Blueschists, feta and kitties – Rocking on Syros Island
Authored by Dominic Hildebrandt.
At the end of March, four team members of the SGT Group went to Syros to conduct field work in the northern part of the island. The main goal of this field campaign was to collect structural geological field data, drone imagery and samples, mainly for my M.Sc. thesis project and complementing other research going on in the SGT group. In the M.Sc. project we study the geological architecture of the Kampos Belt as an example for an exhumed deep subduction shear zone. We are most interested in constraining the internal structure and length scales of rheological heterogeneity within this 3 to 4 km long rock belt, which generally shows a rather complex block-in-matrix structure. With this data we are now compiling a 3D visualization of the Kampos Belt, which will provide us new insights into the make-up of this region in depth. Based on that, we expect to improve our understanding of the processes governing a special kind of seismicity called slow slip and tremor (SST) in the deep portions of subduction zones. This is highly relevant, because this type of ‘silent’ seismicity is potentially mechanistically linked to devastating regular megathrust earthquakes in subduction zone settings.
Syros is a playground for geologists and has long been of great research interest. John Ridley received his PhD thesis dealing with the geology of Syros at the University of Edinburgh in 1982, just before he came to the former Institute of Crystallography and Petrography at ETH Zurich and continued to publish about this region. In that regard, the research of the SGT Group continues a long-standing research tradition in the Cyclades.
However, in addition to classical geological field mapping we now also use leading-edge tools such as drones, digital mapping devices and 3D visualization software – equipment of which former scholars could only dream of. One highlight for me was the use of inflatable packrafts for inspecting outcrops along the steep cliffs at the eastern and western margin of the island near Lia and Grizzas Beach. Combining onshore mapping in the central part of the island with the cross-sections of nappe stacks along the cliff – mapping from land, water and air – enables us to constrain the 3D anatomy of a fossil subduction interface.
Syros is known for its spectacularly preserved blueschists, which makes it not only interesting for researching deep subduction interface processes, but also from an aesthetic point of view. Retrograde overprint is very selective and mostly confined to the southern part of Syros. In some cases, the blueschists contain beautiful pseudomorphs after lawsonite. Consequently, some of the samples we took are not purely dedicated to research.
Apart from that, Syros is an amazing place to work with a pleasant climate for field work (at least early in the year), friendly locals, cute cats or goats all around the island and extremely nice food (feta lovers ;-)). We are lucky that there are still enough ongoing controversies about the geology of the Cyclades so that stimulating research will go on in this location.