October BRGS Meeting: The Interplay between Fluids and Deformation: Comparisons between the Subduction Interface and Oceanic Detachment Faults

** Register Early!! Online Event Registration will close by 10:00 am on the day of the event.**

Join us Friday,  October 9, 2026

as Dr. Eirini Poulaki, 

LSU

presents

Abstract

Fluids, metamorphism and metasomatism including serpentinization and magmatism can weaken the lithosphere and lead to mechanical and chemical processes that affect the strength and slip behavior of fault zones. However, the competing mechanisms that control strain localization and exhumation rates and the nature of fluids during these processes are still poorly understood. In the first part of the talk, I will show the importance of in-situ apatite petrochronology from three subduction complexes in the Hellenic subduction zone. Apatite preserves subduction processes including metamorphism, metasomatism, and underplating due to its ability to deform, recrystallize under pressure/temperatures conditions associated with the base of the seismogenic zone. We show that during exhumation apatite records aqueous fluids that were derived from metamorphic dehydration reactions within the underlying slab and migrated along lithologic contacts, thus revealing the interplay between deformation and fluids that likely contributed to slow slip and tremor along the plate interface. 

In the second part of the talk, I will share new data from recovered cores from IODP Expedition 402. These in-situ sections of serpentinized mantle were exhumed during extension in the Tyrrhenian backarc basin. Two drill sites comprise a sequence of variably deformed granitic gneisses intercalated with ~cm-thick slivers of peridotites and basalts, and a heterogeneous section of primarily serpentinized peridotites with granitoids emplaced between the ultramafics. Zircon and apatite geochronology yield similar ages of ~4 Ma, requiring crystallization at depth followed by rapid exhumation. Macro-scale and thin-section microstructures suggest that these granitoids accommodated the majority of deformation during exhumation along the detachment fault. Lastly, stable isotope constraints infer that serpentinization was largely static and took place shallower and later than the majority of unroofing. Collectively these results demonstrate that heterogeneous lithologies and pre-existing structures have a major impact on the slip behavior of faults and we can constrain the evolution of shear zones processes with in situ petrochronology.

                                                                                                                                           Biography     

Dr. Eirini Poulaki is a structural petrochronologist studying tectonic processes by using the metamorphic rock record.  Using a wide rage of Field- and lab-based techniques, including geochronologic and geochemical analyses, field mapping, (micro)structural observations, thermodynamic modeling, oxygen isotopic analyses, and SEM (EBSD/EDS) analyses, Eirini's research is centered around the understanding of the nature of the fluid-rock interactions and metamorphic and structural behavior of the lithosphere.  She completed her Bachelor's Degree at the National and Kapodistrian University of Athens, Greece, and earned her MS and PhD at the University of Texas at Austin.  She is currently an Assistant Professor in LSU's Department of Geology & Geophysics.  

** Remember to Register Early!! Online Event Registration will close by 10:00 am on the day of the event in order to get the online details out in a timely manner.  In-person registration available until the meeting starts.