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.

这一早期的探索性研究赠款(EIGER)是为了支持一个探索性项目，以调查位于萨摩亚群岛西缘的一座活火山--Savai‘i火山的成分演变。20世纪的一次萨瓦伊火山喷发使整个村庄流离失所，了解这场火山喷发的时间和演化对当地岛民具有重要的社会意义。与其他海洋岛屿(如夏威夷、加那利群岛和毛里求斯)不同，萨瓦伊火山基本上是用大量恢复活力的火山重新铺设的。萨摩亚复活火山的喷发仅限于西部三岛，而且距离汤加海沟北端很近(约150公里)，这表明萨摩亚复活火山活动可能与其他热点地区不同。在过去的500万年(Ma)，由于板块运动和板坯回滚，萨瓦伊与海沟之间的距离减小。因此，与海沟有关的应力和物质可能是萨摩亚恢复活力的熔岩的体积、持续时间和不寻常的富集组分的原因。复兴阶段可能完全暴露在萨瓦伊南侧一个500米深的峡谷中，该峡谷覆盖了2 Ma的历史。这个峡谷提供了一个前所未有的机会，可以品尝到萨摩亚复兴熔岩的长寿序列。需要来自这个峡谷的关键样本来确定汤加海沟的物质是否代表了萨摩亚恢复活力的熔岩，以及这种海沟特征是否随着时间的推移而增加。与夏威夷火山阶段相比，Savai‘i的复兴阶段似乎在体积上更大，寿命更长，地球化学更丰富。目前，返老还童的火山活动的范围和体积受到来自萨瓦伊的一块2 Ma粗面岩鹅卵石的限制，在同位素上与返老还童的熔岩难以区分，发现于一条排干峡谷的溪流中。为了更好地限制成分变化是否表明火山仍处于屏蔽阶段时来源成分发生了变化，需要对遗址进行更详细的采样。这将使两位职业生涯早期的PI(来自德克萨斯大学埃尔帕索的贾斯珀·康特和来自波士顿大学的马修·杰克逊)能够前往萨瓦伊，对该地区进行更全面的采样，以确定是否确实有必要对该岛进行长期的地球化学和岩石学研究。