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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Using submarine lava pillars to record mid-ocean ridge eruption dynamics
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Using submarine lava pillars to record mid-ocean ridge eruption dynamics

机译：使用海底熔岩柱记录海洋中脊喷发的动力学

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摘要

Submarine lava pillars are hollow, glass-lined, basaltic cylinders that occur at the axis of the mid-ocean ridge, and within the summit calderas of some seamounts. Typically, pillars are ～1-20 m tall and 0.25-2.0 m in diameter, with subhorizontal to horizontal glassy selvages on their exterior walls. Lava pillars form gradually during a single eruption, and are composed of lava emplaced at the eruption onset as well as the last lava remaining after the lava pond has drained. On the deep sea floor, the surface of a basaltic lava flow quenches to glass within 1 s, thereby preserving information about eruption dynamics, as well as chemical and physical properties of lava within a single eruption. Investigation of different lava pillars collected from a single eruption allows us to distinguish surficial lava-pond or lava-lake geochemical processes from those operating in the magma chamber. Morphologic, major-element, petrographic and helium analyses were performed on portions of three lava pillars formed during the April 1991 eruption near 9°50'N at the axis of the East Pacific Rise. Modeling results indicate that the collected portions of pillars formed in ～2-5 h, suggesting a total eruption duration of ～8-20 h. These values are consistent with observed homogeneity in the glass helium concentrations and helium diffusion rates. Major-element compositions of most pillar glasses are homogeneous and identical to the 1991 flow, but slight chemical variations measured in the outermost portions of some pillars may reflect post-eruptive processes rather than those occurring in subaxial magma bodies. Because lava pillars are common at mid-ocean ridges (MORs), the concepts and techniques we present here may have important application to the study of MOR eruptions, thereby providing a basis for quantitative comparisons of volcanic eruptions in geographically and tectonically diverse settings. More research is needed to thoroughly test the hypotheses presented here.
机译：水下熔岩柱是空心的，玻璃衬砌的玄武质圆柱体，位于中海脊的轴线处以及某些海山的山顶火山口内。通常，柱子高约1-20 m，直径为0.25-2.0 m，外壁上有水平到水平的玻璃状镶边。熔岩柱在一次喷发过程中逐渐形成，由喷发开始时放置的熔岩以及熔岩池排干后剩下的最后一个熔岩组成。在深海底，玄武岩熔岩流的表面在1 s内骤冷为玻璃，从而保留了有关喷发动力学以及一次喷发中熔岩的化学和物理性质的信息。对从一次喷发中收集到的不同熔岩柱的研究使我们能够将表层熔岩池或熔岩湖地球化学过程与在岩浆室内进行的活动区分开。对1991年4月喷发期间在东太平洋上升沿9°50'N附近形成的三个熔岩柱的一部分进行了形态，主要元素，岩石学和氦气分析。模拟结果表明，在〜2-5 h内形成了收集的柱子部分，表明总喷发持续时间为〜8-20 h。这些值与玻璃氦浓度和氦扩散速率中观察到的均匀性一致。大多数柱状玻璃的主要元素组成是均匀的，与1991年的流动相同，但在某些柱状体的最外层中测得的微小化学变化可能反映出喷发后的过程，而不是亚轴岩浆体中发生的那些。由于熔岩柱在大洋中脊（MOR）上很常见，因此我们在这里提出的概念和技术可能对MOR喷发的研究有重要的应用，从而为定量比较地理和构造不同背景下的火山喷发提供了基础。需要更多的研究来彻底检验此处提出的假设。

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