The Toronto Stock Exchange's S&P/TSX fell 162.74 points, or 1.00 percent, to 16,164.61.
Leading the index were FirstService Corp, up 9.0 percent, Iamgold Corp, up 2.5 percent, and SSR Mining Inc, higher by 2.4 percent.
Lagging shares were MEG Energy Corp, down 9.9 percent, Kelt Exploration Ltd, down 8.8 percent, and Crescent Point Energy Corp, lower by 8.1 percent.
On the TSX 67 issues rose and 172 fell as a 0.4-to-1 ratio favored decliners. There were 15 new highs and 19 new lows, with total volume of 243.2 million shares.
The most heavily traded shares by volume were Encana Corp, First Quantum Minerals Ltd and B2gold Corp.
The TSX's energy group fell 5.88 points, or 3.9 percent, while the financials sector slipped 2.93 points, or 1.0 percent.
West Texas Intermediate crude futures fell 5.39 percent, or $3.31, to $58.11 a barrel. Brent crude fell 4.34 percent, or $3.08, to $67.91 [O/R]
The TSX is up 12.9 percent for the year.
