Collaborative Research: RUI: Probing Caldera-Forming Magmatism: Crystal Accumulation in Large, Upper Crustal Silicic Magma Chambers

下一次火山超级喷发将给人类带来全球后果。在其中一次大规模喷发期间，火山喷发的潜力以及熔岩和火山灰的喷发量在很大程度上受控于地壳浅层岩浆储集层的情况。该项目将两座古老的超级火山--科罗拉多州的湖城火山口、南落基山脉火山场和亚利桑那州的土耳其溪火山口--被困在地下的冻结岩浆储层及其相关的地面火山岩的研究结合在一起。这项研究的结果将对浅层岩浆储集层内发生的导致超级喷发的过程提供前所未有的洞察，并最终将用于预测潜在极其危险的活跃火山地区的行为，如陶波火山带、那不勒斯海湾和爱琴海弧区。正在测试的假设是，湖城火山口和土耳其小溪火山口中的深成斑岩都是火山口坍塌后残留在地壳中的淬火岩浆储集层。如果这一假设得到证实，这些斑岩提供了与超级喷发相关的糊状根带的演化和喷发后条件的独特快照。将应用于火山岩和深成岩岩性的方法有：(1)深成斑岩的详细野外填图和火山单元的野外采样，(2)所有单元的地球化学特征，(3)利用电子探针分析(EPMA)、激光烧蚀电感耦合质谱仪(LA-ICP-MS)和电子背散射衍射(EBSD)对所有单元的原生和副晶体进行定量研究，以及(4)选定岩性中的高分辨率锆石U-Pb定年和微量元素分析(CA-TIMS-TEA)。这种对次火山侵入体和上覆的硅质火山单元的综合分析方法，被用来建立大型分带火成岩与它们的深成根之间的成因关系，并揭示了大型硅质岩浆房的化学分异过程。

The next volcanic super-eruption will have global consequences for humanity. During one of these large eruptions, the explosive potential and the amount of lava and ash erupted are largely controlled by what happens in shallow magma reservoirs in Earth's crust. This project combines the study of frozen magma reservoirs trapped below-ground - plutons - with their associated above-ground volcanic rocks for two ancient super-volcanoes: the Lake City Caldera, Southern Rocky Mountain Volcanic Field in Colorado and the Turkey Creek Caldera in Arizona. The results of this study will provide unprecedented insight into processes occurring within shallow magma reservoirs that lead to super-eruptions, and ultimately will be applied to predict the behavior of potentially extremely hazardous active volcanic regions such as the Taupo Volcanic Zone, the Bay of Naples, and the Aegean Arc. The hypothesis being tested is that the plutonic porphyries in both the Lake City Caldera and the Turkey Creek Caldera are the quenched magma reservoirs remaining in the crust following caldera collapse. If this hypothesis is confirmed, these porphyries provide a unique snapshot of the evolution and post-eruptive conditions of the mushy rootzone associated with a super-eruption. The methods that will be applied to the volcanic and plutonic lithologies are: (1) detailed field mapping of the plutonic porphyries and field sampling of the volcanic units, (2) geochemical characterization of all units, (3) quantitative investigation of primary and accessory crystals in all units using electron microprobe analysis (EPMA), laser ablation inductively coupled mass spectrometry (LA-ICP-MS), and electron backscattered diffraction (EBSD), and (4) high resolution U-Pb dating and trace element analysis of zircons (CA-TIMS-TEA) in selected lithologies. This multi-analytical approach to the sub-volcanic intrusions and overlying silicic volcanic units is applied to establish the genetic relationship between the large, zoned ignimbrites and their plutonic roots, and to unravel the processes involved in chemical differentiation of large silicic magma chambers.