Extractive Chemistry of Equatorial Pacific Pelagic Sediments and Relationship to Nodule Forming Processes

Abstract

In order to help understand early diagenetic processes in sediments potentially important to the formation of marine manganese nodules a series of selective extraction experiments were performed on sediments associated with nodule areas from the eastern equatorial Pacific Ocean. Phase selective extractants used were hydroxylamine hydrochloride (buffered and unbuffered), buffered citrate-dithionite; and hydrochloric acid. In hydroxylamine hydrochloride extractions of red-brown clay a rapid initial release of all metals within the first minute is followed by a slow, long term dissolution. The pH of the extraction solutions rises abruptly in the first minute, levels off, and drops steadily for the rest of the extraction. In sequential, batch-extraction experiments using 0.1N HC1 and hydroxylamine hydrochloride, Cu is readily released in HC1, but the release of Mn, Ni, Co, and Ca is greater in hydroxylamine hydrochloride. Buffering of solutions by dissolution of calcium carbonate in an artificial carbonate/manganese nodule mixture depresses Cu release in HCl, and enhances Mn, Ni, Co, and Fe release in hydroxylamine hydrochloride.