The ∼AD 1250 effusive eruption of El Metate shield volcano (Michoacán, Mexico): magma source, crustal storage, eruptive dynamics, and lava rheology
The ∼AD 1250 effusive eruption of El Metate shield volcano (Michoacán, Mexico): magma source, crustal storage, eruptive dynamics, and lava rheology
复制标题
约公元 1250 年埃尔梅塔特盾火山（墨西哥米却肯州）的喷发：岩浆源、地壳储存、喷发动力学和熔岩流变学
作者：
M. O. Chevrel;Marie;C. Siebe
中型火山，也被称为墨西哥地盾，因为它们的安山质成分和比冰岛地盾略高的坡度，发生在跨墨西哥火山带，占米却肯-瓜纳华托火山区（MGVF）所有火山建筑物的近三分之一。关于它们的起源和喷发动力学的许多问题仍然没有答案。在这里，我们专注于El Metate，最年轻的（公元1250年）MGVF和最庞大的（109.2立方公里的致密岩石当量）在墨西哥全新世喷发的单成盾状火山。通过详细的制图、地球化学分析（主要和微量元素、Sr-Nd-Pb同位素数据）和对厚安山岩流的流变学研究，重建了它的喷发历史。早期和晚期流动单元有不同的形态，化学和矿物成分，和同位素特征表明，这些熔岩是由两个独立的岩浆批次，起源于一个异质地幔源，并遵循不同的分化路径在其上升。热压计计算限制结晶的条件表明，临时存储的最后一批喷发的岩浆在107 - 10公里的深度。熔岩流变学估计使用岩相学特征，地球化学数据和流动尺寸。岩浆粘度从喷发前的102 - 103 Pa·s上升到106 - 108 Pa·s，在熔岩侵位期间增加到109 - 1011 Pa·s。虽然岩浆粘度相当高，但喷发纯粹是喷涌式的。如此大体积的岩浆的爆炸性喷发可能是由于有效的开放系统脱气（除气）的岩浆，因为它上升通过最上层的地壳，并在地表喷发避免。
Medium-sized volcanoes, also known as Mexican shields due to their andesitic composition and slightly higher slope angles in comparison to Icelandic shields, occur across the Trans-Mexican Volcanic Belt and represent nearly one third of all volcanic edifices in the Michoacán-Guanajuato Volcanic Field (MGVF). Many questions about their origin and eruptive dynamics remain unanswered. Here, we focus on El Metate, the youngest (∼AD 1250) monogenetic shield volcano of the MGVF and the most voluminous (∼9.2 km3 dense rock equivalent) Holocene eruption in Mexico. Its eruptive history was reconstructed through detailed mapping, geochemical analysis (major and trace elements, Sr-Nd-Pb isotopic data), and rheological study of its thick andesitic flows. Early and late flow units have distinct morphologies, chemical and mineralogical compositions, and isotopic signatures which show that these lavas were fed by two separate magma batches that originated from a heterogeneous mantle source and followed distinct differentiation paths during their ascent. Thermobarometry calculations constraining the conditions of crystallization indicate a temporary storage of the last erupted magma batch at a depth of ∼7–10 km. Lava rheology was estimated using petrographic characteristics, geochemical data, and flow dimensions. The magma viscosity increased from 102–103 Pa s prior to eruption through 106–108 Pa s during ascent, to 109–1011 Pa s during lava emplacement. Though magma viscosity was quite high, the eruption was purely effusive. The explosive eruption of such a large magma volume was probably avoided due to efficient open system degassing (outgassing) of the magma as it ascended through the uppermost crust and erupted at the surface.
DOI：
10.1098/rspa.2009.0445
发表时间：
2010-04-08
影响因子：
3.5
作者：
Mueller, S.;Llewellin, E. W.;Mader, H. M.
通讯作者：
Mader, H. M.