Leticia Lescano

Asbestiform and non-asbestiform morphologies in a talc and vermiculite mine from the province of Córdoba (Argentina): a case study

Abstract In this work, a talc and vermiculite mine from the province of Córdoba (Argentina) was investigated with special emphasis on the occurrence of asbestiform and non-asbestiform phases. The meta-ultramafic rock was studied by a multimethodological approach, complementing field studies with petrographic-mineralogical, compositional and morphological analyses. Samples were examined by stereomicroscopy, polarizing light microscopy, SEM–EDS, XRD, DSC-TGA and FTIR. Complementary, compositional and textural analyses were performed with FE-SEM–EDS and EPMA. Talc-rich veins with a laminar and fibrous appearance were at first recognized. However, the fibrous morphology observed both in the field and by microscopy is due to an apparent habit because of the sample orientation. To avoid erroneous interpretations, studies by secondary electron images (SEM) are fundamental to carrying out this type of analysis. Tremolite was identified in different zones of the outcrop; however, only ~40% of the crystals located in the vermiculite zone have dimensions to be considered as asbestiform fibres in the range of respirable particles. In these types of complex deposits affected by superimposed metamorphic, igneous and deformational events, multimethodological approaches are necessary to develop models of occurrence of asbestiform morphologies that may be applicable to other with similar characteristics.

Asbestiform Amphiboles in a Serpentinite Quarry in Operation, Province of Córdoba, Argentina

Active serpentinite quarries located in the province of Cordoba (Argentina) provide raw material for metallurgical and construction industries. In the studied Adita quarry, veins with asbestiform minerals occur at the contact between pegmatitic dikes and the serpentinized ultramafics. In the past asbestos have been used for decades, but nowadays the exploitation, import, commercialization and use of asbestos (amphiboles, chrysotile) is prohibited, due to its effect on human health. In this work two different amphiboles were analysed by optical microscopy, SEM-EDS, XRD and chemical analysis. They were identified as anthophyllite and tremolite.

Asbestiform Amphiboles in a Marble Quarry: A Case Study from the Province of Córdoba (Argentina)

Pure and impure marbles in Argentina have been exploited for hundreds of years for different purposes. Marble processing is varies depending on its use and could include chemical treatments, burning, crushing, milling and polishing. More impure marbles are crushed and used for construction, or discarded in spoil heaps in quarries. There are numerous studies related to the physical and mechanical properties of marbles from the province of Cordoba; however, there are no records about the potential presence of asbestos that could be liberated during processing procedures or degraded by natural agents in spoil heaps. Fibrous samples from a metasomatic zone in an abandoned marble quarry in the Altautina area (Cordoba, Argentina) were studied through polarized light microscopy, X-ray diffraction and electron probe microanalyses. Asbestiform (tremolite) and non-asbestiform amphiboles (tremolite and magnesio-hornblende) were identified as the main phases. Asbestiform amphiboles were concentrated and studied through a stirring degradation test to evaluate morphological and size changes in the fibres by simulating natural water degradation. This process was monitored by stereomicroscopy and scanning electron microscopy. During the test, fibres underwent length (L) and width (W) reduction, maintaining or increasing the initial L/W ratio. Although the action of natural agents can differ from data obtained in laboratory tests, results indicate that the asbestiform fibre size decreases reaching values that can be harmful to human health.