Relationship Between Magma Recharge and Eruption Revealed Through In Situ Geochemical Fingerprinting and Crystal Size Distribution Analysis

岩浆补给过程，即较热的岩浆侵入岩浆库底部，被认为是一些火山喷发的催化剂。新侵入的岩浆和静止的岩浆可以混合，通过多种机制中的一种，可能会发生泡沫化。气泡作用导致岩浆库中的压力增加，进而可能导致喷发。前人的工作表明，喷发的爆炸性程度可能严重依赖于侵入速度和补给岩浆的体积：相对少量的补给岩浆的缓慢侵入可能导致温和的喷发，而相对大量的补给岩浆的快速侵入可能导致爆炸性喷发。这些截然不同的情景预测，相关的火山沉积可能会记录到岩浆混合的程度和方式以及相对于喷发的补给时间上的差异。1915年，位于加利福尼亚州东北部的火山中心拉森喷发，这是一次记录极为充分的喷发，其中补给被假设为喷发催化剂。对于这次喷发的火山产物，将利用原位激光烧蚀电感耦合等离子体质谱确定岩浆混合的化学指纹，并通过晶体粒度分布分析确定晶体的形成位置、结晶历史和停留时间。总而言之，这些数据将揭示相对于喷发的补给事件的时间，并将允许描述该储集层中混合的流体动力学。通过这样的研究，将对补给和喷发之间的时间以及补给率、补给量和爆炸性之间的关系产生定量的约束。这些信息将有助于更好地了解火山喷发的动态和时间。

EAR-0073884BohrsonThe process of magma recharge, which is intrusion of hotter magma into the base of a magma reservoir, is thought to be a catalyst for some volcanic eruptions. Newly intruded and standing magma may mix, and by one of a number of mechanisms, vesiculation may occur. Vesiculation leads to increased pressure in the magma reservoir, which, in turn, may lead to eruption. Previous work suggests that the degree of explosivity of the eruption may be critically dependent on the rate of intrusion and volume of recharge magma: slow intrusion of relatively small volumes of recharge magma may lead to gentle eruption whereas rapid intrusion of relatively large volumes of recharge magma may cause explosive eruption. These contrasting scenarios predict that the associated volcanic deposits may record differences in the extent and style of magma mixing and in the timing of recharge relative to eruption. The 1915 eruption of Lassen, a volcanic center located in northeastern California, is an extremely well-documented eruption in which recharge is hypothesized as the eruption catalyst. For volcanic products of this eruption, the chemical fingerprint of magma mixing will be determined using in situ laser-ablation ICP-MS, and the location of formation, crystallization history, and residence times of crystals will be determined from crystal size distribution analysis. Together, these data will reveal the timing of the recharge event relative to eruption and will also permit a description of the fluid dynamics of mixing in this reservoir. Through studies such as this one, quantitative constraints on the timing between recharge and eruption and on the relationships among recharge rate, recharge volume and explosivity will emerge. Such information will lead to enhanced understanding of dynamics and timing of volcanic eruptions.