Naturally Occurring Asbestos in Argentina: a Compilation of Case Studies
Minerals of the asbestos group reaching asbestiform morphologies according to the World Health Organization criteria (Naturally Occurring Asbestos: NOA) have been recognized in the provinces of Córdoba and Mendoza (Argentina) mainly associated with meta-ultramafic rocks and talc, vermiculites and marbles ores in minor proportion. Meta-ultramafic bodies are generally serpentinized and locally steatized leading to talc ores. In the contact to the host rock (mainly gneisses or schists) a narrow zone rich in biotite and/or vermiculite is generally recognized. Chrysotile, occurs in mildly prograde metamorphosed, filling veins, as slip and cross fiber along shear zones. Amphibole asbestos mainly from tremolite –actinolite series, occurs commonly together with a non-asbestiform counterpart within the same area and deposits. These minerals have been found in the talc ores as well as in vermiculite rich sectors Different habits and size have been recognized in these deposits. Associated with talc ores, the tremolite exhibit elongated crystals whit prismatic, tabular and fibrous habit. Also, amphiboles (as impurities in vermiculites) with asbestiform, acicular and fibrous habits were identified. These crystals have dimensions in the range of respirable particles. Marbles from the province of Córdoba appear as lens or tabular banks with different metamorphic grades associated with gneisses, migmatites, amphibolites, and ultramafic rocks. In some sectors metasomatic processes produce biotite and amphioble-rich zones (tabular and prismatic hornblende/tremolite) in the contact to the host rock. Next to the contact zone, white asbestiform tremolite has been found filling veins. Asbestos has been banned in Argentina since year 2000, and therefore mines are currently closed. However, the explioted materials are still in waste piles and exposed to the environment, representing a potential health problem. In addition, there are currently many quarries exploiting meta-ultramafic rocks as well as marbles for different proposes, but studies regarding the potential presence of asbestiform morphologies in those sectors are very scarse This paper summarizes the results from studies on quarries from the provinces of Córdoba and Mendoza (Argentina), in relation to the presence of asbestiform minerals, their morphology, and size of the fibres to evaluate their potential dangerous.