Information from geobotanical surveys

Large-scale mining in Latin America has employed traditional methods of exploration for minerals based on geology (rock colouration), radiometrics, photogeology, thermal analysis, geochemistry and satellite imaging. Thus geobotanical methods of mineral exploration, concerned with the detection of subsurface mineralisation by an interpretation of its vegetative cover or 'indicator plants' (Brooks 1998) are rarely reported in the literature of the Region. Two of the few geobotanical surveys published in the Region are those of Viladevall et al. (1994) in Bolivia and Fernandez-Turiel et al. (1994) in Argentina. Viladevall et al. (1994) suggested that Baccharis incarum (Asteraceae) and Fabiana densa (Solanaceae) are good shrubs or 'tholas' to be used as regional metal indicator plants in geobotanical surveys for Au, As, Sb and other metals in the altiplanic areas of Bolivia, as their leaves are indicators of the metal contents in the subsoil. In the Puna belt of Argentina, however, these species grow on many soil types (Bonaventura et al. 1995). Although these plants cannot be classified as hyperaccumulator plants as they only reached a maximum of 540 mg kg 1 Sb in their leaves, a value below the criteria of >1000 mg kg 1 for Sb-hyperaccumulating plants, they may have metallophyte status. Fernaandez-Turiel et al. (1994) suggested that Prosopis alba (Mimosaceae) and Larrea divaricata (Caesalpiniaceae) growing near an old smelter in the Sierra Pampeanas in Argentina had two to six times more Sr, Cd, Bi, Zn, Ni, Li and Cu than the same plants growing on unpolluted soils. They reported that all the shrubs studied had the same pattern of metal accumulation in above-ground structures as metal levels increased in soils, with the exception of P. alba and P. nigra which accumulated more Zn than the other plants growing in the same soils (700 vs. 200mgkg~1 Zn in ash), a characteristic of metallophytes. Furthermore, with the exception of serpentine floras described in Cuba and Brazil, there are no reports of unusual locations where metallophytes dominate.

Was this article helpful?

0 0

Post a comment