Metamorphic and age constraints on crustal reworking in the western H.U. Sverdrupfjella: implications for the evolution of western Dronning Maud Land, Antarctica

摘要: A petrological and metamorphic comparison of Mesoproterozoic metabasic rocks was conducted on the eastern margin Archaean Kaapvaal–Grunehogna Craton adjacent westernmost Maud Belt (western H.U. Sverdrupfjella), across a major structural discontinuity known as Pencksokket–Jutulstraumen Discontinuity. Thermodynamic phase diagram modelling low- high-grade metabasaltic assemblages either side revealed difference in peak conditions from T  = 340 ± 25 to 700 ± 30°C P  = 0.29 ± 0.08 0.90 ± 0.10 GPa over an extrapolated orthogonal distance 32 km strike discontinuity. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating titanite hornblende–plagioclase–quartz corona around garnet yielded late Pan-African age 491 ± 27 Ma for metamorphism western Sverdrupfjella Belt. The new geochronological constraints indicate that upper amphibolite-facies were achieved at c . 500 Ma; namely, 70–80 Ma after eclogite–high-pressure granulite-facies Sverdrupjella. data argue against previous models invoke only ( 1060–1030 Ma) margin, support concept diachronous orogenic episode. geodynamic model is presented Dronning Land, involving earliest granulite- separate Sverdrupjella terrane between 565 540 Ma, followed by later tectonic accretion arc segment onto crustal (including easternmost margin) involved 500 Ma. inferred sub-glacial boundary (Pencksokket–Jutulstraumen Discontinuity) region represents cratonic thrust, which subsequently reactivated normal faulting during Gondwana break-up. Supplementary materials: Analytical details, representative mineral compositions, geothermometry geobarometry results are available http://www.geolsoc.org.uk/SUP18832.