...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Volcanology and Geothermal Research >Inferring magma ascent timescales and reconstructing conduit processes in explosive rhyolitic eruptions using diffusive losses of hydrogen from melt inclusions
【24h】

Inferring magma ascent timescales and reconstructing conduit processes in explosive rhyolitic eruptions using diffusive losses of hydrogen from melt inclusions

机译：利用熔体包裹体中氢的扩散损失推断岩浆上升时间尺度并重建流纹岩爆发中的导管过程

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

We integrate field observations with geochemical data from quartz-hosted melt inclusions to develop a hydrogen diffusion-based method to shed light on timescales and conduit processes during the opening stages of two supereruptions. We focus on the initial explosive phases (first similar to 5% of the total magma volume erupted) from: (1) the episodic Oruanui eruption, Taupo NZ (530 km(3), 25.4 ka) and (2) the continuous Bishop Tuff eruption, Long Valley (650 km(3), 0.765 Ma). Quartz-hosted melt inclusions for both eruptions exhibit coherent trends for major and trace elements (e.g. Al2O3, SiO2, Nb, U, Rb). However, in the first three phases (of ten) in the Oruanui eruption there is significant variability in measured H2O values (2.6-5.8 wt%), particularly in phases 1 and 3, each of which reflects the opening stages of two respective inferred vent sources. Phase 3 inclusions also record greater scatter in Li concentrations. In contrast, melt inclusions from the first two Bishop Tuff fall layers yield a narrower range of H2O concentrations (4.0-5.8%, with 90% between 4.5 and 5.8 wt%). We interpret the scatter in measured H2O concentrations to represent changes during slow magma ascent or partial stalling within the conduit at lower pressures. Using a diffusion model, we estimate that 61% of the Oruanui melt inclusions experienced modification of original H2O concentrations due to slow ascent in the conduit system prior to eruptive quenching, with the longest timescales (5 days) mostly in phase 3 inclusions. In contrast, only 33% of melt inclusions from the initial Bishop fall layer (F1) experienced diffusive losses from their starting concentrations, implying that most magma spent less than a day ascending from the storage region at the eruption onset. Similarities between the Oruanui and the previously studied Huckleberry Ridge Tuff include comparable extents and distribution of diffusive losses (seen as H and Li scatter), and field evidence for episodic activity. Our observations imply that in these two systems, the first-erupted magmas rose from reservoirs with low degrees of overpressure and that magma mobilization was controlled by external factors (e.g. tectonics) rather than by strong volatile over-pressures. In contrast the Bishop eruption may well have been initiated by overpressure, leading to continuous, escalating activity. (C) 2018 Elsevier B.V. All rights reserved.
机译：我们将现场观测与来自石英的熔融包裹体的地球化学数据相结合，以开发基于氢扩散的方法，以揭示两次超喷发的开启阶段的时间尺度和导管过程。我们关注以下方面的初始爆炸阶段（首先类似于爆发的岩浆总量的5％）：（1）爆发性的Oruanui喷发，新西兰陶波（530 km（3），25.4 ka）和（2）连续的Bishop Tuff长谷喷发（650 km（3），0.765 Ma）。两种喷发的石英质熔体包裹体均显示出主要元素和微量元素（例如Al2O3，SiO2，Nb，U，Rb）的一致趋势。但是，在奥拉努伊火山喷发的前三个阶段（共十个阶段）中，H2O的测量值（2.6-5.8 wt％）存在显着变化，尤其是在阶段1和阶段3中，每个阶段都反映了两个推断出的通气口的开放阶段资料来源。 3期夹杂物还记录了更大的Li浓度散布。相比之下，前两个Bishop Tuff降层中的熔融夹杂物产生的H2O浓度范围较窄（4.0-5.8％，其中90％在4.5至5.8 wt％之间）。我们将测量的H2O浓度解释为散点，以表示在较低压力下管道内缓慢岩浆上升或部分失速期间的变化。使用扩散模型，我们估计61％的Oruanui熔体夹杂物由于喷发淬火之前管道系统中的缓慢上升而经历了原始H2O浓度的变化，其中最长的时间尺度（> 5天）主要出现在3期夹杂物中。相比之下，最初的Bishop坠落层（F1）中只有33％的熔体夹杂物从其初始浓度经历了扩散损失，这意味着大多数岩浆在喷发开始时花费不到一天的时间从存储区域上升。 Oruanui和先前研究过的Huckleberry Ridge Tuff之间的相似之处包括扩散损失的可比程度和分布（被视为H和Li散射），以及现场活动的现场证据。我们的观察结果表明，在这两个系统中，首次喷出的岩浆来自具有较低超压程度的储层，并且岩浆动员是由外部因素（例如构造）控制的，而不是由强烈的挥发性超压控制的。相反，Bishop喷发很可能是由超压引起的，从而导致持续不断的升级活动。 （C）2018 Elsevier B.V.保留所有权利。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号