Eruptive history and magmatic evolution at Corbetti Caldera, Ethiopia

东非裂谷（EAR）是与活火山作用有关的大陆裂谷系统的典型例子。由于大量的第四纪火山活动集中在大型硅质中心周围，EAR的一个部分，即埃塞俄比亚主裂谷（MER）引起了人们的兴趣。埃塞俄比亚有65座火山，近50%的人口居住在距离其中一座火山100公里的范围内，然而，我们对该地区近期火山历史的了解相当缺乏。最近，我们对该地区的了解有所提高，并取得了重要发现，更好地限制了过去喷发的频率和规模，以及在过去300万年中形成火山活动的岩浆过程。由于利用火山中心作为地热能来源的潜力，了解该地区的火山作用变得越来越重要。Corbetti火山口是最南端，也是MER中最大的火山火山口之一。最近的研究已经确定了从3个火山口后建筑（Urji， Artu和Chabbi）发出的多个高震级事件，并表明在过去10年中持续不稳定。虽然已经提出了过去1万年的喷发时间，但在时间、规模和动态方面，它们仍然相对缺乏约束。对~2 ka BP的Wendo Koshe Younger浮石单元进行了一些工作，该浮石层被认为来自乌尔吉，表征了其动态和范围。然而，在该综合体内的任何其他矿床上都没有进行过这样的工作。其中一个原因是，Corbetti的大多数矿床在地球化学和视觉上都是同质的，这使得区分它们变得很困难。解决这一问题的一种方法是使用微量元素分析来帮助近端和远端沉积物之间的相关性，并研究岩浆过程。虽然一些作者已经进行了微量元素分析，但要对喷发事件进行分类，需要一个更大的数据集。此外，火山喷发作用的控制是火山学研究的重点领域之一。Corbetti提供了一个理想的地方来研究这一点，因为Urji和Chabbi分别表现出几乎完全的爆炸性和喷涌性喷发。MER内所有火山的一个一致特征是它们的强过碱性。过碱性岩浆的演化在科学文献中一直存在争议，然而，一个共识已经出现，即这些碱性岩浆主要通过极端的分式结晶演化，这种结晶可能受到地壳同化的轻微影响。这一过程被归因于MER内的几座火山，然而所有这些火山都有含有晶体货物的沉积物，并且在喷发成分中显示出更大的范围。Corbetti的独特之处在于，大多数喷发矿床都是完全干燥的，这可能表明其他过程可能影响岩浆演化或熔体提取。

The East African Rift (EAR) is the type example of a continental rift system associated with active volcanism.One segment of the EAR, the Main Ethiopian Rift (MER), is of interest due to the abundance of Quaternary volcanism focused around large silicic centres. Almost 50% of Ethiopia's population live within 100 km of one of its 65 volcanoes however,our understanding of the recent volcanic history of the region is considerably lacking.Recent attempts to improve our understandingof the region have yielded important findings better constraining the frequency and magnitude of past eruptions and the magmatic processes that have fed volcanism over the last 300 ka.Understanding volcanism in this region is of growing importance due to the potential of utilising volcanic centres as a source of geothermal energy.Corbetti caldera is the southernmost, and one of the largest volcanic calderas within the MER.Recent studies have identified multiple high magnitude events emanating from 3 post caldera edifices(Urji, Artu and Chabbi) and demonstrated continued restlessness over the past 10 years. Whilst timings of eruptions over the last 10,000 years have been proposed, they are still relatively poorlyconstrained in terms of timing, magnitude and dynamics. Some work has been carried out on the ~2 ka BP Wendo Koshe Younger Pumice unit, a pumiceous horizons thought to be sourced from Urji,characterising its dynamics and extent.However, no such work has been done on any other deposits within the complex. One reason for this is that most deposits from Corbetti are both geochemically and visually homogenous, making distinguishing between them challenging. One way to tackle this problem is by using trace element analysis to aid correlation between proximal and distal deposits and to investigate magmatic processes. Whilst some authors have conducted trace element analysis, a significantly larger dataset is required to catalogue eruptive events. In addition, the controls on effusive and explosive volcanism is one of the key areas of investigation in volcanology.Corbetti provides an ideal place to study this as Urji and Chabbi exhibit almost exclusively explosive and effusive eruptions respectively. One feature that is consistent across all volcanoes within the MER is their strong peralkalkinity. The evolution of peralkaline magmas has been debated within scientific literature,however, a consensus has arisen that these alkaline magmas predominantly evolve through extreme fractional crystallisation which may be slightly influenced by crustal assimilation. This has been the process attributed at several volcanoes within the MER, however all these volcanoes have deposits that have a crystal cargo and display a wider range in erupted compositions. Corbetti is somewhat unique in that most eruptive deposits are completely aphyric which may indicate additional processes may be influencing magma evolution or melt extraction.