SEISMIC-REFLECTION PROFILES ACROSS THE MINE SERIES IN THE NORANDA CAMP OF THE ABITIBI BELT, EASTERN CANADA

The Abitibi-Grenville Lithoprobe project completed a regional (line 21 ) and a high-resolution (line 21-1) seismic survey in the Noranda Cent ral Volcanic Complex of the Blake River Group, Abitibi, Quebec. Line 2 1 provides a regional framework in which the Archean crust is divided into three layers, two of which are discussed here: the uppermost laye r, which corresponds to the Blake River Group, is the least reflective , and lies above 4 s (12 km), and the mid-crustal layer, which is comp osed of a complex pattern of generally east-northeast-dipping reflecto rs and lies between 4 and 8 s. Within the regional data, the Mine Seri es of the Central Volcanic Complex is imaged as a semitransparent seri es of reflectors overlying a highly reflective east-facing structure i nterpreted as the subvolcanic Flavrian pluton. The high-resolution dat a (line 21-1) were collected in the vicinity of the Ansil mine. The se ismic images in this region can be controlled by surface geology and e xtensive drill-hole data, and the project was designed to test the app licability of seismic reflection profiling in providing structural and stratigraphic information for use in mineral exploration: shallow-dip ping reflectors correlate well with lithological variations or contact s in the volcanic sequence; strong subhorizontal reflectors correspond to diorite and gabbro dykes and sills; several abrupt lateral changes in the reflectivity coincide with known intrusive contacts such as th e Lac Dufault pluton.