Department of Earth Sciences , University of Cambridge , Cambridge , UK.
Philos Trans A Math Phys Eng Sci. 2019 Feb 25;377(2139):20180021. doi: 10.1098/rsta.2018.0021.
It is well established that magmatism is trans-crustal, with melt storage and processing occurring over a range of depths. Development of this conceptual model was based on observations of the products of magmatism at spreading ridges, including Iceland. Petrological barometry and tracking of the solidification process has been used to show that the Icelandic crust is built by crystallization over a range of depths. The available petrological evidence indicates that most of the active rift zones are not underlain by extensive and pervasive crystal mush. Instead, the microanalytical observations from Iceland are consistent with a model where magmatic processing in the lower crust occurs in sills of decimetric vertical thickness. This stacked sills mode of crustal accretion corresponds to that proposed for the oceanic crust on the basis of ophiolite studies. A key feature of these models is that the country rock for the sills is hot but subsolidus. This condition can be met if the porosity in thin crystal mushes at the margins of the sills is occluded by primitive phases, a contention that is consistent with observations from cumulate nodules in Icelandic basalts. The conditions required for the stabilization of trans-crustal mushes may not be present in magmatic systems at spreading ridges. This article is part of the Theo Murphy meeting issue 'Magma reservoir architecture and dynamics'.
已经证实，岩浆作用是贯穿地壳的，熔融体的储存和处理发生在一系列深度上。这一概念模型的发展是基于对洋中脊岩浆作用产物的观察，包括冰岛。岩石学压力计和对凝固过程的追踪已被用于表明冰岛地壳是通过在一系列深度上的结晶而形成的。现有的岩石学证据表明，大多数活动的裂谷带并不以下伏的广泛而普遍的晶体泥为基础。相反，来自冰岛的微观分析观测结果与一个模型一致，即在下部地壳中岩浆作用发生在几厘米厚的岩床中。这种堆积岩床的地壳增生模式与根据蛇绿岩研究提出的大洋地壳模式相对应。这些模型的一个关键特征是岩床的围岩是热的但未过固相线。如果岩床边缘的薄晶体泥中的孔隙被原始相封闭，就可以满足这种条件，这一论点与冰岛玄武岩中堆积结核的观测结果一致。在洋脊岩浆系统中，可能不存在稳定贯穿地壳泥的条件。本文是“岩浆储层结构和动力学”Theo Murphy 会议专刊的一部分。
