Wieser Penny E, Edmonds Marie, Maclennan John, Jenner Frances E, Kunz Barbara E
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK.
School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes, Buckinghamshire, MK7 6AA, UK.
Nat Commun. 2019 Dec 20;10(1):5797. doi: 10.1038/s41467-019-13518-2.
Olivine-hosted melt inclusions are commonly used to determine pre-eruptive storage conditions. However, this approach relies on the assumption that co-erupted olivines have a simple association with their carrier melts. We show that primitive olivine crystal cargoes and their melt inclusions display a high degree of geochemical disequilibrium with their carrier melts at Kīlauea Volcano, Hawai'i. Within a given eruption, melt inclusions trapped in primitive olivine crystals exhibit compositional diversity exceeding that in erupted lava compositions since 1790 CE. This demonstrates that erupting liquids scavenge crystal cargoes from mush piles accumulating diverse melt inclusion populations over timescales of centuries or longer. Entrainment of hot primitive olivines into cooler, evolved carrier melts drives post-entrapment crystallization and sequestration of CO into vapour bubbles, producing spurious barometric estimates. While scavenged melt inclusion records may not be suitable for the investigation of eruption-specific processes, they record timescales of crystal storage and remobilization within magmatic mush piles.
橄榄石寄主熔体包裹体通常用于确定喷发前的储存条件。然而，这种方法依赖于一个假设，即同时喷发的橄榄石与其携带的熔体有简单的关联。我们发现，在夏威夷基拉韦厄火山，原始橄榄石晶体及其熔体包裹体与其携带的熔体表现出高度的地球化学不平衡。在一次特定的喷发中，被困在原始橄榄石晶体中的熔体包裹体的成分多样性超过了公元1790年以来喷发熔岩成分的多样性。这表明，喷发的岩浆会从堆积了数百年或更长时间、含有多样熔体包裹体群体的岩浆糊中捕获晶体物质。热的原始橄榄石被卷入较冷的、演化的携带熔体中，会驱动捕获后的结晶过程，并将二氧化碳隔离到气泡中，从而产生虚假的气压估计值。虽然捕获的熔体包裹体记录可能不适用于研究特定喷发过程，但它们记录了岩浆糊中晶体储存和再迁移的时间尺度。
