CRUSTAL ABUNDANCE OF ELEMENTS, AND MINERAL RESERVES AND RESOURCES 



23 



and ratio of potential to known reserves is particu- 

 larly interesting and informative. The resource po- 

 tential is calculated from the formula E=2.45AxlO'' 

 as explained belovi^. The rationale for this calcula- 

 tion assumes that (1) McKelvey's relation of re- 

 serves to crustal abundance is valid, (2) U.S. 

 Bureau of Mines reserve figures are of the correct 

 order of magnitude, and (3) trace elements are 

 log-normally distributed in the earth's crust. R is 

 expressed in metric tons and A is expressed in grams 

 per metric ton or parts per million. In the McKel- 

 vey formula, i^^AxlO" ", R is expressed in short 

 tons and A in percent. 



Lead is used as the base of calculation be- 

 cause knovi^n reserves of minable lead ore already 

 exceed i2=AxlO"". Continental crustal abundance 

 of lead is 13 ppm or 0.0013 percent. Substituting 

 in McKelvey's formula, /2=AxlO^°, vi^e get: 

 i2=0.0013xl0i°=13xl0'^ metric tons. Known United 

 States reserves of lead are 31.8x10'* metric tons or 



2.45 times greated than ApbXlO'". This factor (2.45) 

 is greater for lead than for any other commonly 

 sought metal except molybdenum, which has about 

 the same factor. If we use assumptions 1 and 3 

 above, then currently recoverable resources of all 

 trace elements should approach 2.45AX10''. Obvi- 

 ously the 2.45 factor will increase as lead reserves 

 of any other metal increase above 2.45AX10''. An- 

 other very simple method of calculating potential 

 recoverable resource assumes that the resource 

 should approach 0.01 percent of the total amount 

 of each element available in the United States crust 

 to a 1-kilometer depth, as shown in table 3. It is 

 important to remember that the McKelvey formula 

 relates crustal abundance to currently recoverable 

 reserves ; therefore, my use of his formula restricts 

 the calculated resource potential (table 3) to iden- 

 tified and undiscovered resources recoverable under 

 present economic conditions. Paramarginal and sub- 

 marginal resources as defined by McKelvey (1972) 



metals in the earth's crust and in the United States crust 



Calculations ^ mass (metric tons) X abundance (decimalized) = total content of element] 



ntal crust segments — Con. 



Folded belts 



United States crust 



United 

 States 

 crust to 



United States 



Recoverable 

 resource 

 potential 2 



Recoverable Ratio 

 resource of 



potential * potential 



»G/mt MtXlO^ 8G/mt MtXlO '= MtXlO » MtXlO " MtXlO « MtXlO" MtXlO » 



0.43 1.9 0.46 0.41 11.2 0.10 1.1 11 3.6 19 5 Unknown. 



1.6 7.1 1.5 1.4 38 .073 3.7 50 .016 64 4,000 

 .0025 .012 .0029 .0025 .07 .013 .007 .5 .081 .12 1.6 



16 80 18 16 440 .025 44 1,760 2.14 763 360 



46 210 50 46 1,230 77.8 122 1.6 200 2,120 10 0.86 percent. 



.0038 .017 .0036 .003 .085 .002 .0086 4.1 .011 .16 14 



13 60 13 12 330 31.8 31.8 1 .54 650 1,000 3 percent. 



23 100 22 20 660 4.7 54 12 .78 933 1,200 



.086 .39 .08 .072 2.0 .013-.028 .20 16-6.8 .11 3.4 30 



15 1.1 1 27 2.83 2.7 1 2 46.6 23 Unknown. 



53 .240 61 55 1,500 .18 149 830 68 2,590 38 1.5 percent. 



19 90 20 20 560 Unknown 49 Unknown Unknown 848 Unknown 



.022 .13 .028 .026 .71 .00012 .07 660 .009 1.2 133 



.071 .27 .069 .066 1.6 .025 .14 6 .695 2.6 36 



.062 .28 .066 .059 1.6 .05 .16 3.2 .16 2.76 18 



2.4 10.4 23 2.1 57.5 .0015 5.6 4,000 .274 97 354 



.00031 .0016 .00036 .00031 .0085 .0077 .0009 .11 .054 .015 .3 



7.1 32 6.8 6 .160 .64 16.7 31 1 288 288 Unknown. 



1.7 7.7 1.6 1.4 38 3.9 »? 5.8 68 12 0.6 percent. 



1.2 5.4 1.2 1.1 30 .079 2.9 37 1.2 61 42 



2.3 10.4 2.2 2 56 .27 5.4 20 .83 93 112 



77 350 81 73 2,000 31.6 198 6.3 81 3,400 42 4 percent. 



Ratio of Ratio of 



G/mt MtXlO" G/mt MtXlO '= MtXlO 1= MtXlO ° MtXlO « potential MtXlO " MtX 10 " potential to 



to reserve reserve 



82,000 373 83,000 74.5 2,000 8.1 203,000 24,000 1,160 3,519 3,000 



390 1.8 400 .37 10 30.6 980 32 76.4 17 223 



68 .36 77 .070 1.92 1.8 189 387 696 3.26 47 



480 2.1 470 4.30 11.8 4.9 1,151 235 35 20 600 



4,000 217 48,000 43.6 1.200 1,800 118,000 65 87,000 2,035 23 



930 4.6 1,000 .9 24.9 1 2,460 2,460 630 42 67 



1,100 4.9 1,200 .98 26.8 931 2,940 3 16,000 51 34 



6,000 24.4 6,300 4.9 1.30 26 13,000 516 117 226 2,000 



110 .56 120 .11 3 .115 294 2,560 10 6.1 500 



Calculation of ynass of crustal segmentB 



Total earth's crust 24X10" mt. 



Oceanic crust 8.9X10" mt (P7 percent of total crust). 



Continental crust 15.1X10" mt (63 percent of total crust). 



Shield areas 10.6X10 " mt (30 percent of continental crust or 43.8 percent of total crust) . 



Folded belts 4.64X10 " mt (30 percent of continental crust or 19.1 percent of total crust). 



United States crust 0.90X10 '* mt (based upon United States as 1/17 of land area of world's continental crust). 



United States crust to 1-km depth 24.6X10'° mt (based upon average thickness continental crust =36.5 km; therefore 1 km i 



cent of United States crust). 



