Tectonic Ocean Spreading at the Charlie-Gibbs Fracture Zone (TOSCA)

近年来，人们越来越认识到，在许多缓慢和超缓慢扩张的大洋中脊，海底的扩张不是由火山作用提供的，而是由导致洋壳解剖和下伏地幔剥离的构造伸展所调节的。由此形成的构造被称为大洋核杂岩；它们暴露在长寿、低角度拆离断层的下部地壳和上地幔岩石中。查理-吉布斯断裂带中央裂谷的条件最有利于大洋核杂岩的发育。查理-吉布斯断裂带是位于冰岛和亚速尔群岛(北纬52°至53°)之间的大西洋中部海脊向左偏移约350公里的主要断裂带。它由两个地震活跃的东西向转换断层谷组成，中间隔着一条短山脊。预定的房车凯尔特探险者托斯卡(查理-吉布斯断裂带的构造洋扩张)将于2018年5月13日至6月7日举行。这次巡航的主要目的是以跨学科的方法研究查理-吉布斯断裂带长期不对称扩张和相关热液喷发的影响。这项工作的一个组成部分是收集高分辨率反射地震数据，以便对查理-吉布斯断裂带海槽中的沉积序列进行成像。这些数据应该通过基尔大学的高分辨率地震系统收集。地震测量涉及的主要目标包括：1)调查大洋中脊被摧毁并掩埋在远离扩张中心的地方的机制；2)绘制海槽中深海海底大量废弃沉积物的地图，作为过去地震活动的记录；3)对基底地形进行成像。查理-吉布斯断裂带是如此鲜为人知，以至于我们可以将任何数据和材料的恢复视为一次真正的探索，将增加我们对这一关键地区的了解和理解。

In recent years, there has been a growing realisation that seafloor spreading at many slow and ultra-slow spreading mid-ocean ridges is accommodated not by volcanism, but by tectonic stretching resulting in the dissection of the oceanic crust and exhumation of the underlying mantle. The resulting structures are known as oceanic core complexes; they expose lower crustal and upper mantle rocks in the footwalls of long-lived, low-angle detachment faults.Conditions at the central rift of the Charlie-Gibbs Fracture Zone have the optimum attributes for the development of oceanic core complexes. The Charlie-Gibbs Fracture Zone is a major fracture zone that offsets the Mid-Atlantic Ridge approximately 350 km left-laterally, between Iceland and the Azores (52° to 53° N). It comprises two seismically active E-W transform-fault valleys separated by a short ridge. The scheduled RV Celtic Explorer Expedition TOSCA (Tectonic Ocean Spreading at the Charlie-Gibbs Fracture Zone) will take place from May 13th to June 7th 2018. The main objective of this cruise is to study the effects of a long-lived asymmetric spreading and associated hydrothermal venting at the Charlie-Gibbs Fracture Zone in an interdisciplinary approach. An integral part of the work is the collection of high-resolution reflection seismic data in order to image the sedimentary sequence infilling the Charlie-Gibbs Fracture Zone troughs. These data should be collected by means of the high-resolution seismic system of Kiel University. Main objectives addressed by seismic surveying include i) the investigation of the mechanism by which mid-ocean ridges get destroyed and buried away from the spreading centres, ii) to map deep-seafloor mass wasting deposits in the troughs as a record of past seismic activity, and iii) to image the basement topography. The Charlie-Gibbs Fracture Zone is so poorly known that we can look at the recovery of any data and material as a true exploration that will increase our knowledge and understanding of this critical region.