Geochemical Journal, Vol. 49 (No. 6), pp. e21-e26, 2015
Yuichi Morishita1,2* and Akira Usui3
1Shizuoka University, Shizuoka 422-8529, Japan
2Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
3Kochi University, Kochi 780-8520, Japan
(Received August 11, 2015; Accepted September 19, 2015; Online published October 23, 2015)
Heretofore the presence of platinum in the hydrogenetic ferromanganese crust has been known yet, the host to platinum has remained poorly understood. Here we first report on the microanalysis of platinum in ferromanganese crust using secondary ion mass spectrometry (SIMS). SIMS microanalysis revealed that Pt concentration of vernadite was between 0.21 and 1.22 ppm, and that of brown matrix was very low (around the detection limit of 0.036 ppm or less) in a ferromanganese crust. The SIMS spatial resolution was 3 μm by 3 μm on the sample surface, and several tens of nanometers along the depth. A novel Pt detection method using SIMS was performed, in which most SIMS depth profiles show homogeneous Pt concentrations (0.21 to 0.55 ppm), however, some profiles detected local enrichment of Pt on the nm level.
Key words: hydrogenetic ferromanganese crust, platinum, microanalysis, SIMS