The northern edge of Phanerozoic platformal rocks of the Western Canada Sedimentary Basin overlies the Flin Flon Belt (Trans-Hudson Orogen) in Manitoba and Saskatchewan. A program of regional mapping of the Phanerozoic-covered basement has been undertaken, involving the integration of high-resolution aeromagnetic and gravity data with extensive drill core information. Several major domains are recognized in the buried basement, each with a distinct lithotectonic character and potential field anomaly pattern. Three lithotectonic domains in the buried basement (Clearwater, Athapapuskow, and Amisk Lake domains) are characterized by northerly-trending positive gravity and aeromagnetic anomalies and correlate with the 1.92–1.83 Ga volcanic and plutonic rocks of the exposed Flin Flon Belt (Amisk collage and Snow Lake assemblage). An upper amphibolite grade orthogneiss complex (Namew Gneiss Complex), containing calc-alkaline intrusive rocks ranging in age from 1.88 to 1.83 Ga and screens derived from the older volcano-sedimentary rocks, is interpreted as the middle crust of a 1.88–1.84 Ga arc exposed in the Flin Flon Belt. Discordant intrusive complexes, such as the 1.830 Ga Cormorant Batholith, are centred on magnetic–gravity lows and truncate the structural trend of adjacent lithotectonic domains. Correlation of Flin Flon Belt geology with that beneath the Phanerozoic cover shows that its constituent lithotectonic elements have north–south strikes of up to 150 km, and form a predominantly east-dipping crustal section, consistent with Lithoprobe seismic reflection profiles.

Previous gravity models of the Sudbury Structure (1850 Ma) were constrained by surface geology, and by density measurements of surface and borehole rock samples. Recent high‐resolution seismic reflection data provide additional constraints for modeling new gravity observations made along the Sudbury Lithoprobe transect. Results indicate, 1) density distributions constrained by the seismic data yield calculated gravity values matching the Bouguer gravity data, 2) the main sources of gravitational disturbance are external to the Sudbury Structure, 3) the positive gravity anomaly trend south of the Sudbury Structure is associated with mafic rocks of Proterozoic age, and 4) the large, ramplike, gravity anomaly paralleling the northwest margin of the Sudbury Structure is an expression of a northward dipping boundary within the Archean basement. The presence of a hidden mafic layer beneath the Sudbury Structure is not required to model the Bouguer gravity data. An enigma is an 8 mGal, positive, gravity anomaly over the south central Sudbury Structure.

Different types of images generated from gravity, magnetic, and gamma ray spectrometry data from the Rae Province of the Canadian shield were compared with each other and geologic maps to evaluate their effectiveness for displaying the geologically relevant content of the data sets.Shading methods were useful for enhancing weak directional anomalies in the aeromagnetic data. Multidirectional, shaded-relief images produced by overlaying three colored, shaded-relief images are useful for analysis of anomalies associated with structure. Vertical gravity derivative images display a continuous gravity feature linking the Wager Bay and Amer Lake shear zones that is obscured on the Bouguer gravity intensity image. Detailed vertical magnetic derivative images of the shear zone clearly displayed anomalies associated with the internal structure.Composite images generated using three different geophysical parameters show correlations between the magnetic, gravity, and radiometric data which can be related to the geology. Subtle variations in uranium, thorium, and potassium concentrations determined by gamma ray spectrometry can be effectively displayed using ternary radioelement images INTRODUCTION

Traditionally, geoscience data is stored in analog format, however, with the advent of easy to use GIS software, more and more data is now generated and stored in digital format. This allows for easier archiving of the data and for easier sharing of information, a key factor with fewer resources available to both public and private sectors. The data contained on this CD-ROM incorporates Manitoba Energy and Mines mapping and Geological Survey of Canada (GSC) geoscience data compiled and re-formatted for for digital release. It also contains data created manually and imported from other sources. All of the data is royalty-free. Information about the individual datasets can be found in the documentation (refer to \INDEX.HTM). The data are provided in ARC/INFO and common interchange formats (DXF and ARC/INFO E00, DBF, etc.) in UTM zone 14 projection and NAD 27 datum. ArcExplorer is provided on the CD-ROM as a data viewer for PC clients in \software\explorer\aeclient.exe. Refer to http://www.esri.com/software/ for more information). The CD-ROM conforms to the ISO-9660 system-independent standard and works identically on a PC, Macintosh or UNIX workstation, however, no viewer is provided for Macintosh or UNIX users.

The NATMAP Shield Margin Project, which began in 1991, straddles the Manitoba-Saskatchewan border and studied a rectangular area with east-west and north-south extents of approximately 250 and 150 km, respectively. Among the principal objectives of the NATMAP program were a compilation of a digital geoscience database for the study area and development of digital methodology to build this database and its utilization to aid in reaching the geological goals of the project. It was anticipated that these initiatives would encourage integrated interpretation of data, improve the effectiveness of the geological mapping process, and accelerate publication of results. One of the keys to effectively applying digital methods to a geological mapping project is maintaining data in digital form throughout the project, from the field through to publication. Transcription errors are eliminated and the production of both preliminary and final maps and digital products is accelerated. Access to digital data also facilitates application of digital tools for analysis and visualization. Integrated image products generated from geophysical and geological data sets were used throughout the project and assisted in development of geological models and their visualization. Three-dimensional visualization methods were used to combine NATMAP surface and subsurface mapping with Lithoprobe interpretations of seismic reflection data. The digital database was used to prepare a digital archive of the project which will be published in CD-ROM after completion of the project.