The geochemical evolution of Hawaiian magmatism: ODP Leg 197 drilling of the Emperor Seamounts

点击翻译按钮获取中文摘要

Long-lived, intra-plate (hotspot) magmatism, such as occurs on Hawaii, is thought to be the surface expression of mantle plumes: Columns of relatively hot material rising from deeper in the mantle. Geochemical studies of hotspot magmatism can thus give insights into the structure and composition of the Earth's deep interir, which cannot be directly sampled. We plan to carry out a geochemical and isotopic study of samples of volcanic rocks from the Emperor Seamounts, in the northern Pacific Ocean, which will be recovered by drilling on ODP Leg 197 (Juli - August, 2001). The Emperor Seamounts were creted when the Pacific Plate passed over the Hawaiian hotspot, and the samples to be analysed provide a unique, 40 Ma record (from 85 to 45 Ma ago) of the geochemistry of this hotspot. This study will document the geochemical evolution of Hawaiian magmatism over this period. Specific questions to be addressed are, (a) the nature, scale and origin of mantle heterogeneity in mantle plumes, and the temporal evolution of plume composition; (b) the influence of shallow-level processes such as lithospheric contamination, melting and spreading ridge interaction on the composition of intraplate lavas; (c) the origin of shield and post-shield intra-plate magmatism.