Collaborative Research: Non-peridotite Melting in Plume-influenced Extensional Environments: Lithological Heterogeneity of the African Superplume and African Lithosphere

合作研究：受地幔柱影响的伸展环境中的非橄榄岩熔融：非洲超地幔柱和非洲岩石圈的岩性非均质性

• 批准号: 1219647
• 负责人: Tyrone Rooney
• 金额: $ 25.53万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-15 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1219647&HistoricalAwards=false
• 关键词: Collaborative; Research; Non; peridotite; Melting; Collaborative; Research; Non; peridotite; Melting

Intellectual Merit. This project seeks to determine the source lithology (e.g., peridotite, pyroxenite) of mantle melts that contributed to Oligocene Ethiopian continental flood basalt volcanism that preceded development of the East African Rift. Infiltration of mantle melts can play a central role in the initiation and evolution of lithospheric thinning by weakening and focusing strain. Thus, understanding the composition, and in particular the mineralogy, of the sources of mantle melts is critical to constrain the conditions attending melt generation. Non-peridotite lithologies such as pyroxenite in an upwelling plume or metasomes within the lithospheric mantle are potentially fertile mantle sources capable of producing significant volumes of magmas. In contrast typical peridotite lithologies may not produce significant melt under these conditions (i.e., smaller degrees of mantle decompression, or lower values of mantle potential temperature). Moreover, mantle underlying the study area is characterized by significant seismic attenuation, which has been attributed to the presence of an African superplume upwelling of hot mantle material. The proposed study aims to investigate the relative contributions of lithospheric vs. plume-like mantle as primary magma sources. Specifically, mantle source lithologies (i.e. peridotite versus pyroxenite) will be evaluated via geochemical characterization of a well-preserved 2000 m thick section of flood basalts from the western Ethiopian Plateau that has never before been studied. The possible contribution of enriched lithospheric mantle to melt generation will be assessed through a parallel study of unusual Si-undersaturated rocks erupted in a Miocene shield volcano, for which preliminary data imply magma derivation from ancient African lithospheric mantle. The analytical program will involve measurement of major and selected trace elements, Sr-Nd-Pb-Hf isotopes, and minor elements in olivine, and will be interpreted within a temporal framework to be established by new Ar/Ar geochronology and paleomagnetic studies designed to constrain the timing, duration, and eruptive rates of these deposits. Together these data will provide new insights into processes of basalt generation. Broader Impacts. The data resulting from this project will offer the first petrologic insights into the origin of the geophysically-deduced compositional component of the African superplume and will be directly relevant to ongoing geophysical projects ongoing in the region. This project will support the early career research of Tyrone Rooney (Ph.D., 2006), and fosters international collaboration through interactions with researchers at Addis Ababa University. The project represents a new collaboration between scientists at five US institutions (Rooney-MSU, Herzberg-Rutgers, Kappleman/Holt-UT Austin, Spell-UNLV, and Konter-UTEP), all of whom will contribute to the analytical measurements, interpretations, and modeling. The project utilizes and extends the applications of state-of-the-art analytical facilities at Michigan State University (laser ablation ICP-MS), Rutgers University (electron microprobe), UT Austin (paleomagnetic lab), UNLV (Noble gas MS), and UTEP (MC-ICPMS). The project also will support mentoring of a Ph.D. student from MSU through the wide range of collaborative interactions at the five US institutions and researchers in Ethiopia.

智力优点。 该项目旨在确定地幔融化的来源岩性（例如，橄榄岩，脓去石），这导致了埃塞俄比亚大陆洪水盆地盆地火山，这是在东非裂谷发展之前的。地幔熔体的渗透可以通过削弱和聚焦菌株在岩石圈变薄的开始和演变中起核心作用。因此，了解地幔融化来源的组成，尤其是矿物学对于约束融化产生的条件至关重要。岩石圈地幔中上升羽流或变质中的非童岩岩石岩（例如辉石）可能是能够生产大量岩浆的肥沃地幔来源。相比之下，典型的橄榄岩岩性在这些条件下可能不会产生明显的熔体（即较小的地幔减压程度或地幔电势温度的较低值）。此外，研究区域的基础地幔的特征是严重的地震衰减，这归因于热地幔材料的非洲超级pl升上升。 拟议的研究旨在研究岩石圈与羽状地幔作为主要岩浆源的相对贡献。 具体而言，将通过在西部埃塞俄比亚高原的2000 m厚的洪水盆地厚度较厚的洪水层的地球化学表征来评估地幔源岩性（即橄榄岩与辉石岩），这些岩石化学表征从未被研究过。富集岩石圈地幔对熔体产生的可能贡献将通过对中新世屏蔽火山中爆发的异常Si-nodersated Rocks的平行研究进行评估，该岩石的初步数据暗示了古代非洲岩石圈地幔的岩浆衍生物。该分析程序将涉及测量主要和选定的微量元素，SR-ND-PB-HF同位素以及橄榄石中的次要元素，并将在旨在通过新的AR/AR地球人工学和古磁研究确定的时间框架中解释，旨在限制这些时机，持续时间，持续时间，以及这些沉积物的喷发率。这些数据将共同为玄武岩生成过程提供新的见解。更广泛的影响。 该项目产生的数据将为非洲超级胶合物的地球物理成分组成部分的起源提供第一个岩石学见解，并将与该地区正在进行的正在进行的地球物理项目直接相关。该项目将支持泰隆·鲁尼（Tyrone Rooney）的早期职业研究（Ph.D.，2006年），并通过与亚的斯亚贝巴大学（Addis Ababa University）的研究人员进行互动来促进国际合作。该项目代表了美国五个机构（Rooney-MSU，Herzberg-Rutgers，Kappleman/Holt-ut Austin，Spell-UNLV和Konter-UTEP）之间的科学家之间的新合作，所有这些都将有助于分析测量，解释，解释和建模。该项目利用并扩展了密歇根州立大学（激光消融ICP-MS），Rutgers University（Electron Microprobe），UT Austin（Paleomagnetic Lab），UNLV（NOBLE GAS MS）和UTEP（MC-OCPMS）的最先进分析设施的应用。该项目还将支持博士学位的指导。从MSU到埃塞俄比亚五个机构和研究人员的各种协作互动的学生。