FINGERprinting cold subduction and Plate Tectonics using key minerals

Plate Tectonics (PT) is a well-established framework of moving plates made of oceanic and continental lithosphere.

The main driving force of this system is the slab pull, a force imposed as the older and colder subducting plate sinks into the asthenosphere at convergent boundaries, producing Low Temperature/High Pressure (LT-HP) metamorphic rocks.

Although our understanding about PT has improved in the last decades, there are major unknowns remaining, namely when and how its onset took place, a highly controversial topic.

The record of LT-HP metamorphic rocks becomes continuous only from 850-750 Ma onwards, but recent evidence of these rocks at 2100-2000 Ma suggests a similar Tectonic regime operated at this time as well.

An outstanding question arises: did Plate Tectonics, as we know it today, begin to operate only 850Ma ago or did this change take place much earlier but disappeared as the result of a preservation bias affecting LT/HP rocks? FINGER-PT will test this hypothesis using detrital minerals in sedimentary rocks that can track older LT-HP.

Key minerals that can retain pressure, temperature, and age (P-T-t) information will be used, applying chronothermobarometric tools.

Through a multidisciplinary approach, we will (i) combine the existing tools with new ones to obtain reliable P-T-t conditions; ii) test these tools and study the survival of eroded LT-HP terranes via mineral analyses in analogue modern sediments draining an exposed subduction zone; iii) identify and sample the most appropriate units, whose detrital minerals record the last 1000 to 4000 Ma, to trace the secular evolution of cold subduction.

The emerging new tools from FINGER-PT, some that push current technological boundaries, will be widely applied by other petrologists.

Establishing when modern-day PT began will influence the geodynamic mechanisms proposed for the early Earth (e.g. sluggish tectonics), forcing a shift of current conceptual models on the evolution of Earth systems.