Feldspathic leucosomes occur in an ultrahigh temperature (UHT) metamorphosed garnet bearing paragneiss/ quartzite in the Napier Complex, East Antarctica. Coarse (200 400 μ m) zircon grains occurring in the leucosomes display 3 textural domains: (I) dark CL (cathodoluminescence) structured inner core, (II) bright CL structured outer core, and (III) dark CL structureless rim. Chemical compositions, especially chondrite normalized REE patterns obtained by SIMS analysis, correlate with these three domains: the inner core (domain I) shows HREE enrichment with Yb(n)/Gd(n) = 3.3, whereas the outer core (II) and rim (III) have flat to relatively depleted HREE patterns with Yb(n)/Gd(n) = 0.7 0.8. Th/U ratios decrease from 3.2 in the zircon inner core (I) to 1.2 in outer core (II) and to 0.3 in the rim (III).Garnets near such zircon grains display two trace element compositional features. Firstly, high core Zr contents (300 ppm) decrease to 100 ppm within 50 100 μ m of grain rims. Secondly, the HREE distribution between zircon inner core (I) and garnet core is 2 at Gd ( . This marked change in the HREE distribution between zircon and garnet must reflect either a change in the minerals with which the zircon was growing or being modified, a change in the physical and chemical conditions of zircon growth, or a combination of the two. Based on comparisons with recent estimates of equilibrium zircon/garnet HREE distribution coefficients we infer that the inner core (I) did not grow with the garnet that occurs in the paragneiss but grew within a garnet absent melt that was then injected into the gneiss. The resulting leucosome then underwent wall rock reaction with the enclosing garnet bearing gneiss, causing a decrease in garnet to Zr contents to values approaching equilibrium with melt, and precipitating the zircon outer core (II). Finally, the zircon rim (III) and later monazite formed in a HREE depleted environment. Melt injection, reaction and crystallization of the leucosomes took place within the time interval 2496 2471 Ma at the end of the UHT history of the Napier Complex.

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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.

Analysis of new lithological, structural, metamorphic and geochronological data from extensive mapping in Mozambique permits recognition of two distinct crustal blocks separated by the Lurio Belt shear zone.

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