MO Guide to Volume Adjustment for Porous Parafragments

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					MO6 GUIDE FOR ADJUSTING THE TOTAL VOLUME OF POROUS PARAFRAGMENTS
Adjusted Volumes Are Used To Reduce AWC Values POROSITY FACTOR Low Porosity % Volume (granite, basalt) 0.90 5 5 10 9 15 14 20 18 25 23 30 27 35 32 40 36 45 41 50 45 55 50 60 54 65 59 70 63 75 68 80 72 85 77 90 81 High Porosity (tuff, pumice) 0.50 3 5 8 10 13 15 18 20 23 25 28 30 33 35 38 40 43 45

0.85 4 9 13 17 21 26 30 34 38 43 47 51 55 60 64 68 72 77

0.80 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

0.75 4 8 11 15 19 23 26 30 34 38 41 45 49 53 56 60 64 68

0.70 4 7 11 14 18 21 25 28 32 35 39 42 46 49 53 56 60 63

0.65 3 7 10 13 16 20 23 26 29 33 36 39 42 46 49 52 55 59

0.60 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54

0.55 3 6 8 11 14 17 19 22 25 28 30 33 36 39 41 44 47 50

This chart is to be used when calculating AWC when parafragments are present. Depending on the lithology of the parafragment, the amount of pore space in the parafragment available to absorb and release water, will vary. This chart provides very general rough estimates of how much to reduce the volume of the parafragment based on its porosity. The porosity factor is a rough approximation of the amount of pore space. The lower the porosity factor the greater the amount of pore space. The "harder", more dense, materials such as granite and basalt have low porosity. The "softer", less dense, materials such as tuff and pumice have high porosity. Judgement should be used to identify the approximate porosity factor for other materials that fall between the extremes identified. Once the adjusted volume for the parafragments is determined it should be added to the percent rock fragments to determine the total fragment volume. The AWC value for the fine earth fraction is then reduced by an amount equal to the total fragment volume (%rock fragments+%adjusted parafragment volume). AWC is also reduced for salinity.

Prepared by MO6 Staff March 2002


				
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