Diagnosis of environmental problems related to vein gold mining in Colombia

Abstract

Since 1985 the annual gold production in Colombia has been fluctuating between 30 and 35 tons (1–1.4 million ounces troy). Exploitation plants can be found in vein and placer gold deposits.

During 1992 a preliminary study was undertaken, resulting in a diagnosis of problems in small scale mining in 6 gold areas (vein type) of Colombia. In order to evaluate the general impact caused to the environment due to mining activities, six gold districts located in Nariño, Antioquia, Bolivar, Valle and Caldas Departments were visited. Geochemical analysis (ES, AAS, HGAAS, GFAAS) of orebodies, tailings and waters were carried out, with results that showed high levels of heavy metals in the environmental compartments studied.

The intense use of mercury for amalgamation and cyanides for leaching during mining and processing of gold orebodies was notable. The study verified that exploitation of gold deposits in Colombia is mainly done by small scale mining, which is characterized by low technology and recovery rates (about 50%), causing harm to water resources (municipal, industrial and groundwater), sediments, soils, air, vegetation, animals and humans. The study concludes that environmental problems are intimately related to the lack of appropriate technologies for mining and processing gold. This is a key factor causing low economic revenues, and consequently there is no compliance among the miners to invest in the care of the environment.