Figure: Mélanges -

Mélanges

Much of my research focusses on mélanges — typically the mega-scale remnants of plate-boundary-scale faults — which are the archetypal heterogenous rock unit being composed of metre – hundreds of metre sized blocks of one rock type within a matrix of another. I have worked on the Chrystalls Beach Mélange in New Zealand, the Osa Mélange in Costa Rica, and the Gwna Mélange in Wales. Most of my research on these rock units involves mechanical strength tests and micro-structural analysis to determine the present and past rheological relationships between blocks and matrix.

Relevant publications

Clarke, A.P., Vannucchi, P., Morgan, J.P. 2018

Seamount chain–subduction zone interactions: Implications for accretionary and erosive subduction zone behavior

Geology, Volume 46, Issue 4, 367-370,
DOI: 10.1130/G40063.1

Clarke, A.P. 2018

Heterogeneous input in a subduction system & its effect on plate boundary processes: Structural analysis of the Osa Mélange, SW Costa Rica

Doctoral thesis, Royal Holloway, University of London, Egham, UK,

Vannucchi, P., Clarke, A.P., de Montserrat, A., Ougier-Simonin, A., Aldega, L., Morgan, J.P. 2022

A strength inversion origin for non-volcanic tremor

Nature Communications, Volume 13, Issue 1, 2311,
DOI: 10.1038/s41467-022-29944-8

Selected Figures

Interpreted outcrop model from the Chrystalls Beach Mélange

Feb 26 ’26 12:00

Interpreted outcrop model from the Chrystalls Beach Mélange, New Zealand, showing sandstone (yellow) and chert (blue) blocks cut by an anastomosing network of veins and fractures (red and pink).

Interpreted outcrop model from the Chrystalls Beach Mélange

Feb 26 ’26 12:00

Interpreted outcrop model from the Chrystalls Beach Mélange, New Zealand, showing sandstone (yellow) and chert (blue) blocks cut by an anastomosing network of veins and fractures (red and pink).

Altered Basalt Block and Matrix Contact

Feb 26 ’26 12:00

Polished sample photo and SEM-BSE map of the contact between an altered basalt block and its surrounding mudstone matrix revealing pervasive brecciation and alteration of the basalt and lozenge-shaped fragments of altered basalt within the matrix.

Sandstone Block and Matrix Contact with Laminated Vein

Feb 26 ’26 12:00

Polished sample photo and SEM-BSE map of the contact between a sandstone block and its surrounding mudstone matrix. The lower edge of the sample shows a laminated vein which was observed in the field to be part of a pervasive anastomosing network. Coming off this thick vein is another anastomosing network of thin veins.

Block-in-Matrix Structure in the Gwna Mélange

May 01 ’14 12:00

Field photo of the block-in-matrix texture of the Gwna Mélange on Anglesey, Wales.

Geological Map of Gwna Mélange at Llanbadrig

May 01 ’14 12:00

Detailed geological map of the Gwna Mélange at Llanbadrig, Anglesey, Wales.

I’m Alex Clarke

I am a structural geologist working as a Postdoctoral Researcher at Johannes Gutenberg–Universität Mainz and a hobbyist girl-with-camera.

My research focuses on the heterogeneities within large faults, shear zones, and subduction zone mélanges — how to map them, quantify them, and explain their origins. I am especially interested in 3D reconstructions of rocks and outcrops which allow detailed, realistic, and quantifiable models of natural phenomena. I also love to teach and I am interested in innovative and engaging methods of teaching earth sciences, both in the classroom and in the field.

In my free time, I enjoy photography and my images reflects my love of nature and the diverse forms nature can take.