El Timbo mine (Tucuman, Argentina) chronicle of an announced subsidence

摘要

The mine site is located 18 km NE from San Miguel de Tucuman, Argentina. It belongs Santa Barbara morfostructural subsystem. There are two rock salt beds belonging the upper section of Rio Sali Formation, of Tertiary age, interbedded with green and brown claystone. Total thickness of both rock salt beds is about 10 m. Their depths are between 40 and 110 m. Mining is performed by unevenly distributed boreholes in a surface of 15 Ha which pump brines of about 1200 gr/l density. Brine's treatment includes cleaning, evaporation and addition of iodine in order to obtain pure kitchen salt . The environmental impact of this "in situ" natural solution mine of halite deposit, was analized in a former contribution. In this occasion we have concluded that mining subsidence was the principal environmental impact and there was a geological risks because a public route was close to the subsidence area . Recently, the “announced subsidence” affected the public route. In the present paper we have described the problem and the corrective actions in order to mitigate the damage.