90 
80 
70 
PERCENT OF TOTAL Ba 
>|000 
1000-500 500-210 210-105 
105-60 
STATION 2 
M4-X—— 
MIO-O —— 
60-30 30-10 lO-| 
< 
SEDIMENT-SIZE CLASSES, IN pm 
FIGURE 11A.—Relative amount percent of total barium in different size fractions of bottom sediment collected on cruises 4 
and 10 at control station 2 on Georges Bank. 
values between 0.68 X10® and 0.60 X10® Ib for the 
last four cruises (fig. 18). 
The total barium sulfate used in drilling the 
exploratory well at block 312 was 2,387,800 lb 
(Danenberger, 1983). An estimated 630,000 lb was 
left in the hole when the rig was moved off the loca- 
tion. If mud was not lost to porous subsurface rock 
formations while drilling, which is highly unlikely, 
then the total barite discharged to the ocean was 
1,757,800 lb. This estimate is considered an upper 
limit because some loss to porous formations is 
expected. E. P. Danenberger (Minerals Manage- 
ment Service, oral commun., Sept. 21, 1983) 
estimated that, on the basis of drilling records, the 
maximum losses to porous formations would 
reduce the barite discharge to 800,000 lb. 
Danenberger suggested that the most likely range 
of barite discharge is between 1 million and 1.5 
23 
million lb. We will assume the middle value of this 
range, 1,250,000 lb, for the total barite discharged 
to the ocean while drilling this well. 
The net mass of barite added by drilling within 
the 6-km circle at the time of cruise 5 represents 
25 percent of the total amount discharged 
(270,000/(1,250,000*(0.85))(100). The factor 0.85 
represents the fraction of pure BaSO, contained 
in mined barite. 
In our evaluation of the rate at which barite 
decreases within the site-specific survey, we have 
considered only the area between the 0.5- and 2- 
km circles. This choice includes 20 of the 29 sta- 
tions and excludes the area of the outer two rings 
where half of the total area is controlled by as few 
as four stations. We have also excluded the actual 
drill site, where large within-station variability was 
measured. Another advantage in considering this 
