Fabric Transitions in an oceanic detachment fault; IODP Expedition 357

在过去的50年里，我们已经知道欧洲和美洲一直在以每年约2厘米的速度分开，这是由于海底扩张的过程，在大西洋中脊海底产生了新的海洋地壳。这是板块构造的基本过程之一，塑造了我们赖以生存的星球。然而，由于我们不能使用使用电磁辐射的标准遥感技术来研究海底，在许多方面，我们对火星表面的了解比对大西洋海底的了解还要多！在过去的12年里，改进了的大西洋中脊声纳调查揭示了一种新的海底扩张模式，在这种模式下，板块分裂的很大一部分是由长期存在的凸向上分离断层的滑动所占据的，而不是主要由岩浆侵入所占据的。多达一半的大西洋海底可能是这样形成的。在IODP远征357中使用海底钻头进行的新钻探意味着我们比以往任何时候都有更好的海洋剥离断层样本。这些样品将使用扫描电子显微镜和电子探针技术进行研究，以寻找变形的数量，以及通过不同的套印蚀变组合来定位变形的方式。这样我们就能更好地理解这些断层是如何以及为什么会发生变形的。这些研究将与其他科学家的地球化学和同位素研究联系起来，以了解海水衍生流体在局部变形中的作用

e have known for the last 50 years that Europe and America have been moving apart at about 2cm/yr by processes of seafloor spreading that generate new oceanic crust at the submarine mid-Atlantic Ridge. This is one of the fundamental processes of Plate Tectonics, and has shaped the planet that we live on. Yet because we cannot use standard remote sensing techniques using electromagnetic radiation to study the seafloor, in many ways we know more about the surface of Mars than we do about the floor of the Atlantic!Over the last 12 years improved sonar surveys of the mid Atlantic Ridge have revealed a new mode of seafloor spreading where a significant part of the plate divergence is taken up by slip on long-lived, convex upward detachment faults, rather than mainly by magmatic intrusion. Up to half of the Atlantic seafloor may have formed in this way.New drilling using sea bottom drills in IODP Expedition 357 means that we have better samples of an oceanic detachment fault than ever before. These samples will be studied using scanning electron microscope and electron probe techniques to look for the amount of deformation and the way it is localised by different overprinting alteration assemblages. In this way we will understand better how and why deformation takes place on these faults. These studies will be linked to geochemical and isotopic studies by other scientists to understand the role of seawater derived fluids in localising deformation