Superfast Spreading Rate Crust 4: Magnetism of the lower oceanic crust

超快扩张速率地壳 4：下洋壳的磁性

基本信息

批准号：
NE/J005622/1
负责人：
Antony Morris
金额：
$ 1.58万
依托单位：
Plymouth University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ005622%2F1
关键词：
Superfast Spreading Rate Crust Magnetism

项目摘要

Generation of ocean lithosphere by seafloor spreading at mid-ocean ridges is one of the fundamental geological processes operating on Earth. One of the most important yet most intractable problems is to understand how the magma reservoir beneath ridges generates the lower crust, especially at fast spreading rates. Gabbroic rocks from the lower crust are normally inaccessible, but are now within reach of sampling as a result of the previous successes of scientific ocean drilling expeditions to a unique site within superfast spreading rate crust in the Pacific Ocean. A series of three previous expeditions to Integrated Ocean Drilling Program (IODP) Site 1256 have penetrated through 1500m of upper crustal layers, allowing a new expedition to extensively sample the lower crust for the first time. This will be acheived during IODP Expedition 335 which will return to Site 1256 to deepen the hole still further, hopefully providing a unique suite of lower oceanic crustal samples that will yield unique insights into magmatic and tectonic processes involved in seafloor spreading. As part of this endeavour, palaeomagnetic data will be collected from recovered core pieces and will be critical to understanding the evolution of the lower crust at this site. These data will provide valuable information on the direction and strength of magnetization locked into the gabbroic rocks we expect to encounter, providing a marker that can be used to infer the amount of tectonic rotation that has affected the site and insights into the contribution that lower crustal rocks make to marine magnetic anomalies. In addition, we intend to use a combination of palaeomagnetic data and geophysical images of the inside of the borehole wall to reorient some of the core pieces recovered by drilling, thereby allowing other directional properties (e.g. structural data) to be restored to the correct geographical reference frame.

海底散布在海山山脊上的海洋岩石圈是地球上运行的基本地质过程之一。最重要但最棘手的问题之一是了解山脊下面的岩浆储层如何产生较低的外壳，尤其是在快速扩散速率下。来自下层外壳的甘质岩石通常是无法访问的，但由于先前的科学海洋钻井探险队在太平洋超级散布速率地壳中取得了独特的地点，因此现在已经取得了采样的范围。一系列以前的三个集成海洋钻井程序（IODP）站点的探险队已经穿透了1500m的上层地壳层，从而使新的探险队首次广泛采样了下层外壳。这将是在IODP Expedition 335期间实现的，该探险队将返回现场1256，以进一步加深孔，希望提供一套独特的下海洋地壳样品套件，这些样品将产生对岩浆和构造过程中涉及海底传播的岩浆和构造过程的独特见解。作为这项工作的一部分，将从回收的核心碎片中收集古磁数据，对于理解该地点下层地壳的演变至关重要。这些数据将提供有关我们期望遇到的磁化磁化强度方向和强度的有价值的信息岩石使海洋磁异常。此外，我们打算将孔洞墙内部的古磁数据和地球物理图像组合使用，以重新定位通过钻孔恢复的一些核心部分，从而允许将其他方向性（例如结构数据）恢复到正确的地理位置参考框架。