Seismic Study of Deep Eclogitic-Granulitic Crust and Moho in the Bergen Arcs, Norway

挪威卑尔根弧深部榴辉岩-麻粒岩地壳和莫霍面的地震研究

• 批准号: 0409955
• 负责人: Scott Smithson
• 金额: --
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409955&HistoricalAwards=false
• 关键词: Seismic; Study; Deep; Eclogitic; Granulitic

This study involves seismic imaging of eclogite at one of the world's classic localities. Eclogite is a unique rock type because of its physical properties such as high density, which is a response to abnormally high pressure. Eclogite is related to processes of mountain building and associated subduction. Yet we know little about the subsurface distribution of eclogites. The classic eclogite localities that we study are in the Bergen Arcs of western Norway where eclogitization is related to fluid flow along fault zones and regionally in the associated gneisses. The eclogites are formed at such high pressures that they correspond to a depth of up to 100 km. Another presumed role of eclogites is as a trigger for recycling of crustal material back down into the mantle because of their high density. What is the nature of continental crust and crust-mantle boundary beneath an eclogite terrane, where do the eclogites come from and how do they get there? What was the role of deep fluids in eclogite formation? These are the problems that we propose to clarify. With an NSF Small Grant for Exploratory Research, the investigators were able to utilize the University of Bergen research vessel for a combined land-marine seismic recording experiment to image the deep structure of the eclogite terrane. Seismic energy from marine airguns was recorded on 16 ocean bottom seismometers and 15 seismic recorders on land using new IRIS land seismic recorders to yield 250 km long profiles. Because of their unique seismic characteristics, the researchers expect to image eclogite bodies throughout the crust, deep fluid passageways that promoted eclogitization, and faults that brought eclogites up to the surface. Results should provide new information on mountain building and crustal formation, specifically how crust in mountain belts over-thickens and subsequently how deepest crust comes back up to the surface.

这项研究涉及在世界上一个经典的地点之一的榴辉岩的地震成像。榴辉岩是一种独特的岩石类型，因为它的物理性质，如高密度，这是对异常高压的反应。地壳运动与造山运动和相关的俯冲作用有关。然而，我们对榴辉岩的地下分布知之甚少。我们研究的典型榴辉岩地点是在挪威西部的卑尔根弧，榴辉岩化与流体流动有关，沿着断层带和区域性的相关片麻岩。榴辉岩是在如此高的压力下形成的，它们对应于高达100公里的深度。榴辉岩的另一个假定的作用是，由于其高密度，它是地壳物质再循环回到地幔的触发器。榴辉岩下的陆壳和壳幔边界的性质是什么？榴辉岩从何而来？它们是如何到达那里的？深部流体在榴辉岩形成中的作用是什么？这些都是我们建议澄清的问题。在国家科学基金会探索性研究小额赠款的帮助下，调查人员能够利用卑尔根大学的研究船进行陆地-海洋联合地震记录实验，对榴辉岩的深层结构进行成像。16个海底地震仪和15个陆地地震记录仪记录了海洋气枪的地震能量，使用新的IRIS陆地地震记录仪记录了250公里长的剖面。由于它们独特的地震特征，研究人员希望对整个地壳的榴辉岩体、促进榴辉岩化的深部流体通道以及将榴辉岩带到地表的断层进行成像。研究结果应该提供有关造山和地壳形成的新信息，特别是山区地壳如何增厚，以及最深的地壳如何回到地表。