Geochronological constraints on the Late Proterozoic to Cambrian crustal evolution of eastern Dronning Maud Land, East Antarctica: a synthesis of SHRIMP U-Pb age and Nd model age data

Abstract

In eastern Dronning Maud Land (DML), East Antarctica, there are several discrete, isolated magmatic and high-grade metamorphic regions. These are, from west (c. 20°E) to east (c. 50°E), the Sør Rondane Mountains (SRM), Yamato–Belgica Complex (YBC), Lützow-Holm Complex (LHC), Rayner Complex (RC) and Napier Complex (NC). To understand this region in a Gondwanan context, one must distinguish between Pan-African and Grenvillian aged magmatic and metamorphic events. Sensitive high-resolution ion microprobe U–Pb zircon ages and Nd model ages for metamorphic and plutonic rocks are examined in conjunction with published geological and petrological studies of the various terranes. In particular, the evolution of the SRM is examined in detail. Compilation of Nd model ages for new and published data suggests that the main part of eastern Dronning Maud Land, including the SRM, represents juvenile late Mesoproterozoic (c. 1000–1200 Ma) crust associated with minor fragments of an older continental component. Evidence for an Archaean component in the basement of the SRM is lacking. As for central DML, 1100–1200 Ma extensive felsic magmatism is recognized in the SRM. Deposition of sediments during or after magmatism and possible metamorphism at 800–700 Ma is recognized from populations of detrital zircon in metasedimentary rocks. The NE Terrane of the SRM, along with the YBC, was metamorphosed under granulite-facies conditions at c. 600–650 Ma. The SW and NE Terranes of the SRM were brought together during amphibolite-facies metamorphism at c. 570 Ma, and share a common metamorphic and magmatic history from that time. High-grade metamorphism was followed by extensive A-type granitoid activity and contact metamorphism between 560 and 500 Ma. In contrast, TDM and inherited zircon core ages suggest that the LHC is a collage of protoliths with a variety of Proterozoic and Archaean sources. Later peak metamorphism of the LHC at 520–550 Ma thus represents the final stage of Gondwanan amalgamation in this section of East Antarctica.

Detrital zircon provenances for metamorphic rocks from southern Sør Rondane Mountains, East Antarctica: A new report of Archean to Mesoproterozoic zircons

“…6 and Table 1). This age distribution is mostly overlapped with protolith ages reported from metamorphosed igneous rocks in units C and D (e.g., Shiraishi et al, 2008) (Figs. 6, 7a, and 7b).…”

“…The histograms and probability density curves using concordant data of the detrital zircon cores obtained from garnet-sillimanite-biotite gneiss (2102A), clinopyroxene-hornblende calc-silicate rock (1107-01), spinel, staurolite bearing garnet-biotite gneiss (2406D), epidote-hornblende calc-silicate rock (1202B) and biotite gneiss (1703A). The gray field corresponds to age ranges reported from metamorphosed igneous rocks in units C and D in the SW terrane (Shiraishi et al, 2008;Adachi et al, 2013;Nakano et al, 2013;Osanai et al, 2013;Kitano et al, 2014b). Note that the detrital zircon ages in the former four samples are consistent with the protolith ages whereas the ages in biotite gneiss from the Tvihøgda are not.…”

“…Archean to Neoproterozoic detrital zircon ages have been recognized widely in the NE terrane providing strong evidence of the different detrital provenances between the NE and SW terranes . However, even though the SW terrane has been considered as a late Mesoproterozoic to Neoproterozoic basement with the juvenile affinities (e.g., Shiraishi et al, 2008), this terrane contains some Archean to Paleoproterozoic components (Fig. 8).…”

“…Therefore, the mountains would be key to provide critical constraints on the amalgamation process of the supercontinent. With this important geological background, many petrological and geochronological studies of metamorphic rocks have been conducted to reveal the metamorphic evolution in the Sør Rondane Mountains (e.g., Asami et al, 1992;Shiraishi et al, 2008;Osanai et al, 2013). However, studies focused on the protolith formation of metamorphic rocks are limited (e.g., Kamei et al, 2013).…”

“…Recently, the investigations for provenance of metamorphosed sedimentary rocks in the Sør Rondane Mountains have been carried out (e.g., Osanai et al, 2013). The SHRIMP zircon U-Pb ages from metamorphic rocks in the mountains indicated age clusters of inherited ages at~1130, 1000 and 800 Ma with little evidence of Archean to Mesoproterozoic components (Shiraishi et al, 2008;Adachi et al, 2013). Therefore, the mountains were considered to comprise juvenile basements without old recycled materials.…”