A Structural Analysis of Sediment Subduction Off Nicaragua: Why the 10Be Anomaly?

尼加拉瓜近海沉积物俯冲的结构分析：为什么会出现 10Be 异常？

• 批准号: 9521716
• 负责人: Michael Carr
• 金额: $ 2.81万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-09-01 至 1998-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9521716&HistoricalAwards=false
• 关键词: Structural; Analysis; Sediment; Subduction; Off

9521716 Carr This collaboration among researchers at University of Kansas, Washington University and Rutgers University addresses the geological question of how subduction at a continental margin builds or erodes the continent. More specifically, it addresses the question of how much ocean sediment is carried down beneath the continental margin compared to how much is plastered against the margin at the "subduction zone" offshore of Central America (Nicaragua and Costa Rica). The three investigators will carry out a field program sampling volcanoes along the west coast of Central America, and they will analyze these rocks for 10Be, an isotope of beryllium which is known from earlier work to vary from high levels in Nicaragua volcanoes to low levels in volcanoes from nearby Costa Rica. The high levels of 10Be are hypothesized to be a proxy indicator of the amount of young sediment which is scraped off of the oceanic crust and added to the continental margin as crust is subducted beneath the Middle America Trench. The study here will examine volcanic rocks of various ages from Nicaragua and Costa Rica, and it will include investigation of the time variability of the Nicaragua-Costa Rica 10Be transition. The project ties closely to planned scientific drilling by the NSF-supported, international Ocean Drilling Program ship JOIDES Resolution offshore Costa Rica in late 1996. That cruise will collect samples of sediments from beneath the continental slope to examine the direct evidence for subduction and accretion of sediments. A future drilling leg offshore Nicaragua to perform a similar study there is highly ranked by the JOIDES panels which set the JOIDES Resolution drilling program. The Nicaragua-Costa Rica region is of particular interest in this regard because the contrast in 10Be signal here is nearly as large as that observed worldwide. Because the high and low 10Be levels are so close geographically, it tightly constrains the number of variables aside from sediment accretion which may be involved. The project, therefore, can be expected to improve our understanding of the subduction process and the processes of continental growth from ocean crust subduction. ***

9521716卡尔堪萨斯大学、华盛顿大学和罗格斯大学的研究人员的这项合作解决了大陆边缘的俯冲如何建造或侵蚀大陆的地质学问题。更具体地说，它解决的问题是，与中美洲近海“俯冲区”(尼加拉瓜和哥斯达黎加)的边缘相比，有多少海洋沉淀物被带到大陆边缘以下。这三名调查人员将实施一个实地项目，对中美洲西海岸的火山进行采样，他们将分析这些岩石中的10Be，这是一种铍的同位素，根据早期的工作，从尼加拉瓜火山的高水平到附近哥斯达黎加火山的低水平，都有不同。高水平的10Be被认为是从洋壳中刮下来并随着地壳俯冲到中美洲海沟下而添加到大陆边缘的年轻沉淀物数量的替代指标。这项研究将研究尼加拉瓜和哥斯达黎加不同时代的火山岩，并将调查尼加拉瓜-哥斯达黎加10Be过渡的时间变异性。该项目与1996年底由美国国家科学基金会支持的国际海洋钻探计划船JOIDES Resolve在哥斯达黎加近海进行的科学钻探计划密切相关。这艘邮轮将从大陆斜坡下收集沉积物样本，以检查沉积物俯冲和吸积的直接证据。未来尼加拉瓜近海进行类似研究的钻探支线在JOIDES小组中排名很高，JOIDES小组制定了JOIDES决议钻井计划。尼加拉瓜-哥斯达黎加地区在这方面特别感兴趣，因为这里10Be信号的对比度几乎与全世界观测到的10Be信号的对比度一样大。由于10Be的高水平和低水平在地理上是如此接近，它严格限制了可能涉及的除沉积物积累之外的变量的数量。因此，该项目有望提高我们对俯冲过程和洋壳俯冲过程中大陆生长过程的理解。***