Origin & Eruptive History of Quaternary Volcanism in Nosy Be and Itasy-Ankaratra, Madagascar

起源

• 批准号: 1523442
• 负责人: Elisabeth Widom
• 金额: $ 30万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1523442&HistoricalAwards=false
• 关键词: Origin; & Eruptive; History; Quaternary

Madagascar, the fourth largest island in the world, has experienced a complex history related to continent assembly and breakup, associated with a prolonged history of volcanism. Despite growing evidence for young volcanism in Madagascar, as well as highly active tectonics and associated seismicity, there has been very limited study of the recent volcanism. Nosy Be, a popular tourist destination, is considered to be the youngest of the volcanic fields in northern Madagascar, and is characterized by active geothermal systems and seismic activity with earthquakes as large as Richter magnitude 6. The Istasy-Ankaratra region, located in very close proximity to the capital city, Antananarivo, has been active as recently as 8,500 years ago and has a history of explosive volcanism, and should therefore be considered a volcanically active and potentially hazardous area. This study will utilize geochemical techniques to evaluate the sources and causes of volcanism in these two volcanic regions, and will establish baseline age data for evaluating the prevalence of recent volcanism - and likelihood of future volcanism - in these regions.Fundamental questions still remain about the cause(s) and source(s) of recent volcanism in Madagascar, as well as the likelihood of future eruptive activity. Key questions range widely in scope and include: Does the ancient, metasomatized subcontinental lithospheric mantle contribute significantly as a magma source, either in situ or as isolated blocks destabilized during events associated with the assembly and/or subsequent rifting of Gondwana?; What are the relative roles of Indian MORB mantle versus other potential asthenospheric sources in the Quaternary volcanism?; and How prevalent is Pleistocene and Holocene volcanism in Madgascar, and what are the recurrence intervals and potential hazards associated with this recent volcanism? This project will involve comprehensive field sampling of mafic lavas and mantle xenoliths, radiometric dating (Ar-Ar and 14C), and geochemical and isotopic analyses (Sr-Nd-Pb-Hf-Os and U-series disequilibria) of the youngest Quaternary eruptive products in these volcanic regions in order to resolve the nature and age of the underlying lithospheric mantle, to distinguish between lithospheric and asthenospheric mantle sources contributing to the Quaternary magmatism, and to provide constraints on the scope and frequency of recent eruptive events.

马达加斯加是世界第四大岛屿，经历了与大陆议会和分手有关的复杂历史，与长期的火山史有关。尽管马达加斯加的年轻火山以及高度积极的构造和相关的地震活动的证据越来越有限，但对最近的火山主义的研究非常有限。诺西·贝（Nosy Be）是一个受欢迎的旅游目的地，被认为是马达加斯加北部的火山田中最年轻的地方，其特征是活跃的地热系统和地震活动，地震与里奇特（Richter）级别一样大。因此，应将其视为火山活动且潜在的危险区域。这项研究将利用地球化学技术评估这两个火山区域的火山源的来源和原因，并将建立基线年龄数据来评估最近的火山主义的普遍性，以及未来火山主义的可能性 - 在这些地区 - 在这些地区的可能性仍然存在于这些原因和近期众多的活动，以及Madags in Madagis中的现象，以及Madag的活动。关键问题在范围中广泛范围，包括：古老的，代理的次洲次大陆岩石圈地幔是否作为岩浆来源显着贡献，无论是原位还是孤立的块，在与组装和/或随后的贡德瓦纳（Gondwana）相关的事件期间不稳定？印度医疗地幔与其他潜在的软圈源在第四纪火山主义中的相对作用是什么？ Madgascar的更新世和全新世火山主义的流行程度如何，与最近的火山主义相关的复发间隔和潜在危害是什么？ This project will involve comprehensive field sampling of mafic lavas and mantle xenoliths, radiometric dating (Ar-Ar and 14C), and geochemical and isotopic analyses (Sr-Nd-Pb-Hf-Os and U-series disequilibria) of the youngest Quaternary eruptive products in these volcanic regions in order to resolve the nature and age of the underlying lithospheric mantle, to区分岩石圈和微弱的地幔源，这些岩层有助于第四纪岩浆作用，并提供有关最近喷发事件的范围和频率的约束。