RAPID: A Nonmagnetic Sinker Bar for Magnetic Logging on IODP Expedition 330

学术成就：国际海洋学发展方案第330次考察路易斯维尔海隆于2010年12月12日从新西兰奥克兰出发。在路易斯维尔火山链钻探的主要目的是记录路易斯维尔热点在80和50 Ma之间的可能运动。需要高质量的古地磁数据来记录这种运动，并与在这段时间内观察到的夏威夷热点的15°偏移进行比较。这些数据以及详细的放射性年龄将为校准和测试各种地球动力学模型提供基础，最可靠的古纬度信息将来自对方位不定向岩心样品的详细退磁研究。此外，我们将部署哥廷根钻孔磁力计（GBM）进行三分量磁性钻孔测量。GBM的主要好处是，光纤gryos应允许完全定向的组件磁异常被确定和磁化衰减估计，便于识别个别流量和热点和太平洋板块运动的更强大的估计。测试表明，GBM使用的沉降杆和扶正器都产生大量的磁异常（在1米的距离上高达10，000 nT）。这些大的信号，以及重要的是这些信号在不同部署上的可能变化，损害了磁测井的优点。因此，我们建议制造一个磁沉降棒，以便在远征330和随后的远征中确定准确的分量磁异常（和回波磁偏角）。8月记录了现有沉降杆和扶正器的大型磁性特征;距离330远征开始的时间很短，需要快速制造该工具。更广泛的影响：需要高质量的古地磁和年龄数据来记录路易斯维尔热点的运动，这是330远征的主要目标。建议的GBM磁测井有可能在钻孔中提供完全定向的矢量磁异常，显著增强对路易斯维尔热点和太平洋板块运动的过去运动的约束。考察队的一些参与者将参与解释钻孔磁力计的结果，并将这些结果与从回收的岩心材料中获得的数据结合起来。

Intellectual Merit: IODP Expedition 330 to the Louisville Seamounts starts 12 December 2010 from Auckland, New Zealand. A primary objective of drilling at the Louisville volcanic chain is to document the possible motion of the Louisville hotspot between 80 and 50 Ma. High quality paleomagnetic data are required to document this motion and to compare with the 15° shift observed for the Hawaiian hotspot over this time interval. These data, together with detailed radiometric ages, will provide the basis for calibrating and testing various geodynamic models.The most robust paleolatitude information will be derived from detailed demagnetization studies of the aziumuthally-unoriented core samples. In addition, we will deploy the Göttingen Borehole Magnetometer (GBM) to make 3-componentmagnetic borehole measurements. The main benefit of the GBM is that fiber-optic gryos should allow fully oriented component magnetic anomalies to be determined and magnetization declination to be estimated, facilitating identification of individual flows and a more robust estimate of hotspot and Pacific plate motions. Tests reveal that the sinker bar and centralizer to be used with the GBM both generate substantial magnetic anomalies (up to 10,000 nT at a distance of 1m). These large signals, and importantly the likely changes in these signals on different deployments, compromise the benefits of the magnetic logging.We therefore propose fabrication of a nonmagnetic sinker bar that will allow determination of accurate component magnetic anomalies (and remanent declinations) on Expedition 330 and subsequent expeditions. The large magnetic signature of the existing sinker bar and centralizer were documented in August; the short time before Expedition 330 begins requires rapid requires rapid fabrication of this tool.Broader Impacts: High quality paleomagnetic and age data are required to document the motion of the Louisville hotspot, a primary goal of Expedition 330. The proposed GBM magnetic logging has the potential to provide fully oriented vector magnetic anomalies in the borehole, significantly enhancing the constraints on the past motion of the Louisville hotspot and Pacific plate motion. A number of Expedition participants will be involved in interpretation of the borehole magnetometer results and integrating these results with data from the recovered core material.