Collaborative Research: The Transition from Rifting to Seafloor Spreading at the Western Tip of the Cocos-Nazca Rift

合作研究：科科斯-纳斯卡裂谷西端从裂谷到海底扩张的转变

• 批准号: 2128781
• 负责人: Ross Parnell-Turner
• 金额: $ 21.5万
• 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: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-04-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2128781&HistoricalAwards=false
• 关键词: Collaborative; Research; Transition; Rifting; Seafloor

A long-standing question in the study of mid-ocean ridges focuses on how they initiate and evolve. Our research cruise to the Galapagos Triple Junction in the eastern equatorial Pacific Ocean will characterize the transition from initial rifting to seafloor spreading, and the associated development of ridge axis segmentation. In this region, the western tip of the Cocos-Nazca Rift is breaking into ~0.5 Ma crust accreted on the east flank of the East Pacific Rise, and each stage in the transition from rifting to magmatic seafloor spreading can be studied. In order to examine along-axis changes as a function of distance from the rift tip, we will collect geophysical data on morphology, gravity and magnetic variations, rock samples for chemical analyses, and water column data for identifying hydrothermal activity. Our findings on oceanic rifting will complement on-going studies of these processes in continental rift settings. Our study area extends eastward from the site of initial rifting of the Cocos-Nazca spreading center to nucleation of magmatic spreading at the Hess Deep rift, to full magmatic spreading, thus exhibiting progressive stages in the initiation and development of rifting and segmentation. Multibeam bathymetry, gravity, and magnetic data will be collected to reconstruct the tectonic evolution from initial rifting through seafloor spreading, and in particular, changes in segment and offset characteristics as they develop. Chemical analysis of rock samples collected along the spreading axes and along flow lines will shed light on the evolution of mantle melting and melt delivery systems and their relationship to the tectonic segmentation. Graduate and undergraduate students (Duke and MIT/WHOI), will participate in the cruise and on-shore research, gaining valuable seagoing experience and learning to conduct collaborative research. In addition, we will develop activities based upon this work for use in a yearly science-immersion program for minority, middle school girls.

对中山脊的研究中的一个长期存在的问题集中在它们的发起和发展方式上。我们的研究巡游到东部赤道太平洋的加拉帕戈斯三连接处将表征从初始裂缝到海底扩散的过渡，以及脊轴分割的相关发展。在该地区，纳粹裂谷的西端正在东太平洋崛起的东侧面分裂成〜0.5 mA的壳，并且可以研究从裂谷到岩浆海底蔓延的每个阶段。 为了检查轴的变化，与距离裂谷尖端的距离的变化，我们将收集有关形态学，重力和磁化变化的地球物理数据，用于化学分析的岩石样品以及用于识别热液活性的水柱数据。我们关于海洋裂谷的发现将补充大陆裂谷环境中这些过程的持续研究。我们的研究区域从Cocos Nazca扩散中心的初始裂缝的地点向东延伸到Hess Deep Rift的Magmatic扩散成核，再到完全的岩浆扩散，从而在裂变和分段的开始和发展中表现出渐进阶段。将收集多微光测深，重力和磁数据，以重建从初始裂缝通过海底扩散，尤其是在开发时段和偏移特性的变化的构造演化。沿着扩散轴和流量线收集的岩石样品的化学分析将阐明地幔熔化和熔体递送系统的演变及其与构造分割的关系。 研究生和本科生（杜克大学和麻省理工学院/Whoi）将参加巡航和岸研究，获得宝贵的海上经验并学习进行合作研究。此外，我们将根据这项工作开发活动，以用于少数中学女孩的年度科学浸入式计划。

项目成果

Gravity Anomalies and Implications for Shallow Mantle Processes of the Western Cocos‐Nazca Spreading Center

重力异常及其对西科科斯·纳斯卡扩张中心浅地幔过程的影响

• DOI: 10.1029/2022gl102133
• 发表时间: 2023
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Zheng, Tingting;Lin, Jian;Schouten, Hans;Smith, Deborah K.;Klein, Emily;Parnell‐Turner, Ross
• 通讯作者: Parnell‐Turner, Ross