Abstract
A critical study was made to determine the optimum conditions for assaying uranium in marine sediments by delayed neutron counting after thermal neutron fission of ²³�U. The fast, simple, precise, sensitive and non-destructive method was applied to measure uranium concentrations in sediments deposited under varying conditions. The world-wide spatial distribution of uranium concentrations in a large number of samples of marine sediments of different types were studied. Several interesting relationships were observed. (1) There is an approximately proportional trend between per cent organic carbon and uranium in sediments deposited in an anoxic environment -- 7% organic carbon and 7 ppm uranium to 14% organic carbon and 30 ppm uranium. (2) For manganese nodules an approximately linear trend is indicated between uranium and calcium concentrations with both decreasing with increasing depth of deposition -- for nodules from the Pacific, 4 ppm uranium with 0.2% calcium, found at 4500 meters and 13 ppm uranium with 1.2% calcium, found at 1000 meters; for modules from the Atlantic 13 ppm uranium with 14% calcium, found at 494 meters and 7 ppm uranium with 0.2% calcium found at 1029 meters. (3) Relatively high uranium was found in carbonates deposited in: a) the deepest parts of the Gulf of Mexico -- up to 2.7 ppm in microgastropods and about 0.4 ppm in foraminifera, up to 5.75 ppm in Campeche Bank carbonates and 2.57 ppm in the Yucatan Shelf carbonates b) the Florida Shelf area -- 2.22 to 4.77 ppm in skeletal sands containing 76 to 61% calcium carbonate respectively c) the Atlantic Ocean -- 2.68 to 4.28 ppm uranium in the Barbados corals and about 0.57 ppm uranium in cores which have about 86% calcium carbonate d) the Pacific Ocean -- about 0.63 ppm in cores which have about 86% calcium carbonate e) the Red Sea -- up to 5.94 ppm uranium in the skeletal sands. These findings seem to invalidate the usual practice of expressing uranium data on a calcium carbonate free basis in which it is assumed that the calcium carbonate fraction has negligible uranium. Approximate calculations indicate that the annual rate of input of uranium to the Gulf of Mexico from rivers in the surrounding land areas is balanced by its removal in carbonate sediments of the Yucatan and Florida Shelves in the Campeche Bank.
Mo, Maung Tin (1971). Uranium concentrations in marine sediments. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -172510.