Collaborative Research: Timescales of Continental Magmatism and Development of Large Silicic Systems: Insights from Accessory Phases

“这项奖励是根据2009年美国复苏和再投资法案（公法111-5）资助的。”知识价值。该项目将研究安第斯山脉中部Altiplano Puna火山复合体（APVC）中岩石级硅岩浆系统的组装和组织的时间尺度。提出的工作建立在最近的努力上，即探索大型硅火山场（lsvf）作为进入大陆地壳基础的上地壳基岩顶部的窗口。火山活动的时空-体积记录表明，lsvf在岩浆爆发期间发展，并作为平行超级喷发的脉冲间歇性爆发，随着时间的推移变得更加强烈。这一记录通常被认为反映了相关上地壳基的成藏记录。然而，如果这一观点得到证实，关于火山和深成领域之间联系的关键问题仍有待解决。其中包括：(1)火山活动的地表模式对深部深部系统的发育有何启示？这些喷发是代表了喷发前形成的一批独特岩浆的撤离，还是代表了一个长期存在的区域岩浆体的周期性喷发？(2)大型破火山口系统的旋回性和火山喷发的区域协调性对其下方岩浆系统的发育意味着什么？静止期是否代表下一岩浆批次发育的时间尺度，还是喷发岩浆发育的时间尺度比静止期短得多？3)单个岩浆岩系统的自组织，例如分区系统的发展，告诉我们这些系统分化和演化的动力学和时间尺度是什么？在APVC成熟的时空-体积记录的基础上，我们将特别关注以下三个假设来研究这些问题：(1)APVC的超级喷发疏散了在喷发前几十万年内积累的不同岩浆批；(2)旋回超火山体系的休止期明显长于下一次可喷发岩浆批次发育的时间尺度；(3)岩基尺度的硅质岩浆房在几十万年的时间尺度上可形成明显的分带。这些想法将在地质年代学、微量元素地球化学和辅助相（尤其是锆石）的温度测量的基础上进行评估（初步数据表明这一建议很有可能成功）。更广泛的影响。由于大型硅质岩浆体系的构造和演化的时间尺度、火山-深成联系以及超级火山的发育等问题近年来一直是人们讨论的主题，因此提出的工作是及时的，将具有广泛的意义。此外，该区域的其他研究也补充了这个项目。π吗?他们正在合作调查阿根廷的塞罗加兰火山口复生群，俄勒冈州立大学的同事安妮塔·格兰德正在智利的奥坎奎尔查火山群研究类似的问题。这些数据集的结合将有助于在不同规模的系统之间进行比较，并提供安第斯中部的广泛视角。国际合作将使首席PI能够继续他的合作和指导一个新兴的玻利维亚火山学小组，重点关注APVC。科学成果的出版和传播，研究生和本科生的培训，以及将内容纳入未来的课程作业，都将扩大更广泛的影响。此外，通过俄勒冈州SMILE计划的在职和职前教师讲习班以及高知名度的火山世界网站传播结果，将研究结果传递给更多的非正式科学听众和英国大学选区。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Intellectual Merit. This project will address the time scales of assembly and the organization of batholith-scale silicic magma systems in the Altiplano Puna Volcanic Complex (APVC) of the Central Andes. The proposed work builds on recent efforts that explore the recognition of large silicic volcanic fields (LSVFs) as windows into the tops of upper crustal batholiths that are the foundations of the continental crust. The space-time-volume record of volcanism indicates that LSVFs develop during magmatic flare-ups and erupt episodically as pulses of parallel supereruptions that become more intense with time. This record is often assumed to mirror the accumulation record of the associated upper crustal batholith. However, key questions about the link between the volcanic and plutonic realms remain to be addressed if this view is to be substantiated. Among these are: (1) What does the surface pattern of volcanism imply concerning the development of plutonic systems at depth? Do these eruptions represent evacuation from a distinct batch of magma that formed just prior to eruption or do they represent the periodic tapping of a long lived regional magma body? (2) What does the cyclicity of large caldera systems and the regional concordance of eruptions imply concerning the development of the magmatic systems beneath? Does the repose period represent the time scale of development of the next magma batch or does the erupted magma develop in a timescale much shorter than the repose period. 3) What does the self-organization of single batholithic scale magmatic systems, for instance the development of a zoned system, tell us about the dynamics and time scales over which these systems differentiate and evolve? Building on the maturing space-time-volume record of the APVC, these issues will be examined by specifically focusing on three hypotheses: (1) Supereruptions in the APVC evacuated distinct magma batches that accumulated within a few hundred thousand years prior to eruption; (2) The repose period of cyclic supervolcanic systems is considerably longer than the time scale to develop the next eruptible magma batch; and (3) Batholith scale-silicic magma chambers can develop significant zonations on time scales of a few hundred thousand years. These ideas will be evaluated on the basis of geochronology, trace element geochemistry, and thermometry of accessory phases most notably zircon (for which preliminary data suggest strong likelihood of success of this proposal.Broader Impacts. The proposed work is timely and will be of broad interest because time scales of construction and evolution of large silicic magmatic systems, the volcano-plutonic connection and the development of supervolcanoes have been the subject of considerable discussion in recent years. Moreover, this project is complemented by other studies in the region. The PI?s are collaborating on an investigation of the Cerro Galan resurgent caldera complex in Argentina, and Oregon State University colleague Anita Grunder is working on similar problems at the Aucanquilcha Volcanic Cluster, Chile. Combination of these datasets will facilitate comparison across different scales of systems and provide a Central Andean wide perspective. International collaboration will allow the lead PI to continue his collaboration and mentoring of a burgeoning Bolivian volcanological group focused on the APVC. Publication and dissemination of the scientific results, the training of a graduate and an undergraduate student, and incorporation of content into future coursework all amplify the broader impacts. Moreover, dissemination of results through in-service and pre-service teacher-workshops with the SMILE program in Oregon and the high profile VolcanoWorld website will transmit findings to the larger informal scientific audience and K-U constituency.