Garg Deepak, Papale Paolo, Colucci Simone, Longo Antonella
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Via della Faggiola 32, 56126, Pisa, Italy.
Sci Rep. 2019 Mar 1;9(1):3321. doi: 10.1038/s41598-019-40160-1.
Magmas discharged during individual volcanic eruptions commonly display compositional variations interpreted as new arrivals at shallow depth of more primitive, hotter, volatile-rich magma batches mixing with resident, colder, partially degassed magma. Heterogeneities in eruption products are often interpreted as evidence of short times of order tens of hours from new magma arrival to eruption, raising concerns for emergency planning. We show here, through numerical simulations, that magma convection and mixing in a shallow magma chamber can result in long-lived, dynamically stable configurations with coexistence of magmas from nearly pure to variably mixed end-member compositions. Short mixing time scales may therefore relate to sin-eruptive processes, as heterogeneities found in the eruptive products are not necessarily the fingerprint of new magma arrival shortly preceding or triggering the eruption.
在单次火山喷发期间喷出的岩浆通常显示出成分变化，这种变化被解释为更原始、更热、富含挥发物的岩浆批次在浅部深度与原地较冷、部分脱气的岩浆混合的新产物。喷发产物中的不均匀性通常被解释为从新岩浆到达至喷发的数十小时短时间顺序的证据，这引发了对应急规划的担忧。我们在此通过数值模拟表明，浅部岩浆房中的岩浆对流和混合可导致长期存在、动态稳定的构型，其中存在从近乎纯净到可变混合端元成分的岩浆共存。因此，短混合时间尺度可能与喷发过程有关，因为在喷发产物中发现的不均匀性不一定是紧接喷发之前或引发喷发的新岩浆到达的特征。
