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

海底扩张中心？地球上的火山脊地球的构造板块分离并形成洋壳？又细分为？片段？代表着火山地壳形成的基本单位。板块通常有几十到几百公里长，并沿其长度形成沿着地壳，但厚度朝板块末端逐渐减小。这些断层段通常沿称为转换断层的剪切带相互沿着偏移。转换断层产生的疤痕，称为断裂带，追踪了板块的运动，是海洋盆地最长和最突出的特征之一。海底扩张中心火山地壳的分段性质造成了海底的大规模结构，并控制着来自浅地幔的物质流动、熔化和就位的方式，形成了构成地球表面三分之二的分层洋壳。然而，分段是海底扩张的一个动态方面，可以突然或逐步演变。片段可以形成，增长，缩短或通过与其他片段合并而被消除。是什么控制了这种进化，这一直是一个争论不休的话题。一些模型认为，下伏地幔的流动和温度的大规模变化是重要的。其他的模型则认为构造板块本身的运动是主要的控制因素。该项目将进行海洋地球物理调查，以研究是什么控制着冰岛南部北大西洋1 000公里长的海底扩张中心雷克雅内斯海脊的形成、演变和分段的消除。为了研究可能控制这一演变的因素，该项目将绘制板块运动突变后这些板块最初是如何形成的，以及它们是如何逐渐重新合并以消除沿着从冰岛开始的地幔熔融梯度的分段的。该项目将支持研究生的培训和教育，并将本科生和实习生带到研究船上进行海上体验和培训。将制作一部关于海岭分段演化的电影，以帮助解释板块构造的过程。雷克雅内斯海岭可能是当今地球上分段和转换断层系统形成和消除的最好例子。该项目将调查雷克雅内斯海脊的两个共轭侧翼地区，在那里形成了分段和转换断层，随后被消除。 调查范围将从北部的冰岛大陆架附近到南部的Bight断裂带，包括远离冰岛的地幔熔融的显著梯度。 该调查将使用多波束扫描和海底下声纳剖面图绘制海底的构造和火山结构图，使用拖曳式磁力计测量准确绘制确定地壳形成过程日期的磁线理图，并使用船舶重力计测量估计地壳厚度变化。这些数据将用于研究地幔熔融和板块运动变化如何影响大洋中脊的形成、演化和分割的消除，这些洋脊构成了整个海洋盆地的大规模构造和地壳结构。该奖项反映了NSF的法定使命，通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.