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

• Main Authors: Eugene G. Grosch, Hartwig E. Frimmel, Tamer Abu-Alam, Jan Košler
• Format: Dataset
• Language: unknown
• Published: 2016
• Subjects: Geology; Craton; metamorphism; Sverdrupfjella crustal segment; H.U; Thermodynamic phase diagram modelling; age constraints; Dronning Maud Land; laser ablation inductively; geochronological constraints; westernmost Maud Belt; Pencks ökket Discontinuity; crustal reworking; Sverdrupjella terrane; orthogonal distance; petrological data; Sverdrupfjella region; metabasaltic assemblages; Maud Belt; geodynamic model; Kaapvaal; diachronous tectonic accretion; Sverdrupjella arc segment; Mesoproterozoic metabasic rocks; Grunehogna; Jutulstraumen; Sverdrupfjella; Antarc*; Antarctica
• Online Access: https://doi.org/10.6084/m9.figshare.3453962.v1; https://figshare.com/articles/Metamorphic_and_age_constraints_on_crustal_reworking_in_the_western_H_U_Sverdrupfjella_implications_for_the_evolution_of___western_Dronning_Maud_Land_Antarctica/3453962

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