Elastic properties of high-grade metamorphosed igneous rocks from Enderby Land and eastern Dronning Maud Land, Antarctica: evidence for biotite-bearing mafic lower crust
M. Ishikawa, E. Shingai, M. Arima, 2008. "Elastic properties of high-grade metamorphosed igneous rocks from Enderby Land and eastern Dronning Maud Land, Antarctica: evidence for biotite-bearing mafic lower crust", Geodynamic Evolution of East Antarctica: A Key to the East–West Gondwana Connection, M. Satish-Kumar, Y. Motoyoshi, Y. Osanai, Y. Hiroi, K. Shiraishi
Download citation file:
Ultrasonic measurements of P-wave velocity (Vp) and S-wave velocity (Vs) were conducted at high pressures up to 1.0 GPa and high temperatures up to 400 °C for ultrahigh-temperature (UHT) metamorphosed rocks from Mount Riiser-Larsen, in the Archaean Napier Complex of Enderby Land. The results at 1.0 GPa and 400 °C are Vp=7.17 km s−1, Vs=4.24 km s−1, Vp/Vs=1.69, Poisson's ratio (σ)=0.23 for pyroxenite (SiO2=44.2 wt%, density (ρ)=3.41 g cm−3); Vp=6.93 km s−1, Vs=3.81 km s−1, Vp/Vs=1.82, σ=0.28 for mafic granulite (SiO2=52.2 wt%, ρ=3.02 g cm−3); Vp=6.88 km s−1, Vs=3.72 km s−1, Vp/Vs=1.85, σ=0.29 for mafic granulite (SiO2=49.5 wt%, ρ=2.88 g cm−3); and Vp=6.17 km s−1, Vs=3.59 km s−1, Vp/Vs=1.72, σ=0.24 for orthopyroxene-bearing felsic gneiss (SiO2=65.4 wt%, ρ=2.68 g cm−3). Vp and Vp/Vs of these UHT rocks are not comparable with the previously proposed seismic velocity model (Vp=6.56 km s−1, Vp/Vs=1.70) for the lower crust beneath the Mizuho Plateau of eastern Dronning Maud Land. Combining the available measured velocity and density data with the seismic velocity profile defined for the Mizuho Plateau, we suggest that relatively low Vp and Vs characteristics of the lower crust beneath the Mizuho Plateau may be attributed to higher abundance of biotite in the mafic lower crustal rocks. It is proposed that the biotite-bearing lower crustal rocks were formed by metasomatic processes associated with Pan-African orogeny.
Figures & Tables
Geodynamic Evolution of East Antarctica: A Key to the East–West Gondwana Connection
Geological correlations of East Antarctica with adjoining continents have been puzzling geologists ever since the concept of a Gondwana supercontinent surfaced. Despite the paucity of outcrops because of ice cover, difficulty of access and extreme weather, the past 50 years of Japanese Antarctic Research Expeditions (JARE) has successfully revealed vital elements of the geology of East Antarctica. This volume presents reviews and new research from localities across East Antarctica, especially from Dronning Maud Land to Enderby Land, where the geological record preserves a history that spans the Archaean and Proterozoic. The reviews include extensive bibliographies of results obtained by geologists who participated in the JARE. Comprehensive geological, petrological and geochemical studies, form a platform for future research on the formation and dispersion of Rodinia in the Mesoproterozoic and subsequent assembly of Gondwana in the Neoproterozoic to Early Palaeozoic.