Geochemistry and mineralogy of garnet grains from ODP Sample 183-1137A-33R-3,50-53@en

On Elan Bank, a southwestern promontory of the Kerguelen Plateau in the southern Indian Ocean, we cored an interval of conglomerate and minor sandstone within a thick section of Cretaceous flood basalts. Most of the detritus in these sedimentary rocks is volcanic with the exception of a small amount of conspicuous material of probable continental derivation. The anomalous clasts include several pebbles of gneiss (Nicolaysen et al., 2001, doi:10.1130/0091-7613(2001)029<0235:POPGBG>2.0.CO;2) and garnet sand grains. The presence of continental material on the plateau bears significantly on the interpretation of Indian Ocean basalts (Weis et al., 2001, doi:10.1130/0091-7613(2001)029<0147:OOCCII>2.0.CO;2). The purpose of the present study was to determine the composition of the garnets to provide additional constraints on the nature of the source area.在南印度洋凯尔盖朗高原（Kerguelen Plateau）的西南岬角埃兰浅滩（Elan Bank）上，我们在一套厚层白垩纪溢流玄武岩（flood basalts）中钻取了一段砾岩夹少量砂岩的岩心。这套沉积岩中的大部分碎屑为火山成因，仅含少量特征显著的、可能源自大陆的物质。其中的异常岩屑包括数块片麻岩（gneiss）砾石与石榴石（garnet）砂粒（Nicolaysen等人，2001，doi:10.1130/0091-7613(2001)029<0235:POPGBG>2.0.CO;2）。该高原上大陆物质的存在，对印度洋玄武岩的成因解释具有重要意义（Weis等人，2001，doi:10.1130/0091-7613(2001)029<0147:OOCCII>2.0.CO;2）。本研究的目的在于测定石榴石的成分，以此为物源区的性质提供额外的约束依据。