Formation and Elimination of Segmetation and Transform Faults on the Reykjanes Ridge

雷克雅内斯山脊分段和转换断层的形成和消除

• 批准号: 1756760
• 负责人: Fernando Martinez
• 金额: $ 67.99万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1756760&HistoricalAwards=false
• 关键词: Formation; Elimination; Segmetation; Transform; Faults

Seafloor spreading centers?the volcanic ridges where Earth?s tectonic plates separate and form oceanic crust?are subdivided into ?segments? that represent basic units of volcanic crustal formation. Segments are typically tens to hundreds of kilometers long and form crust along their length but with decreased thickness toward the segment ends. Often the segments are offset from each other along shear zones called transform faults. The scars produced by transform faults, referred to as fracture zones, trace out the motion of the plates and are among the longest and most prominent features of ocean basins. The segmented nature of volcanic crustal production on seafloor spreading centers creates the large-scale structure of the seafloor and controls the way in which material from the shallow mantle flows, melts and is emplaced to form the layered oceanic crust that forms two-thirds of the surface of the Earth. Yet segmentation is a dynamic aspect of seafloor spreading and can evolve abruptly or progressively. Segments can form, grow, shorten or be eliminated by merging together with other segments. What controls this evolution has long been a subject of debate and controversy. Some models propose that large-scale variations in flow and temperature of the underlying mantle are important. Other models propose a predominant control by the motion of the tectonic plates themselves. This project will conduct a marine geophysical survey to examine what controls the formation, evolution and elimination of segmentation on the Reykjanes Ridge, a 1000-km-long seafloor spreading center in the North Atlantic Ocean south of Iceland. In order to study what may be controlling this evolution this project will map how the segments first formed following the abrupt change in plate motion and how they progressively re-merged to eliminate segmentation along the gradient in mantle melting away from Iceland. The project will support the training and education of a graduate student in the research and bring undergraduates and interns out on the research vessel for at sea experience and training. A movie will be made of the ridge segmentation evolution to help explain the processes involved in plate tectonics.The Reykjanes Ridge is probably the best example of the systematic formation and elimination of segmentation and transform faults on Earth today. The project will survey two conjugate flank areas of the Reykjanes Ridge where segmentation and transform faults formed and were subsequently eliminated. The survey will span the area from near the Iceland shelf in the north to the Bight Fracture Zone in the south, encompassing the prominent gradient in mantle melting away from Iceland. The survey will use multibeam swaths and sub-bottom sonar profiles to map the tectonic and volcanic structure of the seafloor, towed magnetometer measurements to accurately map the magnetic lineations that date the crustal formation process, and ship gravimeter measurements to estimate crustal thickness changes. These data will be used to examine how variations in mantle melting and plate motion changes affect the formation, evolution and elimination of segmentation on mid-ocean ridges that frame the large-scale tectonic and crustal structure of entire ocean basins.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.

海底扩张中心——地球板块分离并形成洋壳的火山脊——被细分为“部分”。代表火山地壳形成的基本单位。节段通常有数十至数百公里长，并沿其长度形成地壳，但朝向节段末端厚度逐渐减小。通常，这些片段沿着称为转换断层的剪切带彼此偏移。由转换断层产生的疤痕（称为断裂带）追踪板块运动，是洋盆最长、最显着的特征之一。海底扩张中心火山地壳生产的分段性质创造了海底的大规模结构，并控制着来自浅地幔的物质流动、熔化和安置形成层状洋壳的方式，而洋壳构成了三分之二的海洋地壳。地球表面。然而，分割是海底扩张的一个动态方面，可以突然或渐进地演变。片段可以通过与其他片段合并在一起来形成、增长、缩短或消除。是什么控制了这种演变长期以来一直是争论和争议的话题。一些模型提出，地幔流动和温度的大规模变化很重要。其他模型提出了构造板块本身运动的主要控制。该项目将进行海洋地球物理调查，以研究是什么控制着雷克雅内斯海脊分割的形成、演化和消除。雷克雅内斯海脊是冰岛南部北大西洋长达 1000 公里的海底扩张中心。为了研究可能控制这种演化的因素，该项目将绘制板块运动突然变化后板块如何首先形成的图，以及它们如何逐渐重新合并以消除沿着远离冰岛的地幔融化梯度的板块。该项目将支持研究生的研究培训和教育，并让本科生和实习生登上研究船进行海上体验和培训。将制作一部关于山脊分段演化的电影，以帮助解释板块构造所涉及的过程。雷克雅内斯山脊可能是当今地球上分段和转换断层系统形成和消除的最佳例子。该项目将调查雷克雅内斯山脊的两个共轭侧翼区域，这些区域形成了分段和转换断层，随后被消除。 该调查将覆盖从北部冰岛陆架附近到南部海湾断裂带的区域，涵盖远离冰岛的地幔融化的显着梯度。 该调查将使用多波束和海底声纳剖面来绘制海底的构造和火山结构图，使用拖曳磁力计测量来准确绘制确定地壳形成过程日期的磁线，并使用船舶重力计测量来估计地壳厚度变化。这些数据将用于研究地幔熔化和板块运动变化的变化如何影响洋中脊分段的形成、演化和消除，洋中脊构成了整个大洋盆地的大尺度构造和地壳结构。该奖项反映了美国国家科学基金会的法定使命，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。

项目成果

The Iceland Microcontinent and a continental Greenland-Iceland-Faroe Ridge

冰岛微大陆和大陆格陵兰-冰岛-法罗海岭

• DOI: 10.1016/j.earscirev.2019.102926
• 发表时间: 2020-07
• 期刊: Earth-Science Reviews
• 影响因子: 12.1
• 作者: Foulger, Gillian R.;Doré, Tony;Emeleus, C. Henry;Franke, Dieter;Geoffroy, Laurent;Gernigon, Laurent;Hey, Richard;Holdsworth, Robert E.;Hole, Malcolm;Höskuldsson, Ármann;et al
• 通讯作者: et al

Mantle melting, lithospheric strength and transform fault stability: Insights from the North Atlantic

地幔熔化、岩石圈强度和转换断层稳定性：来自北大西洋的见解

• DOI: 10.1016/j.epsl.2021.117351
• 发表时间: 2022-02
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Martinez, Fernando;Hey, Richard
• 通讯作者: Hey, Richard

Reykjanes Ridge evolution: Effects of plate kinematics, small-scale upper mantle convection and a regional mantle gradient

雷克雅内斯海脊演化：板块运动学、小规模上地幔对流和区域地幔梯度的影响

• DOI: 10.1016/j.earscirev.2019.102956
• 发表时间: 2020-07-01
• 期刊: Earth-Science Reviews
• 影响因子: 12.1
• 作者: F. Martínez;R. Hey;Á. Höskuldsson
• 通讯作者: Á. Höskuldsson