MINERALOGICAL AND GEOCHEMICAL CHARACTERIZATION OF SANDS FROM AN ACTIVE DUNE SYSTEM NEAR TONOPAH, NEVADA: CHARACTERIZATION OF AN ENVIRONMENTAL REFERENCE MATERIAL FOR CENTRAL NEVADA

Sand dunes are important for several reasons, including climate, ecological and sedimentological studies. Sand dunes in the Basin and Range collect sand from a wide geographic area and thus are functionally a composite sample of the surrounding geology and environment. Accordingly, sand dunes can serve as excellent environmental reference materials for a variety of studies. Although extensive studies of sand dunes in southern and western Nevada have been conducted there are no detailed mineralogical or geochemical studies of the sand dune system immediately west of Tonopah. Sands from this system could well serve environmental investigations of Tonopah and surrounding areas which have an extensive history of mining that has produced abundant mine waste. Powder X-ray diffraction indicates that feldspar minerals are common and include calcian albite and other plagioclase minerals. Quartz is also common as are minor amounts of other minerals including amphiboles. Powder diffraction patterns show minor variation in the relative abundance of major minerals. Scanning electron microscopy indicates the presence of a wide degree of roundedness and grain size commonly varies between 200 and 400 micrometers. SEM indicates that quartz, iron titanium oxide, potassium feldspars, and calcite coatings occur in some grains. Lithic grains with zircon and complex textures are also observed commonly. Preliminary X-ray Fluorescence data indicates the following concentrations for major elements: P₂O₅ (0.10 wt%), SiO₂ (70.17 wt%), TiO₂ (0.27 wt %), Al₂O₃ (14.99 wt%), Fe₂O₃ (1.48 wt%), MgO (0.35 wt%), CaO (2.21 wt %), MnO (0.09 wt%), S (0.02 wt%), Na₂O (3.62 wt%), K₂O (4.41 wt %). With respect to elements of environmental concern concentrations were below detection limits for As and Ni and concentrations were 1070 ppm for V, 0.99 wt% for Cr, 690 ppm for Cu, 0.11 wt % for Zn, and 100 ppm for Pb. Results suggest the sands are a suitable environmental reference material.