The magmatic and geochemical evolution of oceanic intraplate volcanoes: constraints from the Louisville Seamounts (IODP Leg 330) and other Pacific hotspots

寿命长、年龄递增的海山链的火山可能是地幔柱从移动的岩石圈板块下面的上地幔甚至下地幔上升的结果。火山在数百万年的时间里经历了从盾状构造到盾状构造后甚至侵蚀后阶段的不同阶段。通常情况下，主要元素组成范围从拉斑玄武岩到SiO2-不饱和岩浆，随着熔岩年龄的降低。所观察到的地球化学变化的深度和程度的变化的影响，部分熔融，但也可能受到矿物和地球化学组成的地幔源。这些参数可能取决于地幔柱相对于岩石圈板块的位置。地幔柱的温度，动力学和组成对这些地球化学变化的影响知之甚少。该项目旨在分析路易斯维尔海山链海山（IODP 330航次）和其他太平洋热点（Macdonald、Society、Pitcairn、Juan费尔南德斯）的火山玻璃和橄榄石，以调查在快速移动的古老岩石圈上喷发的原始熔体的成分变化。样品在埃尔兰根和基尔很容易获得。与全岩分析相比，玻璃的组成允许更好地约束初始熔体的组成。此外，还将测量不同热点地区玻璃和橄榄石的氧同位素组成，以确定地幔柱中氧同位素的变化。结合已发表的年龄和地球化学数据，这是第一个系统的研究地幔熔体在不同的热点设置的变化及其与地幔柱相对于岩石圈板块定位的关系。

The volcanoes of long-lived, age-progressive seamount chains are likely the result of mantle plumes rising from the upper and possibly even lower mantle underneath moving lithosphere plates. The volcanoes evolve through distinct stages from a shield-building to a post-shield or even post-erosional stages over a period of several millions of years. Typically, the major element compositions range from tholeiitic to SiO2-undersaturated magmas with decreasing age of the lava. The geochemical variability observed is influenced by changes of depth and degree of partial melting but may also be influenced by the mineralogical and geochemical composition of the mantle source. These parameters likely depend on the positioning of the mantle plume relative to the lithospheric plate. The impact of mantle plume temperature, dynamics and composition on these geochemical changes is only poorly understood. This project aims at analysing volcanic glasses and olivines from seamounts of the Louisville Seamount Chain (IODP Leg 330) and other Pacific Hotspots ((Macdonald, Society, Pitcairn, Juan Fernandez) to investigate the compositional variability of primitive melts erupted on old, fast moving lithosphere. The samples are readily available in Erlangen and Kiel. The composition of the glasses allows to better constrain the composition of the primary melt compared to whole rock analyses. In addition, the O isotope composition of glasses and olivines from different hotspots will be measured to determine the O isotope variability in mantle plumes. Combined with published ages and geochemical data this is the first systematic study on the variability of mantle melts in different hotspot settings and its relationship with the mantle plume positioning relative to the lithospheric plate.