Estimation of continental 187Os/186Os values by using 187Os/186Os and 143Nd/144Nd ratios in marine manganese nodules

AUTOR(ES)

Turekian, Karl K.

RESUMO

The relationship between 187Os/186Os and 143Nd/144Nd in different manganese nodule fields is used to determine the 187Os/186Os ratio of the continental terrains bounding the major ocean basins. The Atlantic Ocean drainages yield 187Os/186Os of about 11; the Pacific Ocean, between 25 and 36; and the western Indian Ocean, 20. By assuming a two-component continental crust composed of “ultramafic rocks” (high Os concentration, low 187Os/186Os) and “granite” with only radiogenic 187Os produced in accessory Re-bearing molybdenite, the ultramafic contribution to weathering is about 0.2%. Some or most of this may come from the alteration of oceanic ultramafics.

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