隱沒帶高磁力異常帶與地幔蛇紋岩化物質之關係探討

Serpentinization of fore-arc mantle is a common feature that has been observed in many subduction zones worldwide and plays an important role in dynamic subduction processes. Abundant fluids are released by the dehydration of subducting oceanic crust and sediments; these fluids ascend upward into and hydrate the overlying mantle. The major physical characteristics of serpentinization are its ability to reduce velocities and densities as well as increase the intensity of magnetization. The serpentinization of mantle rocks is a special case featuring very high magnetization simultaneously with low density, which can result in relatively high magnetic and low gravity anomalies. In that case, high-amplitude magnetic anomaly zone with low gravity anomaly should display in the fore-arc region in subduction zones. However, we do not observe this feature in each subduction zone. According to the characteristics of serpentinization, in this study, I estimate the magnetization-density ratio (MDR) in subduction zone to investigate the relationship between the high-amplitude magnetic anomalies and serpentinized fore-arc mantle. The advantage of using this method is that we can estimate the MDR of subsurface materials directly using magnetic and gravity anomalies.