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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Magmatic controls on eruption dynamics of the 1950 yr B.P. eruption of San Antonio Volcano, Tacana Volcanic Complex, Mexico-Guatemala
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Magmatic controls on eruption dynamics of the 1950 yr B.P. eruption of San Antonio Volcano, Tacana Volcanic Complex, Mexico-Guatemala

机译：岩浆动力学对公元前1950年喷发动力学的控制墨西哥-危地马拉塔卡纳火山群的圣安东尼奥火山喷发

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摘要

San Antonio Volcano, in the Tacana Volcanic Complex, erupted -1950 yr. B.P., with a Pelean type eruption that produced andesitic pyroclastic surges and block-and-ash flows destroying part of the volcano summit and producing a horse-shoe shaped crater open to the SW. Between 1950 and 800 yr B.P. the eruption continued with effusive andesites followed by a dacite lava flow and a summit dome, all from a single magma batch. All products consist of phenocrysts and microphenocrysts of zoned plagioclase, amphibole, pyroxene, magnetite ± ilmenite, set in partially crystallized groundmass of glass and microlites of the same mineral phases, except for the lack of amphibole. Included in the andesitic blocks of the block-and-ash flow deposit are basaltic andesite enclaves with elongated and ellipsoidal forms and chilled margins. The enclaves have intersertal textures with brown glass between microphenocrysts of plagiodase, hornblende, pyroxene, and olivine, and minor proportions of phenocrysts of plagioclase, hornblende, and pyroxene. A compositional range obtained of blocks and enclaves resulted from mixing between andesite (866 ℃ ± 22) and basaltic andesite (enclaves, 932 ℃ ± 22), which may have triggered the explosive Pelean eruption. Vestiges of that mixing are preserved as complex compositional zones in plagioclase and dinopyroxene-rich reaction rims in amphibole in the andesite. Whole-rock chemistry, geothermometry, experimental petrology and modeling results suggest that after the mixing event the eruption tapped hybrid andesitic magma (＜900 ℃) and ended with effusive dacitic magma (～825 ℃), all of which were stored at ～200 MPa water pressure. A complex open-system evolution that involved crustal end-members best explains the generation of effusive dacite from the hybrid andesite. Amphibole in the dacite is rimmed by reaction products of plagioclase, orthopyroxene, and Fe-Ti oxides produced by decompression during ascent. Amphibole in the andesite, however, lacks such rims. Because the andesite was at 866 ± 22 ℃ and the dacite was at ～825 ℃, the reaction rims indicate that the andesitic magma ascended at 0.023 m s~(-1) during the explosive phase of the eruption, whereas the dacitic.magma rose more slowly at ～0.002-0.004 m s~(-1).
机译：塔卡纳火山群中的圣安东尼奥火山爆发了-1950年。 B.P.，具有Pelean型喷发，产生的安山岩热碎屑潮和块状灰烬流摧毁了火山顶峰的一部分，并产生了向西南开放的马蹄形火山口。在1950年至800年之间喷发继续是喷出的安山岩，接着是达奇熔岩流和顶峰穹顶，全部来自单个岩浆批次。所有产品均由分区斜长石，闪石，辉石，辉石，磁铁矿±钛铁矿的微晶和微晶构成，它们固定在部分矿物相的玻璃和微晶玻璃的部分结晶化地基中，除了缺少闪石。块状和灰分流沉积物的安山岩块体中包括玄武岩安山岩飞地，它们具有细长和椭圆形的形状以及冷边缘。这些飞地在斜纹酶，角闪石，辉石和橄榄石的微表皮之间和在斜角晶石，角闪石和辉石的微晶之间具有棕色玻璃间质结构。块状和飞地的组成范围是由安山岩（866℃±22）和玄武质安山岩（飞地932℃±22）之间的混合引起的，这可能引发了爆发的Pelean喷发。这种混合的味道被保留为斜长石中复杂的组成区域和安山岩中闪石中富含富二茂基的反应边缘。全岩石化学，地热测定，实验岩石学和模拟结果表明，在混合事件之后，喷发带出了杂种安山岩浆（＜900℃），并以喷出的胶状岩浆（〜825℃）结束，它们都在〜200 MPa下储存。水压力。复杂的开放系统演化涉及地壳末端成员，这最好地解释了混合安山岩产生冒泡的钠铝榴石的过程。上升过程中减压产生的斜长石，邻位邻苯二酚和Fe-Ti氧化物的反应产物使闪锌矿中的闪石闪闪发光。但是，安山岩中的角闪石缺乏这种边缘。由于安山岩的温度为866±22℃，而菱镁矿的温度为〜825℃，因此反应边缘表明，在喷发爆发阶段，安山岩的岩浆在0.023 ms〜（-1）处上升，而山泥岩的岩浆上升得更多。缓慢地在〜0.002-0.004 ms〜（-1）。

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