Melt inclusions in Iceland olivines as tracers of primary mantle melt compositions

本项目的目的是通过对冰岛苦苦岩和橄榄拉斑玄武岩中早期形成的斑晶中的玻璃包裹体所代表的原生熔体进行原位分析(主量元素和微量元素和同位素)来研究冰岛羽流的来源化学。我们以前已经证明，在夏威夷拉斑玄武岩中，熔体包裹体中看到的极端化学和同位素不均一性反映了真正的源区不均一性，除了显示出渐进部分熔融的影响外。通过研究冰岛羽流，那里的融化程度比夏威夷下面浅得多，我们希望能对羽流来源化学的变化有更清晰的了解。显然，冰岛和夏威夷的相似之处在于，这两个羽流都含有回收的洋壳，而这种前洋壳的特定成分，如辉长岩，可以通过它们的地球化学指纹来识别。此外，我们希望更好地了解熔体提取的机制和冰岛羽流可能的化学分区。地震层析成像显示，冰岛羽状物的直径(100公里)明显小于岛屿(250公里)。这应该使我们能够绘制出源化学，并将其与羽流的断层“图像”联系起来。

The aim of this project is to investigate the source chemistry of the Iceland plume by insitu analysis (major and trace elements and isotopes) of primary melts represented by glassy inclusions in early-formed phenocrysts from Iceland picrites and olivine tholeiites. We have previously shown that in Hawaiian tholeiites, extreme chemical and isotopic heterogeneities seen in melt inclusions reflect true source heterogeneities, in addition to displaying the effects of progressive fractional melting. By studying the Iceland plume, where melting is at a much shallower level than beneath Hawaii, we hope obtain a clearer picture of the variations of source chemistry of a plume. Apparently, Iceland resembles Hawaii in that both plumes contain recycled ocean crust, and specific components of this former crust, such as gabbros, can be recognized by their geochemical fingerprints. In addition, we expect to gain a better understanding of mechanisms of melt extraction and of possible chemical zoning of the Iceland plume. Seismic tomography indicates that the diameter of the Iceland plume (100 km) is significantly smaller that of the island (250 km). This should enable us to map out the source chemistry and relate it to the tomographic "image" of the plume.