라우분지 FRSC(Fonualei Rift and Spreading Center)에서의 심해견인자력탐사 연구

Abstract

A deep-tow magnetic survey was carried out over the mound of FRSC(Fonualei Rift and Spreading Center, 16? 22'S, 174? 35'W) located on the Lau basin by the R/V Onnuri 05'KODOS-03 Cruise. The FRSC comprises the spreading centers extending south of the MTJ (Mangatolu Triple Junction, also known as the Kings Triple Junction). The MTJ has reoriented during the Brunhes Chron. South of the MTJ, the positive Brunhes and surrounding negative Matuyama anomalies can be recognized. Earthquakes data of the FRSC show normal faulting consistent with active rifting(Zellmer et al, 2001). \\\\\\\\\\\\\\\\Generally, low magnetization at crust is strongly correlated with active hydrothermal vent field. The acidic and corrosive fluids that constitute marine hydrothermal vent systems can quickly alter or replace the iron-rich magnetic minerals, which reduce the magnetic remanence of the crustal rocks, in some cases to zero. \\\\\\\\\\\\\\\\Deep-tow magnetic field data were collected along axis track from south to north by using high sensitivity total field proton magnetometer which is towed 300~500m above the seafloor. The data were first merged with the ship navigation and upward continued to a level plane(-1.5km) using the Guspi(1987) method. The upward continued magnetic field was inverted for crustal magnetization using Parker(1974) inversion approach, which takes bathymetry into account assuming a constant layer thickness and then sufficient annihilator is added to magnetization solution to balance the positive and reverse polarity amplitudes. In this study, all inversions assume a 500m source thickness. \\\\\\\\\\\\\\\\The peaks in the crustal magnetization profile were found along track line. The peak which located over the mound of FRSC with low amplitude(1.5A/m) is estimated the effect of hydrothermal vent. However, it is necessary to compare and analyze with other geophysical studies because the low magnetization can be occurred by mass wasting or normal fault.