EAGER: Cause and Duration of Extensive Rejuvenated Volcanism on Savai'i, Samoa.

EAGER：萨摩亚萨瓦伊岛大规模复活火山活动的原因和持续时间。

• 批准号: 0946752
• 负责人: Jasper Konter
• 金额: $ 1.84万
• 依托单位: University of Texas at El Paso
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0946752&HistoricalAwards=false
• 关键词: EAGER; Cause; Duration; Extensive; Rejuvenated

This Early Grant for Exploratory Research (EaGER) is to support an exploratory project to investigate the compositional evolution of an active, but yet understudied volcano, Savai'i, located on the western fringe of the Samoan Islands. A 20th century Savai'i eruption displaced an entire village, and understanding the timing and evolution of this volcanism is of social importance for the local islanders.Savai'i was essentially repaved with large volumes of rejuvenated volcanism, in contrast to other ocean islands (e.g., Hawaii, the Canary Islands and Mauritius). Eruption of Samoan rejuvenated volcanism is limited to the western three islands, and their close proximity (~150 km) to the northern terminus of the Tonga trench suggest that Samoan rejuvenated volcanism may have a different origin than in other hotspots. In the last 5 million year (Ma), the distance between Savai'i and the trench has decreased due to plate motion and slab roll-back. Thus, trench-related stresses and materials may be responsible for the volume, duration and unusual enriched compositions of Samoan rejuvenated lavas. The rejuvenated stage may be completely exposed in a 500m deep gorge on the south side of Savai'i that covers a 2 Ma history. This gorge offers an unprecedented opportunity to sample a long-lived sequence of Samoan rejuvenated lavas. Key samples from this canyon are needed to determine whether material from the Tonga trench is represented in Samoan rejuvenated lavas, and whether such a trench signature increases with time. In comparison to Hawaiian volcanic stages, the rejuvenated stage at Savai'i seems volumetrically larger, longer-lived, and geochemically more enriched. Currently, the extent and volume of the rejuvenated volcanism is constrained by one 2Ma trachyte cobble from Savai'i, isotopically indistinguishable from rejuvenated lavas, and found in a stream that drains the gorge. In order to better constrain if the compositional change could indicate a shift in source composition while the volcano was still in its shield stage, a more detailed sampling of the site needs to be performed. This EaGER will enable two early-career PIs (Jasper Konter from UT-El Paso and Matthew Jackson from Boston University) to travel to Savai'i for a more complete sampling of the area to ascertain if a long term geochemical and petrologic study of the island is indeed justified.

这项探索性研究早期补助金（EaGER）是为了支持一个探索性项目，以调查位于萨摩亚群岛西部边缘的一座活跃但尚未得到充分研究的萨瓦伊火山的成分演变。20世纪世纪的一次萨瓦伊火山爆发使整个村庄流离失所，了解火山活动的时间和演变对当地岛民具有重要的社会意义。萨瓦伊岛基本上是用大量复活的火山活动重新铺设的，与其他海洋岛屿形成对比（例如，夏威夷、加那利群岛和毛里求斯）。萨摩亚再生火山的喷发仅限于西部三个岛屿，它们与汤加海沟北方终点的接近程度（约150公里）表明，萨摩亚再生火山可能与其他热点地区有不同的起源。在过去的500万年（Ma），萨瓦伊和海沟之间的距离由于板块运动和板块回滚而缩短。因此，沟槽有关的应力和材料可能是负责的量，持续时间和不寻常的丰富成分的萨摩亚再生熔岩。再生阶段可能完全暴露在萨瓦伊岛南侧500米深的峡谷中，覆盖了2 Ma的历史。这个峡谷提供了一个前所未有的机会，可以对长期存在的萨摩亚复兴熔岩序列进行采样。从这个峡谷的关键样本需要确定是否从汤加海沟的物质是代表在萨摩亚再生熔岩，以及是否这样的海沟签名随时间而增加。与夏威夷火山阶段相比，萨瓦伊岛的复兴阶段似乎体积更大，寿命更长，地球化学更丰富。目前，复兴火山活动的范围和体积受到来自Savai'i的一个2Ma粗面岩鹅卵石的限制，同位素与复兴熔岩无法区分，并在峡谷排水的溪流中发现。为了更好地限制成分变化是否可能表明火山仍处于屏蔽阶段时源成分的变化，需要对现场进行更详细的采样。 该EaGER将使两名职业生涯早期的PI（来自UT埃尔帕索的碧玉康特和来自波士顿大学的马修杰克逊）前往萨瓦伊，对该地区进行更完整的采样，以确定是否确实有理由对该岛进行长期的地球化学和岩石学研究。