Petrology of the explosive deposits from the April 2021 eruption of La Soufrière volcano, St Vincent: a time-series analysis of microlites
Petrology of the explosive deposits from the April 2021 eruption of La Soufrière volcano, St Vincent: a time-series analysis of microlites
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圣文森特拉苏弗里埃尔火山 2021 年 4 月喷发的爆炸性沉积物的岩石学：微晶石的时间序列分析
DOI：
10.1144/sp539-2022-291
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Joseph, E. P.
中科院分区：
文献类型：
--
作者：
Frey, H. M.;Manon, M. R.;Barclay, J.;Davies, B. V.;Walters, S. A.;Cole, P. D.;Christopher, T. E.;Joseph, E. P.
经过三个多月的熔岩圆顶挤压，La soufri<e:1>（圣文森特）在2021年4月过渡到一系列爆炸性喷发。在此，我们对爆炸前48小时的斑晶和微晶种群进行了时间序列岩石学分析，以约束驱动行为变化的上升条件和过程。原生喷发产物为富含晶体（45-50 vol%）的玄武岩安山岩，具有相似的斑晶相组合和成分。喷发方式的变化与无水微岩结晶引起的二次沸腾引起的超压一致。微晶岩在不同的爆炸阶段表现出不同的变化，有两个种群：(1)“继承”-正常分带的高安斜长石(> An 70)+橄榄石(fo62 - 79)+斜辉石+钛磁铁矿，推测在深度> 15 km和高压下结晶；(2)“少年”—无带斜长石(An 45-65)+斜辉石+正辉石+中间辉石(Wo 12-38)+钛磁铁矿，推断为由于减压和脱气而在上升过程中结晶。第一次爆炸产生的矿渣具有广泛的地质体结晶和显著的“遗传”微岩种群的特征。后来的爆炸有更丰富的“幼年”微岩种群和更低的结晶度，这与从深处上升得更快一致，这是由最初的爆炸和熔岩穹窿破坏后的减压引起的。
After more than three months of lava dome extrusion, La Soufrière (St Vincent) transitioned to a series of explosive eruptions in April 2021. Here we present a time-series petrologic analysis of the phenocryst and microlite populations during the first c. 48 h of explosivity to constrain ascent conditions and processes that drove changes in behaviour. Primary eruptive products were crystal-rich (45–50 vol%) basaltic andesites with similar phenocryst phase assemblages and compositions. The change in eruptive style is consistent with overpressurization as a consequence of second boiling from anhydrous microlite crystallization. The microlites display variation between the explosive phases, with two populations:(1)‘inherited’− normally zoned high-An plagioclase (> An 70)+ olivine (Fo 62–79)+ clinopyroxene+ titanomagnetite, inferred to have crystallized at depths> 15 km and high water pressures;(2)‘juvenile’− unzoned plagioclase (An 45–65)+ clinopyroxene+ orthopyroxene+ intermediate pyroxene (Wo 12–38)+ titanomagnetite, inferred to have crystallized upon ascent due to decompression and degassing. Scoria from the first explosions featured extensive groundmass crystallization and a significant ‘inherited’microlite population. Later explosions had a more abundant ‘juvenile’microlite population and lower crystallinity, consistent with more rapid ascent from depth, initiated by decompression following initial blasts and destruction of the lava dome.