Collaborative Research: Magmatic and Mechanical Extension of the Challenger Deep Forearc Segment: Insights into Subduction Initiation

合作研究：挑战者号深弧前段的岩浆和机械延伸：对俯冲起始的见解

• 批准号: 2054495
• 负责人: Emily Chin
• 金额: $ 11.35万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2054495&HistoricalAwards=false
• 关键词: Collaborative; Research; Magmatic; Mechanical; Extension; Collaborative; Research; Magmatic; Mechanical; Extension

The sinking of oceanic lithosphere in subduction zones drives the fundamental Earth process of plate tectonics. To understand plate tectonics, it is important to understand how new subduction zones form. This project will study a new example of subduction initiation in the Western Pacific near the Challenger Deep and Guam USA using a research vessel and a tethered remotely-operated vehicle (ROV) capable of working down to 3 miles deep. Investigators will study 9 sites during a 23-day expedition. Collected samples will be subjected to several laboratory tests. The team of young and senior geoscientists will provide important training of new marine geoscientists and an unusually strong internet connectivity will allow a handicapped geoscientist to participate in expeditionary science.How new subduction zones form is a key topic of geoscientific research that requires identifying and studying active examples. Investigators in this study will conduct a novel interdisciplinary marine geologic study of a newly recognized active example of subduction initiation in the Western Pacific. They will study the Challenger Deep Forearc Segment (CDFS) located in the inner trench wall of the Mariana Trench SW of Guam. ROV Jason/Medea will be used to study 9 sites distributed along 220 km of the CDFS above 6500m water depth. They will sample and examine a full cross-section of oceanic crust and upper mantle rocks during a 23-day marine expedition. The CDFS formed by extension associated with opening of the Mariana Trough backarc basin over the past 5 Ma or so, suggesting an extension rate of ~40mm/y. Such strong extension in a forearc is very unusual and provides an opportunity to investigate a wide range of important tectonic and magmatic processes that will advance understanding of the role of water in lithospheric extension and how new subduction zones form, at the same time explore a new region for Moho exposures and forearc seeps and vent communities. The investigators hypothesize that, because subduction is more advanced in the eastern CDFS than in the west, there will be measurable along-strike changes in water contents, trace element compositions, rock fabrics, thermal histories, and oxygen fugacity in rocks from the mantle, lower crust, and upper crust and perhaps the distribution of forearc venting. They expect to collect ~450 samples of young basalts, Eocene crust, and upper mantle and will study a subset of these petrographically, for mineral abundances and compositions, for major and trace element compositions, for radiometric ages, for mantle fabrics, and for water concentrations in mantle and young fresh basaltic glass. The team of young and senior geoscientists will provide important training of new marine geoscientists and an unusually strong internet connectivity will allow a handicapped geoscientist to participate in expeditionary science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

俯冲带中海洋岩石圈的下沉驱动了板块构造的基本地球过程。要了解板块构造学，重要的是要了解新的俯冲区如何形成。该项目将使用研究船和一个束缚的远程操作车（ROV）研究西太平洋附近的西太平洋俯冲启动的新例子，能够工作至3英里。调查人员将在23天的探险中研究9个地点。收集的样品将经过几项实验室测试。 年轻和高级地球科学家团队将对新的海洋学家进行重要培训，并且异常强大的互联网连接将使残障的地球科学家参与远征科学。新的俯冲区形式如何是地球科学研究的关键主题，需要识别和研究积极的例子。这项研究中的研究人员将对西太平洋的新认可的俯冲启动例子进行新的跨学科海洋地质研究。 他们将研究位于关岛Mariana Trench SW内部沟渠壁上的Challenger Deep前臂段（CDF）。 ROV Jason/Medea将用于研究9个位点，该地点沿着6500m水深高于6500m的CDF分布。 他们将在23天的海洋探险中进行采样并检查Oceanic Crust和上地幔岩石的完整横截面。与在过去5 mA左右开放的玛丽安娜槽后退盆地相关的延伸相关的CDF形成，表明延伸速率约为40mm/y。 前臂中如此强烈的陈述非常不寻常，并提供了一个机会来研究各种重要的构造和岩浆过程，这些过程将促进对水在岩石圈延伸中的作用以及如何形成新的俯冲区，同时探索新​​的俯冲区，同时探索了Moho曝光和前肢和前肢和通知社区的新区域。 研究人员假设，由于俯冲在东部CDF中比西方更先进，因此在水含量，痕量元素成分，岩石织物，热历史和氧气散发的岩石中，将在岩石，下壳，下壳以及上甲壳和可能的前肢发射的岩石中进行可测量的变化。 他们预计将收集约450个年轻的玄武岩，始新世外壳和上地幔样品，并将在这些岩石学上研究这些子集，以用于矿物质的丰度和成分，以用于主要和痕量元素成分，用于辐射年龄，用于地幔织物，以及用于地幔和年轻的新鲜底层玻璃的水。年轻和高级地球科学家的团队将对新的海洋学家进行重要培训，异常强大的互联网连接将使残障的地球科学家能够参与远征科学。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力和更广泛影响的评估来通过评估来支持的，这是值得的。