The incompatible element characteristics of an ancient subducted sedimentary component in ocean island basalts from French Polynesia

被引:46
作者
Dostal, J [1 ]
Cousens, B
Dupuy, C
机构
[1] St Marys Univ, Dept Geol, Halifax, NS B3H 3C3, Canada
[2] Carleton Univ, Dept Earth Sci, Ottawa Carleton Geosci Ctr, Ottawa, ON K1S 5B6, Canada
[3] Univ Montpellier 2, Ctr Geol & Geophys, F-34905 Montpellier, France
关键词
EMI; HIMU; Polynesia; sediments; subduction;
D O I
10.1093/petrology/39.5.937
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The concentrations of incompatible elements in basaltic rocks from the Cook-Austral and Pitcairn-Gambier island chains of French Polynesia were determined to refine geochemical models for the origin of EMI-type ocean island basalts. It has been proposed previously that the addition of pelagic sediment to a HIMU source could yield mantle with EMI-like characteristics. The vg, high abundances of many large ion lithophile elements (e.g. Pb) in pelagic sediments would control incompatible element ratios in the proposed EMI source. Calculations indicate that partial melts of this HIMU-pelagic sediment mix would have incompatible element ratios that do not overlap with those of EMI basalts. An investigation of the effect of subduction on a pelagic sediment composition shows that this is a critical process: the sediment undergoes significant loss of large ion lithophile elements during sub-an devolatilization and metamorphism. Incompatible element ratios in partial melts of a model EMI source which includes this residual metasediment component are shown to be consistent with the range of EMI-type lavas from French Polynesia. In addition, the EMI source map include a smaller ratio of altered oceanic crust to depleted mantle peridotite than is present in a HIMU source.
引用
收藏
页码:937 / 952
页数:16
相关论文
共 57 条