ATYPICAL MASSIVE SULFIDE CHIMNEYS OF THE ISLE-DIEU DEPOSIT, MATAGAMI,QUEBEC - EXPLORATION STRATEGY-DEVELOPMENT

The Isle-Dieu volcanogenic massive sulfide deposit is located in the M atagami Camp of the Archean Abitibi Subprovince. The geometry of this deposit can be compared to the geometry of typical volcanogenic massiv e sulfide deposits. Two distinct massive sulfide bodies are recognized , the mound which is straitform with a lenticular geometry and the chi mneys which are discordant with respect to the stratigraphic sequence. However, some chimneys of the Isle-Dieu deposit are unique in their h igh content of massive sulfides. The chimneys are subdivided into thre e types: the sulfide, the magnetite and the talc chimney, each chimney type is in tum subdivided into a massive and a stringer subtype. The chimneys either cross-cut the base of the mound or the entire mound im plying that the chimneys are contemporaneous to the formation of the m ound. The textures are progressively changed from brecciated to banded toward the center of the chimney. A growth mechanism implying periodi c repetition of opening and closing is proposed to explain the develop ment of these chimneys. These chimneys are interpreted as fluid discha rge channels. The exploration method must consider the atypical charac teristics of the Isle-Dieu deposit. An exploration strategy has been d eveloped both to optimize the search for massive sulfide chimneys in d eep ground and to ore recovery.