Pilet Sébastien, Baker Michael B, Stolper Edward M
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2008 May 16;320(5878):916-9. doi: 10.1126/science.1156563.
Recycled oceanic crust, with or without sediment, is often invoked as a source component of continental and oceanic alkaline magmas to account for their trace-element and isotopic characteristics. Alternatively, these features have been attributed to sources containing veined, metasomatized lithosphere. In melting experiments on natural amphibole-rich veins at 1.5 gigapascals, we found that partial melts of metasomatic veins can reproduce key major- and trace-element features of oceanic and continental alkaline magmas. Moreover, experiments with hornblendite plus lherzolite showed that reaction of melts of amphibole-rich veins with surrounding lherzolite can explain observed compositional trends from nephelinites to alkali olivine basalts. We conclude that melting of metasomatized lithosphere is a viable alternative to models of alkaline basalt formation by melting of recycled oceanic crust with or without sediment.
再生洋壳，无论有无沉积物，常被认为是大陆和海洋碱性岩浆的源成分，以解释其微量元素和同位素特征。另外，这些特征也被归因于含有脉状、交代岩石圈的源区。在1.5吉帕斯卡压力下对天然富含角闪石的脉体进行的熔融实验中，我们发现交代脉体的部分熔体能够重现海洋和大陆碱性岩浆的关键主量和微量元素特征。此外，角闪石岩与二辉橄榄岩的实验表明，富含角闪石脉体的熔体与周围二辉橄榄岩的反应能够解释从霞石岩到碱性橄榄玄武岩所观察到的成分趋势。我们得出结论，交代岩石圈的熔融是一种可行的替代模型，可替代有或无沉积物的再生洋壳熔融形成碱性玄武岩的模型。
