thermal and compositional evolution has influenced the dynamics of subduction processes over deep geologic time. The research will also be an important contribution to the Egyptian Geological survey’s work reconstructing the tectonic history during the Late Precambrian of East Africa.

A special thanks!

Alissa and I would like to thank Dr. Nada Abdel-Hak’s (Assistant Professor at the University of Cairo) for establishing the collaboration, organising logistics and working very hard to acquire the permits needed for fieldwork in the remote Eastern Desert. Nada invited us to visit the department of Earth Sciences at Cairo University after the fieldwork, in which we received a warm welcome from and the department had had many great discussions about our field observations. We met the Dean of the Faculty of Sciences - Prof. Dr. Sohair Ramadan Fahmy, who also played an important role in acquiring the permissions for fieldwork. Also a special thank you to Dr. Khaled Zaghlol (Senior Exploration geologist at the Egyptian Geological Survey) for organising the logistics required for field work in an extremely remote region, ensuring safety in the field and sharing his extensive experience as a field geologist in the region. It was a pleasure to learn with them in the field and we look forward to continuing this exciting collaboration between Utrecht and Cairo. We are also incredibly grateful for the support from the Dr. Schürmann Foundation, who provided the funding for the fieldwork. We are very happy the fieldwork was a success and excited to see what new discoveries will emerge from this research!

*Field work location: 22°45'07.2"N 34°01'22.0"E (contact between the weathered mantle peridotites overlying the metamorphic sole!)

Photos in the slideshow:

•  Dr. Alissa Kotowski looking out from the peak of the Wadi Haimur Ophiolite

• Coarse garnet crystals in a metasomatic schist

• Dr. Khaled, Dr Nada and Dr. Kotowski working on the sole

• Ben and Dr. Khaled heading down off the moutain after a big day collecting rocks

• Our vehicle in the desert.

• Alissa standing on the paleo-plate boundary

• Ben and Alissa collecting rocks and gathering structural data on a transect