Zircon reveals protracted magma storage and recycling beneath Mount St. Helens
Zircon reveals protracted magma storage and recycling beneath Mount St. Helens
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DOI：
10.1130/g31285.1
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发表时间：
2010-11-01
期刊：
影响因子：
5.8
通讯作者：
Wooden, Joseph L.
中科院分区：
文献类型：
--
作者：
Claiborne, Lily L.;Miller, Calvin F.;Wooden, Joseph L.
圣海伦斯火山（美国华盛顿）目前的数据和模型表明，从岩浆生成到喷发的迁移相对较快，没有证据表明岩浆长期储存或再循环。然而，我们在这里表明，复杂的锆石年龄人口从喷发年龄延伸到几十万年前，表明岩浆定期在地壳中停滞，在火山下冷却和结晶，然后被更热的年轻岩浆重新激活并合并到地表。估计的溶解时间表明，夹带锆石一般居住在振兴岩浆不超过约世纪。锆石的元素组成反映了随着时间的推移，镁铁质输入到系统中的影响越来越大，记录了在镁铁质岩浆出现在地表之前数万年的较热、较不演化的岩浆的生长，或全岩地球化学和岩石学的变化，并提供了一个新的、与时间相关的独立于喷发历史的演化记录。因此，锆石数据揭示了圣海伦火山系统中隐藏的、长期存在的侵入部分的历史，在那里，熔体和晶体被储存了长达数十万年，并与喷发前穿过侵入储层的新鲜岩浆相互作用。
Current data and models for Mount St. Helens volcano (Washington, United States) suggest relatively rapid transport from magma genesis to eruption, with no evidence for protracted storage or recycling of magmas. However, we show here that complex zircon age populations extending back hundreds of thousands of years from eruption age indicate that magmas regularly stall in the crust, cool and crystallize beneath the volcano, and are then rejuvenated and incorporated by hotter, young magmas on their way to the surface. Estimated dissolution times suggest that entrained zircon generally resided in rejuvenating magmas for no more than about a century. Zircon elemental compositions reflect the increasing influence of mafic input into the system through time, recording growth from hotter, less evolved magmas tens of thousands of years prior to the appearance of mafic magmas at the surface, or changes in whole-rock geochemistry and petrology, and providing a new, time-correlated record of this evolution independent of the eruption history. Zircon data thus reveal the history of the hidden, long-lived intrusive portion of the Mount St. Helens system, where melt and crystals are stored for as long as hundreds of thousands of years and interact with fresh influxes of magmas that traverse the intrusive reservoir before erupting.