Structure and extent of the Tonian Oceanic Arc Super Terrane, eastern Dronning Maud Land, based on new geophysical data
Sør Rondane and adjacent regions in eastern Dronning Maud Land (DML) are of major interest regarding our understanding of the architecture of crustal fragments that were involved in the amalgamation and breakup history of Rodinia and Gondwana. Within a long-standing collaboration between Alfred Wege...
| Main Authors: | , , , , |
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| Format: | Conference Object |
| Language: | unknown |
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2018
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/45868/ https://hdl.handle.net/10013/epic.52019 |
| Summary: | Sør Rondane and adjacent regions in eastern Dronning Maud Land (DML) are of major interest regarding our understanding of the architecture of crustal fragments that were involved in the amalgamation and breakup history of Rodinia and Gondwana. Within a long-standing collaboration between Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the Federal Institute for Geosciences and Natural Resources (BGR) the combination of surface geology from sparse exposures with aeromagnetic data provide a powerful tool to characterize the sub-ice geology and therefore the cryptic interior of East Antarctica. During the austral summers 2014 and 2015, ca. 40.000 line kilometre of new magnetic, gravity and ice-penetrating radar data were collected with 10 km line spacing. Here, we report on magnetic anomaly data to the east and south of Sør Rondane. These data are integrated with exposure information from Sør Rondane, the Belgica Mountains, and the Yamato Mountains. Main emphasis was placed on estimating the spatial extent of the recently discovered Tonian Oceanic Arc Super Terrane (TOAST), which is interpreted as Neoproterozoic juvenile crustal additions within the East African-Antarctic Orogen. Earlier studies revealed a major magnetic anomaly, the Forster Magnetic Anomaly (FMA), and a province of subdued SE-striking parallel positive magnetic anomalies in the mostly ice-covered region of central DML and south-eastern DML, respectively. The FMA is interpreted as western extent of the TOAST, whereas geological investigations showed that the subdued magnetic anomaly pattern can be correlated with exposures in Sør Rondane and scattered nunataks west of it. U-Pb ages of ca. 1000-900 Ma, are documented from zircons of gabbro–trondhjemite–tonalite–granodiorite (GTTG) suites in both areas. Further, geochemical analyses prove a juvenile character of the GTTG complex, which is interpreted as oceanic arc complexes. Glacial drift from southern Sør Rondane point to an inland continuation of the TOAST, however, of unknown dimensions. The new magnetic data constrain the southern and eastern minimum extent of the TOAST, which corresponds in size to at least 5% of the whole of East Antarctica. The juvenile Tonian rocks developed outside Rodinia and represent major remnants of the Mozambique Ocean. They resemble rocks of the Arabian-Nubian shield, but are slightly older. Thus, the Late Neoproterozoic/Early Paleozoic East African-Antarctic Orogen is characterised by major Neoproterozoic crustal additions on either ends. |
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