Site Survey for IODP Proposal 646-Full:- Icelandic V-Shaped-Ridges

这一紧急赠款提案旨在利用现场调查机会，支持英国领导的IODP钻探北大西洋基底的提案。去年10月，史蒂夫·琼斯（都柏林的Trinity学院）和布拉姆利·默顿（NOCS）向科学基金会、爱尔兰和爱尔兰海洋研究所投标，获得了45万欧元的船期。凯尔特探险家已经提供给琼斯和莫顿之间的四月中旬和五月中旬2008年。为了支持这次考察，寻求资金来移动和设置一个便携式多波束exchosounder（Reson 8160），并从NMFD租用几个挖泥船。成本不高，约占运输时间的2.5%。科学目标是绘制冰岛西南部Rejkanes海脊西侧暴露的V形海脊走向的地图并沿其沿着取样。这项紧急拨款提案是为了支持一项由英国领导的重大IODP提案（646-Full），该提案解决了有关火山热点活动波动原因及其对地球环境（包括气候）影响的基本问题。地幔深部上升流、局部温度和成分异常或浅地幔流是否会引起热点波动？所涉及的时间尺度和比率是什么？当地幔流从热点流出时，它的命运是什么？为了解决这些问题，我们建议采样的时间海侵功能是常见的热点与洋中扩张脊的相互作用。这些现象是非常清楚的冰岛-雷克雅未克海脊对，其中一系列的穿时V形脊（VSR的）保存在过去的35 Ma，在北大西洋的地板上的热点活动的变化记录。与冰岛热点的这些波动有关的是北大西洋成分水（NACW）通量的变化，NACW驱动着“全球海洋输送带”，其回流表现为北大西洋漂移，缓和了欧洲西北部的气候。冰岛VSR作为热点波动过程指标的重要性已在最近的大型火成岩省IODP研讨会（Colrain，2007年）中得到认可。通过在北大西洋的Reykajnes海岭的侧翼钻探对穿时振动时效进行取样是获得这一地质记录的唯一途径。我们建议从雷克雅内斯山脊西侧暴露的最年轻的VSR之一的横断面沿着采集熔岩样本。这些熔岩的地球化学将有助于了解VSR的成因，从而了解热点波动的原因和过程。所处理问题的性质和我们的方法是从过去四年中国际赞助的四个独立讲习班中了解到的。在最近的一次UK-IODP研讨会“Rift 2 Ridge '07”（南安普顿，2007年）中，我们发现了该提案与Wright等人（正在准备中）的另一个IODP提案之间的重要联系。的目的是调查冰岛上的VSR的开始和NACW溢流强度的波动之间的相关性。

This Urgency Grant Proposal aims to take advantage of a site survey opportunity in support of a UK-led IODP proposal to drill the North Atlantic basement. A bid made last October to the Science Foundation, Ireland and the Irish Marine Institute by Steve Jones (Trinity Colege, Dublin) and Bramley Murton (NOCS) resulted in 450,0000 euros of ship-time being awarded. The Celtic Explorer has been made available to Jones and Murton between mid-April and mid-May 2008. To support this expedition, funds are sought to mobalise and set-up a portable multibeam exchosounder (Reson 8160), and to hire several dredges from NMFD. The costs are modest, at about 2.5% of the ship-time. The scientific objectives are to map and sample along the strike of a V-shaped ridge that is exposed on the western flank of the Rejkanes Ridge, southwest of Iceland. This Urgency Grant Proposal is in support of a major, UK-led, IODP proposal (646-Full) that addresses fundamental questions about the causes of fluctuations in the activity of volcanic hotspots and their effects on the Earth's environment including climate. Does deep upwelling in the mantle, localized temperature and compositional anomalies, or shallow-mantle flow cause hotspot fluctuations? What are the time scales and rates involved? Where mantle flow is involved, what is its fate as it flows away from a hotspot? To address these issues, we propose to sample time-transgressive features that are common where hotspots interact with mid-ocean spreading ridges. These phenomena are exceptionally clearly developed for the Iceland-Reykjanes Ridge couplet where a series of diachronous V-shaped ridges (VSR's) preserve a record of changing hotspot activity, over the last 35Ma, on the floor of the North Atlantic. Linked to these fluctuations in the Iceland hotspot are variations in the flux of North Atlantic Component Water (NACW) that drives the 'global ocean conveyor' and whose return flow is manifest as the North-Atlantic Drift that moderates the climate of northwestern Europe. The significance of the Iceland VSR's as indicators of the processes of hotspot fluctuations has been recognised in the recent Large Igneous Province IODP Workshop (Colrain, 2007). Sampling the diachronous VSR's by drilling on the flanks of the Reykajnes Ridge in the North Atlantic is the only way to access this geological record. We propose to sample lavas from a transect along one of the youngest VSR's, exposed on the western flank of Reykjanes Ridge. The geochemistry of these lavas will yield insights into the genesis of the VSR's, and hence the causes and processes of hotspot fluctuation. The nature of the questions being addressed and our methodology have been informed from four separate, internationally sponsored workshops over the past 4 years. During the most recent, an UK-IODP workshop 'Rift2Ridge '07', Southampton, 2007, we identified an important link between this proposal and another IODP proposal by Wright et al, (in prep.) that aims to investigate the correlation between the initiation of VSR's on Iceland and fluctuations of NACW overflow strength.