. "Tectonics of the West Antarctic Rift System: New Light on the History and Dynamics of Distributed Intracontinental Extension--C. S. Siddoway." Antarctica: A Keystone in a Changing World. Washington, DC: The National Academies Press, 2008.
The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Antarctica: A Keystone in a Changing World
FIGURE 3 Tectonic correlation between terranes of north Victoria Land, West Antarctica, and New Zealand/Campbell Plateau, compiled from Bradshaw (1989) and Bradshaw et al. (1997). Reconstruction of the Cretaceous East Gondwana margin is based on Gaina et al. (1998) and Kula et al. (2007), with oceanic plates configuration based on Sutherland and Hollis (2001) and Larter et al. (2002). Representation of oceanic plateaus is based on Taylor (2006) and Hoernle et al. (2004). Lower Paleozoic orogenic sediments are shown in olive green and tan. Belt of Cretaceous magmatism is shown in violet. Paparoa metamorphic core complex in the Western Province (WP), Fosdick gneiss dome in Marie Byrd Land (MBL), and detachment systems are marked by ellipses. TAS = Tasmania; RBT = Robertson Bay terrane; EP = Eastern Province; Sw = Swanson Formation; LHR = Lord Howe Rise; CR = Chatham Rise; TI = Thurston Island terrane.
a Ford Granodiorite source for the leucogranites (Saito et al., 2007) at T, P conditions of 820-870°C and 6.5-7.5 kbar determined from mineral equilibria modeling (Korhonen et al., 2007a,b). There is evidence of metamorphic zircon growth as early as ca. 140 Ma. A summary of U-Pb SHRIMP analyses of igneous and metamorphic zircon from Fosdick Mountains migmatites (Figure 6) reveals that there is a bimodal distribution of ages. Whereas HT metamorphism and zircon growth is recorded as early as 150 Ma, a majority of points analyzed thus far fall within the interval of 120-100 Ma. Anatectic leucosomes from sites in MBL’s Amundsen Province, the Demas Range (Figure 2) yield ages of 128 Ma to 113 Ma for igneous zircon (Mukasa and Dalziel, 2000). The MBL data fall within the 126-107 Ma age range of the youngest arc-related intrusions identifid in NZ by Muir et al. (1997, 1998), those of the Separation Point and Rahu suites in the Western Province and the deeper level Fiordland Orthogneiss in Fiordland. The Rahu suite granites are interpreted to derive from crustal melting of preexisting rocks (Ireland and Gibson, 1998). Thus, the conditions for HT metamorphism and granite genesis in the Fosdick Mountains were attained and overlapped in time with arc plutonism in the Median Batholith and in the Amundsen Province.
By contrast, the alkaline plutonism attributed to back-arc extension occurred in eastern MBL (Figure 5) at 105-102 Ma (Weaver et al., 1992, 1994; Mukasa and Dalziel, 2000), distinctly later than onset of high temperature metamorphism. In western MBL the Ford Ranges experienced alkalic plutonism at 105-103 Ma and ca. 99 Ma (Richard et al., 1994) and in Edward VII Peninsula at 103-98 Ma (Mukasa and Dalziel,