Iron in silicate glasses and melts: implications for volcanological processes
Iron in silicate glasses and melts: implications for volcanological processes
复制标题
硅酸盐玻璃和熔体中的铁：对火山过程的影响
DOI：
10.1002/essoar.10503261.1
复制
发表时间：
2020
影响因子：
3.5
通讯作者：
D. Neuville
中科院分区：
文献类型：
--
作者：
C. Le Losq;M. Cicconi;D. Neuville
铁以两种价态存在于岩浆中，其浓度范围从小于1wt%到大于10wt%。一般来说，Fe 2+是熔体结构中的网络改性剂，而Fe 3+是弱网络形成剂。比例Fe 3 +/（Fe 3 ++ Fe 2+）取决于温度、压力、氧逸度和熔体组成。参数模型允许其计算，但熔体组成，铁氧化态和配位之间的复杂联系可以使用离子聚合物模型进一步合理化。限制铁的浓度和氧化态对于确定岩浆密度和粘度至关重要，而岩浆密度和粘度驱动着地球中的物质和热量交换。在高压下，元素（包括铁）的配位变化会使岩浆变硬和致密，从而可能影响动力学和地球化学过程。在地表附近，含铁相的结晶改变了残余熔体的组成，包括铁含量和氧化态以及挥发分浓度，最终导致岩浆的密度和粘度发生巨大变化，从而导致火山系统中流体流动的动态变化。因此，岩浆铁含量与氧化态、主元素化学、晶体和挥发分含量之间的复杂相互作用可以对火山系统的动力学起很大作用。
Iron is present in magmas at concentrations ranging from less than 1 wt% to more than 10 wt% in two valence states. In general, Fe2+is a network modifier in the melt structure while Fe3+is a weak network former. The ratio Fe3+/(Fe3++Fe2+) depends on temperature, pressure, oxygen fugacity, and melt composition. Parametric models allow its calculation, but the complex links between melt composition, iron oxidation state, and coordination can be further rationalized using a ionic‐polymeric model. Constraining concentration and oxidation state of iron is critical for determining magma density and viscosity, which drive exchanges of matter and heat in the Earth. At high pressures, changes in the coordination of elements, including iron, yield a stiffening and densification of magmas, potentially influencing dynamic and geochemical processes. Near surface, crystallization of Fe‐bearing phases changes the residual melt composition, including iron content and oxidation state as well as volatile concentration, ultimately driving large changes in density and viscosity of magmas, and, hence, in the dynamic of fluid flow in volcanic systems. The complex interplay between magma iron content and oxidation state, major element chemistry, crystal and volatile contents thus can play a large role on the dynamic of volcanic systems.