SGER: The 2007 - 2008 Explosive Eruption of the World's Only Active Carbonatite Volcano: Gas Emissions From Oldoinyo Lengai, Tanzania

这项探索性研究小额赠款（SGER）由国际科学与工程办公室以及地球科学部的岩石学和地球化学项目共同赞助。 该研究将探讨Oldoinyo Lengai火山岩浆和火山气体的近期地球化学变化，Oldoinyo Lengai火山是目前世界上唯一活跃的碳酸盐岩火山。它的喷发活动主要是喷溢式喷发，喷出粘度非常低的低温（约540°C）熔岩流。自2007年9月以来，Oldoinyo Lengai进入了一个新的火山活动时期，其特点是剧烈爆炸。这样的爆炸性事件大约每50年才发生一次。该项目是与坦桑尼亚科学家的全面合作，这些科学家已经能够从这些喷发中获得样本。这些样品的成分与火山喷发期间通常排出的熔岩完全不同：它含有约20%的SiO2。这次SGER的结果将与2005年7月至2006年5月期间发生的前一次喷发事件进行比较，当时该团队收集了Oldoinyo Lengai产生的火山气体，这些气体没有严重污染空气。尽管熔岩与大洋中脊玄武岩（MORB）有很大的不同，而且发生在远离大洋中脊的环境中，但气体在化学和同位素上与上地幔、大洋中脊气体难以区分。 目前的火山活动将提供第一次机会来测试关于这个特定系统的一些假设。 例如，有人提议测试世界上唯一的活动碳酸岩火山现在是否正在向喷发高硅岩浆过渡，这种过渡是否伴随着来自幔源熔体的二氧化硫通量的增加，并以高度爆炸性喷发为特征，这种过渡是否是由上地幔化学和同位素组成特征的气体排放造成的。 Oldoinyo Lengai是坦桑尼亚的主要旅游景点，因为它靠近恩戈罗恩戈罗火山口，塞伦盖蒂野生动物保护区和纳特龙湖。几个马塞人村庄位于火山底部。每年有数百名游客爬上火山口，其中许多人在活火山的火山口露营。通过描述和更好地了解火山的爆炸活动，可以更好地评估对游客和当地居民的危害，并可以更好地了解目前的前驱活动。该提案还将支持一名研究生，并进一步加强P.I.坦桑尼亚达累斯萨拉姆大学的科学家们合作。

This Small Grant for Exploratory Research (SGER) is co-sponsored by the Office of International Science and Engineering, and the Petrology and Geochemistry program of the Division of Earth Sciences. The study will address the recent geochemical variations of magmas and volcanic gases in Oldoinyo Lengai, the only currently active carbonatite volcano in the world. Its eruptive activity is dominated by effusive eruptions that emit very low viscosity and low temperature (~540°C) lava flows. Since September 2007, Oldoinyo Lengai has entered a new episode of volcanic activity that is characterized by violent explosions. Such explosive episodes occur only about every 50 years. The project is a full collaboration with Tanzanian scientists that have been able to obtain samples from these eruptions. The composition of these samples is quite different from the lavas usually discharged during the effusive periods of the volcano: it contains approximately 20% SiO2. The results from this SGER will be compared to those of a prior eruption episode that took place between July 2005 and May 2006, when the team collected volcanic gases emanating from Oldoinyo Lengai that were not severely air contaminated. Gases are chemically and isotopically indistinguishable from upper mantle, mid-ocean-ridge gases, despite the fact that lavas are very different from mid-ocean-ridge basalts (MORB) and occur in a setting far removed from oceanic ridges. The current activity of the volcano will provide the first opportunity to test a number of hypotheses about this particular system. For instance, it is proposed to test if the world's only active carbonatite volcano is now transitioning to erupting higher-silica magmas, and if this transition is accompanied by an increase in SO2 flux from mantle-derived melts and characterized by highly explosive eruptions, and if such transition is caused by gas emissions that are characteristic of upper mantle chemical and isotopic compositions. Oldoinyo Lengai is a major tourist attraction in Tanzania as it is located close to Ngorongoro Crater, the Serengeti wildlife reserve and lake Natron. Several Massai villages are located on the base of the volcano. Hundreds of tourists climb the crater each year many of them camp in the crater of the active volcano. By characterizing and better understanding the explosive activity of the volcano, hazards to tourists and the local population can be better assessed and pre-cursor activity may be better understood as is currently the case. The proposal will also support a graduate student and further strengthen collaboration of the P.I. with Tanzanian scientists based at the University of Dar Es Salaam.