Three component magnetic survey 2011, 2012 using ROV in TA25 and TA26 of the Lau Basin, , the southwestern Pacific

Abstract

We conducted magnetic survey at Apr., 2011 and Jan., 2012 in TA25 and TA26, the Lau Basin, the southwestern Pacific using ROV(Remotely Operated Vehicle) and three component magnetometer. At 2011, the survey area was only the western slope of the caldera of TA25 using IBRV(Ice Breaker Research Vessel) ARAON of KORDI(Korea Ocean Research and Development Institute) and ROV of Oceaneering Co. The 2011 deep-sea three component magnetic survey lines were the 13 N-S lines. And, at Jan. 2012, the magnetic survey was conducted in the 2 areas of the caldera of TA25 and the 1 area of TA26 using German R/V SONNE and ROV of ROPOS Co. In the 2012 magnetic survey, the 29 N-S lines(TA25-East : 12 lines, TA25-West : 11 lines, TA26 : 6 lines) were conducted. Also, we conducted 8 figure circle rotation of ROV for magnetic calibration at 2011 and 2012. For the magnetic survey, the magnetometer sensor was attached with the line frame of ROV and the data logger and motion sensor in ROV. The three component magnetometer measure the X(North), Y(East) and Z(Vertical) vector components of a magnetic field. A motion sensor(Octans) provided us the data of pitch, roll, yaw for the correction of the magnetic data to the motion of ROV. In the survey, ROV followed the tracks of the plan at 50 m above seafloor. The data of the magnetometer sensor and the motion sensor and USBL(Ultra Short Base Line) data were recorded on a notebook through the optical cable of ROV using Mag software. Hydrothermal fluids over Curie temperature can quickly alter or replace the iron-rich magnetic minerals, reducing the magnetic remanence of the crustal rocks, in some cases to near 0 A/m magnetization. The magnetization distribution of 2011 magnetic data show low magnetization zones that suggest the possible hydrothermal zone, matched with the known chimney or vent sites. We have processed and interpreted the 2012 magnetic data with other geological and geochemical results of this project. Therefore, the obtained th