Structural Model For the Saddle Reef and Associated Gold Veins In the Meguma Group, Nova Scotia

CIM Bulletin, Vol. 69, No. 774, 1976

J. Duncan Keppie, Geologist, Nova Scotia Department of Mines, Halifax, N.S.

Auriferous quartz veins occupy zones of dilation. Fold-generated dilation zones are systematically distributed and are dependent upon the folding mechanism. Comparison of natural and theoretical folds indicates that different mechanisms operated in the Halifax and Goldenville formations. In the slates of the Halifax Formation, the folds are of similar type and internal strain is most intense in the limbs. This internal strain is probably accommodated with little or no dilation. In the meta-sandstone and slates of the Goldenville Formation, a combined flexural and tangential longitudinal strain mechanism, modified by pure strain, produced the folds. Tension fissures produced by this -mechanism are: (a) saddle reef veins in slate horizons, (b) veins normal to bedding in meta-sandstone layers in the fold hinges, (c) veins along faults in the cores of tight fold hinges and (d) zones of en-echelon veins in slate horizons in the limbs of folds. Because veins in fold hinges (a, b and c above) account for most of the gold production in the Meguma Group, other factors controlling the distribution and size of these veins are summarized below.

Keywords: Structural geology, Gold veins, Meguma Group, Vein mineralization, Halifax Formation, Goldenville Formation, Folding, Dilation zones, Curvature Index.