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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The -31 ka rhyolitic Plinian to sub-Plinian eruption of Tlaloc Volcano, Sierra Nevada,central Mexico
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The -31 ka rhyolitic Plinian to sub-Plinian eruption of Tlaloc Volcano, Sierra Nevada,central Mexico

机译：墨西哥中部内华达州特拉洛克火山的-31 ka流纹质Plinian到亚Plinian喷发

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摘要

Tlaloc is a late Pleistocene stratovolcano located NE of Mexico City. It is the northernmost volcano of the N-S Sierra Nevada Volcanic Range, which consists from north to south of Tlaloc, Telapon, Iztacrihuatl, and Popocatepetl volcanoes. Tlaloc has always been considered the oldest (and extinct) volcano of the Sierra Nevada Volcanic Range. Recent field data revealed that Tlaloc was very active during late Pleistocene through a series of explosive eruptions. One of these eruptions produced the Multilayered White Pumice (MWP) a rhyolitic pyrodastic sequence. The eruption began with a 24-km high Plinian column MWP-F1 that was dispersed to the NE by prevailing winds. It was interrupted by fountaining of the column with the generation of a pyrodastic density current that emplaced MWP-S1 layer. Then, followed five unstable sub-Plinian columns (MWP-F2 to F6) that reached altitudes between 16 and 19 km. Fall deposits as a whole are 1 m thick at 12 km from the vent, cover a minimum area of 577 km~2 for a total volume of 4.68 km~3(DRE1.58 km~3). The eruption ejected a total mass of 3.45×10~(12) kg at different mass discharges. The last sub-Plinian column (MWP-F6) collapsed and produced dense pyrodastic density currents that deposited pumiceous pyrodastic flows (MWP-PF) following main ravines to the north and east of the vent. These density currents filled gullies with 23 m-thick deposits at a distance of 12 km from the vent totaling a minimum DRE volume of 0.2 km~3. Pyrodastic flow deposits charred tree trunks that yielded an age of 31,490 +1995/-1595 yr B.P. that closely date the age of the eruption. Rain during this phase of the eruption generated syn-eruptive lahars (MWP-DF). Post-eruptive lahars (MWP-ED) finally swept the volcano flanks. The MWP deposits consist of abundant white pumice (up to 96 vol.%), rare gray pumice, cognate lithics, accidental altered lithics, xenocrysts. White and gray pumice clasts contain phenocrysts of quartz, plagiodase, sanidine, biotite, rare Fe-Ti oxides, monazite, zircon and apatite. Xenocrysts are represented by plagiodase, microdine, orthoclase and quartz likely coming from a deeper plutonic body. Both pumices have a rhyolitic composition (74.98 ± 1 wt.% SiO_2 in water free basis) representing one of the most acidic products of Tlaloc and the entire Sierra Nevada Volcanic Range. The rhyolitic liquid was likely extracted from a mush-like plutonic body reaching the minimum predicted vesicularity values for Plinian fragmentation for which the triggering mechanism of the MWP eruption is attributed to the high viscosity of the magma that provoked overpressure of the magmatic system. The parameters studied suggest that eruption behavior evolved from Plinian to sub-Plinian eruptive columns over time due to conduit dynamics rather than variations in magma properties of the MWP products.
机译：Tlaloc是位于墨西哥城东北的晚更新世平流层火山。它是N-S内华达山脉火山山脉的最北端的火山，从北到南由Tlaloc，Telapon，Iztacrihuatl和Popocatepetl火山组成。 Tlaloc一直被认为是内华达山脉火山山脉中最古老（且已绝种）的火山。最近的现场数据显示，Tlaloc在更新世晚期通过一系列爆炸性爆发非常活跃。这些喷发之一产生了流纹火山岩序列的多层白浮岩（MWP）。喷发始于24公里高的普利尼安柱MWP-F1，该柱被盛行风吹散至东北。它被柱子的喷泉打断，并产生了热缩密度电流，该电流覆盖了MWP-S1层。然后，跟随五根不稳定的次普林尼柱（MWP-F2至F6），其高度达到16至19 km。距喷口12公里处的秋季沉积物总体厚度为1 m，最小面积为577 km〜2，总体积为4.68 km〜3（DRE1.58 km〜3）。在不同的质量排放下，喷发喷出的总质量为3.45×10〜（12）kg。最后一个次普林尼柱（MWP-F6）坍塌并产生致密的焦岩流，在主要沟壑之后向喷口的北部和东部沉积了浮岩性的岩浆流（MWP-PF）。这些密度流在距通风口12 km处充满23 m厚的沉积物的沟壑中，最小DRE体积为0.2 km〜3。火山热流沉积物烧焦了树干，该树干年龄为公元前31490年+ 1995 / -1595年。与喷发年龄密切相关。在喷发的这一阶段，雨水产生了喷发拉瓦尔（MWP-DF）。火山爆发后的拉哈斯（MWP-ED）终于席卷了火山的侧面。 MWP沉积物包括丰富的白色浮石（含量高达96％（体积）），稀有的灰色浮石，同源石块，意外蚀变的石块和异晶。白色和灰色的浮石碎片包含石英，斜长石酶，山梨酸，黑云母，稀有的Fe-Ti氧化物，独居石，锆石和磷灰石的隐晶。异种晶状体的代表可能是来自深部的深成岩体的斜生胶酶，微粉，正原酶和石英。两种浮石均具有流变组成（无水基础上为74.98±1 wt。％SiO_2），代表Tlaloc和整个内华达山脉的最酸性产物之一。流变液很可能从糊状的深部小体中提取，达到了普林尼亚碎裂的最小预测水泡度值，为此，MWP爆发的触发机制归因于岩浆的高粘度，导致岩浆系统超压。研究的参数表明，由于导管动力学而不是MWP产品岩浆性质的变化，喷发行为会随时间从Plinian到亚Plinian喷发柱演化。

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  • 作者

    H. Rueda; J.L. Marias; J.L. Arce; J.E. Gardner; P.W. Layer;

  • 作者单位

    Posgrado en Ciencias de la Tierra, Institute de Geofisica, Universidad National Autonoma de Mexico, Coyoacan 04510, Mexico D.F., Mexico;

    Institute de Geofisica, Subsede Michoacan, Universidad National Autonoma de Mexico, Ex-Hacienda de San Jose de La Huerta C.P. 58190, Morelia, Michoacan, Mexico;

    Institute de Geologla, Departamento de Geologia Regional, Universidad National Autonoma de Mexico, Coyoacan 04510, Mexico D.F., Mexico;

    Department of Geological Stiences, Jackson School of Geosciences, The University of Texas at Austin, TX 78712, USA;

    Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, USA;

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  • 原文格式 PDF
  • 正文语种 eng
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  • 关键词

    plinian; sub-plinian; rhyolite; conduit dynamics;

    机译：普林尼安亚普林尼安流纹岩管道动力学;

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