GEOMORPHIC CONTROLS ON THE MORPHOLOGY OF POTENTIALLY HAZARDOUS FIBROUS AMPHIBOLES, CLARK COUNTY, NEVADA, USA

There are six hazardous fibrous minerals including five amphiboles that are characterized and regulated as ‘asbestos.’ However, other fibrous amphiboles have been linked to diseases and certain cancers and have remained unregulated. Fiber morphology and chemistry directly relate to hazardous potential: longer and thinner fibers are thought to be more harmful. Recently, fibrous amphiboles were found in a 0.05km² plutonic outcrop in the McCullough Range in southern Clark County, Nevada. Particles from the outcrop erode out as part of an associated alluvial fan that spans at least 0.41km². This project will collect samples of alluvium and determine how the length and width of fibrous amphiboles vary with (a) geomorphic age and (b) distance from source. Fiber length, width, and mineral chemistry will be measured using SEM/EDS. A detailed map will also be made using ArcGIS that identifies bedrock geology and geomorphic surfaces across the fan and on surrounding slopes. In addition, spectroscopy will be used to analyze amphibole samples to attempt to locate amphiboles using multispectral imagery. Remote sensing will be done using the highest spatial resolution with ASTER at 15m/90m and NAIP at 1m/pixel. Preliminary results show fibers with aspect ratios beyond the 1:20 ratio considered dangerous, some even above 1:40. Our data suggests that fibrous amphiboles break along two planes of cleavage, and may continue to split perpendicular to their length. This suggests that as these amphiboles weather they become more fibrous (e.g. thinner) but reach stability at a median length. Amphibole fibers have been found in both ancient and modern soils in varying shapes. In addition, VNIR spectroscopy suggests this amphibole has unique blue wavelength characteristics that may help identify it using remote sensing techniques. This work is innovative because to our knowledge there are no previous studies directed at understanding how geomorphic processes may affect the distribution and morphology of carcinogenic minerals across a landscape. This project uniquely links geomorphic processes, arid soil science, and medical geology together to improve land use planning and benefit the health of citizens in the region.