Stable Vanadium Isotopes in the Igneous Rocks of the Shatsky Rise: IODP Expedition 324

点击翻译按钮获取中文摘要

We live in a constantly changing world. The surface of our Earth is in perpetual motion, with hard outer surface 'plates' moving about at rates of centimeters every year. It is the movement of these plates as they pull apart and collide with one another that causes most of the Earth's earthquakes and volcanic activity. On this dynamic surface, there is a much larger area covered by sea than by land. In some places, massive amounts of volcanic rocks make isolated undersea plateaus. We call these 'Large Igneous Provinces' or 'LIPs'. Why are they there? Some people think that they might have formed when plates broke apart and let the hotter interior of the Earth melt, making lava, and cooling to form the LIPs. Other people think that LIPs are related to something coming from much deeper and hotter in the Earth. An example of this is Hawaii, where there are no plate boundaries, but lots and lots of rock. These places are sometimes called 'hotspots'. How do we test a deep hotspot origin versus shallow plate origin for LIPs? There is a LIP in the Pacific Ocean called the Shatsky Rise that is almost 150 million years old and covers an area about the size of Japan. What makes this LIP special, however, is that it sits on an old plate boundary that is no longer active. One thing that makes 'hotspot' rocks like Hawaii different from rocks formed at mid-ocean ridges where plates break apart is their chemical compositions. Therefore the Integrated Ocean Drilling Program (IODP) is going on an expedition to drill into the Shatsky volcanic rocks. The samples that we bring back can then be analyzed to help us decide whether these rocks come from deep, hot 'plumes', or if they look more like mid-ocean ridge rocks that form where plates break apart. This is an exciting expedition. We first have to drill down through over 3000 meters of water to get to the rocks below. That is the length of almost 300 football pitches lined up together. The rocks that we bring back will let us discover what was happening to cause the formation of the Shatsky LIP over 100 million years ago. Whether Shatsky resulted from a deep hot plume, or was just the result of surface plate processes will tell us a great deal about how the interior of the Earth evolves and manages its heat budget.