TY  - JOUR
A1  - Möller, Andreas
A1  - Post, Nicholas J.
A1  - Hensen, Bastiaan J.
T1  - Crustal residence history and Gamet Sm-Nd ages of high-grade metamorphic rocks from the Windmill Islands area, East Antarctica
N2  - Nd whole-rock data from the Windmill Islands area yield early Proterozoic to middle Archaean Nd model ages. These crustal residence times are consistent with regional correlations with other parts of Antarctica (Bunger Hills, Denman Glacier area) and the Albany-Fraser Orogen of south-western Australia during the Mid-Proterozoic and thus support reconstructions with a continuous Mid-Proterozoic orogen in these areas. The new Nd isotope data provide strong evidence that no age boundary exists between the higher- and lower-grade parts of the Windmill Islands area, and that the metamorphic complex represents a single terrane with a common crustal history. The data support the notion of a time- link between the occurrence of intrusive charnockites (C-type magmas) and high-grade metamorphism. The magmatic rocks and orthogneisses in the area are interpreted to have a mixed source consisting of older crustal components, i.e. older sediments (ca. 3.2-2.6 Ga) and a younger mafic component (ca. 1.9 Ga). Two garnet Sm-Nd isochrons yield ages of 1156±17 Ma and 1137±2.5 Ma and are identical to SHRIMP U-Pb results on monazite from these samples. A garnet Sm-Nd age of 1123±13 Ma for the Ford granite is significantly younger than the SHRIMP U-Pb zircon age for this sample. The difference relates to the different closure temperature of each isotopic system and is thus interpreted as initial cooling after granulite facies metamorphism. Keywords. East Antarctica - Granulites - Garnet-whole rock isochrons - Intrusive charnockite - Nd model ages
Y1  - 2002
UR  - http://link.springer.de/link/service/journals/00531/contents/02/00291/paper/s00531-002-0291-x.pdf
ER  - 
TY  - JOUR
A1  - Möller, Andreas
A1  - Hensen, Bastiaan J.
A1  - Armstrong, Richard A.
A1  - Mezger, Klaus
A1  - Ballévre, Michel
T1  - U-Pb zircon and monazite age constraints on granulite-facies metamorphism and deformation in the Strangways Metamorphic Complex (central Australia)
N2  - The age of Proterozoic granulite facies metamorphism and deformation in the Strangways Metamorphic Complex (SMC) of central Australia is determined on zircon grown in syn-metamorphic and syn-deformational orthopyroxene-bearing, enderbitic, veins. SHRIMP zircon studies suggest that M1-M2 and the correlated periods of intense deformation (D1-D2) are part of a single tectonothermal event between 1,717-2 and 1,732-7 Ma. It is considered unlikely that the two metamorphic phases (M1, M2) suggested by earlier work represent separate events occurring within 10-25 Ma of each other. Previous higher estimates for the age of M1 granulite metamorphism in the SMC (Early Strangways event at ca. 1,770 Ma) based on U-Pb zircon dating of granitic, intrusive rocks, are not believed to relate to the metamorphism, but to represent pre-metamorphic intrusion ages. Conventional multi-grain U-Pb monazite analyses on high-grade metasediments from three widely spaced localities in the western SMC yield 207Pb/235U ages between 1,728-11 and 1,712-2 Ma. The age range of the monazites corresponds to the SHRIMP zircon ages in the granulitic veins and is interpreted to record monazite growth (prograde in the metasedimentary rocks). The data imply a maximum time-span of 30 Ma for high-grade metamorphism and deformation in the SMC. There is, thus, no evidence for an extremely long period of continuous high- temperature conditions from 1,770 to ca. 1,720 Ma as previously proposed. The results firmly establish that the SMC has a very different high-grade metamorphic history than the neighbouring Harts Range, where upper amphibolite facies metamorphism in the Palaeozoic caused widespread growth or recrystallization of monazite.
Y1  - 2003
UR  - http://www.springerlink.com/app/home/ content.asp?wasp=nnkjymtwwjhb0ylpgw97&referrer=contribution&format=2&page=1&pagecount=18
ER  -