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

• 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

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.

洋中脊海底扩张形成海洋岩石圈是地球上的基本地质过程之一。最重要但最棘手的问题之一是了解洋脊下的岩浆库如何生成下地壳，特别是在快速扩张的情况下。下地壳的辉长岩通常无法获取，但由于科学海洋钻探探险以前成功地到达了太平洋超快扩张速率地壳内的一个独特地点，现在可以取样。此前对综合大洋钻探计划（IODP）1256号站点的一系列三次考察已经穿透了1500米的上地壳层，使新的考察队能够首次对下地壳进行广泛的采样。这将在IODP Expedition 335期间实现，该探险将返回1256站点进一步加深该洞，希望提供一套独特的下大洋地壳样本，从而对海底扩张所涉及的岩浆和构造过程产生独特的见解。作为这项工作的一部分，将从回收的岩芯碎片中收集古地磁数据，这些数据对了解该地点下地壳的演变至关重要。这些数据将提供有关我们预计会遇到的辉长岩的磁化方向和强度的宝贵信息，提供一个标记，可用于推断影响该地点的构造旋转量，并深入了解下地壳岩石对海洋磁异常的贡献。此外，我们打算结合使用古地磁数据和井壁内部的地球物理图像来重新定向通过钻探回收的一些岩心块，从而允许将其他方向属性（例如结构数据）恢复到正确的地理参考框架。

项目成果

Magmatic accretion and thermal convection at the sheeted dike complex-gabbro boundary in superfast spreading crust, ODP Hole 1256D

超快扩张地壳片状岩脉杂岩-辉长岩边界处的岩浆增生和热对流，ODP 孔 1256D

• DOI: 10.1016/j.tecto.2015.08.023
• 发表时间: 2015
• 期刊: Tectonophysics
• 影响因子: 2.9
• 作者: Trela J