Accomplishment Based Renewal: The Architecture and Tectonics of the Ultraslow Spreading SW Indian and Gakkel Ridges

基于成就的更新：超慢速扩张的西南印度洋山脊和加克尔山脊的建筑和构造

• 批准号: 2114652
• 负责人: Richard Murray
• 金额: $ 99.68万
• 依托单位: Woods Hole Oceanographic Institution
• 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: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2114652&HistoricalAwards=false
• 关键词: Accomplishment; Based; Renewal; Architecture; Tectonics

This project will photograph, describe, and curate a large collection of oceanic crustal rocks from two ultraslow spreading ridges – the Gakkel Ridge (GR) in the Arctic Ocean and the Southwest Indian Ridge (SWIR) in the oceans that surround southern Africa. These ridges represent two distinctly different ultraslow spreading centers with the SWIR having a large number of fracture zones and hot spot activity while the GR has no transform faults and no evidence of hotspots. The rock collection will be integrated with previously collected geophysical data (magnetics, gravity, multibeam maps and seismic data) and newly acquired electron microprobe data from a subset of representative samples to estimate chemical compositions of the crust and mantle rocks. Together these will be used to estimate the thickness and architecture of the ocean crust and assess the amount of interaction they have with seawater and the underlying mantle. This work provides future researchers with on-line access to the entire collection of slow-spreading crustal rocks collected over the past 50 years. This project is a three year research program with several important goals. First, it will provide a photo-archive of thousands of seafloor crustal samples previously collected and housed at Woods Hole Oceanographic Institute. As part of this archival, it will allow researchers to synthesize descriptive data with archives of geophysical, magnetic, and geochemical data available in this region. New chemical compositional data will be added through electron microprobe analysis on a subset of representative crustal rocks from two ultraslow spreading ridges – the SW Indian Ridge (SWIR) and the Gakkel Ridge. This study will also integrate petrological and geochemical data with the extensive collection of multibeam maps of the SWIR and existing seismic, magnetics, and gravity data, and the uniquely comprehensive rock sampling performed along the ridge axis and rift mountains. The goal is to test the hypothesis that spreading centers along the Ridge are not supported by deep mantle plumes, but by the depleted residues of hydrous mantle melting beneath ancient island arcs and back arc basins related to the closure of the Mozambique Ocean in the Neoproterozoic. It further attempts to determine the origin of the associated hotspots, and how they are interacting with the SWIR as evidenced by the geochemistry and petrology of the modern ridge, and the off-axis bathymetry and magnetics across the seafloor to the hotspots and their conjugate positions. In addition, a parallel synthesis of the ultraslow spreading Gakkel Ridge will be completed providing the first detailed analysis of the geology of the ridge based on the 190 successful dredge and rock core stations along the 1,000 km stretch mapped along it during the AMORE Expedition. At present analysis of the AMORE data, including the bathymetry, has been largely limited to the isotopic, major and trace element geochemistry of the lavas, and peridotites. This ridge is a near perfect contrast to the Ultraslow SWIR. The Gakkel Ridge has no transform faults (the SWIR has many) thus providing a unique opportunity to examine the causes and extent of geochemical variability and magmatic segmentation in their absence, and what features are due to ultraslow spreading and which to transforms. Finally, the funding will allow the researcher to finish a detailed manuscript comparing the dike-gabbro transitions at fast, slow and ultraslow-spreading ridges, providing direct evidence for a shallow melt lens at the dike-gabbro transition at the former, and its general absence at the latter.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.

该项目将拍摄，描述和策划大量从两个Ultraslow传播山脊的海洋地壳岩石 - 北极海洋中的Gakkel Ridge（GR）和南非周围海洋中的西南印度山脊（SWIR）。这些山脊代表了两个截然不同的Ultraslow扩展中心，SWIR具有大量的断裂区域和热点活动，而GR没有变换故障，也没有热点的证据。岩石收集将与先前收集的地球物理数据（磁性，重力，多束图和地震数据）集成在一起，并将来自代表性样品子集的新获得的电子微探针数据集成，以估计地壳和地幔岩石的化学组成。这些将共同用于估计海角的厚度和结构，并评估它们与海水和基础地幔的相互作用量。这项工作为未来的研究人员提供了在线访问过去50年收集的整个慢速地壳岩石集合的访问。该项目是一个三年的研究计划，具有多个重要目标。首先，它将提供以前在伍兹霍尔海洋学院收集和安置的数千个海底地壳样品的照片。作为该档案的一部分，它将允许研究人员与该区域可用的地球物理，磁性和地球化学数据的档案合成描述性数据。将通过电子微探针分析添加新的化学成分数据，以对来自两个Ultraslow扩散山脊的一部分代表性地壳岩石 - SW Indian Ridge（SWIR）和Gakkel Ridge。这项研究还将将岩石学和地球化学数据与SWIR的多束图以及现有的地震，磁性和重力数据以及沿山脊轴和裂谷山脉进行的独特综合岩石采样集成。目的是检验以下假设：沿着山脊的扩散中心不受深壁羽的支持，而是由在古岛弧下和背部弧形贝斯在Neoperoteroterocic中关闭的含水层融化的深度弹性。它进一步尝试确定相关热点的起源，以及它们如何与SWIR相互作用，这是现代山脊的地球化学和岩石学的证明，以及横跨海底的轴测测深和磁化剂，与热点及其共轭位置所证明。此外，将完成对超速散布的Gakkel Ridge的平行综合，从而在Amore Expedition期间，基于190个成功的挖掘机和岩石岩心站，对山脊的地质进行了首次详细分析。包括测深的数据在很大程度上仅限于熔岩的同位素，主要和痕量元素地球化学和橄榄岩。这个山脊与Ultraslow Swir几乎是完美的对比。 Gakkel Ridge没有变换故障（SWIR有很多），因此提供了一个独特的机会来检查地球化学变异性和岩浆分割的原因和程度，并且在它们不在的情况下，以及哪些特征是由于Ultraslow扩散以及转化的变换。最后，资金将使研究人员能够完成一份详细的手稿，以快速，缓慢和超大型的伸展山脊进行比较，从而直接证明了前者的Dike-Gabbro过渡的浅层晶状体的直接证据，并在后来的一般缺乏范围内，通过Infortifor Intortional in Infortional of Supportion。影响审查标准。