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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Thermal history of volcanic debris flow deposits on the eastern flanks of Mt. Taranaki, New Zealand: Implications for future hazards
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Thermal history of volcanic debris flow deposits on the eastern flanks of Mt. Taranaki, New Zealand: Implications for future hazards

机译：山东部两侧火山泥石流沉积的热历史。新西兰塔拉纳基市：对未来危害的影响

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We use palaeomagnetic methods to decipher the thermal histories of a succession of massive to weakly stratified debris flow deposits (Ngatoro and Te Popo formations) of late Holocene age located on the eastern lower flanks of Mt. Taranaki/Egmont Volcano, western North Island, New Zealand. Results from two sites, Vickers Quarry and Surrey Road Quarry, both c. 9.6 km from the present-day summit, enable us to distinguish between clast incorporation temperatures of about 400 degrees C and emplacement temperatures between 150 and 200 degrees C, consistent with observation of superficial charring and desiccation of outer podocarp-hardwood tree trunks at Vickers Quarry. Analysis of palaeomagnetic directions and lithofacies architecture suggest that these deposits were likely initiated as a closely-spaced succession of block-and-ash flows (BAFs) that rapidly cooled as they descended the volcano flanks. Radiocarbon chronology and the widespread occurrence of a palaeosol between the products of the preceding Inglewood eruptive phase, c. 3.4 cal. ka B.P., and the overlying Ngatoro Formation suggest that these two events are temporally unrelated. Certainly, there is no field evidence of contemporaneous explosive volcanic activity that might be related to the emplacement of Ngatoro Formation. However, we suggest that these low-temperature deposits might either relate to collapse of a small emergent lava dome or a cooling dome remnant, possibly emplaced in the aftermath of the Inglewood eruption. How collapse was initiated remains uncertain: the remnant dome may have been rendered unstable by volcano-tectonic or tectonic seismic events and/or by adverse meteorological events. Nevertheless, this study demonstrates that edifice collapse events generating potentially hazardous debris flows can occur independent of specific eruptive activity. (C) 2018 Elsevier B.V. All rights reserved.
机译：我们使用古地磁方法来解密位于新山晚期东侧的全新世晚期的一系列大规模至弱分层的泥石流沉积物（Ngatoro和Te Popo地层）的热历史。塔拉纳基/埃格蒙特火山，新西兰北岛西部。维克斯采石场和萨里路采石场两个站点的结果，均c。距今天的峰会9.6公里，使我们能够区分出碎屑合并温度（大约400摄氏度）和进位温度在150摄氏度至200摄氏度之间，这与在维克斯采石场观察到的表面炭化和外部罗汉松-硬木树干的干燥一致。对古地磁方向和岩相构造的分析表明，这些沉积物可能是由于块状和灰烬流（BAF）紧密间隔开来而形成的，这些流在火山岩下降时迅速冷却。放射性碳年代学和前英格伍德爆发阶段的产物之间古土壤的广泛发生； c。 3.4卡路里ka B.P.和上覆的Ngatoro组表明这两个事件在时间上是无关的。当然，没有现场证据表明同时爆发的火山活动可能与Ngatoro组的进入有关。但是，我们建议这些低温沉积物可能与小型涌出的熔岩穹顶的塌陷或冷却穹顶的残留物有关，可能是在英格伍德火山爆发后发生的。塌陷是如何开始的仍然是不确定的：由于火山-构造或构造地震事件和/或不利的气象事件，残余穹顶可能变得不稳定。尽管如此，这项研究表明，建筑物坍塌事件会产生潜在的危险泥石流，而与特定的喷发活动无关。 （C）2018 Elsevier B.V.保留所有权利。

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