Circum-Arctic Mapping Project: New Magnetic Anomaly map Linked to the Geology of the Arctic

Recent Circum-Arctic digital compilations of magnetic, gravity and bathymetry data have been analyzed in order to provide a consistent view of the tectonically complex Arctic basins and surrounding continents. The new grids have been mathematically filtered in order to assist in the regional characterization of magnetic and gravity domains and boundaries. In particular, we have analyzed the frequency content, amplitudes, and patterns of regional magnetic anomalies in areas with disputed crustal structure and tectonic evolution (like Alpha-Mendeleev Ridge). The interpretation of potential field and its derivatives has been compared with recently released map of Arctic geology. CIRCUM-ARCTIC MAPPING PROJECT: NEW MAGNETIC AND ANOMALY MAP OF THE ARCTIC An international effort to compile Circum-Arctic geophysical and bedrock data has been conducted by several national agencies (Russia-VSEGEI and VNIIO, Sweden-SGU, Finland-GTK, Denmark-GEUS, USA-USGS, Canada-GSC and Norway-NGU) since 2005. This project aimed to produce an atlas with geological and geophysical digital maps at a scale of 1: 5 million for the Arctic region bounded by the 60 degrees northern latitude. Here we mainly present the new Circum Arctic Magnetic Anomaly map (with a resolution of 2 km, upward continued 1 km, Fig. 1) and link it to the Circum Arctic Gravity Anomaly map (Free Air and Bouguer corrected, 10 km gridded data) and the Circum Arctic geology. New published and classified magnetic and gravity anomaly gridded data from each participant group were gathered and converted to a common datum (WGS84) and format. The magnetic anomaly compilation relies on 1 km gridded data for Canada (based on the Canadian Aeromagnetic Data Base), Alaska (based on Alaska USGS aeromagnetic database) and NW Europe (Fennoscandia compilation and the NGU NE Atlantic compilation) regions, and 5 km gridded data for oceanic and Russian regions (see Figure 2 for location of various contributions). The Greenland region magnetic anomaly grid ([14]) has been updated with new aeromagnetic surveys performed in West Greenland between 1992-2001 ([12]), and in NW Greenland ([1,9]). The oceanic area east of Greenland (NE Atlantic) contains most of the aeromagnetic data used in the [14] s compilation (pre-1990) plus new aeromagnetic surveys over offshore Norway collected up to 2007 ( [3,10,11]). The gridded data has been upward continued to 1 km above ground or sea-level and trimmed around the areas of major overlaps. The Alaska USGS aeromagnetic compilation has been used as the “master grid” for merging the major gridded data sets together and the downward continued lithospheric magnetic field model MF6 derived from satellite data [7] has been used as a regional reference surface. We have used a blending function over the area of overlap in order to smooth the transition from one grid to the other (GridKnit, GEOSOFT). The resulting grid has been re-sampled to a 2 km grid cell. In order to construct the final Circum-Arctic magnetic anomaly grid (CAMP-M) we have adopted the approach used by several research groups for compiling the World Digital Magnetic Anomaly Map (WDMAM) and used near-surface magnetic data for the short wavelength component of the compilation and the satellite derived magnetic anomalies for the long wavelength ([5,6]). MF6 extends to spherical harmonics degree 130 (333 km wavelength) and therefore it is able to provide consistent long wavelength information between 300 and 400 km. This information is mainly related to regional deeper and/or thicker portions of the magnetic sources within the crust. Fig. 1. a) CAMP-M magnetic anomaly map; b) Magnetic anomaly map: gridded data sources; c) MF6 satellite magnetic field model (geoid altitude, upward continued 1 km, [7]) has been used as regional base for leveling the magnetic anomaly compilation and to fill the “no data” gaps. MF6 extends to spherical harmonics degree 130 (333 km wavelength) and therefore it is able to provide consistent long wavelength information between 300 and 400 km. This information is mainly related to regional deeper and/or thicker portions of the magnetic sources within the crust. The new CAMP-GM compilation is superior to similar gridded data over the Circum-Arctic area due to its better coverage (includes updated aeromagnetic data in the High Arctic, west and north of Greenland and in the NE Atlantic), preserves smaller wavelength structures by keeping the grid resolution at 2 km, and has a consistent regional long wavelength component introduced by the MF6 satellite based lithospheric magnetic model. DERIVATIVES OF THE CAMP-GM MAGNETIC ANOMALY GRID: WHAT CAN WE LEARN ABOUT

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