Using Loihi Basaltic Rocks to Understand the Hawaiian Plume

利用 Loihi 玄武岩了解夏威夷羽流

• 批准号: 1737284
• 负责人: Michael Garcia
• 金额: $ 20.99万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737284&HistoricalAwards=false
• 关键词: Using; Loihi; Basaltic; Rocks; Understand

Hotspot volcanoes are thought to tap the Earth's deep mantle, and to provide fundamental insights into understanding its composition and processes. Hawaii is an excellent venue for studying hotspot lavas because of its distant location from any continent or tectonic plate boundary (2500 km), and the high temperature (1500 degrees C) and volume output (100,000 cubic meters/year) of its hotspot. This proposal focuses on Loihi, the youngest and still underwater Hawaiian volcano. Loihi lavas have the potential to provide important constraints on the mantle plume beneath the islands because: 1) The volcano's youth (preshield stage) allows for the characterization of its mantle source before it has been extensively melted. 2) Loihi basalts are one of the key geochemical end members for Hawaiian basalts. Thus, analyses of its lavas (especially from previously unsampled areas) will provide a unique perspective into melting processes and source heterogeneity within the Hawaiian hotspot, the Earth's hottest mantle plume. Loihi lavas are especially noteworthy for their primordial noble gas signatures. 3) Loihi's interior and early history are exposed by major landslides on its eastern flank (1 km thick stratigraphic section) and in ~300 m deep craters at its summit. 4) An extensive suite (196 samples) of Loihi basalts collected by submersible are available from its summit pit craters, its dissected east flank and the full extent of its two rift zones. Most of these samples have received limited geochemical characterization. These samples will be made available to the Earth science community for other geochemical studies. This project supports the training of a graduate student at the University of Hawaii.The goals of this project are: 1) Determine the lifespan of Hawaiian shield volcanoes using Loihi lavas to document the duration of the early stage, which is the major missing puzzle piece for resolving this issue. Current estimates range widely. 2) Better understand the structure of the Hawaiian plume (e.g., whether it is bilaterally asymmetrical as currently thought). Loihi is at the young end of the LOA trend but paradoxically, it shares geochemical features with KEA trend lavas. 3) Evaluate whether the Hawaiian mantle plume source varies in time and space. Lavas from Loihi deep interior and submarine flanks will provide a new perspective on the Loihi compositional end member of the Hawaiian plume. 4) Determine how crustal contamination works at a submarine Hawaiian volcano. Do rift zone magmas bypass the summit magma reservoir and more faithfully preserve mantle source signatures? Previous studies of Loihi summit lavas showed they were extensively modified by crustal contamination, whereas rare gas compositions of deep south rift lavas suggest they were uncontaminated. Loihi basalts are ripe for geochemical characterization using a new generation of geochemical instruments for determining ages, crustal and mantle processes, and source variations. These analyses will provide fundamental insights into the workings of the Hawaiian hotspot. The newly geochemically characterized Loihi samples, all precisely located and collected by submersible, will be made available to the Earth science community for other complementary future geochemical studies (e.g., Os isotopes, platinum group elements, rare gases).

人们认为，热点火山可以利用地球的深层地幔，并为理解其组成和过程提供基本的见解。夏威夷是研究热点熔岩的绝佳场所，因为其距离任何大陆或构造板边界（2500 km）以及高温（1500摄氏度）和体积输出（100,000立方米/年），因此它的位置遥远。该提案的重点是洛希（Loihi），最年轻，水下夏威夷火山。 Loihi Lavas有潜力在岛屿下面的地幔羽流上提供重要的限制，因为：1）火山的年轻人（Preshield阶段）允许在广泛融化之前对其地幔来源进行表征。 2）Loihi玄武岩是夏威夷玄武岩的主要地球化学最终成员之一。因此，对其熔岩的分析（尤其是从以前未采样的区域）将为融化过程和源异质性提供独特的视角，夏威夷热点（地球最热的地幔羽流）内。 Loihi熔岩因其原始贵重气体签名而引起人们的注意。 3）Loihi的内部和早期历史在其东部侧面（1公里厚的地层区域）和大约300 m的山顶上暴露在其山顶上的大约300 m深的山口。 4）可从山顶坑，其解剖的东侧面以及其两个裂谷区域的全部范围内获得一套由潜水收集的宽玄武岩的广泛套房（196个样本）。这些样品中的大多数都获得了有限的地球化学表征。这些样本将提供给地球科学界的其他地球化学研究。 该项目支持夏威夷大学的研究生培训。该项目的目标是：1）确定使用Loaihi Lavas记录早期阶段的夏威夷盾牌火山的寿命，这是解决此问题的主要缺失拼图。当前估计值范围广泛。 2）更好地了解夏威夷羽流的结构（例如，它是否是双侧不对称的）。 Loihi处于LOA趋势的年轻末端，但自相矛盾的是，它与KEA趋势熔岩具有地球化学特征。 3）评估夏威夷地幔羽流是否在时间和空间上有所不同。 Loihi深层内部和海底侧面的熔岩将为夏威夷羽流的Loihi构图最终成员提供新的视角。 4）确定在夏威夷海底火山下地壳污染的工作原理。裂谷区岩浆是否绕过山顶岩浆水库和更忠实地保留地幔源签名？先前对Loihi Summit熔岩的研究表明，它们是通过地壳污染进行了广泛修饰的，而深南裂谷熔岩的稀有气体成分表明它们未经污染。 Loihi玄武岩是使用新一代的地球化学仪器来确定年龄，地壳和地幔过程以及源变化的新一代地球化学表征的成熟。这些分析将为夏威夷热点的运作提供基本的见解。新地球化学特征的Loihi样品，所有这些样品，所有这些样品都精确地位于潜水和收集的地球科学界，用于其他互补的未来地球化学研究（例如，OS同位素，铂群元素，稀有气体）。

项目成果

Carbon isotope composition of basalts from Loihi Seamount: Primordial or recycled carbon in the Hawaiian mantle plume?

• DOI: 10.1016/j.epsl.2023.118248
• 发表时间: 2023-09
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: D. Graham;P. Michael;T. B. Truong

2019. Hydrogen isotopes in high 3He/4He submarine basalts: Primordial vs. recycled water and the veil of mantle enrichment. , 508, .

2019. 高 3He/4He 海底玄武岩中的氢同位素：原始水与循环水以及地幔富集的面纱。

• 发表时间: 2019
• 期刊: Earth and planetary science letters
• 影响因子: 5.3
• 作者: Loewen, Matthew W.

A possible sea-level fall trigger for the youngest rejuvenated volcanism in Hawaiʻi

海平面下降可能引发夏威夷最年轻的火山活动

• DOI: 10.1130/b36615.1
• 发表时间: 2023
• 期刊: GSA Bulletin
• 作者: Jicha, Brian R.;Garcia, Michael O.;Lormand, Charline
• 通讯作者: Lormand, Charline

Slow changes in lava chemistry at Kama‘ehuakanaloa linked to sluggish mantle upwelling on the margin of the Hawaiian plume

卡马埃瓦卡纳罗亚熔岩化学成分的缓慢变化与夏威夷地幔柱边缘缓慢的地幔上升有关

• DOI: 10.1130/g51350.1
• 发表时间: 2023
• 期刊: Geology
• 影响因子: 5.8
• 作者: Pietruszka, Aaron J.;Garcia, Michael O.;Carlson, Richard W.;Hauri, Erik H.
• 通讯作者: Hauri, Erik H.