Page 75 - Geologic Investigations in the Lake Valley Area, Sierra County, New Mexico

distributions are listed in table 1 and depicted in figure 2A. The estimated central range of element concentrations, in which about Ä 68 percent of the population is estimated to occur, is given by Ä GM/GD to GM × GD. The expected range, estimated to contain about 95 percent of the population of concentrations, is given by GM/GD1.96 to GM × GD1.96. The listed geometric deviations Ä bear no resemblance to the often-used standard deviation, a linear quantity that is added to or subtracted from the arithmetic mean to estimate distribution of a normal population. The GD is a multi- plier or divisor to the GM and, as such, has a compelling advan- tage over the arithmetic standard deviation. The central and expected ranges encompass only positive numbers, whereas arith- metic (standard) deviations often result in meaningless negative numbers for the lower part of the distribution range.
Results
Trace Elements of the Lake Valley District Mine Dumps and Water Leach Studies
On average, all mine dump samples from the district are Ä enriched in the following economic and geoenvironmentally sig-Ä nificant trace elements: Ag, As, Cd, Mn, Pb, and Zn. Less signif icant enrichments of Sr and V also occur. For Ag, As, Ba, Cd,
Cu, Cr, Mn, Pb, V, and Zn, there are several individual mine dumps that are enriched well above the district geometric mean concentration for each of these elements (table 1). Consistent correlation is generally exhibited for these elements in most
100000 10000 1000 100 10 1 0.1 0.01
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Mn Ag As Ba Cd Co Cr Cu Hg Mo Ni Pb Sb Sn Th V Zn Bi
Central ranges of concentrations of trace elements, symmetrically distributed about the geometric mean, for A, Composited (blue bar) and grab (green bar) samples of < 2 mm material on mine dumps in Lake Valley; B, Composited solid samples (in parts per million) (blue bar) and water leachate concentrations (in parts per billion) (green bar) for < 2 mm material on mine dumps in Lake Valley.
Figure 2.
Geochemistry of Mine Dump Material from the Lake Valley Mining District 69
Mn, pct Ag, ppm As, ppm Ba, ppm Cd, ppm Co, ppm Cr, ppm Cu, ppm Hg, ppm Mo, ppm Ni, ppm Pb, ppm Sb, ppm Sn, ppm Th, ppm
V, ppm Zn, ppm Bi, ppm CO2, pct Total S, pct