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首页> 外文期刊>Journal of Volcanology and Geothermal Research2012V243-244NOCT,15 >Eruptive chronology of Tungurahua volcano (Ecuador) revisited based on new K-Ar ages and geomorphological reconstructions
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Eruptive chronology of Tungurahua volcano (Ecuador) revisited based on new K-Ar ages and geomorphological reconstructions

机译：基于新的K-Ar年龄和地貌重建，重新审视了通古拉瓦火山（厄瓜多尔）的喷发年表

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摘要

This study focuses on the evolution through time of Tungurahua volcano (Ecuador), and provides new information regarding its history. Eighteen new K-Ar ages constrain its construction and the activity of its three successive edifices. We show that the volcano is much younger than expected. Indeed, the older edifice activity only began around 293 +/- 10 ka, and ended at 79 +/- 3 ka. After similar to 50 ka of quiescence, the second edifice started growing at 29 +/- 2 ka after a major sector collapse, and itself collapsed at similar to 3 ka. Since then, the third edifice filled the amphitheatre and is still active. Together with numerical reconstructions of the morphology of the three edifices flanks before erosion, these new ages allow us to quantify the magmatic productivity rates during their construction, from 0.6 +/- 0.3 and 0.9 +/- 02 km(3)/ka for the two older edifices to 2.5 +/- 1.0 km(3)/ka for the youngest, as well as an erosion rate of 0.2 +/- 0.1 km(3)/ka, occurring since the end of Tungurahua I construction. Major and trace element contents of lavas from the three edifices display rather similar trends. Combined with our new ages, the magmatic signature through time does not seem to have been significantly affected either by the sector collapses experienced by the volcano, or by changes of the deep magmatic source. Finally, our results show that the K-Ar dating method by the unspiked Cassignol-Gillot technique performed on groundmass can be successfully applied to lava flows older than the Holocene, while the uncertainties related to younger units can prevent an accurate age determination. Particularly, this method can be applied to Quaternary volcanoes from the Ecuadorian arc, with many of them remaining without knowledge of the timing of their past activity. (C) 2018 Elsevier B.V. All rights reserved.
机译：这项研究的重点是通古拉瓦火山（厄瓜多尔）随时间的演变，并提供有关其历史的新信息。 18个新的K-Ar年龄限制了它的构造和三个连续大厦的活动。我们表明，火山比预期的年轻得多。实际上，较早的建筑物活动仅在293 +/- 10 ka左右开始，并在79 +/- 3 ka结束。在接近50 ka的静止时间之后，第二个建筑物在主要扇形塌陷之后以29 +/- 2 ka开始生长，而其本身也以约3 ka塌陷。从那时起，第三座大厦就座满了圆形剧场，并且仍然活跃。结合侵蚀前三个建筑物侧面的形态的数值重建，这些新纪元使我们能够量化其构造期间的岩浆生产率，从0.6 +/- 0.3和0.9 +/- 02 km（3）/ ka。自通古拉瓦（Tungurahua）一期工程结束以来，最年轻的两座老建筑至2.5 +/- 1.0 km（3）/ ka，侵蚀速率为0.2 +/- 0.1 km（3）/ ka。来自三个建筑物的熔岩的主要和微量元素含量显示出相当相似的趋势。结合我们的新纪元，随着时间的推移，岩浆特征似乎并没有受到火山所经历的扇形塌陷或深部岩浆源变化的显着影响。最后，我们的结果表明，采用未加标的Cassignol-Gillot技术对地基进行的K-Ar测年方法可以成功地应用于比全新世更老的熔岩流，而与年轻单元有关的不确定性可能会妨碍准确的年龄确定。特别是，该方法可以应用于厄瓜多尔弧系的第四纪火山，其中许多仍不知道其过去活动的时间。 （C）2018 Elsevier B.V.保留所有权利。

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