PGE geochemistry and mineralogy within the Jurassic Dufek-Forrestal layered mafic intrusion,Antarctica
Selected samples from the Dufek-Forrestal layered mafic intrusion,Antarctica,have been analysed for platinum-group elements and their mineralogical siting to study their low-pressure fractionation behaviour within the ~3.5 km thick exposed profile.Samples analysed comprise variably composed gabbros,anorthosites,pyroxenites and magnetitites from both the Dufek Massif and the Forrestal Range sections.The PGE totals,generally dominated by the Pt-PGE,range from 5 to 792 ppb with the highest contents analysed in Ti-magnetite-rich gabbros and Ti-magnetitites from the basal ~300 m of the Forrestal Range section,which represents the upper ~ 1.7 km of the intrusion.The observed PGE enrichment until Ti-magnetite fractionation indicates sulphur-under-saturation during low-pressure differentiation of a tholeiitic magma originated by high-degree partial melting of a S-poor subcontinental lithospheric mantle source.The final PGE fractionation is caused by a delayed S-saturation ultimately released by Fe-Ti oxide crystallisation at an advanced level of magma differentiation.However,the lack of distinct trace element correlations as well as the platinum-group mineral assemblage identified in these Ti-magnetite-rich rocks indicate that their PGE composition is not only controlled by the base-metal sulphides present.Thus,both high-temperature and subsolidus redistribution processes are responsible for the PGE distribution found within the stratigraphic profile of the Dufek-Forrestal intrusion.
R.Hanemann L.Viereck-Goette F.Melcher S.B.Mukasa
Institute for Geosciences,University of Jena,Burgweg 11,07747 Jena,Germany ricarda Federal Institute for Geosciences and Natural Resources,Stilleweg 2,30655 Hannover,Germany Department of Earth Sciences,University of New Hampshire,Durham,NH 03824,U.S
国际会议
贵阳
英文
100-103
2012-06-16（万方平台首次上网日期，不代表论文的发表时间）