Decadal transition from quiescence to supereruption: petrologic investigation of the Lava Creek Tuff, Yellowstone Caldera, WY
Decadal transition from quiescence to supereruption: petrologic investigation of the Lava Creek Tuff, Yellowstone Caldera, WY
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DOI：
10.1007/s00410-019-1570-x
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发表时间：
2019-04
影响因子：
3.5
通讯作者：
H. Shamloo;C. Till
中科院分区：
文献类型：
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作者：
H. Shamloo;C. Till
引发自然界最具破坏性喷发的岩浆过程及其相关的时间尺度仍然知之甚少。黄石火山口是一个大型硅质火山系统，在其 2.1 Ma 历史上发生过 3 次超级喷发，其中最近一次产生了熔岩溪凝灰岩 (LCT)。第631章在这里，我们对 LCT 火山灰中的斑晶（特别是长石和石英）进行了岩石学研究，以研究导致 LCT 喷发的时间和潜在触发因素。 LCT斑晶具有再吸收的核心，与它们的晶体核心相比，晶体边缘记录了稍微升高的温度和富集的亲岩元素，例如透石中的Ba和Sr以及石英中的Ti。化学数据与矿物测温、地压测量和流纹岩熔体模型相结合表明，在晶体边缘观察到的化学特征很可能是通过将更多的新生硅质岩浆注入 LCT 地下火山储层，然后进行减压驱动的晶体生长而产生的。地温测量和气压测量表明，LCT 岩浆源的再生后、喷发前温度和压力为 790–815 °C 和 80–150 MPa。利用透硅石中的 Ba 和 Sr 以及石英中的 Ti 进行扩散建模，结合晶体生长速率，得出再生和喷发之间数十年至数年的保守估计。因此，我们认为再生是最有可能在不到十年的时间内产生触发 LCT 超级喷发所需的超压的机制。
The magmatic processes responsible for triggering nature’s most destructive eruptions and their associated timescales remain poorly understood. Yellowstone Caldera is a large silicic volcanic system that has had three supereruptions in its 2.1-Ma history, the most recent of which produced the Lava Creek Tuff (LCT) ca. 631 ka. Here we present a petrologic study of the phenocrysts, specifically feldspar and quartz, in LCT ash in order to investigate the timing and potential trigger leading to the LCT eruption. The LCT phenocrysts have resorbed cores, with crystal rims that record slightly elevated temperatures and enrichments in magmaphile elements, such as Ba and Sr in sanidine and Ti in quartz, compared to their crystal cores. Chemical data in conjunction with mineral thermometry, geobarometry, and rhyolite-MELTS modeling suggest the chemical signatures observed in crystal rims were most likely created by the injection of more juvenile silicic magma into the LCT sub-volcanic reservoir, followed by decompression-driven crystal growth. Geothermometry and barometry suggest post-rejuvenation, pre-eruptive temperatures and pressures of 790–815 °C and 80–150 MPa for the LCT magma source. Diffusion modeling utilizing Ba and Sr in sanidine and Ti in quartz in conjunction with crystal growth rates yield conservative estimates of decades to years between rejuvenation and eruption. Thus, we propose rejuvenation as the most likely mechanism to produce the overpressure required to trigger the LCT supereruption in less than a decade.