Collaborative Research: Magma-Host Rock Interaction Processes of Assimilation in the Mid-Crustal Hortavær Intrusive Complex, North Central Norway

456 Ma霍尔塔瓦侵入杂岩是挪威中北部加里东时代本达尔岩基的一部分。它由碱性岩石组成，呈数百或数千个类似岩墙的岩体，分布在不同的寄主岩石(混合岩、石英岩、大理岩和钙硅酸片麻岩)中。从橄榄辉长岩到正长岩的火成岩范围、化学变化和碳同位素特征表明，岩浆就地同化了钙硅酸盐和硅酸盐岩石。霍尔塔瓦对原位同化作用的认识使其成为解决控制中地壳岩浆与其寄主岩石之间相互作用的机制的理想场所：寄主岩石是否被整体同化？或者固体是根据它们溶解在遭受污染的岩浆中的能力而被同化的？或者，寄主岩石是否先部分熔化，只有熔体成分被同化？我们将使用综合场分析和微观分析方法来验证碳酸盐+硅酸盐同化作用在早期岩浆演化中起重要作用，但硅酸盐同化作用主导后期岩浆演化的假说。由于碳酸盐在封闭系统中的同化是无效的，我们还将测试这种同化在开放系统中发生的可能性。这项研究将涉及一个由教师和学生组成的国际团队。它将在新的文化和学术环境中为所有参与者提供丰富的合作机会。它还将涉及与挪威地质调查局和挪威科技大学的科学家和学生，以及当地一名中学教师和业余地质学家的合作。

The 456 Ma Hortavar intrusive complex is part of the Caledonian-age Bindal Batholith in north-central Norway. It consists of alkaline rocks emplaced as hundreds or thousands of dike-like bodies into diverse host rocks (migmatite, quartzite, marble, and calc-silicate gneiss). The range of the igneous rocks, from olivine gabbro through syenite, their chemical variation, and their carbon isotope signatures indicates that the magmas assimilated calc-silicate and silicate rocks in situ. Recognition of in situ assimilation at Hortavar makes it an ideal place to address the mechanisms that control interactions between magmas and their host rocks in the middle crust: Are host rocks assimilated en masse? Or are solids assimilated according to their ability to dissolve in the magma undergoing contamination? Alternatively, are host rocks partly melted first, with only the melt component assimilated? We will use integrated field and microanalytical methods to test the hypothesis that carbonate + silicate assimilation was important during early magma evolution, but that silicate assimilation dominated later evolution. Because carbonate assimilation in a closed system is ineffectual, we will also test the likelihood that such assimilation occurred in an open system. The research will involve an international team of faculty and students. It will provide all participants with a rich, collaborative venture in new cultural and academic environments. It will also involve collaboration with scientists and students from the Norwegian Geological Survey and the Norwegian University of Science and Technology, and a local middle school teacher and amateur geologist.