GEOCHEMISTRY OF JURASSIC DOLERITE INTRUSIONS IN THE OHIO RANGE AND SOUTHERN QUEEN MAUD MOUNTAINS, ANTARCTICA
Dolerites exposed in the 400 km segment of the TAM extending from the southern Queen Maud Mtns. through the Ohio Range have been poorly studied because of limited exposure, rugged terrain, and remoteness of the area. Reconnaissance geologic mapping of the region was conducted in the early 1960’s (Long, 1964; Treves, 1965). The petrography of the dolerite sills has been briefly described but no systematic examination of the chemistry has been previously conducted. Collections from the prior field work are currently housed in the U.S. Polar Rock Repository at Ohio State University. While the samples are small and not specifically collected for geochemical analysis (some suffer from secondary alteration and in situ differentiation), they contribute important information on the geographic variation in chemistry within the FLIP. We have measured the chemistry of ~40 samples using XRF and ICP-MS. The most primitive samples (SiO2=52%, MgO=13%) come from the lower 70 m of a 250 m thick olivine-bearing intrusion in the Nilsen Plateau. The samples are all medium grained (~2 mm) and the chemistry may be slightly influenced by mafic mineral accumulation. The most evolved samples in the region (SiO2=57%, MgO=3.3%) come from the sill capping the section in the Ohio Range. Overall the chemistry is consistent with models suggesting a single source for the FLIP and long distance lateral transport of magmas.