Constructing a 1.5-million-year time series of magmatic and hydrothermal activity at the Juan de Fuca ridge

构建胡安德富卡海岭 150 万年的岩浆和热液活动时间序列

• 批准号: 2323102
• 负责人: Charles Langmuir
• 金额: $ 25.58万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-01-01 至 2027-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2323102&HistoricalAwards=false
• 关键词: Constructing; 1.5; million; year; time

Ocean ridges are the sites of 80% of Earth’s volcanism. These features emit carbon dioxide and exert an important control on the chemical composition of the oceans through deep sea hot springs. The volcanoes are aligned along the 60,000 kilometer long ocean ridge system, where plates spread apart to create the sea floor. Studies of these volcanoes have been restricted to recent volcanic activity, because as the plates spread apart the volcanoes are covered by sediment and become inaccessible. For this reason, there is a present day snapshot of ocean ridge volcanism, but little possibility to study how it varies with one of the most important parameters of Earth science—time. Many aspects of geological phenomena cannot be understood without knowledge of their variations through time, called “time series”. For example, time series of climate show that that Earth passes into and out of ice ages, and that global warming is happening. New discoveries now permit the construction time series for ocean ridges by taking sediment cores along transects perpendicular to ocean ridges. The cores will be used to study volcanic glass that is preserved in the sediment. In particular, the time series will allow tests of the hypothesis that ice age cycles may influence cycles of ocean ridge volcanism and associated hydrothermal activity. Cruises to the Juan de Fuca ridge just off the coasts of Oregon and Washington will permit time series of one million years or more to be obtained for the first time. This project will provide support for undergraduate students to participate in the research cruise. In addition, the project will support an international conference and contribute to a museum exhibit at the Harvard Museum of Natural History.The European Research Council (ERC) has awarded a research grant for the scientific analyses to investigate time-series of ridge processes through a systematic coring program along transects perpendicular to the Juan de Fuca Ridge. The ERC grant to four principle investigators (three at GEOMAR in Germany and one at Harvard) did not include funding for collecting the sediment cores at sea. This proposal funds the ship time to obtain the necessary samples. A preliminary 11 day leg with the AUV SENTRY will obtain sediment thickness as well as high resolution bathymetry to guide the coring. Then, a 21 day leg will carry out 70 cores on three transects, two to the west of the ridge at different distances from the ridge transform intersection, and one to the east. The cruise would produce the first continuous, co-registered time series of glass compositions, hydrothermal activity and bathymetry over the 0 to 1Ma time scales. Time-series of basalt and sediment compositions at ocean ridges have been inaccessible because sea floor is rapidly covered by sediment and basalts are altered or have low potassium contents, making dating problematic. The 104-106 year time scale in particular is central for testing a host of hypotheses for mid-ocean ridges, from the existence and time scales of tectonic/magmatic cycles, to the continuity of magma chambers and hydrothermal systems, to possible relationships between glacial cycles and ridge processes since the Pleistocene. Preliminary data from cores near the ridge axis show that each core is likely to preserve 50-100ka time series of fresh glasses with interesting variations. Closely spaced cores will be used to obtain overlapping time series with the aim of constructing a long a continuous time series back to one million years. The Juan de Fuca region has the benefit of previous cores that show robust age models are possible. The program includes sediment geochemistry for age models and hydrothermal activity, major and trace elements of glasses, radiogenic isotope analyses, volcanological evaluation, modeling of mantle melting, and quantitative statistical and time-series modeling. This program holds the promise of opening new frontiers of time and methodology that may have far-reaching implications for the investigation and understanding of ocean ridges. Broader impacts include training multiple graduate students and post-docs in state of the art techniques, education and participation of Harvard undergraduates on the cruises, an international conference on interactions between glacial cycles and solid earth processes, and an exhibit at the Harvard Natural History Museum which receives more than 250,000 visitors per year including many K-12 students.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.

海洋脊是地球上 80% 的火山活动的场所，这些特征排放二氧化碳，并通过深海温泉对海洋的化学成分产生重要的控制作用。火山沿着 60,000 公里长的海洋脊系统排列。对这些火山的研究一直是最近的火山活动，因为随着板块的扩张，火山被沉积物覆盖，因此无法进入。原因是，现在有洋脊火山活动的快照，但研究它如何随着地球科学最重要的参数之一——时间的变化而变化的可能性很小，如果不了解地质现象随时间的变化，就无法理解它们。例如，气候时间序列表明地球进入和退出冰河时代，并且全球变暖正在发生，现在新的发现允许通过沿垂直断面获取沉积物核心来构建海脊时间序列。到海洋这些岩心将用于研究沉积物中保存的火山玻璃，特别是，该时间序列将允许检验冰河时代循环可能影响胡安岛火山活动循环和相关热液活动的假设。俄勒冈州和华盛顿州海岸附近的德富卡海岭将首次获得一百万年或更长时间的时间序列，该项目将为本科生参与研究巡航提供支持。支持一个国际会议，并为哈佛自然历史博物馆的博物馆展览做出贡献。欧洲研究理事会 (ERC) 授予了一项研究经费，用于科学分析，通过沿着垂直于地平线的横断面的系统取芯程序来研究山脊过程的时间序列。 Juan de Fuca Ridge。ERC 向四名主要研究人员（三名来自德国 GEOMAR，一名来自哈佛大学）提供的资助不包括用于收集海上沉积物岩心的资金 A 初步 11。日腿使用 AUV SENTRY 获取沉积物厚度以及高分辨率水深测量数据来指导取芯，然后，为期 21 天的航程将在三个横断面上进行 70 个岩心采集，其中两个位于山脊以西，距山脊变换交叉点的距离不同。一个在东边，该航行将产生第一个连续的、共同记录的玻璃成分、热液活动和水深测量的时间序列，范围为 0 到 1Ma 的时间序列。海脊处的玄武岩和沉积物成分一直无法获取，因为海底很快就被沉积物覆盖，玄武岩发生了改变或钾含量较低，这使得 104-106 年的时间尺度对于检验许多假设至关重要。大洋中脊，从构造/岩浆循环的存在和时间尺度，到岩浆房和热液系统的连续性，到自古以来冰川循环和洋脊过程之间可能的关系更新世靠近山脊轴的岩心的初步数据表明，每个岩心可能保存有有趣变化的 50-100ka 时间序列，紧密间隔的岩心将用于获得重叠的时间序列，目的是构建一个长的连续的时间序列。胡安德富卡地区的时间序列显示出强大的年龄模型是可能的，该项目包括年龄模型和热液活动、主要和微量的沉积物地球化学。该项目有望开辟时间和方法的新领域，这可能对调查和理解产生深远的影响。更广泛的影响包括培训多名研究生和博士后最先进的技术、哈佛本科生的教育和参与游轮、关于冰川循环与固体地球过程之间相互作用的国际会议以及在哈佛自然历史博物馆每年接待超过 250,000 名游客，其中包括许多 K-12 学生。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。