INVESTIGATING SERPENTINIZATION WITHIN THE COOK INLET BASIN, ALASKA FROM THE INVERSION OF MAGNETIC DATA

Southcentral Alaska is a tectonically active region with an unusual subduction geometry. Cook Inlet basin (CIB) and the Kenai Peninsula, located in the southcentral Alaska, has a topographic transition from low to high lands, respectively. GPS observation indicates a topographic transition due to uplift of the Kenai Peninsula and a corresponding subsidence of CIB. Analysis of tectonic processes suggests that the subsidence is related to the formation of an unusually hydrated and serpentinized mantle wedge with lateral variations in heat flow due to a shallow-eastward subducting slab.

This research investigates the thickness and location of the serpentinized body using magnetic data to determine the Curie Point Depth (CPD) using 3D inversion methods. Seismic refraction models of the crust beneath the CIB will be used as a constraint for the CPD analysis. The CPD and seismic models will be compared to thermal models to best interpret the zone of serpentinization. CPD analysis from the 3D inversions shows that the top of serpentinized body is at ~2.5 km and the bottom at ~30 km. The crustal thickness within forearc region is greater than 20 km and this indicates that the magnetic anomaly is within the crustal rock of the North American plate. The models show the magnetic anomaly is not within the mantle wedge. Seismic models and thermal model of CIB will be used to further ascertain the possible rocks with the magnetic anomalies.