Geochemical Analysis and Integrated Modelling of Basalt Samples from V-Shaped Ridges of North Atlantic Ocean

北大西洋 V 形海脊玄武岩样品的地球化学分析和综合模拟

• 批准号: NE/W007150/1
• 负责人: Nicholas White
• 金额: $ 3.21万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FW007150%2F1
• 关键词: Geochemical; Analysis; Integrated; Modelling; Basalt

Deep within the Earth's interior underneath Iceland there sits a gigantic hot upwelling or plume. This plume is the biggest on Earth and has been in existence for about sixty million years. It has had a profound effect upon the shape of the seabed beneath the North Atlantic Ocean which is about two kilometres shallower than it should be. The existence of this plume also explains why the British Isles stick up in the air. There is considerable interest in the way these hot plume change over time. Luckily, the North America tectonic plate and the European tectonic plate are spreading apart exactly on top of the Icelandic plume. As a result, we have a really convenient window into the way in which this particular plume evolves over time. Changes within the plume are faithfully recorded by thickened trails of crust along the ocean floor. This summer, a group of scientists will sail into the middle of the Atlantic Ocean south of Iceland and drill holes into these crustal trails. These holes will be about ten centimetres across and hundreds of metres deep. The samples of lava recovered by this complex operation provide an invaluable record of the way temperature has changed through time deep within the plume's interior. In that sense, we will be using the rock samples as plume thermometers. Once the samples are recovered, we will bring them back to the lab and measure concentrations of familiar elements such as iron, potassium, lead and many others. These concentrations will be used to aid computer modeling of deep temperature changes. In the end, we will be able to take the 'pulse' of the Icelandic plume over many millions of years. The final piece of the jigsaw puzzle concerns how plume activity has made the seabed around Iceland bob up and down over long periods of time. This bobbing about has affected how deep water currents flow southwestward from the Greenland-Norwegian Sea into the rest of the Atlantic Ocean. It is a bit like a canal lockgate mechanism where the ridge between Greenland and Scotland that crosses Iceland moves up and down. This motion affects how much deep water escapes into the rest of the Atlantic Ocean. Fossil bugs that once lived on the seabed and which are can be sampled in exactly the same hole that are drilled into lava help us to measure how much deep water flows across the canal lockgate at different times in the past. This trick works because the bugs once lived in deep water and made their shells from the tiny amounts of calcium carbonate dissolved in that deep water. When the flow of deep water shuts on and off, the bugs inadvertently record these changes in the composition of their shells. Hey Presto! Our ultimate goal is to link the bobbing of the seafloor which changes deep water flow with the throbbing pulse of the hot plume.In this way, we hope to show how processes going on deep within the Earth influence ocean currents which in turn control our climate.

在地球内部深处的冰岛之下，有一个巨大的热上升流或羽流。这个羽流是地球上最大的，已经存在了大约6000万年。它对北大西洋海底的形状产生了深远的影响，比应有的深度浅了大约两公里。这种烟羽的存在也解释了为什么不列颠群岛在空中耸立。人们对这些热羽随时间变化的方式相当感兴趣。幸运的是，北美构造板块和欧洲构造板块正好在冰岛地幔柱的顶部分开。因此，我们有一个非常方便的窗口来了解这种特殊的烟羽随时间的演变方式。沿着沿着洋底增厚的地壳痕迹忠实地记录了羽流内部的变化。今年夏天，一组科学家将航行到冰岛南部的大西洋中部，在这些地壳痕迹上钻孔。这些洞大约有10厘米宽，几百米深。通过这种复杂的操作回收的熔岩样本提供了一个宝贵的记录，记录了羽流内部深处温度随时间变化的方式。从这个意义上说，我们将使用岩石样本作为羽流温度计。一旦样品被回收，我们将把它们带回实验室，并测量铁、钾、铅等熟悉元素的浓度。这些浓度将用于帮助计算机模拟深部温度变化。最终，我们将能够在数百万年的时间里掌握冰岛羽流的“脉搏”。拼图的最后一块是关于羽流活动如何使冰岛周围的海床在很长一段时间内上下波动。这种波动影响了从格陵兰-挪威海向西南流入大西洋其余部分的深水洋流。这有点像一个运河闸门机制，格陵兰岛和苏格兰之间的山脊穿过冰岛上下移动。这种运动会影响到有多少深水逃逸到大西洋的其余部分。曾经生活在海床上的化石昆虫可以在熔岩中钻的同一个洞里取样帮助我们测量过去不同时间有多少深水流过运河闸门。这个把戏之所以有效，是因为这些虫子曾经生活在深水中，它们的外壳是由溶解在深水中的微量碳酸钙制成的。当深水的流动时断时续时，这些虫子会不经意地记录下它们外壳成分的变化。嘿，普雷斯托！我们的最终目标是将海底的起伏变化与热羽流的脉动联系起来。通过这种方式，我们希望展示地球深处发生的过程如何影响洋流，从而控制我们的气候。