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REV95387
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REV95387
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Entry Properties
Last modified
8/25/2016 3:20:27 AM
Creation date
11/21/2007 11:49:08 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1988112
IBM Index Class Name
Revision
Doc Date
11/16/1998
Doc Name
BMRI SAN LUIS MINE PN M-88-112
From
BATTLE MOUNTAIN GOLD
To
DMG
Type & Sequence
TR15
Media Type
D
Archive
No
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~ 1 BMRI-San Luis <br />199811ackfill Geochemi~ry <br />mass of leachable sulfate ranges from 23.8 mg SOa in composite 3 to 75.4 mg S04 in <br />composite 2. The median leached mass was 54.9 mg from composite 1, and this value <br />' is close to (but slightly higher than) the average of 51.4 mg for the three tests. For <br />populations, the form of whose distribution is not known, the median is the best <br />unbiased estimator of central tendency, and the median value will be used for <br />' subsequent calculations. <br /> In rocks and soils (excluding salt deposits, which obviously are not relevant here), the <br />' total concentration and the leachable concentration of an element have no close <br /> connection because the solubility of the primary mineral phases is very low. The <br /> sulfate-release values calculated from the experimental, kinetic-test data represent the <br />' mass of sulfur that can be transferred from the primary Sulfide minerals to secondary, <br /> soluble sulfates by repeated, periodic wetting and drying cycles while the rook is <br />' present in the vadose zone. The samples tested in the kinetic tests were demonstrably <br />not acid-generating, so the amount of sulfate generated by their oxidation during the <br /> tests was low. Based on the total sulfur content of the test charges (which ranged from <br /> 0.61 wt9G for Composite 3 to 3.15 wt% for Composite 1), the total leachable sulfur is <br />' less than 1 S6 of the total sulfur mass present in the rock. <br />' It should be noted that these sulfate-release values represent the mass of sulfate that is <br /> leachable from the rock under a regime in which the tendency to oxidize sulfide is <br /> maximized compared to weathering rates in the real world. In the humidity-cell <br />' procedure, one forces air (which contains 200,000 ppmv Oz) through rock that has been <br /> crushed (and therefore has a higher specific surface area than would full-scale, <br /> backfilled rock). The cycling of high-humidity air as a step in the HCT pros@ss <br />' ensures that there is sufficient HBO for the pyrite oxidation reaction to proceed. The <br /> rinsing cycle removes build-up of secondary phases on surfaces that might otherwise <br /> restrict mass transfer of oxygen into the pyrite and of sulfate out of the altering solid <br />' and into the aqueous phase. The test procedure is a form of "accelerated-fife testing" <br /> that is intended to simulate many long-term cycles of weathering in a manageable time <br />' frame by increasing the rate at which the system is stressed. This form of testing is <br />standard in materials and industrial engineering, as, for example, rapidly cycling of <br /> current is used experimentally to evaluate the longevity of electric light bulbs. <br />' As shown in Figure 1 and Tables 1 and 2, the humidity cell tests stopped producing <br /> sulfate at detectble levels after a number of rinsing cycles. As discussed above (e.g., <br />' Posey, 1946), the sulfate production should drop to negligible levels once the backfill <br /> has been saturated. Therefore, the existing data are adequate to show the maximum <br /> credible sulfate concentrations that can be generated from these materials, even though <br />1 the leachable sulfate amounts to only a small portion of the total sulfur present in the <br /> rocks. <br />' Each of the HCT experiments used a test charge of approximately 200 g of solid. <br /> Therefore, using the median sulfate production value of 54.9 mg, the expected release <br /> <br /> Geochimicq Irtc. 16-Nov-98 <br /> I <br />
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