See more from this Division: Topical Sessions
See more from this Session: Strengthening Links between Metamorphic Conditions and Time: New Advances in High-Temperature Geochronology and Tracing P-T-t Paths of Metamorphic Terranes
Abstract:
Here we present CA-TIMS data from the Western Gneiss Region ultrahigh-pressure terrane, Norway, which was subducted to and exhumed from depths of ≥150 km. The entire cycle lasted ~40 Myr, from ~420380 Ma; thus, our ability to precisely pinpoint individual stages within this cycle will yield rates of burial, exhumation, cooling, etc., and increase our understanding of the evolution of ultrahigh-pressure terranes in general.
An undeformed, garnet-bearing aplite dike from within the Blåhø nappe near Volda yields a lower intercept age of 402.3 ± 2.0 Ma from 4 CA-TIMS steps (MSWD=0.85). Decreasing Th-U ratio closer to the lower intercept is consistent with metamorphic growth, and indicates no post-burial, amphibolite-facies deformation. An undeformed pegmatite dike from the Sørøyane UHP domain yielded strongly inherited zircons, which display a lower intercept of 398.9 ± 4.6 Ma (MSWD=0.88) in 4 steps; all of these steps have high Th-U ratios, indicating that amphibolite-facies melting followed quickly on the heels of the peak metamorphism.
See more from this Division: Topical Sessions
See more from this Session: Strengthening Links between Metamorphic Conditions and Time: New Advances in High-Temperature Geochronology and Tracing P-T-t Paths of Metamorphic Terranes