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

这项研究涉及世界上最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。榴辉岩与造山过程和俯冲作用有关。然而，我们对榴辉岩的地下分布知之甚少。我们研究的经典榴辉岩产地是挪威西部卑尔根弧，那里的榴辉岩化与沿断裂带和伴生片麻岩中的流体流动有关。榴辉岩是在相当高的压力下形成的，其深度可达100公里。榴辉岩的另一个假定作用是触发地壳物质再循环回到地幔，因为它们的密度很高。榴辉岩地体下的陆壳和壳幔边界的性质是什么，榴辉岩来自哪里，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。在美国国家科学基金会的探索研究小额赠款的帮助下，研究人员能够利用卑尔根大学的研究船进行陆地-海洋地震记录实验，以成像榴辉岩地体的深层结构。使用新的IRIS陆地地震记录仪，在16台海底地震仪和15台陆地地震记录仪上记录了海洋气枪产生的地震能量，产生了250公里长的剖面。由于它们独特的地震特征，研究人员希望成像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。结果应该提供有关造山和地壳形成的新信息，特别是山脉带中的地壳是如何增厚的，以及随后最深的地壳如何回到地表。

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.