Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.
Science. 2019 Jul 19;365(6450):260-264. doi: 10.1126/science.aax4092.
The lower crust plays a critical role in the processing of mantle melts and the triggering of volcanic eruptions by supply of magma from greater depth. Our understanding of the deeper parts of magmatic systems is obscured by overprinting of deep signals by shallow processes. We provide a direct estimate of magma residence time in basaltic systems of the deep crust by studying ultramafic nodules from the Borgarhraun eruption in Iceland. Modeling of chromium-aluminum interdiffusion in spinel crystals provides a record of long-term magmatic storage on the order of 1000 years. This places firm constraints on the total crustal residence time of mantle-derived magmas and has important implications for modeling the growth and evolution of transcrustal magmatic systems.
下地壳在幔源熔体的处理和火山喷发的触发中起着关键作用，它为深部提供岩浆。我们对岩浆系统深部的了解因浅层过程对深部信号的叠加而变得模糊不清。我们通过研究冰岛博尔加拉火山喷发的超镁铁质岩结核，对深部地壳玄武质系统中的岩浆居留时间进行了直接估算。尖晶石晶体中铬-铝互扩散的模拟为长期岩浆储存提供了记录，时间约为 1000 年。这对幔源岩浆在整个地壳中的居留时间施加了严格的限制，并对跨壳岩浆系统的生长和演化模型具有重要意义。
