Method development for 234U and 230Th determination and application to fossil deep-water coral and authigenic carbonate dating from the Campos Basin - Brazil

摘要

A 234U and 230Th determination method based on an extraction chromatographic separation followed by ICP-MS with quadrupole (ICP-QMS) was developed. For authigenic carbonates, a second separation step with ion exchange chromatography in a HNO3 solution was added. These methods were applied to seven fossil deep-water coral and two authigenic carbonate samples from the continental slope of the Campos Basin - Brazil. The ages determined for the fossil corals samples from the same sediment core ranged from 9 to 202 ky with a 1% uncertainty, consistent with the values determined by 14C dating and with those determined by 230Th/234U using flow injection coupled to an ICP-QMS. One of the authigenic carbonates analyzed presented an age of approximately 80 ky. The other sample exhibited a 230Th/234U activity ratio close to equilibrium and out of the application range of the method.