The strike at the Escondida mine weighed heavily on the downward revision.
The latest news from junior mining companies operating in Mexico, Argentina, Peru and Brazil.
Three exploration companies provide operating updates from Argentina, Nicaragua and Mexico.
Leftist ruling party candidate Lenín Moreno was the winner of Sunday's vote, but former banker Guillermo Lasso has alleged foul play and is challenging the results.
Peru's first mining strike this year ended after union members at the country's biggest copper mine returned to work after a three-week stoppage.
The Chilean state copper giant attributed the positive results to over US$400mn in savings last year, which managed to offset weaker ore grades, output and prices, according to CEO Nelson Pizarro.