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

像发生在夏威夷的长期板内（热点）岩浆活动被认为是地幔柱的表面表现：相对较热的物质柱从地幔深处升起。因此，对热点岩浆活动的地球化学研究可以深入了解无法直接取样的地球深部岩浆的结构和组成。我们计划对来自北方太平洋Emperor海山的火山岩样品进行地球化学和同位素研究，这些样品将在ODP第197航次（2001年7月至8月）通过钻探获得。皇帝海山是在太平洋板块经过夏威夷热点时形成的，待分析的样品提供了该热点独特的40 Ma地球化学记录（85至45 Ma前）。这项研究将记录这一时期夏威夷岩浆活动的地球化学演化。需要解决的具体问题是：（a）地幔柱中地幔不均匀性的性质、规模和起源，以及地幔柱成分的时间演变;（B）浅层次过程，如岩石圈污染、熔融和扩张脊相互作用对板内熔岩成分的影响;（c）盾和盾后板内岩浆活动的起源。

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.