Genesis of Harrat Basalts in Western Saudi Arabia

沙特阿拉伯西部哈拉特玄武岩的成因

• 批准号: 2218248
• 负责人: Tanya Furman
• 金额: $ 33.26万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2218248&HistoricalAwards=false
• 关键词: Genesis; Harrat; Basalts; Western; Saudi

This project seeks to understand the formation of large-volume basalt lava fields that erupt onto continental crust, where they provide important nutrients for terrestrial and aquatic life as well as geothermal and mineral resources for human use. The research is pursued in Western Saudi Arabia because the thermal and material structure of the crust itself is a barrier to basalt volcanism, and yet the study areas have been volcanically active for up to 30 million years. The work uses the geochemistry of basalt lavas as a lens through which to explore the long-term evolution of the lowermost crust, i.e., the “underlayer” of the continent that cannot be observed directly. The research project will determine how plate tectonic processes acting in the region have affected crustal thickness and integrity, potentially thinning and weakening the continent substantially and thereby encouraging volcanic activity. The work is conducted in partnership with Saudi colleagues who are interested in diversifying their economic portfolio beyond petroleum and natural gas resources. Funds from this project support a doctoral candidate and several undergraduate students from backgrounds that are underrepresented in the geosciences; help develop a middle-school learning unit in cooperation with a local teacher and a museum display focused on the artistic, cultural, religious and ecological significance of the Saudi lava fields. This work will create new knowledge about the long-term evolution of our planet that helps us prepare for a sustainable and diverse future. Continental basalts are the most common subaerial volcanic features on Earth but melting beneath thick continental crust is difficult to achieve. Geochemical and geochronologic data, integrated with geophysical evidence, will be used to determine the mechanism(s) of mantle melting and the mineralogic, isotopic and thermo-barometric parameters of mantle source domains that contribute to alkaline mafic volcanism in two long-lived western Arabian Harrats (Uwayrid and Ash Shaam). The geochemical and isotopic investigation will document evolution of source domains and mantle melting mechanisms in a region of complex tectonics and will test whether rejuvenated mafic alkaline volcanism in two Arabian harrats results from lithospheric drip magmatism. Geochemical evidence for this process has focused on documenting individual small-volume volatile-rich melt batches, contributions from a pyroxenitic source, small-scale temporal trends of increasing melting depth and temperature, and a positive correlation between depth and degree of mantle melting. The research will pursue this evidence through robust major and trace element analysis of lavas and individual crystals in lavas and xenoliths from Harrats Uwayrid and Ash Shaam. High precision 40Ar/39Ar dating will establish temporal trends in magma chemistry, and Sr-Nd-Pb-Hf-He isotopic study of lavas and xenoliths will establish source characteristics. The research explores contributions from the Afar plume, ambient upper mantle and metasomatized lithosphere, and documents spatial and temporal variations to these contributions across the Arabian plate. The findings have implications for transport of plume material, for the development of gravitationally unstable zones in metasomatized lithospheric mantle, and for evolution of the Dead Sea Fault and northern Red Sea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目旨在了解喷发到大陆地壳上的大量玄武岩熔岩场的形成，它们为陆地和水生生物提供重要的营养物质，并为人类提供地热和矿物资源。这项研究之所以在沙特阿拉伯西部进行，是因为地壳本身的热和物质结构是玄武岩火山活动的障碍，而研究地区的火山活动长达3000万年。这项工作使用玄武岩熔岩的地球化学作为一个透镜，通过它来探索最低地壳的长期演化，即，无法直接观察到的大陆“底层”。该研究项目将确定在该区域发生作用的板块构造过程如何影响地壳厚度和完整性，从而可能使大陆大大变薄和变弱，从而鼓励火山活动。这项工作是与沙特同事合作进行的，他们有兴趣在石油和天然气资源之外实现经济组合的多样化。该项目的资金支持一名博士候选人和几名来自地球科学背景的本科生;帮助与当地教师合作开发一个中学学习单元，并在博物馆展出沙特熔岩场的艺术，文化，宗教和生态意义。这项工作将创造有关我们星球长期演变的新知识，帮助我们为可持续和多样化的未来做好准备。大陆玄武岩是地球上最常见的陆上火山特征，但在厚厚的大陆地壳下融化是很难实现的。地球化学和地质年代学数据，结合地球物理证据，将用于确定地幔熔融的机制和地幔源域的矿物学，同位素和热气压参数，有助于在两个长寿的阿拉伯西部Harrats（Uwayrid和Ash Shaam）的碱性镁铁质火山活动。地球化学和同位素调查将记录源域的演化和地幔熔融机制在一个地区的复杂构造，并将测试是否复活的镁铁质碱性火山作用在两个阿拉伯harrats岩石圈滴岩浆活动的结果。这个过程的地球化学证据集中在记录个别小体积的挥发分丰富的熔体批次，贡献的辉石源，小规模的时间趋势增加熔融深度和温度，深度和程度之间的正相关性地幔熔融。该研究将通过对Harrats Uwayrid和Ash Shaam的熔岩和捕虏体中的熔岩和单个晶体进行强有力的主元素和微量元素分析来寻求这一证据。高精度的40 Ar/39 Ar定年将确定岩浆化学的时间趋势，而熔岩和捕虏体的Sr-Nd-Pb-Hf-He同位素研究将确定源区特征。该研究探讨了阿法尔羽，环境上地幔和交代岩石圈的贡献，并记录了阿拉伯板块的时空变化。这些发现对羽流物质的运输、交代岩石圈地幔中重力不稳定区的发展以及死海断层和北方红海的演变都有影响。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。