Published:January 01, 1991
Two general types of Archean gold deposits are known in the Quebec segment of the Abitibi belt (Robert 1990) (Table 1). Firstly, there are gold-quartz vein deposits where gold is commonly associated with the development of quartz-carbonate vein systems. These deposits are typified by the deposits of such as the Pierre Beauchemin, Silidor and Donalda and Sigma deposits (Robert and Brown 1986). Secondly there are pyritic gold deposits where quartz-carbonate veins are less important and where sulphide generally form a major part of the ore. Deposits of the Bousquet area are good examples of this second type. This classification, although satisfactory to distinguish Archean gold deposits in general sense, needs be further refined in consideration of the broad characteristics of many individual deposits (Tourigny et al. 1989; Tourigny, this volume).
The Francoeur #3 deposit presents distinct geological characteristics which make it difficult to classify in either the Au-quartz vein or pyritic gold deposit type. During this mine visit, we will show that there exists a distinct type of gold-only deposit which present significant common geological differences resulting from possible different ore forming processes. The study of such deposits is thus important considering that proposed models might not fully explain their differences nor adequately predict their occurrences.
Figures & Tables
Control on Base Metal and Gold Mineralizations, Bousquet—Rouyn-Noranda Area*
The Archean Abitibi belt is one of the largest and most studied greenstone terranes in the world. This is due not only to its precious and base meta 1 production, but also to its excellent bedrock exposure which permits observation of many Archean geological features in the south part of the belt lying between Rouyn-Noranda and Val d'Or.
The main objective of the regional field trips and the mine visits is to present the rna in stratigraphic, st ructura 1 and ore characteristics of the southern part of the Abitibi Belt. This regional field trip is scheduled to cover the Rouyn-Noranda and Cadi 11 ac-Bousquet mining camps. Operating mines will also be visited: Francoeur, Pierre-Beauchemin, Ansil, Mobrun, Doyon and Bousquet. The delegates will be able to examine the main volcanic, plutonic and sedimentary rocks as well as the various structural features in this part of the Abitibi. Ore deposits will include both massive sulphide and gold deposits. The various geological and structural environments of these deposits will also be examined.
The southern part of the Abitibi Belt in Quebec is dominated by a prominent deformation corridor, the Cadillac-Larder Lake Fault Zone. This zone is oriented E-W and separates a volcanic domain in the north from an essentially sedimentary domain in the south. This sedimentary domain, comprising clastic rocks and various granitic complexes, belongs to the Pontiac Subprovince. The volcanic domain is composed of various “blocks” of volcanic assemblages intruded by granitic masses, separated from one another by fault zones, discordances and inear sedimentary units. On the regional scale, the imbricated volcanic “blocks” are lozenge-shaped, with E-W orientd long axes. In most cases, the relationships between these volcanic and sedimentary “blocks” remain ambiguous.