Seamount formation structure of the Tofua Arc 12 in the Lau basin: Constraints based on bathymetry and magnetic modeling

Abstract We examined the seamount formation structures of Tofua Arc (TA) 12 in the South West Pacific by applying magnetization vector inversion (MVI) modeling to determine the structure of submarine hydrothermal deposits using bathymetric and magnetic data. Our model revealed that while ascending from deep to shallow layers, a strong concentration of magnetic susceptibility shifts from the surrounding slopes of the seamount to the caldera rim summits and directly under the caldera depression. The strong magnetic susceptibility estimated in the model correlated with the first eruption-forming seamounts and additional magma intrusion (second eruption) of the magnetic material displaced from the surrounding slope. The low magnetic susceptibility near the seafloor within this study area supports hydrothermal alteration around the inner ring fault created by the occurrence of landslides inside the caldera. Our study revealed the formation structure and the three-stage formation process of the TA 12 seamount. Data Source Description bathymetry : ta12-seadepm(utm)_resize_surfv6byOM.xyz Geomagnetic Intensity : ta12-totallevel(utm)_resize_surfv6byOM.xyz Total Magnetic Intensicy : ta12-anolevel(utm)_resize_surfv6byOM.xyz Analytic Singal : ta12-anal(utm)_resize_surfv6byOM.xyz Reduce to the Pole : ta12-rtp(utm)_resize_surfv6byOM.xyz 3D Magnetization Vector Inversion : MVI_Zadd_2019_03_09_02_02_31.xyz摘要 本研究针对西南太平洋汤加弧（Tofua Arc, TA）12号海山的形成构造展开研究，通过磁化矢量反演（magnetization vector inversion, MVI）建模，结合测深与磁测数据，解析海底热液矿床的构造特征。模型结果显示，当磁性磁化率强异常体从深部向浅部运移时，其赋存位置从海山周缘斜坡逐渐转移至破火山口边缘峰顶，并直接位于破火山口凹陷下方。模型中估算得到的强磁化率异常，与首批形成海山的喷发事件以及从周缘斜坡位移而来的磁性物质的额外岩浆侵入（第二次喷发）具有相关性。本研究区域内海底附近的低磁化率异常，佐证了破火山口内部滑坡引发的内环断层周边发生了热液蚀变作用。本研究阐明了TA 12号海山的形成构造与三期形成过程。 数据来源说明 测深数据：ta12-seadepm(utm)_resize_surfv6byOM.xyz 地磁强度数据：ta12-totallevel(utm)_resize_surfv6byOM.xyz 总磁场强度数据：ta12-anolevel(utm)_resize_surfv6byOM.xyz 解析信号数据：ta12-anal(utm)_resize_surfv6byOM.xyz 化极数据：ta12-rtp(utm)_resize_surfv6byOM.xyz 三维磁化矢量反演数据：MVI_Zadd_2019_03_09_02_02_31.xyz