Pan-African Tectonism in the Western Maud Belt: P-T-t Path for High-grade Gneisses in the H.U. Sverdrupfjella, East Antarctica
Extensive high-grade polydeformed metamorphic provinces surrounding Archaean cratonic nuclei in the East Antarctic Shield record two tectono-thermal episodes in late Mesoproterozoic and late Neoproterozoic–Cambrian times. In Western Dronning Maud Land, the high-grade Mesoproterozoic Maud Belt is jux...
| Published in: | Journal of Petrology |
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| Main Authors: | , , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
2005
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| Subjects: | |
| Online Access: | http://petrology.oxfordjournals.org/cgi/content/short/46/4/671 https://doi.org/10.1093/petrology/egh093 |
| Summary: | Extensive high-grade polydeformed metamorphic provinces surrounding Archaean cratonic nuclei in the East Antarctic Shield record two tectono-thermal episodes in late Mesoproterozoic and late Neoproterozoic–Cambrian times. In Western Dronning Maud Land, the high-grade Mesoproterozoic Maud Belt is juxtaposed against the Archaean Grunehogna Province and has traditionally been interpreted as a Grenvillian mobile belt that was thermally overprinted during the Early Palaeozoic. Integration of new U–Pb sensitive high-resolution ion microprobe and conventional single zircon and monazite age data, and Ar–Ar data on hornblende and biotite, with thermobarometric calculations on rocks from the H.U. Sverdrupfjella, northern Maud Belt, resulted in a more complex P – T – t evolution than previously assumed. A c . 540 Ma monazite, hosted by an upper ampibolite-facies mineral assemblage defining a regionally dominant top-to-NW shear fabric, provides strong evidence for the penetrative deformation in the area being of Pan-African age and not of Grenvillian age as previously reported. Relics of an eclogite-facies garnet–omphacite assemblage within strain-protected mafic boudins indicate that the peak metamorphic conditions recorded by most rocks in the area ( T = 687–758°C, P = 9·4–11·3 kbar) were attained subsequent to decompression from P > 12·9 kbar. By analogy with limited U–Pb single zircon age data and on circumstantial textural grounds, this earlier eclogite-facies metamorphism is ascribed to subduction and accretion around 565 Ma. Post-peak metamorphic K-metasomatism under amphibolite-facies conditions is ascribed to the intrusion of post-orogenic granite at c . 480 Ma. The recognition of extensive Pan-African tectonism in the Maud Belt casts doubts on previous Rodinia reconstructions, in which this belt takes a pivotal position between East Antarctica, the Kalahari Craton and Laurentia. Evidence of late Mesoproterozoic high-grade metamorphism during the formation of the Maud Belt exists in the form of c . 1035 Ma ... |
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