TIME VARIANT FLAT SLAB GEOMETRIES AND THEIR EFFECTS ON THE OVERRIDING CONTINENTAL LITHOSPHERE (Invited Presentation)

Flat slabs are often associated with tectonic processes that affect the evolution of the overriding continental lithosphere. These include an inboard deflection and/or cessation of arc volcanism, the formation of inland basement cored uplifts, and the emplacement of ore deposits, among others. It is instructive, however, to look closely at both the fine scale details of modern flat slab geometries along with their histories when discussing the spatio-temporal correlations of these effects, especially if any attempt at causation is to be made. In this talk, we will show recent work combining a broad suite of seismic observations to determine the detailed geometries and temporal evolution of the Peruvian and Pampean flat slabs. We will discuss how differences in geometry and evolution affect how flat slabs interact with and affect the overriding lithosphere. The Pampean flat slab is deeper, older, and colder, whereas the Peruvian flat slab is laterally broader and has a more complex geometry and tectonic evolution. Both of these flat slabs have been linked to a cessation of arc volcanism, inland deformation, and ore deposits, but any causal linkages between these observations and the flat slabs beneath them must accommodate the substantial differences in geometry and history between these flat slabs. These differences will likely also affect the consequences of ultimate flat slab failure due to differences in hydration and metasomatism between the two flat slab regions. Ultimately, answers will only come through continued multi-disciplinary efforts to assess the causes and consequences of flat slab subduction in regions with different tectonic histories and geometries. These types of studies are critical for understanding a raft of flat-slab-related tectonic processes that have dramatically affected the continental lithosphere throughout much of Earth’s history.