The role of silicic magmas in crust formation: A case study of Iceland

该项目是在“冰岛合作研究”的总体框架内进行的，该方案的重点是冰岛羽流与大西洋中部相互作用的结果，即地壳的形成。我们的项目解决了冰岛地壳生成中的岩浆作用。我们的目标是确定形成的玄武岩浆和玄武岩浆的相对数量，以及玄武岩浆的起源（例如，岩浆分异和/或地壳重熔？我们的初步研究发现，冰岛火山喷发岩浆的相对比例被大大低估了，主要是由于对火山灰体积的估计不足。在冰岛喷发的火山岩浆的体积对确定当地的岩浆生产率和冰岛地壳内剩余的富含斜长石的堆积物的数量具有重要意义。因此，我们计划1）重建体积和冰岛自末次冰期以来的岩浆活动的历史，2）评估岩浆分异与地壳重熔在当地岩浆生成中的相对重要性，3）建立构造背景和岩浆岩成因之间的关系。我们将利用火山学、岩石学和地球化学方法对冰岛具有代表性的中央火山系统进行研究。我们将重点关注不同构造背景下的系统，这些系统的特征是不同的岩浆产生速率和成分。（过去10.000年）将通过火山爆发的文献记录，当地地层学研究，并与北大西洋地区的灰岩地层记录进行对比。我们将使用这些结果来限制冰岛在全新世的平均岩浆生产率。

This project is carried out within the overall framework of "Iceland Cooperative Studies", a program which focuses on crustal formation as a result of interactions between the Iceland plume and the mid atlantic ocean. Our project addresses the role of silicic magmatism in the generation of Icelandic crust. We aim to determine the relative amounts of silicic and basaltic magma formed, and the origin of the silicic magmas (e.g., from magma differentiation and/or crustal remelting?). Our preliminary studies have found that the relative proportion of silicic magma erupted on Iceland has been significantly underestimated, primarily due to inadequate estimates of tephra volumes. The volume of silicic magma erupted at Iceland has major implications for determing local magma production rates and the amounts of residual plagioclase-rich cumulates within the Icelandic crust. We therefore plan to 1)reconstruct the volume and the history of silicic magmatism at Iceland since the Last Glacial period, 2) evaluate the relative importance of magmadifferentiation versus crustal remelting in local silicic magma generation, and 3) establish a relationship between tectonic setting and genesis of silicic rocks. We will use volcanological, petrological and geochemical methods to investigate represantative central volcanic systems on Iceland. We will focus on systems in differing tectonic settings, which are characterized by variable magma production rates and compositions.A compilation of the composition and volume of differentiated magmas erupted from each of these volcanic systems during the Holocene (the last 10.000 years) will be established through literature records of eruptions, local stratigraphic studies, and correlation of these with tephrostratigraphic records from the North Atlantic region. We will use these results to constrain average magma production rates for Iceland during the Holocene.