Fibrous Tremolite in Central New South Wales, Australia MARC HENDRICKX* Marc Hendrickx and Associates, Australia, P.O. Box 61, Berowra Heights, New South Wales, Australia, 2082
Key Terms: NOA, Asbestos, Tremolite, Elongated Mineral Particles, Australia, Toxicology ABSTRACT Tremolite schists in Ordovician meta-volcanic units in central New South Wales (NSW) consist of fine fibrous tremolite-actinolite. They host tremolite asbestos occurrences, and small quantities of asbestos were mined from narrow vein deposits in central NSW during the last century. When pulverized, the tremolite schist releases mineral fragments that fall into the classification range for countable mineral fibers and may be classed as asbestos despite not having an asbestiform habit. The ambiguity in classification of this type of natural material raises significant health and safety, legal, and environmental issues that require clarification. While the health effects of amphibole asbestos fibers are well known, the consequences of exposure to non-asbestiform, fibrous varieties is not well studied. This group of elongated mineral particles deserves more attention due to their widespread occurrence in metamorphic rocks in Australia. Toxicological studies are needed to assess the health risks associated with disturbance of these minerals during mining, civil construction, forestry, and farming practices. INTRODUCTION
This article documents preliminary results of a geological assessment for natural occurrences of asbestos (NOA) undertaken in Rockley and Byng Volcanics between Orange and Dog Rock State Forest in central NSW (Figure 2). The assessment included review of available geological information, such as new NOA potential maps (HACA, 2015a, 2015b), and included new geological mapping and assessment of regional airborne geophysics (aeromagnetic and radiometric datasets) to improve base geology maps along with sampling and mineral analysis. The work was undertaken following discovery of tremolite asbestos veins during minor roadworks (Figure 3). GEOLOGICAL SETTING The area occurs in the eastern Lachlan Fold Belt, a major geological province in eastern Australia that was active from the Cambrian to the Carboniferous. The geological history of the area includes marine sedimentation in troughs and basins adjacent to a long volcanic arc that was active through the Ordovician to early Silurian. Ordovician volcanism and sedimentation across the central Lachlan Fold Belt was terminated in the early Silurian by a regional deformation event termed the Benambran Orogeny. This caused extensive shortening across the region, folding and
Lower Ordovician meta-volcanics in central New South Wales (NSW) are host to minor asbestos occurrences. Some of these were mined in the first half of the 1900s, yielding small quantities of poorquality tremolite asbestos used mainly to line boilers (Hendrickx, 2009). The host rock to asbestos occurrences are tremolite-actinolite-chlorite schists in the Rockley, Byng, and Sofala Volcanics that form distinctive outcrops throughout the region (Figure 1). When crushed for industrial use as a road construction material, the schists release crystal fragments with size and aspect ratios that fall into the classification for countable fibers and may be classed as asbestos. These elongated mineral particles (EMPs) raise health and safety, legal, and environmental issues that require clarification. *Corresponding author email: marchgeo@gmail.com
Figure 1. Outcrop of tremolite-actinolite-chlorite schist from Byng Volcanics, near Orange, central NSW (−33.27537, 149.19834).
Environmental & Engineering Geoscience, Vol. XXVI, No. 1, February 2020, pp. 73–77
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