MANOP Sites S and R manganese nodules chemical composition determined by atomic absorption spectrometry (AAS)

Manganese nodules were sampled from box cores collected at the Manganese Nodule Program (MANOP) site S (Clarion-Clipperton Fracture Zone) and site R (Murray Fracture Zone) in the Central Pacific ocean. For these sites nodule tops are smoother than nodule bottoms, which commonly have a gritty texture. The top/bottom orientation of each manganese nodule was labeled during curation. Most of the nodutes studied were cut in haIf, and a 3-5 mm layer was scraped from nodule tops and bottoms. The chemical analysis was performed on both top and bottom sides as well as on the whole specimen. They were analysed at the U.S. Geological Survey, Menlo Park using instrumental neutron activation analysis with high-resolution lithium-drifted germanium detectors. This method involves the meeasurement of gamma-ray emission after proper irradiation of the samples.