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The apparent enrichment of chlorite in the suspended<br />

matter is probably due to the uncertainty involved in<br />

o<br />

resolving the contribution of chlorite to the small 3.5 A<br />

doubl et in the di ffractogram of these 1 ow-concentrati on<br />

samples.<br />

The major mineralogical difference between suspended<br />

and bottom sedi ment from the Greater Anti 11 es Outer Ri dge<br />

is in the relative abundances of illite and montmorillonite<br />

plus mixed-layer minerals. The maximum concentration of<br />

suspended matter recovered on any Millepore or Nuclepore<br />

filter was about .172 mg/cm2; although the residueconcen-<br />

tration on the silver filters could not be determined, it<br />

almost certainly falls below this value and thus is in the<br />

209<br />

range where montmori 11 oni te and mi xed-l ayer montmori 11 oni te-<br />

illite are not fully detected (Fig. 7.6). The effect is<br />

stri ki ngly ill ustrated by a compari son of the di ffractogram<br />

of a glycolated suspended-matter sample to that of a low and<br />

a high concentration, glycolated, bottom-sediment sample<br />

(Fig. 7.7).<br />

It is conceivable that the suspended-matter samples<br />

are actually, rather than apparently, depleted in mont-<br />

morillonite. However, in view of the arguments outlined<br />

concerni ng the montmori 11 oni te-depl eti on effect, it is<br />

assumed that the mineralogy of the suspended matter and<br />

subjacent bottom sediment are quite similar, if not<br />

i denti ca 1. Thi s asserti on, together wi th evi dence of the<br />

depositional regime presented in the next section, argues<br />

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