He-Ne-Ar-N2-CO2 Isotope Characterization of the East Africa Rift System

该项目旨在对东非裂谷系统(EAR)进行全面研究，重点分析东非目前裂谷和火山活动的所有三个分支的地质样品的主要(CO2)和微量挥发性(He-Ne-Ar-N2)特征。它们是：埃塞俄比亚的主要裂谷，包括阿法尔大萧条，以及肯尼亚和西部的裂谷。这项研究的目的是利用挥发分的同位素和相对丰度系统学来确定下伏地幔(一个或两个深地幔热柱)的性质，并了解其与整个东非大陆岩石圈的相互作用。研究计划包括分析地热流体、地幔包体、岩浆和冰盖岩层，以获得这一活动区的挥发性特征的史无前例的概述，该活动区包括大陆裂谷、动态抬升和新生洋壳的形成。通过综合分析轻惰性气体(He-Ne-Ar)和其他挥发物(氮气和二氧化碳)，该小组将确定支撑埃塞俄比亚穹顶的假设地幔热柱是耳朵下方唯一的深层异常，还是第二个热柱对肯尼亚穹顶的抬升负责。在这方面，他们将测试埃塞俄比亚主要裂谷和阿法尔凹陷的高3He/4He省是否具有独特的挥发性同位素特征，可以确定和利用这些特征来绘制埃塞俄比亚深部羽流影响的空间范围。此外，假设肯尼亚和西部裂谷省，即图尔卡纳凹陷以南，也具有可以确定的独特的挥发性同位素特征，这将成为检验次大陆地幔岩石圈和/或第二股岩柱参与肯尼亚穹顶岩浆成因的基础。所有目标挥发物--无论是单独的(例如，3He/4He)还是与其他挥发物(例如，CO2/3He)的组合，都具有使它们成为深部地幔来源的灵敏示踪剂的特征，从而能够区分来自岩石圈的岩浆来源和来自浅层的岩浆来源。总而言之，这项研究将提供基本的挥发性数据库，解决关键问题，测试整个大陆的非洲超级油井与整个耳朵不同地区的岩浆来源特征之间的关系。

This project is to undertake a comprehensive study of the East African Rift System (EARS) concentrating on the analyses of the major (CO2) and trace volatile (He-Ne-Ar-N2) characteristics of geological samples from all three branches of current rifting and volcanism in eastern Africa. These are: the Main Ethiopian Rift, including the Afar Depression, and the Kenyan and Western rifts. The aim of the study is to utilize the isotopic and relative abundance systematics of the volatiles to define the nature of the underlying mantle (one or two deep-seated mantle plumes) and to understand its interaction with the overlying continental lithosphere throughout eastern Africa. The research plan involves analyzing geothermal fluids, mantle xenoliths, phyric lavas and tephras to gain an unprecedented overview of the volatile characteristics of this active region which incorporates continental rifting, dynamic uplift and formation of nascent oceanic crust. Through an integrated approach combining analyses of the light noble gases (He-Ne-Ar) and other volatiles (N2 and CO2), the team will determine if the postulated mantle plume supporting the Ethiopian Dome is the sole deep-seated anomaly beneath the EARS or whether a second plume is responsible for uplift of the Kenyan Dome. In this respect, they will test if the high 3He/4He provinces of the Main Ethiopian Rift and Afar Depression have unique volatile isotopic characteristics that can be defined and exploited to map the spatial extent of the deep-seated Ethiopian plume influence. Additionally, the hypothesis that provinces of the Kenyan and Western rifts, i.e., south of the Turkana Depression, also have unique volatile isotopic characteristics that can be defined will form the basis of testing the involvement of subcontinental mantle lithosphere (SCLM) and/or a second plume in the petrogenesis of magmas from the Kenyan Dome. All targeted volatiles - either alone (e.g., 3He/4He) or in combination with other volatiles (e.g., CO2/3He) possess characteristics that make them sensitive tracers of deep mantle provenance that allows distinction between magmatic sources that are derived from the lithosphere and which are shallow. Taken together, this study will provide the essential volatile database that addresses key questions that test the relationship between the continent-wide African superswell and magma source characteristics throughout different regions of the EARS.