Does Bubble Nucleation Occur Heterogeneously in Magmas Feeding Explosive Rhyolite Eruptions? Insights From the Rock Magnetic Properties of Pumice

IF 4.6 1区地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Geophysical Research Letters Pub Date : 2025-08-21 DOI:10.1029/2025GL115789

Kelly N. McCartney, Julia E. Hammer, Thomas Shea, Stefanie Brachfeld, Thomas Giachetti, Bruce F. Houghton

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Abstract

Nanometer-scale titanomagnetite crystals have been detected in nominally aphyric rhyolite pumice, but whether they are numerous enough to impact bubble nucleation in explosive silicic volcanism was unresolved. This study examines sub-micron crystals using rock magnetic techniques, Rhyolite-MELTS modeling, and physical characterization. We analyzed pumice from four eruptions spanning wide ranges in intensity, storage depth, and bubble number density (10¹⁶ to 10¹³ m⁻³ liquid): 1060 CE Glass Mountain, 1912 CE Novarupta, 232 CE Taupo, and 0.45 Ma Pudahuel. Calculations assuming monospecific assemblages of 10 and 1,000 nm cubic particles yield titanomagnetite number densities of 10²¹ to 10¹³ m⁻³ dense rock equivalent, respectively. In all cases, titanomagnetite is thermodynamically stable at pre-eruptive storage conditions and magnetic susceptibility (χ_LF) is independent of vesicularity and permeability, indicating that crystals likely formed prior to vesiculation. The existence of nm-scale Fe-Ti oxides in four diverse cases suggests that heterogeneous bubble nucleation is a general feature of explosive rhyolite volcanism.

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气泡成核是否在岩浆中非均质发生？从浮石的岩石磁性性质的见解

纳米级钛磁铁矿晶体已在名义上的石英流纹浮石中被检测到，但它们的数量是否足以影响爆炸硅酸火山作用中的气泡成核尚未解决。本研究使用岩石磁性技术、流纹岩熔体建模和物理表征来检测亚微米晶体。我们分析了四个火山喷发的浮石，这些火山喷发的强度、储存深度和气泡数密度（1016 ~ 1013 m−3液体）范围很宽：1060 CE Glass Mountain火山、1912 CE Novarupta火山、232 CE Taupo火山和0.45 Ma Pudahuel火山。假设10和1,000 nm立方颗粒的单特异性组合，计算得出的钛磁铁矿数密度分别为1021至1013 m−3致密岩石当量。在所有情况下，钛磁铁矿在喷发前的储存条件下热力学稳定，磁化率（χLF）与囊泡性和渗透性无关，表明晶体可能在囊泡形成之前形成。四种不同情况下存在纳米级Fe-Ti氧化物，表明非均质气泡成核是爆炸流纹岩火山活动的普遍特征。

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来源期刊

Geophysical Research Letters 地学-地球科学综合

CiteScore

9.00

自引率

9.60%

发文量

1588

审稿时长

2.2 months

期刊介绍： Geophysical Research Letters (GRL) publishes high-impact, innovative, and timely research on major scientific advances in all the major geoscience disciplines. Papers are communications-length articles and should have broad and immediate implications in their discipline or across the geosciences. GRLmaintains the fastest turn-around of all high-impact publications in the geosciences and works closely with authors to ensure broad visibility of top papers.