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

近年来，越来越多的人认识到，在许多缓慢和超缓慢扩张的洋中脊上，海底扩张不是由火山作用调节的，而是由构造伸展作用调节的，这种伸展作用导致了海洋地壳的分离和下面地幔的挖掘。由此产生的结构被称为海洋核复合物；它们暴露了长寿命、低角度滑脱断层下盘的下地壳和上地幔岩石。查理-吉布斯断裂带中央裂谷的条件最适合洋核杂岩发育。查理-吉布斯断裂带是一个主要的断裂带，位于冰岛和亚速尔群岛（北纬52°至53°）之间，左旋约350公里，与大西洋中脊相接。它包括两个地震活跃的东西向转换断层山谷，由一条短脊隔开。预定的RV凯尔特探险队TOSCA （Charlie-Gibbs断裂带的构造海洋扩张）将于2018年5月13日至6月7日进行。这次巡航的主要目的是用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口的影响。该工作的一个组成部分是收集高分辨率反射地震数据，以便对填充查理-吉布斯断裂带槽的沉积序列进行成像。这些数据应通过基尔大学的高分辨率地震系统收集。地震测量的主要目标包括：1)调查洋中脊被破坏和掩埋的机制，2)绘制海沟深处的物质浪费沉积物，作为过去地震活动的记录，3)绘制基底地形的图像。我们对查理-吉布斯断裂带知之甚少，因此我们可以将任何数据和材料的恢复视为一次真正的探索，这将增加我们对这一关键区域的认识和理解。

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.