The generation of felsic magmas in the oceanic crust: assimilation-fractional crystallization processes versus re-melting of the crust

该提议的目的是对洋壳内长英质岩浆的形成进行地球化学和实验岩石学相结合的研究，这将有助于了解1)导致长英质地壳物质的分馏过程，2)洋壳中岩浆上升的动力学，以及3)岩浆与热液蚀变围岩的相互作用。首先，我们建议对阿曼蛇绿岩的长英质岩浆岩及其相关的镁铁质岩石进行详细的研究，这些岩石可能代表母岩浆和可能被演化的岩浆同化或部分熔融而产生长英质熔体的热液蚀变围岩。其次，我们将研究来自太平洋-南极隆起的一套玄武岩、安山岩和英安岩熔岩，这是一个快速扩张的山脊，具有丰富的长英质火山作用。我们打算对样品中的全岩、火山玻璃、斑晶和捕虏晶进行地球化学和同位素分析，并利用具有代表性的样品进行实验研究，以确定矿物-液体平衡、微量元素分配系数和可能的熔融或结晶关系。这两种不同的方法将由两名博士生进行，他们将密切合作，使用相同的样本材料。

The aim of the proposal is a combined geochemical and experimental petrological study of the formation of felsic magmas within the oceanic crust which will help to understand 1) fractionation processes leading to felsic crustal material, 2) the dynamics of magma ascent in the oceanic crust, and 3) the interaction of magmas with hydrothermally altered wall rocks. Firstly, we suggest to study in detail felsic magmatic rocks of the Oman Ophiolite as well as related mafic rocks which could represent parental magmas and hydrothermally altered wall rocks which may have been assimilated by evolving magmas or may have been partially molten to yield the felsic melts. Secondly, we will study a suite of basaltic, andesitic and dacitic lavas from the Pacific-Antarctic Rise, a fast-spreading ridge with abundant felsic volcanism. We intend to perform geochemical and isotopic analyses on the whole rocks, volcanic glasses, phenocrysts and xenocrysts in the samples and use the representative samples for the experimental study to define mineral-liquid equilibria, trace element partition coefficients, and possible melting or crystallization relationships. These two different approaches will be carried out by two PhD students who will work closely together and use the same sample material.