Knipping Jaayke L, Webster James D, Simon Adam C, Holtz François
Institut für Mineralogie, Leibniz Universität Hannover, Callinstraße 3, 30167, Hannover, Germany.
Department of Earth and Planetary Science, American Museum of Natural History, Central Park West at 79th Street, New York, NY, 10024-5192, USA.
Sci Rep. 2019 Mar 7;9(1):3852. doi: 10.1038/s41598-019-40376-1.
Magnetite (FeO) is an iron ore mineral that is globally mined especially for steel production. It is denser (5.15 g/cm) than Earth's crust (~2.7 g/cm) and is expected to accumulate at the bottom of melt-rich magma reservoirs. However, recent studies revealed heterogeneous fluid bubble nucleation on oxide minerals such as magnetite during fluid degassing in volcanic systems. To test if the attachment on fluid bubbles is strong enough to efficiently float magnetite in silicate magma, decompression experiments were conducted at geologically relevant magmatic conditions with subsequent annealing to simulate re-equilibration after decompression. The results demonstrate that magnetite-bubble pairs do ascend in silicate melt, accumulating in an upper layer that grows during re-equilibration. This outcome contradicts the paradigm that magnetite must settle gravitationally in silicate melt.
磁铁矿（FeO）是一种铁矿石矿物，全球都有开采，尤其用于钢铁生产。它的密度（5.15克/立方厘米）比地壳（约2.7克/立方厘米）大，预计会在富含熔体的岩浆储层底部聚集。然而，最近的研究表明，在火山系统的流体脱气过程中，磁铁矿等氧化物矿物上会出现非均匀流体气泡成核现象。为了测试附着在流体气泡上的力是否足够强，能使磁铁矿在硅酸盐岩浆中有效上浮，我们在与地质相关的岩浆条件下进行了减压实验，随后进行退火处理，以模拟减压后的再平衡过程。结果表明，磁铁矿 - 气泡对确实会在硅酸盐熔体中上升，并在再平衡过程中生长的上层中聚集。这一结果与磁铁矿必须在硅酸盐熔体中因重力沉降的范式相矛盾。
