Effect of water on the rheology of the lithospheric mantle in young extensional basin systems as shown by xenoliths from the Carpathian-Pannonian region

Incorporation of hydrogen as structural hydroxyl (commonly referred to water) in nominally anhydrous mantle minerals is known for the ‘hydrolytic weakening’ effect, which decreases strength and electrical resistivity rock. Recent models have provided means calculating rheological properties from geochemical data upper xenoliths. In Carpathian-Pannonian region, xenoliths can be found on surface at five locations, both marginal central regions basin system. this study we present a comprehensive overview water contents these xenoliths, including previously lacking two outcrops (Füzes-tó Tihany) Bakony-Balaton Highland Volcanic Field first time. The Tihany significantly higher (< 1–5, 116–353 327–1394 ppm olivine, orthopyroxene clinopyroxene, respectively) than Füzes-tó (0–2.7, 6.2–114 3.1–213 respectively). This explained with older eruption age their host basalt greater depth origin, they likely represent an asthenospheric layer that became part lower lithosphere during thermal relaxation. contrast, lot dryer portion are assumed been more affected by decompression-induced loss resulting decreased activity extension. general, xenolith locations associated prior supra-subduction environment, contain (with exception locality) were extension-related lithospheric thinning. To reveal differences rheology inferred different contents, calculated effective viscosities resistivities other locationss region using published input. Based results, (1.4?10 20 –2.2?10 21 Pa s) (48–913 ?m) compared (9.3?10 19 –6.8?10 s 36–182 ?m, respectively), suggesting rigid former latter areas. may common feature extensional basins, extension leads ‘drying’ mantle, whereas subduction zones keep hydrating overlying wedge. However, accurate estimations, factors such regional strain rate or potential presence melts fluids need considered well. • Water lowers viscosity tectonic environments Central back-arc drier areas Rheological distinct parts extension-subduction systems Decompression related results strengthening