Volcanism at the Antarctic Rift Margin: An Isotopic and Trace-Element Study

南极裂谷边缘的火山活动：同位素和微量元素研究

• 批准号: 0003702
• 负责人: Kurt Panter
• 金额: $ 7万
• 依托单位: Bowling Green State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-08-01 至 2003-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0003702&HistoricalAwards=false
• 关键词: Volcanism; Antarctic; Rift; Margin; Isotopic

0003702PanterThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports an investigation of Cenozoic volcanic rocks from the western flank of the West Antarctic Rift System. Cenozoic (35 million years ago to presently active) volcanism in West Antarctica has been attributed to: 1) mantle melting by 'passive' rifting that has thinned the crust and mantle lithosphere, 2) mantle melting by 'active' rifting associated with a hot, upwelling mantle plume, and 3) a combined 'active-passive' scenario that involves the melting of an ancient mantle plume source by passive rifting. Making sense of the underlying causes of rifting and volcanism in Antarctica has important implications to our understanding of continental breakup. In this regard the proposed work will engage models of rifting and separation of New Zealand from West Antarctica.This project will undertake new geochemical research in an attempt to unravel processes of mantle melting and continental breakup using a suite of basaltic volcanic rocks from the foothills of the Royal Society Range, South Victoria Land. Because the basalts represent near-primary melts of the mantle, they will be used as geochemical tracers of the Earth's interior. Basaltic volcanism in the Royal Society Range offers a unique opportunity to study 14 million years of mantle evolution along a major tectonic boundary separating the West Antarctic rift system from the East Antarctic continental shield. The principal objective of this project is to provide the first detailed isotopic and trace-element investigation of basalts in this area. The new results will be integrated into regional studies to build better models for West Antarctic volcanism and rifting. A preliminary survey of the geochemical data suggests that there has been a change in the degree and depth of melting beneath this portion of the rift. Previous work on basalts in other areas of the rift has shown that variations in the degree and depth of melting correlate with changes in isotopic composition. Because isotopes measured in primary basalts provide a 'fingerprint' of long-lived chemical reservoirs within the Earth's mantle, the variations must indicate that melting of different reservoirs is producing the basalt. A better understanding of the type and origin of distinct mantle reservoirs is critical to models of rifting and volcanism. For instance, previous studies have shown that the isotopic signature of many West Antarctic basalts, as well as some basalts from New Zealand, have a common mantle component; one whose composition is characteristic of a mantle plume source. This has led development of a model for plume-assisted breakup. A complete high-quality geochemical data set for Royal Society Range basalts will allow this project to test theories of mantle plume activity and plume involvement in the breakup of New Zealand from Antarctica. This work is collaborative with investigators at the New Mexico Institute of Mining and Technology and at Royal Holloway, University of London.

0003702Panter 该奖项由极地项目办公室的南极地质和地球物理项目提供，支持对南极西部裂谷系统西翼新生代火山岩的调查。南极洲西部的新生代（3500万年前至今活跃）火山活动归因于：1）“被动”裂谷导致地幔熔化，使地壳和地幔岩石圈变薄；2）与热的、上涌的地幔柱相关的“活跃”裂谷导致地幔熔化；3）涉及古代地幔熔化的“主动-被动”综合情景 被动裂谷羽流来源。了解南极洲裂谷和火山活动的根本原因对于我们理解大陆分裂具有重要意义。在这方面，拟议的工作将涉及新西兰与西南极洲的裂谷和分离模型。该项目将进行新的地球化学研究，试图利用来自南维多利亚州皇家学会山脉山麓的一组玄武质火山岩来揭示地幔熔化和大陆分裂的过程。由于玄武岩代表了地幔的近乎原生熔化，因此它们将被用作地球内部的地球化学示踪剂。皇家学会山脉的玄武岩火山活动为研究沿分隔西南极裂谷系统和东南极大陆盾的主要构造边界的 1400 万年地幔演化提供了独特的机会。 该项目的主要目标是对该地区的玄武岩进行首次详细的同位素和微量元素调查。新的结果将被纳入区域研究中，以建立更好的南极西部火山活动和裂谷模型。对地球化学数据的初步调查表明，这部分裂谷下方的熔化程度和深度发生了变化。先前对裂谷其他区域玄武岩的研究表明，熔化程度和深度的变化与同位素组成的变化相关。 由于在原生玄武岩中测量的同位素提供了地幔内长寿命化学储层的“指纹”，因此这些变化必定表明不同储层的融化正在产生玄武岩。更好地了解不同地幔储层的类型和起源对于裂谷和火山作用模型至关重要。例如，之前的研究表明，许多西南极玄武岩以及新西兰的一些玄武岩的同位素特征具有共同的地幔成分；其成分具有地幔柱来源的特征。这导致了羽流辅助破碎模型的开发。 皇家学会山脉玄武岩的完整高质量地球化学数据集将使该项目能够测试地幔柱活动和地幔柱参与新西兰从南极洲分裂的理论。这项工作是与新墨西哥矿业技术学院和伦敦大学皇家霍洛威学院的研究人员合作进行的。