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

学术价值：IODP第330次路易斯维尔海山探险于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一个主要目标是记录路易斯维尔热点在80至50 Ma之间可能的运动。需要高质量的古地磁数据来记录这一运动，并与在此时间间隔内观察到的夏威夷热点的15°移动进行比较。这些数据，连同详细的辐射年龄，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角未定向的岩心样品的详细退磁研究。此外，我们将部署Göttingen钻孔磁强计(GBM)进行三分量磁性钻孔测量。GBM的主要好处是，光纤陀螺应该能够确定完全定向的分量磁异常，并估计磁化偏角，便于识别单独的流动，并更可靠地估计热点和太平洋板块运动。试验表明，与GBM一起使用的下沉杆和扶正器都会产生很大的磁异常(在1米处高达10,000 nT)。这些大信号，以及重要的是这些信号在不同部署下可能发生的变化，损害了磁测井的好处。因此，我们建议制造一种非磁性沉降杆，它将能够在Expedition330和随后的探险中确定准确的组件磁异常(和剩余倾角)。现有的沉降杆和扶正器的大磁性特征在8月份被记录下来；在330勘探开始之前的短时间内，需要快速制造这个工具。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勘探的主要目标。拟议的GBM磁测井有可能在井眼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过去运动和太平洋板块运动的约束。若干考察队的参与者将参与解释钻孔磁力仪的结果，并将这些结果与回收的岩心材料的数据结合起来。

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.